Problems of drilling oil wells. General information about drilling oil and gas wells. Works during drilling for oil or gas

Drilling is the construction of a directional mine opening of small diameter and great depth. The wellhead is located on the surface of the earth, and the bottom is at the bottom. Today, drilling oil and gas wells to extract related minerals is widespread.

Objectives and goals of drilling for oil and gas

Nowadays, oil and gas are extracted from wells. Despite the large number of different ways to make a well, they are still being developed, new methods are being developed aimed at speeding up work and reducing their cost.

The modern drilling process consists of the following stages:

Shaft sinking
Formation isolation
Well development and operation

The drilling of wells is divided into two stages, which must take place parallel to each other: deepening the face and clearing it of destructible rocks. Rock separation is also carried out in two stages: installation of casing pipes, joining them and sealing them together.

Despite the fact that no one will drill an industrial well for oil and gas at home, it is interesting to know how much an oil well costs and which methods are most widespread.

The process of drilling oil wells - video

Basic drilling methods

Today, various methods of drilling oil wells are practiced, but the most widespread among them are:

Rotary drilling with caisson for well
Turbine drilling
Screw drilling

Rotary drilling of oil wells is one of the popular methods. The bit, which penetrates deep into the soil rocks, rotates together with the drill pipes. The torque of such a system primarily depends on the resistance of the rocks that get in the way.

Rotary well drilling owes its popularity to such advantages as the ability to withstand large differences in the load on the bit, independence of settings from extraneous factors, and large penetration in one trip.

Turbine drilling of oil wells is carried out using an installation in which the bit interacts with the turbodrill turbine. The installation is driven into rotation by a flow of liquid that circulates under high pressure through a system of stators and rotors. Due to this, the lifting and pumping of well water is also carried out.

Torque does not depend on well depth, rock properties, rotation speed and axial load. At the same time, the transmission coefficient during turbine drilling is an order of magnitude higher than during rotary drilling, but the cost of the work is higher due to the need for a large amount of energy, and it is impossible to quickly reconfigure the installation parameters.

Screw drilling of oil and gas wells is that the main working mechanism consists of a large number of screw mechanisms, due to which the optimal bit rotation speed is achieved. Despite all the prospects, this method has not yet received proper distribution, but has enormous potential for this.

Price issue

Having found out for yourself how oil wells are drilled, the question of how much you have to spend to drill another meter of a funnel probably becomes interesting.

Today, the cost of drilling an oil well is very huge and depends on a large number of factors:

Well depth
The need to purchase plastic casing pipes for wells
Ambient conditions
Set deadlines

If we talk about exact figures, the price of a well with a depth of 2000-3000 meters will range from 30 to 60 million rubles. Exploration drilling will cost about 40-50% of the drilling cost.

Initially, our country used drilling for the construction of salt wells. Information about drilling wells for oil exploration dates back to the 30s of the 19th century in Taman. At the suggestion of mining engineer N.I. Voskoboynikov, in 1848, a well was drilled on Bibi-Heybat using a drill, from which oil was obtained. It was the first oil well in the world to be constructed by drilling using a method of continuously clearing the drilled rock from the well using fluid flushing.

Wells are drilled vertical, inclined, horizontal. The method of directional cluster drilling has become widely used, when 15 or more wells are drilled using an inclined method from one site. This method is successfully used in wetlands, when drilling wells from offshore drilling platforms, to preserve fertile arable land, etc.

Concept of a well

A well is a mine working (vertical or inclined) of circular cross-section, with a depth of several meters to several kilometers, of various diameters, constructed in the thickness of the earth’s crust. The top of the well is called the mouth, the bottom of the well is called the bottom, and the side is called the wellbore. The distance from the wellhead to the bottom along the axis of the wellbore is called the well length. The projection of the length onto the vertical axis is called the well depth.

Wells can be oil, gas, gas condensate, injection, observation, appraisal, etc. The design of wells must meet the following requirements:

1. Ensure the mechanical stability of the wellbore walls and reliable separation of all (oil, gas, water) layers from each other, free access to the bottom of the wells for lowering equipment, and prevention of rock collapse in the wellbore.
2. Effective and reliable connection of the well bottom with the productive (oil or gas) formation.
3. The possibility of sealing the wellhead and ensuring the direction of the extracted product into the system for collecting, preparing and transporting oil and gas or injecting an impact agent into the formation.
4. Possibility of carrying out research work in wells, as well as various geological, technical and maintenance work.

The stability of the wellbore walls and the separation of layers from each other is achieved by drilling and lowering several pipes into the well, called casing. First, the well is drilled to a depth of 50-100 meters, a steel pipe is lowered into it (1 = 500 mm or more - direction. The space between the outer wall of the pipe and the wall of the well (rock) is filled with a special cement mortar under pressure in order to prevent the collapse of the upper rocks and flows between the upper layers. Then the well is drilled with a smaller bit diameter to a depth of 500-600 m, a pipe with a diameter of 249-273 mm is lowered into it and cemented, as well as the direction, to the mouth. This string of pipes is called a conductor and is designed to prevent erosion of the upper layers, and also to create a channel for drilling clay mud. After this, the well is drilled to the design bottom. A production string (steel pipe with a diameter of 146-168 mm) is lowered into it, and the space between the pipe and the rock is filled under pressure with cement slurry to the mouth. Volume of cement slurry its injection pressure is determined by calculation.After the cement mortar hardens (usually 48 hours), a cement stone is formed in the interpipe space between the outer wall of the pipe and the rock, which separates the layers from each other.

Depending on the characteristics of the deposit, its reservoir pressure, geological section, etc., the well design can be single-column or multi-column (two or three). The last column is called the production column.

After completion of drilling, lowering of the production casing, its cementation in the well in the interval of the oil or gas formation, through holes are made through a steel pipe and cement stone using special perforators.

After this, the well is developed and put into operation. The well can have a closed or open bottom. An open face is used when the productive formation is composed of dense rocks - carbonate, calcareous or dense sandstones. With an open bottom hole, the well is drilled to the top of the productive formation, the production casing is lowered and cemented. Then, using a bit of a smaller diameter, the productive formation is opened (drilled) through the production casing. In this case, perforation is not required, because the productive formation is not blocked by a metal pipe.

If the productive formation consists of unstable and weakly cemented sandstones or limestones, then the bottom of the well is equipped with a closed one. In this case, the well is drilled to the design depth (a so-called “sump” is created slightly below 15-20 m of the productive formation), a production string is lowered into it, which is cemented, and then the productive sections of the formation are perforated to communicate the formation with the bottom of the well. If the formation is represented by weakly cemented sandstones or siltstones, then the productive formation can be opened with an open bottom, followed by lowering the liner filter. The filter is represented as holes in the production string in the productive formation interval.

Methods of drilling oil and gas wells.

There are several drilling methods, but mechanical drilling has found industrial use. Mechanical drilling is divided into impact and rotary. When percussion drilling, the drilling tool consists of a bit 1, a hammer rod 2, a rope lock 3. A mast 12 is installed on the well being drilled, which has a block 5 in the upper part, a balancer pulley roller 6, an auxiliary roller 8 and a drilling machine drum 11. The rope is wound on drum 11 of the drilling rig. The drilling tool is suspended on a rope 4, which is thrown over the block 5 of the mast 12. When the gears 10 rotate, the connecting rod 9, performing a reciprocating movement, raises and lowers the balancing frame 6. When the frame is lowered, the pulley roller 7 pulls the rope and lifts the drilling tool above the bottom of the well . When the frame is raised, the rope lowers, the bit falls onto the face and destroys the rock. To clean the face of destroyed rock (sludge), the drilling tool is lifted from the well and a bailer (an elongated bucket-type cylinder with a valve in the bottom) is lowered into it. To increase the efficiency of percussion-rope drilling, it is necessary to promptly clean the bottom of the well from drilled rock.

Rotary drilling.

Oil and gas wells are currently drilled using the rotary drilling method. During rotary drilling, rock destruction occurs due to a rotating bit. Under the weight of the tool, the bit enters the rock and, under the influence of torque, destroys the rock. Torque is transmitted to the bit using a rotor installed at the wellhead through the drill string. This drilling method is called rotary drilling. If torque is transmitted to the bit from a downhole motor (turbo drill, electric drill), then this method is called turbine drilling.

A turbodrill is a hydraulic turbine driven into rotation by means of flushing fluid pumped into the well by pumps.

An electric drill is a sealed electric motor; electric current is supplied to it through a cable from the surface.

A drilling derrick is a metal structure above a well for lowering and lifting a drilling tool with a bit, downhole motors, casing pipes, placing drill stands after they are lifted from the well, etc.

Towers are available in several modifications. The main characteristics of towers are lifting capacity, height, “magazine” capacity (space for drill pipe plugs), dimensions of the lower and upper bases, weight (mass of the tower).

The lifting capacity of the tower is the maximum, maximum permissible load on the tower during the drilling process. The height of the tower determines the length of the candle that can be removed from the well, the length of which determines the duration of tripping operations.

For drilling wells to a depth of 400-600 m, a tower with a height of 16-18 m is used, for a depth of 2000-3000 m - a height of 42 m, and for a depth of 4000 to 6500 m - 53 m. The capacity of the “magazine” shows the total length of the drilling pipes with a diameter of 114-168 mm can be placed in them. The dimensions of the upper and lower foundations characterize the conditions of the drilling crew, taking into account the placement of drilling equipment, drilling tools and means of mechanization of hoisting operations. The dimensions of the upper base of the towers are 2x2 or 2.6x2.6 m, and the bottom - 8x8 or 10x10 m.

The total mass of drilling rigs is tens of tons.

Well construction cycle.

Before drilling begins at the well site, the site is cleared of foreign objects; if there is forest, it is cut down and uprooted. If drilling will be carried out in a swampy area, then first fill the road to the drilling site, and also fill the site, eliminating the swamp, under the drilling rig. They plan the site, install power lines, communications and water conduits.

Drilling derricks, if the terrain and distance allow, are transported without disassembly on special tracked carts or on sleds with runners, and the pneumatic movement method is also possible. After transportation and installation of the drilling rig at the site, installation of the remaining equipment begins, i.e. installation of diesel driven piston pumps or electric driven pumps; drilling mud cleaning system, electrical room, wellhead equipment (rotor, preventer, hydraulic weight indicator), drilling shelter for above-ground structures, etc. If drilling begins in a new area, remote from the place of drilling operations, in this case all equipment, including the drilling rig, pumping unit, treatment facilities, etc., is delivered disassembled to the drilling site and here they begin to assemble the drilling rig and all other equipment.

After installing the drilling rig and all equipment, preparatory work for drilling the well begins.

Preparatory work includes:

1. Equipping the traveling block and crown block with steel rope and suspending the lifting hook.
2. Installation and testing of small-scale mechanization equipment.
3. Assembling and hanging a square swivel (drive pipe) to the hook, connecting a flexible high-pressure hose to the riser pipe and to the swivel.
4. Tower alignment.
5. Installation of the rotor.
6. Drilling the direction of the well.

Wells are drilled vertical, directional and horizontal. For a long time, the main type of well drilling was vertical drilling. In recent years, the method of directional drilling has increasingly begun to be used, i.e. when, according to drilling plans, the well is drilled along a trajectory with a deviation from the vertical. Typically, it is advisable to drill inclined wells under the bottom of the sea, river, lake, as well as under mountains and ravines; in swampy areas, protected forests, for large industrial facilities, cities and villages. Inclined wells are also used in the elimination of open oil and gas gushers, as well as for the purpose of preserving fertile lands, in order to reduce the cost of drilling wells by reducing preparatory work and communications (communications, electricity, water pipelines, etc.). To deviate the well profile from the vertical, special devices are used. These include: curved sub, curved drill pipe, various types of whipstocks, etc. More and more in our country in recent years, horizontal drilling of wells and drilling of horizontal lateral wellbores in depleted and unprofitable wells where there are undeveloped layers with oil are used.

Well perforation. After the casing pipes are lowered into the well and cemented, holes are made in the production casing and cement stone against the productive part of the formation using perforators to connect the productive part of the formation with the bottom of the well. This operation is called perforation. Various methods of well perforation are used: bullet, torpedo, cumulative and hydrosandblasting.

A bullet perforator (PP) is a pipe 1 m long and 100 mm in diameter, which is loaded with compressed gunpowder and 10 steel bullets. On a logging cable, a bullet perforator is lowered into a well filled with clay solution, installed against a given interval of the productive formation, and shots are fired. The depth of the holes in the rock does not exceed 5-7 cm. Many bullets get stuck in the production column, in the cement stone, and only a small number of them pierce the column and cement stone. It is practically not used at present.

Torpedo perforator (TP). Torpedo perforation is carried out by devices lowered on a cable and firing explosive shells with a diameter of 22 mm. The apparatus consists of sections, each of which has two horizontal trunks. The projectile is equipped with a pin-type detonator. When the projectile stops, the internal charge explodes and the surrounding rock cracks. The depth of the channels, according to test data, is 100-160 mm, the diameter of the channel is 22 mm. No more than four holes are made per 1 m of productive part of the formation, since torpedo perforation often causes destruction of the casing. Just like bullet, torpedo perforation is used very limitedly.

Currently, cumulative perforation (PC) is mainly used. Cumulative perforators have charges with a conical recess, which allow you to focus explosive gas flows and direct them at high speed perpendicular to the walls of the well.

A block of compressed powdered explosive material, which has a conical recess lined with a metal die, is inserted into a cumulative perforator.

Cumulative perforation is carried out by firing perforators that do not have bullets or shells. The penetration of the column, cement stone and rock is achieved through a focused explosion. This focusing is due to the conical shape of the surface of the explosive charge, lined with a thin metal coating (copper sheet 0.6 mm thick). The energy of the explosion in the form of a thin beam of gases - lining products - pierces the channel. The cumulative jet has a speed at the head of up to 6-8 km/s and creates a pressure of 3-5 thousand MPa.

When fired with a shaped charge, a narrow perforation channel with a depth of up to 350 mm and a diameter in the middle part of 8-14 mm is formed in the column and cement stone.

In oil fields, a hydrosandblasting perforator (GSP) is also used.

A hydrosandblasting hammer consists of a thick-walled body into which up to ten nozzles made of abrasive-resistant material (ceramics, hard alloys) with hole diameters of 3-6 mm are screwed.

A hydrosand-jet perforator is lowered into the well using pump and compressor pipes. Before perforating a well, a ball is thrown from the surface into the tubing, which blocks the through hole of the perforator. After this, using pumping units AN-500 or AN-700, liquid with sand is pumped into the well through the tubing. The injected liquid with sand comes out only through the nozzles. When leaving the nozzles, enormous speeds of the abrasive jet develop. As a result, in a short time, holes are made in the casing pipes, cement stone and rock, and the wellbore is connected to the productive formation. Depending on the diameter of the nozzles, their number and the speed of liquid injection, the depth of the perforations reaches 40-60 cm. At the same time, the tightness of the cement stone behind the column is maintained. During hydrosandblast perforation, a pressure of up to 40 MPa is created at the wellhead. The pumping rate of liquid with sand is 3-4 l/s per nozzle. In this case, the volumetric velocity of the jet in the nozzle reaches 200-300 m3/day, and the pressure drop is 18-22 mPa. The duration of perforation of one interval is 15-20 minutes. Upon completion of perforation of a given interval, the perforator is raised and placed at the next interval, and the operation is repeated.

call inflow into the well.

In field practice, the following methods are used to cause an influx of liquid from the productive formation to the bottom of the well: tarting, pistoning, replacing the liquid in the well with a lighter one, the compressor method, pumping a gas-liquid mixture, pumping with deep-well pumps. Before the well is developed, fittings are installed at the wellhead. In any case, a high-pressure valve must be installed on the casing flange to shut off the wellbore in emergency situations.

Pistoning. When pistoning (swabbing), the piston, or swab, is lowered into the tubing on a steel rope. The piston (swab) is a pipe with a diameter of 25-37.5 mm with a valve at the bottom that opens upward. Rubber cuffs (3-4 pieces) reinforced with wire mesh are installed on the outer surface of the pipe (at the joints). When the swab is lowered below the level, the liquid in the well flows through the valve into the space above the piston. When the swab is lifted, the valve closes, and the cuffs, expanded by the pressure of the liquid column above them, are pressed against the walls of the tubing and compacted. During one lift, the piston carries out a column of liquid equal to the depth of its immersion under the liquid level. The immersion depth is limited by the strength of the tartar rope and is usually 100-150 m.

Tartanization is the extraction of liquid from a well with a bailer lowered on a steel (16 mm) rope using a winch on a tractor (car). A bailer is made from a pipe 7.5-8 m long, which has a valve in the lower part with a rod that opens when the rod is pressed against it. At the top of the bailer there is a bracket for fastening the rope. The bailer diameter should not exceed 0.7 of the casing diameter. During one run, the bailer removes liquid from the well with a volume of no more than 0.06 m3.

Tartanning is a labor-intensive and low-productivity method. At the same time, tarting makes it possible to extract clay solution from the bottom and control the fluid level in the well. Repeated lowering and raising of the piston leads to a gradual decrease in the liquid level in the well. The big disadvantage of this method is that you have to work with an open mouth, which is associated with the danger of liquid release and open gushing. Therefore, piston is used mainly in the development of injection wells.

Replacing fluid in the well. A well completed by drilling is usually filled with clay mud. If we replace the clay solution in the well with water or degassed oil, we will reduce the bottomhole pressure. This method is used to develop wells with high reservoir pressure and good reservoir properties.

Compressor method of development. The compressor method is more widely used in well development. Before development, pump and compressor pipes are lowered into the well, and the wellhead is equipped with a Christmas tree. A mobile compressor or a high-pressure gas line from a gas compressor station is connected to the interpipe space through a discharge pipeline. When gas is injected into the well, the liquid in the annulus is pushed to the tubing shoe or to the starting hole (3-4 mm) in the tubing, made in advance at a depth of 700-800 m from the wellhead, and breaks through into the tubing. Gas entering the tubing aerates the liquid in them. As a result, the pressure at the bottom is significantly reduced. By adjusting the gas flow, they change the density of the gas-liquid mixture in the pipes, and, accordingly, the pressure at the bottom of the well. When the bottomhole pressure is below reservoir pressure, the influx of liquid and gas into the well begins. After receiving a stable inflow, the well is transferred to a stationary operating mode. This method allows you to relatively quickly obtain significant drawdowns on the formation, which is especially important for effective cleaning of the wellbore zone. In conditions of hard rocks (sandstones, limestones), this leads to intensive cleaning of the pore space from calmatizing (clogging) material, and in conditions of loose rocks - to the destruction of the bottom-hole zone of the formation. To ensure a smoother start-up of the well, aerated oil is pumped through the annulus using a compressor, a washing unit and a mixer. After the gas-liquid mixture is released through the flow line into the receiving tank, the supply of aerated oil is gradually reduced until it stops completely.

Development of wells with compressed air is mainly carried out using mobile compressors UKP-80 or KS-100. The UKP-80 compressor develops a pressure of 8 MPa with an air supply of 8 m3/min, and the KS-100 develops a pressure of 10 MPa with an air supply of 16 m3/min. It should be noted that when developing wells with compressed air, explosions are possible, since when the content of hydrocarbon gas in a mixture with air is from 6 to 15%, an explosive mixture is formed.

Development of wells by injection of carbonated liquid.

Well completion with carbonated liquid involves pumping a mixture of gas and liquid (water or oil) into the annulus instead of gas or air. The density of such a gas-liquid mixture depends on the ratio of the flow rates of injected gas and liquid, which allows you to adjust the parameters of the development process. Taking into account the fact that the density of the gas-liquid mixture is greater than the density of pure gas, this method makes it possible to develop deep wells with compressors that create lower pressure.

Development of injection wells. Injection wells must have high injectivity throughout the entire thickness of the productive formation. This can be achieved by good cleaning of the bottomhole zone of the productive formation from dirt and other calmatizing materials. The bottomhole zone of the formation is cleaned before launching an injection well for injection using the same methods as during the development of oil production wells, but drainage of the bottomhole zones of the formation takes much longer. The duration of flushing reaches one day or more and depends on the amount of mechanical impurities contained in the water leaving the well. The content of mechanical impurities at the end of washing should not exceed 10-20 mg/l.

Maximum cleaning of the pore space of the near-wellbore zone of the formation occurs using drainage methods that make it possible to create very high depressions in the formation, ensuring high rates of fluid filtration to the bottom of wells under unsteady conditions. Most often, formation drainage is carried out using self-discharge methods, liquid aeration, pumping using high-performance submersible centrifugal pumps, etc.

When developing injection wells, the variable pressure method (VPM) has become widely used. When using this method, high injection pressure is periodically created into the bottomhole zone of the formation through tubing using pumping units for a short time, which is then abruptly released through the annulus (a “discharge” is carried out). When fluid is injected at high pressure in the near-wellbore zone of the formation, existing cracks open and new ones form, and when the pressure is released, fluid flows to the bottom at high speed. Good results are obtained when using the method of periodic drainage of bottomhole zones by creating multiple instantaneous high depressions at the bottom.

Sometimes poor injectivity of injection wells occurs either due to the low natural permeability of the formation rocks, or a large number of clay interlayers, which cannot be developed by drainage of the near-wellbore zones. In such cases, to increase the injectivity of injection wells, other methods of influence are used, which make it possible to increase the diameters of filtration channels or create a system of cracks in the formation rocks. Such methods include various acid treatments, thermal methods, hydraulic fracturing, crevice unloading, oxidation treatment of the formation, etc.

Construction of oil and gas wells developed and refined in accordance with the specific geological conditions of drilling in a given area. It must ensure the fulfillment of the assigned task, i.e. achieving the design depth, opening the oil and gas deposit and carrying out the entire planned range of studies and work in the well, including its use in the field development system.

The design of the well depends on the complexity of the geological section, the drilling method, the purpose of the well, the method of opening the productive horizon and other factors.

The initial data for designing a well structure includes the following information:

purpose and depth of the well;

design horizon and characteristics of the reservoir rock;

geological section at the location of the well, highlighting zones of possible complications and indicating reservoir pressures and hydraulic fracturing pressures by interval;

the diameter of the production string or the final diameter of the well, if running the production string is not provided.

Design order oil and gas well designs next.

Selected well bottom section design . The design of a well in the productive formation interval should provide the best conditions for the flow of oil and gas into the well and the most efficient use of reservoir energy of the oil and gas deposit.

The required number of casing strings and depths of their descent. For this purpose, a graph of changes in the anomaly coefficient of reservoir pressures k, and the absorption pressure index kabs. is plotted.

The choice is justified diameter of the production string and the diameters of casing strings and bits are agreed upon. Diameters are calculated from bottom to top.

Cementing intervals are selected. From the casing shoe to the wellhead the following are cemented: conductors in all wells; intermediate and production strings in exploration, prospecting, parametric, reference and gas wells; intermediate columns in oil wells more than 3000 m deep; on a section of at least 500 m in length from the intermediate casing shoe in oil wells up to 3004) m deep (provided that all permeable and unstable rocks are covered with cement slurry).

The cementing interval of production strings in oil wells can be limited to the area from the shoe to a section located at least 100 m above the lower end of the previous intermediate string.

All casing strings in wells constructed in offshore areas are cemented along their entire length.

Stages of designing a hydraulic program for flushing a well with drilling fluids.

A hydraulic program is understood as a set of adjustable parameters for the well flushing process. The range of adjustable parameters is as follows: indicators of the properties of the drilling fluid, the flow rate of the drilling pumps, the diameter and number of nozzles of the jet bits.

When drawing up a hydraulic program it is assumed:

Eliminate fluid ingress from the formation and loss of drilling fluid;

Prevent erosion of the well walls and mechanical dispersion of transported cuttings in order to avoid the accumulation of drilling fluid;

Ensure removal of drilled rock from the annular space of the well;

Create conditions for maximum use of the hydromonitor effect;

Rational use of the hydraulic power of the pumping unit;

Eliminate emergency situations when stopping, circulating and starting mud pumps.

The listed requirements for the hydraulic program are satisfied subject to the formalization and solution of a multifactor optimization problem. Known schemes for designing the process of flushing wells being drilled are based on calculations of hydraulic resistance in the system based on specified pump flow rates and parameters of the properties of drilling fluids.

Such hydraulic calculations are carried out according to the following scheme. First, based on empirical recommendations, the speed of movement of the drilling fluid in the annular space is set and the required flow rate of the mud pumps is calculated. Based on the specifications of the mud pumps, the diameter of the bushings capable of providing the required flow is selected. Then, using the appropriate formulas, hydraulic losses in the system are determined without taking into account pressure losses in the bit. The area of the nozzles of hydraulic jet bits is selected based on the difference between the maximum rated injection pressure (corresponding to the selected bushings) and the calculated pressure losses due to hydraulic resistance.

Principles for choosing a drilling method: basic selection criteria, taking into account the depth of the well, temperature in the wellbore, complexity of drilling, design profile and other factors.

The choice of a drilling method, the development of more effective methods for destroying rocks at the bottom of a well and the solution of many issues related to the construction of a well are impossible without studying the properties of the rocks themselves, the conditions of their occurrence and the influence of these conditions on the properties of the rocks.

The choice of drilling method depends on the structure of the formation, its reservoir properties, the composition of the liquids and/or gases contained in it, the number of productive interlayers and the anomaly coefficients of formation pressures.

The choice of a drilling method is based on a comparative assessment of its effectiveness, which is determined by many factors, each of which, depending on the geological and methodological requirements (GMT), purpose and drilling conditions, can be of decisive importance.

The choice of method for drilling a well is also influenced by the intended purpose of the drilling work.

When choosing a drilling method, one should be guided by the purpose of the well, the hydrogeological characteristics of the aquifer and its depth, and the volume of work to develop the formation.

Combination of BHA parameters.

When choosing a drilling method, in addition to technical and economic factors, it should be taken into account that, in comparison with BHAs based on a downhole motor, rotary BHAs are much more technologically advanced and more reliable in operation, more stable on the design trajectory.

Dependence of the deflection force on the bit on the well curvature for stabilizing BHAs with two centralizers.

To justify the choice of drilling method in post-salt deposits and confirm the above conclusion about a rational drilling method, the technical indicators of turbine and rotary well drilling were analyzed.

If you choose a drilling method with downhole hydraulic motors, after calculating the axial load on the bit, you must select the type of downhole motor. This choice is made taking into account the specific torque on the bit rotation, the axial load on the bit and the density of the drilling fluid. The technical characteristics of the selected downhole motor are taken into account when designing the bit rotation speed and the hydraulic program for flushing the well.

Question about choosing a drilling method should be decided on the basis of a feasibility study. The main indicator for choosing a drilling method is profitability - the cost of 1 m of penetration. [ 1 ]

Before you start choosing a drilling method To deepen a hole using gaseous agents, it should be borne in mind that their physical and mechanical properties introduce certain limitations, since some types of gaseous agents are inapplicable for a number of drilling methods. In Fig. 46 shows possible combinations of various types of gaseous agents with modern drilling methods. As can be seen from the diagram, the most universal from the point of view of using gaseous agents are the rotary and electric drilling methods, the less universal is the turbine method, which is used only when using aerated liquids. [ 2 ]

The power supply of the MODU has less influence on choice of drilling methods and their varieties, than the power supply of the installation for drilling on land, since in addition to the direct drilling equipment, the MODU is equipped with auxiliary equipment necessary for its operation and retention at the drilling point. In practice, drilling and auxiliary equipment operate alternately. The minimum required power supply of a drilling rig is determined by the energy consumed by the auxiliary equipment, which may be greater than that required for the drilling drive. [ 3 ]

The eighth, section of the technical project is devoted to choosing a drilling method, standard sizes of downhole motors and drilling lengths, development of drilling modes. [ 4 ]

In other words, the choice of one or another well profile determines to a large extent choice of drilling method5 ]

The transportability of the MODU does not depend on the metal consumption and power supply of the equipment and does not affect choice of drilling method, since it is towed without dismantling the equipment. [ 6 ]

In other words, the choice of one or another type of well profile determines to a large extent choice of drilling method, bit type, hydraulic drilling program, drilling mode parameters and vice versa. [ 7 ]

The rolling parameters of the floating foundation should be determined by calculation already at the initial stages of hull design, since the operating range of sea waves at which normal and safe operation is possible depends on this, as well as choice of drilling method, systems and devices to reduce the impact of motion on the work process. Reducing pitching can be achieved by rational selection of housing sizes, their relative position and the use of passive and active means of combating pitching. [ 8 ]

The most common method of exploration and exploitation of groundwater remains the drilling of wells and wells. Choosing a drilling method determine: the degree of hydrogeological knowledge of the area, the purpose of the work, the required reliability of the obtained geological and hydrogeological information, the technical and economic indicators of the drilling method under consideration, the cost of 1 m3 of produced water, the life of the well. The choice of well drilling technology is influenced by the temperature of groundwater, the degree of its mineralization and aggressiveness towards concrete (cement) and iron. [ 9 ]

When drilling ultra-deep wells, preventing borehole curvature is very important due to the negative consequences of borehole curvature when deepening it. Therefore, when choosing methods for drilling ultra-deep wells, and especially their upper intervals, attention should be paid to maintaining the verticality and straightness of the wellbore. [ 10 ]

The question of choosing a drilling method should be decided on the basis of a feasibility study. The main indicator for choosing a drilling method is profitability - the cost of 1 m of penetration. [ 11 ]

Thus, the speed of rotary drilling with flushing with clay solution exceeds the speed of percussion-rope drilling by 3 - 5 times. Therefore, the decisive factor when choosing a drilling method there must be an economic analysis. [ 12 ]

The technical and economic efficiency of a project for the construction of oil and gas wells largely depends on the validity of the deepening and flushing process. Technology design for these processes includes choice of drilling method, the type of rock-destructive tool and drilling modes, the design of the drill string and the layout of its bottom, the hydraulic deepening program and indicators of the properties of the drilling fluid, types of drilling fluids and the necessary quantities of chemical reagents and materials to maintain their properties. The adoption of design decisions determines the choice of the type of drilling rig, which depends, in addition, on the design of the casing strings and the geographical conditions of drilling. [ 13 ]

The application of the results of solving the problem creates a wide opportunity to conduct a deep, extensive analysis of bit performance in a large number of objects with a wide variety of drilling conditions. In this case, it is also possible to prepare recommendations for selection of drilling methods, downhole motors, mud pumps and flushing fluid. [ 14 ]

In the practice of constructing water wells, the following drilling methods have become widespread: rotary with direct circulation, rotary with reverse circulation, rotary with air blowing and percussion-rope. The conditions for using various drilling methods are determined by the technical and technological features of the drilling rigs, as well as the quality of the well construction work. It should be noted that when choosing a well drilling method for water, it is necessary to take into account not only the speed of drilling wells and the manufacturability of the method, but also ensuring such parameters for opening the aquifer at which the deformation of rocks in the bottom-hole zone is observed to a minimum extent and its permeability does not decrease in comparison with the formation. [ 1 ]

It is much more difficult to choose a drilling method to deepen a vertical wellbore. If, when drilling an interval selected based on drilling practice using drilling fluids, bending of the vertical shaft can be expected, then, as a rule, air hammers with the appropriate type of bit are used. If no curvature is observed, then choice of drilling method is carried out as follows. For soft rocks (soft shales, gypsum, chalk, anhydrites, salt and soft limestones), it is advisable to use electric drilling with bit speeds up to 325 rpm. As the hardness of rocks increases, drilling methods are arranged in the following sequence: positive displacement motor, rotary drilling and rotary percussion drilling. [ 2 ]

From the point of view of increasing the speed and reducing the cost of constructing wells with MODUs, the method of drilling with hydraulic core transport is interesting. This method, with the exception of the above-mentioned limitations of its use, can be used in the exploration of placers with PBUs at the prospecting and prospecting-evaluation stages of geological exploration. The cost of drilling equipment, regardless of drilling methods, does not exceed 10% of the total cost of the MODU. Therefore, changes in the cost of drilling equipment alone do not have a significant impact on the cost of manufacturing and servicing the MODU and on choice of drilling method. An increase in the cost of a MODU is justified only if it improves working conditions, increases safety and speed of drilling, reduces the number of downtime due to weather conditions, and extends the drilling season. [ 3 ]

Selecting the type of bit and drilling mode: selection criteria, methods of obtaining information and processing it to establish optimal modes and regulate parameter values .

The choice of bit is made on the basis of knowledge of the rocks (g/p) composing a given interval, i.e. by hardness category and by abrasiveness category.

In the process of drilling an exploration and sometimes production well, rocks are periodically selected in the form of untouched pillars (cores) to compile a stratigraphic section, study the lithological characteristics of the drilled rocks, identify the oil and gas content in the pores of the rocks, etc.

To extract the core to the surface, core bits are used (Fig. 2.7). Such a bit consists of a drill head 1 and a core set attached to the drill head body using a thread.

Rice. 2.7. Diagram of the core bit device: 1 - drilling head; 2 - core; 3 - ground carrier; 4 - core set body; 5 - ball valve

Depending on the properties of the rock in which drilling and core sampling is carried out, roller-cone, diamond and carbide drill heads are used.

Drilling mode is a combination of parameters that significantly affect the performance of the bit, which the driller can change from his console.

Pd [kN] – load on the bit, n [rpm] – bit rotation speed, Q [l/s] – industrial flow rate (feed). g-ti, H [m] – penetration per bit, Vm [m/hour] – fur. penetration speed, Vav=H/tB – average,

Vm(t)=dh/dtB – instantaneous, Vр [m/hour] – routine drilling speed, Vр=H/(tB + tSPO + tB), C [rub/m] – operating costs for 1m of penetration, C=( Cd+Sch(tB + tSPO + tB))/H, Cd – cost of the bit; Cch – cost of 1 hour of drill work. rev.

Stages of searching for the optimal mode - at the design stage - operational optimization of the drilling mode - adjustment of the design mode taking into account the information obtained during the drilling process.

During the design process we use information. obtained while drilling a well. in this

region, analogue conv., data on goelog. well section, drill manufacturer's recommendations. tools, operating characteristics of downhole motors.

2 ways to select a bit at the bottom: graphical and analytical.

The cutters in the drill head are mounted in such a way that the rock in the center of the hole bottom is not destroyed during drilling. This creates conditions for the formation of core 2. There are four-, six- and then eight-cone drill heads designed for drilling with core selection in various rocks. The arrangement of rock-destroying elements in diamond and carbide drill heads also makes it possible to destroy rock only along the periphery of the bottom of the well.

When the well is deepened, the resulting rock column enters a core set consisting of a housing 4 and a core pipe (soil carrier) 3. The body of the core set is used to connect the drill head to the drill string, place the carrier and protect it from mechanical damage, as well as to pass the flushing fluid between him and the ground carrier. The soil carrier is designed to receive core, preserve it during drilling and when lifting to the surface. To perform these functions, core grabbers and core holders are installed in the lower part of the soil carrier, and at the top there is a ball valve 5, which allows the liquid displaced from the soil carrier to pass through itself when filling it with core.

According to the method of installing the soil carrier in the core set body and in the drilling head, there are core bits with a removable and non-removable soil carrier.

Core bits with a removable soil carrier allow you to lift the core carrier with core without lifting the drill string. To do this, a catcher is lowered into the drill string on a rope, with the help of which the soil carrier is removed from the core set and raised to the surface. Then, using the same catcher, an empty soil carrier is lowered and installed in the body of the core set, and drilling with core selection continues.

Core bits with a removable soil carrier are used in turbine drilling, and those with a non-removable core are used in rotary drilling.

Schematic diagram of testing a productive horizon using a formation tester on pipes.

Formation testers are very widely used in drilling and provide the greatest amount of information about the object being tested. A modern domestic formation tester consists of the following main components: a filter, a packer, the tester itself with equalization and main inlet valves, a shut-off valve and a circulation valve.

Schematic diagram of single-stage cementing. Changes in pressure in the cementing pumps involved in this process.

The one-stage well cementing method is the most common. With this method, the cement solution is supplied at a given interval in one go.

The final stage of drilling operations is accompanied by a process that involves cementing wells. The viability of the entire structure depends on how well these works are carried out. The main goal pursued in the process of carrying out this procedure is to replace the drilling mud with cement, which has another name - cement slurry. Cementing wells involves introducing a composition that should harden into stone. Today, there are several ways to carry out the process of cementing wells, the most commonly used of them is more than 100 years old. This is a single-stage casing cementing method, introduced to the world in 1905 and used today with only some modifications.

Cementing scheme with one plug.

Cementing process

The technology for cementing wells involves carrying out 5 main types of work: the first is mixing the cement slurry, the second is pumping the composition into the well, the third is supplying the mixture using the selected method into the annulus, the fourth is hardening the cement mixture, the fifth is checking the quality of the work performed.

Before starting work, a cementing scheme must be drawn up, which is based on technical calculations of the process. It will be important to take into account the mining and geological conditions; the length of the interval that needs strengthening; characteristics of the wellbore design, as well as its condition. In the process of carrying out calculations, experience in carrying out such work in a certain area should also be used.

Figure 1. Single-stage cementing process diagram.

In Fig. 1 you can see a diagram of the single-stage cementing process. “I” – start of feeding the mixture into the barrel. “II” is the supply of the mixture injected into the well when the solution moves down the casing, “III” is the start of pushing the cement composition into the annulus, “IV” is the final stage of pushing the mixture. In diagram 1 there is a pressure gauge, which is responsible for monitoring the pressure level; 2 – cementing head; 3 – plug located on top; 4 – bottom plug; 5 – casing; 6 – well walls; 7 – stop ring; 8 – liquid intended for pressing the cement mixture; 9 – drilling fluid; 10 – cement mixture.

Schematic diagram of two-stage cementing with a time gap. Advantages and disadvantages.

Step cementing with a time gap. The cementing interval is divided into two parts, and a special cementing sleeve is installed at the interface near the interface. Centering lights are placed on the outside of the column above and below the coupling. First, the lower part of the column is cemented. To do this, 1 portion of CR is pumped into the column in the volume required to fill the CP from the column shoe to the cementing sleeve, then the displacement fluid. To cement stage 1, the volume of the displacement fluid must be equal to the internal volume of the column. Having pumped the pump, they drop the ball into the column. Under the force of gravity, the ball falls down the column and lands on the lower bushing of the cementing sleeve. Then they begin to pump the pan into the column again: the pressure in it above the plug increases, the sleeve moves down all the way, and the pan goes beyond the column through the opened holes. The well is flushed through these holes until the cement mortar hardens (from several hours to a day). Then pump in the 2nd portion of CR, releasing the top plug and displace the solution with 2 portions of CR. The plug, having reached the sleeve, is strengthened with pins in the body of the cementing sleeve and moves it down; in this case, the bushing closes the coupling holes and separates the column cavity from the gearbox. After hardening, the plug is drilled out. The location for installing the coupling is chosen depending on the reasons that prompted the resort to cementing mortars. In gas wells, the cementing sleeve is installed 200-250m above the roof of the productive horizon. If there is a risk of lost circulation when cementing a well, the location of the coupling is calculated so that the sum of the hydrodynamic pressures and the static pressure of the solution column in the annulus is less than the fracture pressure of the weak formation. The cement sleeve should always be placed against stable impermeable rocks and centered with lanterns. Apply: a) if solution absorption is inevitable during single-stage cementing; b) if the formation is opened with high pressure pressure and during the setting period of the solution after one-stage cementing, cross-flows and gas manifestations may occur; c) if single-stage cementing requires the simultaneous participation of a large number of cement pumps and mixing machines in the operation. Flaws: a large time gap between the end of cementing the lower section and the beginning of cementing the upper. This disadvantage can be largely eliminated by installing an external packer approximately below the cemented sleeve. If, upon completion of cementing the lower stage, the annulus of the well is sealed with a packer, then you can immediately begin cementing the upper section.

Principles of calculating casing string for axial tensile strength for vertical wells. Specifics of calculating columns for inclined and curved wells.

Casing calculation start with determining excess external pressures. [ 1 ]

Calculation of casing columns carried out during design in order to select wall thicknesses and strength groups of the casing pipe material, as well as to check the compliance of the standard safety factors laid down during the design with those expected, taking into account the current geological, technological, and market conditions of production. [ 2 ]

Calculation of casing columns with trapezoidal threads, tensile testing is carried out based on the permissible load. When lowering casing strings in sections, the length of the column is taken as the length of the section. [ 3 ]

Casing calculation involves identifying the factors influencing casing damage and selecting the most appropriate grades of steel for each specific operation in terms of reliability and economy. The design of the casing must meet the requirements for the casing during completion and operation of the well. [ 4 ]

Calculation of casing columns for directional wells differs from that adopted for vertical wells in the choice of a tensile strength factor depending on the intensity of the wellbore curvature, as well as in the determination of external and internal pressures, in which the position of points characteristic of an inclined well is determined by its vertical projection.

Calculation of casing columns are carried out according to the maximum values of excess external and internal pressures, as well as axial loads (during drilling, testing, operation, repair of wells), while taking into account their separate and combined effects.

Main difference casing calculations for directional wells from the calculation for vertical wells is to determine the tensile strength factor, which is made depending on the intensity of the wellbore curvature, as well as the calculation of external and internal pressures taking into account the elongation of the wellbore

Selection of casing pipes and casing calculation strength tests are carried out taking into account the maximum expected excess external and internal pressures with complete replacement of the solution with formation fluid, as well as axial loads on pipes and fluid aggressiveness at the stages of construction and operation of the well based on existing structures.

The main loads when calculating the strength of a column are axial tensile loads from its own weight, as well as external and internal excess pressure during cementing and well operation. In addition, other loads act on the column:

· axial dynamic loads during unsteady column motion;

· axial loads from the friction forces of the column against the walls of the well during its descent;

· compressive loads from part of its own weight when unloading the column to the face;

· bending loads occurring in curved wells.

Calculation of production string for an oil well

Conventions used in the formulas:

Distance from the wellhead to the column shoe, m L

Distance from the wellhead to the cement slurry, m h

Distance from the wellhead to the liquid level in the column, m N

Density of testing fluid, g/cm 3 r coolant

Density of drilling fluid behind the column, g/cm 3 r BR

Liquid density in the column r B

Density of cement slurry behind the column r CR

Excess internal pressure at depth z, MPa P VIz

Excessive external pressure at depth z P NIz

Excess critical external pressure, at which the voltage

The pressure in the pipe body reaches the yield point P KR

Reservoir pressure at depth z Р PL

Crimping pressure

Total weight of the column of selected sections, N (MN) Q

Cement ring unloading coefficient k

Safety factor when calculating for external excess pressure n KR

Safety factor for tensile calculations n STR

Figure 69. Well cementing diagram

At h > H We determine excess external pressures (at the end of operation stage) for the following characteristic points.

1: z = 0; Р n. иz = 0.01ρ b.r * z; (86)

2: z = H; R n. and z = 0.01ρ b. p * H, (MPa); (87)

3: z = h; P n. and z = (0.01 [ρ b.p h - ρ in (h - N)]), (MPa); (88)

4: z = L; R n. and z = (0.01 [(ρ c.r - ρ in) L - (ρ c.r - ρ b.r) h + ρ in H)] (1 - k), (MPa). (89)

Building a diagram ABCD(Figure 70). To do this, in the horizontal direction on the accepted scale we set aside the values ρ n.i z at points 1 -4 (see diagram) and these points are sequentially connected to each other by straight segments

Figure 70. Diagrams of external and internal

excess pressure

We determine excess internal pressures from the condition of testing the casing for tightness in one step without a packer.

Pressure at the mouth: P y = P pl - 0.01 ρ V L (MPa). (90)

The main factors influencing the quality of well cementing and the nature of their influence.

The quality of isolation of permeable layers by cementing depends on the following groups of factors: a) the composition of the plugging mixture; b) composition and properties of cement slurry; c) cementing method; d) completeness of replacement of the displacement fluid with cement slurry in the annulus of the well; e) the strength and tightness of the adhesion of the cement stone to the casing and the walls of the well; f) the use of additional means to prevent the occurrence of filtration and the formation of suffusion channels in the cement slurry during the period of thickening and setting; g) well rest mode during the period of thickening and setting of the cement slurry.

Principles for calculating the required quantities of cementing materials, mixing machines and cementing units for preparing and pumping cementing slurry into the casing. Scheme of piping cementing equipment.

It is necessary to carry out cementing calculations for the following conditions:

- reserve coefficient at the height of the rise of the cement mortar, introduced to compensate for factors that cannot be taken into account (determined statistically based on the cementing data of previous wells); and - respectively, the average diameter of the well and the outer diameter of the production string, m; - the length of the cementing section, m; - the average internal diameter of the production string, m; - the height (length) of the cement cup left in the string, m; - the reserve factor of the displacement fluid , taking into account its compressibility, - = 1.03; - - coefficient taking into account the loss of cement during loading and unloading operations and preparation of the solution; - - - density of the cement solution, kg/m3; – density of the drilling mud, kg/m3; n - relative water content; - density of water, kg/m3; - bulk density of cement, kg/m3;

Volume of cement slurry required for cementing a given well interval (m3): Vс.p.=0.785*kp*[(2-dн2)*lс+d02*hс]

Volume of displacement fluid: Vpr=0.785* - *d2*(Lc-);

Volume of buffer liquid: Vb=0.785*(2-dн2)*lb;

Mass of Portland cement cement: Mts= - **Vtsr/(1+n);

Volume of water for preparing cement slurry, m3: Vv= Mts*n/(kc*pv);

Before cementing, dry cement material is loaded into the hoppers of mixing machines, the required number of which is: nc = Mts/Vcm, where Vcm is the volume of the mixing machine hopper.

Methods for equipping the lower section of a well in the productive formation zone. Conditions under which each of these methods can be used.

1. A productive reservoir is drilled without first covering the overlying rocks with a special string of casing pipes, then the casing string is lowered to the bottom and cemented. To communicate the internal cavity of the casing with the productive reservoir, it is perforated, i.e. a large number of holes are shot through the column. The method has the following advantages: easy to implement; allows selective communication of the well with any layer of the productive reservoir; the cost of the actual drilling work may be less than with other entry methods.

2. First, the casing string is lowered and cemented to the roof of the productive deposit, isolating the overlying rocks. The reservoir is then drilled with smaller diameter bits and the wellbore is left open below the casing shoe. The method is applicable only if the productive deposit is composed of stable rocks and is saturated with only one liquid; it does not allow selective exploitation of any interlayer.

3. It differs from the previous one in that the wellbore in the productive reservoir is covered with a filter, which is suspended in the casing; The space between the filter and the column is often isolated with a packer. The method has the same advantages and limitations as the previous one. Unlike the previous one, it can be adopted in cases where the productive deposit is composed of rocks that are not sufficiently stable during operation.

4. The well is lined with a string of pipes to the top of the productive deposit, then the latter is drilled out and covered with a liner. The liner is cemented along its entire length and then perforated against a specified interval. With this method, significant contamination of the reservoir can be avoided by selecting a flushing fluid only taking into account the situation in the reservoir itself. It allows selective exploitation of various layers and allows you to quickly and cost-effectively develop a well.

5. It differs from the first method only in that after drilling out a productive deposit, a casing string is lowered into the well, the lower section of which is pre-composed of pipes with slotted holes, and in that it is cemented only above the roof of the productive deposit. The perforated section of the column is placed against the productive deposit. With this method, it is impossible to ensure selective exploitation of one or another layer.

Factors taken into account when selecting cementing material for cementing a specific well interval.

The choice of cementing materials for cementing casing strings is determined by the lithofacies characteristics of the section, and the main factors determining the composition of the cementing slurry are temperature, formation pressure, hydraulic fracturing pressure, the presence of salt deposits, type of fluid, etc. In general, the cementing slurry consists of cementitious cement, a medium mixing, reagents-accelerators and retarders of setting times, reagents-filtration rate reducers and special additives. Grouting cement is selected as follows: the grade of cement is specified based on the temperature interval, the interval for measuring the density of the cement slurry, and the types of fluid and deposits in the cementation interval. The mixing medium is selected depending on the presence of salt deposits in the well section or the degree of salinity of the formation water. To prevent premature thickening of the cement slurry and watering of productive horizons, it is necessary to reduce the filtration rate of the cement slurry. NTF, gipan, CMC, PVS-TR are used as reducers of this indicator. To increase the heat resistance of chemical additives, structure dispersion systems and remove side effects when using certain reagents, clay, caustic soda, calcium chloride and chromates are used.

Selecting a core set to obtain high-quality core.

A core receiving tool is a tool that provides for receiving, separating from the reservoir rock mass and preserving the core during the drilling process and during transportation through the well. up to the point of removing it to the surface for research. Varieties: - P1 - for rotary drilling with a removable (removable via BT) core receiver, - P2 - non-removable core receiver, - T1 - for turbine drilling with a removable core receiver, - T2 - with a permanent core receiver. Types: - for core selection from an array of dense reservoirs (double core projectile with a core receiver, isolated from the pancreas ducts and rotating with the projectile body), - for core selection in reservoirs that are fractured, crumpled, or alternating in density and hardness (non-rotating core receiver, suspended on one or more bearings and reliable core breakers and core holders), - for core sampling in bulk hydrocarbons, easy to disassemble. and erosion. RV (should ensure complete sealing of the core and closing of the core receiving hole at the end of drilling)

Design features and areas of application of drill pipes.

Drilling drive pipes are used to transmit rotation from the rotor to the drill string. Drill pipes usually have a square or hexagonal cross-section. They are made in two versions: prefabricated and solid. Drill pipes with upset ends come with upset ends outward and inward. Drill pipes with welded connecting ends are manufactured in two types: TBPV - with welded connecting ends along the upset part and TBP - with welded connecting ends along the part not upset outside. Drill pipes with blocking collars TBB differ from standard pipes with upset ends in the presence of blocking collars at the ends of the pipe, cylindrical thread with a pitch of 4 mm, persistent connection of the pipe with the lock, tight connection with the lock. Drill pipes with stabilizing bands differ from standard pipes by the presence of smooth sections of the pipe directly behind the screwed-on nipple and coupling of the lock and stabilizing sealing bands on the locks, conical (1:32) trapezoidal thread with a pitch of 5.08 mm with a mate along the internal diameter……….

Principles for calculating the drill string when drilling with a downhole motor .

Calculation of BC when drilling the 3D section of a straight-inclined section of a directional well

Qprod=Qcosα; Qnorm=Qsinα; Ftr=μQн=μQsinα;(μ~0.3);

Pprod=Qprod+Ftr=Q(sinα+μsinα)

LI>=Lbuilding+Lubt+Lnc+lI1+…+l1n If not, then lIny=LI-(Lbuilding+Lubt+Lnc+lI1+…+l1(n-1))

Calculation of BC when drilling 3D in a curved section of a directional well.

Pi=FIItr+QIIproject QIIproject=|goR(sinαк-sinαн)|

Pi=μ|±2goR2(sinαк-sinαн)-goR2sinαкΔα±PнΔα|+|goR2(sinαк-sinαн)|

Δα=-- If>, thencos “+”

“-Pn” – when curvature is set “+Pn” – when curvature is reset

it is believed that on the site the BC consists of one section =πα/180=0.1745α

Principles of calculating the drill string when drilling using the rotary method.

Static calculation, when alternating cyclic stresses are not taken into account, but constant bending and torsion stresses are taken into account

For sufficient strength or endurance

Static calculation for vertical wells:

;

Kz=1.4 – at normal. conventional Kz=1.45 – in case of complications. conventional

for sloping areas

;

Drilling mode. Methodology for its optimization

Drilling mode is a combination of parameters that significantly affect the performance of the bit and which the driller can change from his console.

Pd [kN] – load on the bit, n [rpm] – bit rotation speed, Q [l/s] – industrial flow rate (feed). g-ti, H [m] – penetration per bit, Vm [m/hour] – fur. speed of penetration, Vср=H/tБ – average, Vм(t)=dh/dtБ – instantaneous, Vр [m/hour] – routine drilling speed, Vр=H/(tБ + tSPO + tВ), C [rub/m ] – operating costs for 1 m of penetration, C=(Cd+Sch(tB + tSPO + tB))/H, Cd – cost of the bit; Cch – cost of 1 hour of drill work. rev. Optimization of drilling mode: maxVp – exploration. well, minC – exp. well..

(Pd, n, Q)opt=minC, maxVр

C=f1(Pd, n, Q) ; Vp=f2(Pd, n, Q)

During the design process we use information. obtained while drilling a well. in this region, in analogue. conv., data on goelog. well section, drill manufacturer's recommendations. tools, operating characteristics of downhole motors.

2 ways to select a top bit at the bottom:

- graphic tgα=dh/dt=Vm(t)=h(t)/(topt+tsp+tv) - analytical

Classification of inflow stimulation methods during well development.

Development means a set of works to stimulate the influx of fluid from the productive formation, clean the near-wellbore zone from contamination and provide conditions for obtaining the highest possible productivity of the well.

To obtain inflow from the productive horizon, it is necessary to reduce the pressure in the well significantly below the reservoir pressure. There are different ways to reduce pressure, based either on replacing heavy flushing liquid with a lighter one, or on gradually or sharply lowering the liquid level in the production string. To induce inflow from a formation composed of weakly stable rocks, methods are used to gradually reduce pressure or with a small amplitude of pressure fluctuations in order to prevent destruction of the reservoir. If the productive formation is composed of very strong rock, then the greatest effect is often obtained by the sudden creation of large depressions. When choosing a method for inducing inflow, the magnitude and nature of the depression creation, it is necessary to take into account the stability and structure of the reservoir rock, the composition and properties of the liquids saturating it, the degree of contamination during opening, the presence of permeable horizons located nearby above and below, the strength of the casing and the condition of the well support. With a very sudden creation of a large depression, the strength and tightness of the support may be compromised, and with a short-term but strong increase in pressure in the well, fluid may be absorbed into the productive formation.

Replacing heavy liquid with lighter one. The tubing string is lowered almost to the bottom if the productive formation is composed of well-resistant rock, or approximately to the upper perforation holes if the rock is not stable enough. Fluid replacement is usually carried out using the reverse circulation method: a liquid whose density is less than the density of the flushing fluid in the production casing is pumped into the annulus using a mobile piston pump. As lighter fluid fills the annulus and displaces heavier fluid into the tubing, the pressure in the pump increases. It reaches its maximum at the moment when light fluid approaches the tubing shoe. p umt = (p pr -r cool)qz nct +p nct +p mt, where p pr and p cool are the densities of heavy and light liquids, kg/m; z tubing is the depth of running the tubing string, m; p tubing and p mt - hydraulic losses in the tubing string and in the annulus, Pa. This pressure should not exceed the pressure test pressure of the production casing p umt< p оп.

If the rock is weakly stable, the amount of density reduction during one circulation cycle is reduced even more, sometimes to p -p = 150-200 kg/m3. When planning work to call the influx, you should take this into account and prepare in advance containers with a supply of liquids of appropriate densities, as well as equipment for regulating the density.

When pumping a lighter fluid, the condition of the well is monitored using pressure gauge readings and the ratio of flow rates of fluids pumped into the annulus and fluids flowing out of the tubing. If the flow rate of the exiting fluid increases, this is a sign that inflow from the formation has begun. In the event of a rapid increase in flow rate at the outlet of the tubing and a drop in pressure in the annulus, the outgoing flow is directed through a line with a fitting.

If replacing heavy drilling fluid with clean water or degassed oil is not enough to obtain a steady flow from the formation, other methods of increasing drawdown or stimulation are resorted to.

When the reservoir is composed of weakly stable rock, a further reduction in pressure is possible by replacing water or oil with a gas-liquid mixture. To do this, a piston pump and a mobile compressor are connected to the annulus of the well. After flushing the well to clean water, adjust the pump flow so that the pressure in it is significantly lower than what is permissible for the compressor, and the downward flow speed is approximately 0.8-1 m/s, and turn on the compressor. The air flow pumped by the compressor is mixed in the aerator with the water flow supplied by the pump, and a gas-liquid mixture enters the inter-tube space; the pressure in the compressor and pump will begin to increase and reach a maximum at the moment when the mixture approaches the tubing shoe. As the gas-liquid mixture moves along the tubing string and displaces still water, the pressure in the compressor and pump will decrease. The degree of aeration and reduction of static pressure in the well is increased in small steps after the completion of one or two circulation cycles so that the pressure in the annulus at the wellhead does not exceed that permissible for the compressor.

A significant drawback of this method is the need to maintain sufficiently large flow rates of air and water. It is possible to significantly reduce air and water consumption and effectively reduce pressure in the well by using two-phase foam instead of a water-air mixture. Such foams are prepared on the basis of mineralized water, air and a suitable foaming surfactant.

Reducing pressure in the well using a compressor. To induce inflow from formations composed of strong, stable rocks, a compressor method is widely used to reduce the liquid level in the well. The essence of one of the varieties of this method is as follows. A mobile compressor pumps air into the annulus in such a way as to push the liquid level in it as deep as possible, aerate the liquid in the tubing and create a depression necessary to obtain inflow from the productive formation. If the static fluid level in the well before the start of the operation is at the mouth, the depth to which the level in the annulus can be pushed back when air is injected.

If z sn > z tubing, then the air pumped by the compressor will break into the tubing and begin to aerate the liquid in them as soon as the level in the annulus drops to the tubing shoe.

If z sn > z tubing, then before lowering the tubing into the wells, special starting valves are installed in them. The upper start valve is installed at a depth of z" start = z" sn - 20m. When the compressor pumps air, the start valve will open at the moment when the pressures in the tubing and in the annulus at the depth of its installation are equal; in this case, air will begin to escape through the valve into the tubing and aerate the liquid, and the pressure in the annulus and in the tubing will decrease. If, after reducing the pressure in the well, the inflow from the formation does not begin and almost all the fluid from the tubing above the valve is displaced by air, the valve will close, the pressure in the annulus will increase again, and the fluid level will drop to the next valve. The installation depth z"" of the next valve can be found from the equation if we put in it z = z"" + 20 and z st = z" sn.

If before the start of the operation the static liquid level in the well is located significantly below the mouth, then when air is pumped into the annulus and the liquid level is pushed back to a depth z cn, the pressure on the productive formation increases, which can cause the absorption of part of the liquid into it. It is possible to prevent fluid absorption into the formation by installing a packer at the lower end of the tubing string, and a special valve inside the tubing and using these devices to separate the productive formation zone from the rest of the well. In this case, when air is pumped into the annulus, the pressure on the formation will remain unchanged until the pressure in the tubing string above the valve drops below the formation pressure. As soon as the depression is sufficient for the influx of formation fluid, the valve will lift and the formation fluid will begin to rise along the tubing.

After receiving an influx of oil or gas, the well must operate for some time at the highest possible flow rate so that the drilling fluid and its filtrate, as well as other silty particles that have penetrated there, can be removed from the near-wellbore zone; the flow rate is regulated so that the destruction of the collector does not begin. Periodically, samples of the fluid flowing from the well are taken in order to study its composition and properties and monitor the content of solid particles in it. The reduction in the content of solid particles is used to judge the progress of cleaning the near-trunk zone from contamination.

If, despite the creation of a large depression, the well's flow rate turns out to be low, then they usually resort to various methods of stimulating the formation.

Classification of inflow stimulation methods during well development.

Based on the analysis of controllable factors, it is possible to construct a classification of methods of artificial stimulation both on the formation as a whole and on the bottom-hole zone of each specific well. According to the principle of action, all methods of artificial influence are divided into the following groups:

1. Hydrogasdynamic.

2. Physico-chemical.

3. Thermal.

4. Combined.

Among the methods of artificial stimulation of the reservoir, the most widely used are hydro-gas-dynamic methods associated with controlling the magnitude of reservoir pressure by injecting various fluids into the reservoir. Today, more than 90% of oil produced in Russia is associated with methods of regulating reservoir pressure by injecting water into the reservoir, called reservoir pressure maintenance (RPM) waterflooding methods. At a number of fields, pressure maintenance is carried out by gas injection.

Analysis of field development shows that if the reservoir pressure is low, the supply circuit is sufficiently distant from the wells, or the drainage regime is not active, the rate of oil recovery may be quite low; The oil recovery factor is also low. In all these cases, the use of one or another PPD system is necessary.

Thus, the main problems of managing the process of reserve development through artificial stimulation of the reservoir are associated with the study of waterflooding.

Methods of artificial influence on the bottomhole zones of a well have a significantly wider range of possibilities. The impact on the wellbore zone is carried out already at the stage of the initial opening of the productive horizon during the well construction process, which, as a rule, leads to deterioration of the properties of the bottom-hole zone. The most widespread are the methods of influencing the bottomhole zone during the operation of wells, which, in turn, are divided into methods of influx intensification or injectivity and methods of limiting or isolating the influx of water (repair and isolation work - RIR).

The classification of methods of influencing the reservoir zone in order to intensify the inflow or injectivity is presented in table 1, and to limit or isolate water inflows - in table 2. It is quite obvious that the given tables, being quite complete, contain only the most practice-tested methods of artificial influence on the CCD. They do not exclude, but on the contrary, suggest the need for additions both in the methods of influence and in the materials used.

Before moving on to the consideration of methods for managing the process of reserve development, we note that the object of study is a complex system consisting of a deposit (oil-saturated zone and recharge area) with its reservoir properties and saturating fluids and a certain number of wells systematically placed on the deposit. This system is hydrodynamically unified, which means that any change in any of its elements automatically leads to a corresponding change in the operation of the entire system, i.e. This system is auto-adjustable.

Describe the technical means for obtaining operational information during the drilling process.

Information support for the process of drilling oil and gas wells is the most important link in the well construction process, especially when introducing and developing new oil and gas fields.

The requirements for information support for the construction of oil and gas wells in this situation are to transfer information technologies into the category of information-supporting and information-influencing, in which information support, along with obtaining the required amount of information, would give an additional economic, technological, or other effect. These technologies include the following complex works:

control of surface technological parameters and selection of the most optimal drilling modes (for example, selection of optimal loads on the bit, ensuring high penetration rates);

downhole measurements and logging while drilling (MWD and LWD systems);

measurements and collection of information, accompanied by simultaneous control of the drilling process (control of the trajectory of a horizontal well using controlled downhole orientators based on data from downhole telemetry systems).

In information support of the well construction process, a particularly important role is played by geological and technological research (GTI). The main tasks of the geological and technical investigation service are to study the geological structure of the well section, identify and evaluate productive formations and improve the quality of well construction based on the geological, geochemical, geophysical and technological information obtained during the drilling process. The operational information received by the GTI service is of great importance when drilling exploratory wells in poorly studied regions with complex mining and geological conditions, as well as when drilling directional and horizontal wells.

However, due to new requirements for information support of the drilling process, the tasks solved by the geological and technical inspection service can be significantly expanded. Highly qualified operators of the GTI batch, working at the drilling rig, throughout the entire well construction cycle, with the availability of appropriate hardware and methodological tools and software, are able to solve practically a full range of tasks for information support of the drilling process:

geological, geochemical and technological research;

maintenance and work with telemetering systems (MWD and LWD systems);

maintenance of autonomous pipe-borne measurement and logging systems;

control of drilling fluid parameters;

quality control of well casing;

studies of formation fluid during sampling and testing of wells;

wireline logging;

supervisory services, etc.

In a number of cases, combining these works in geophysical survey batches is economically more profitable and allows saving on unproductive costs of maintaining specialized, highly targeted geophysical parties, and minimizing transportation costs.

However, there are currently no technical and software-methodological tools that would allow combining the listed works into a single technological chain at a gas-technical inspection station.

Therefore, there was a need to develop a more advanced GTI station of a new generation, which would expand the functionality of the GTI station. Let's consider the main directions of work in this case.

Basic requirements for modern GTI station- reliability, versatility, modularity and information content.

Station structure shown in Fig. 1. It is built on the principle of distributed remote collection systems, which are interconnected using a standard serial interface. The main downstream acquisition systems are concentrators designed to decouple the serial interface and connect through them individual components of the station: gas logging module, geological instrument module, digital or analogue sensors, information boards. Through the same hubs, other autonomous modules and systems are connected to the collection system (to the operator’s recording computer) - a well casing quality control module (manifold block), ground modules of downhole telemetry systems, geophysical data recording systems of the “Hector” or “Vulcan” type and etc.

Rice. 1. Simplified block diagram of the GTI station

Hubs must simultaneously provide galvanic isolation of communication and power circuits. Depending on the tasks assigned to the GTI station, the number of concentrators can be different - from several units to several dozen pieces. The software of the GTI station ensures full compatibility and coordinated operation of all technical means in a single software environment.

Process parameter sensors

Process parameter sensors used in GTI stations are one of the most important components of the station. The effectiveness of the geological and technical inspection service in solving problems of monitoring and operational management of the drilling process largely depends on the accuracy of the readings and the reliability of the sensors. However, due to harsh operating conditions (wide temperature range from –50 to +50 ºС, aggressive environment, strong vibrations, etc.), sensors remain the weakest and most unreliable link in the GTI technical equipment.

The sensors used in production batches of GTI were mostly developed in the early 90s using domestic components and primary measuring elements of domestic production. Moreover, due to the lack of choice, publicly available primary converters were used, which did not always meet the stringent requirements of work in drilling conditions. This explains the insufficiently high reliability of the sensors used.

The principles of measuring sensors and their design solutions were chosen in relation to old-style domestic drilling rigs, and therefore their installation on modern drilling rigs, and even more so on foreign-made drilling rigs, is difficult.

From the above it follows that the development of a new generation of sensors is extremely relevant and timely.

When developing GTI sensors, one of the requirements is their adaptation to all drilling rigs existing on the Russian market.

The availability of a wide selection of high-precision sensors and highly integrated, small-sized microprocessors allows the development of high-precision, programmable sensors with greater functionality. The sensors have a unipolar supply voltage and simultaneously digital and analogue outputs. Calibration and adjustment of sensors are carried out programmatically from a computer from the station; the possibility of software compensation for temperature errors and linearization of sensor characteristics is provided. The digital part of the electronic board for all types of sensors is the same and differs only in the internal program settings, which makes it unified and interchangeable during repair work. The appearance of the sensors is shown in Fig. 2.

Rice. 2. Sensors of technological parameters

Load sensor on hook has a number of features (Fig. 3). The operating principle of the sensor is based on measuring the tension force of the hoisting rope at the “dead” end using a strain gauge force sensor. The sensor has a built-in processor and non-volatile memory. All information is recorded and stored in this memory. The memory capacity allows you to save a month's worth of information. The sensor can be equipped with an autonomous power supply, which ensures operation of the sensor when the external power source is disconnected.

Rice. 3. Weight sensor on hook

Driller information board designed to display and visualize information received from sensors. The appearance of the scoreboard is shown in Fig. 4.

On the front panel of the driller's console there are six linear scales with an additional digital display to display the following parameters: torque on the rotor, inlet fluid pressure, inlet fluid density, fluid level in the tank, inlet fluid flow rate, outlet fluid flow rate. The parameters of weight on the hook and load on the bit, by analogy with GIV, are displayed on two dial scales with additional duplication in digital form. At the bottom of the display there is one linear scale to display the drilling speed, three digital indicators to display parameters - bottomhole depth, position above the bottom, gas content. The alphanumeric indicator is designed to display text messages and warnings.

Rice. 4. Appearance of the information board

Geochemical module

The geochemical module of the station includes a gas chromatograph, a total gas content analyzer, a gas-air line and a drilling fluid degasser.

The most important component of the geochemical module is the gas chromatograph. For error-free, clear identification of productive intervals in the process of opening them, you need a very reliable, accurate, highly sensitive device that allows you to determine the concentration and composition of saturated hydrocarbon gases in the range from 110 -5 to 100%. For this purpose, to complete the GTI station, a gas chromatograph "Rubin"(Fig. 5) (see article in this issue of NTV).

Rice. 5. Field chromatograph "Rubin"

The sensitivity of the geochemical module of the GTI station can also be increased by increasing the degassing coefficient of the drilling fluid.

To isolate bottomhole gas dissolved in drilling fluid, two types of degassers(Fig. 6):

passive float degassers;

active degassers with forced fragmentation of the flow.

Float degassers are simple and reliable in operation, but provide a degassing coefficient of no more than 1-2%. Degassers with forced flow fragmentation can provide a degassing coefficient of up to 80-90%, but are less reliable and require constant monitoring.

Rice. 6. Drilling mud degassers

a) passive float degasser; b) active degasser

Continuous analysis of the total gas content is carried out using remote total gas sensor. The advantage of this sensor over traditional total gas analyzers located at the station is the efficiency of the information received, since the sensor is placed directly at the drilling site and the delay time for gas transportation from the drilling site to the station is eliminated. In addition, to complete the stations, we have developed gas sensors to measure the concentrations of non-hydrocarbon components of the analyzed gas mixture: hydrogen H2, carbon monoxide CO, hydrogen sulfide H2S (Fig. 7).

Rice. 7. Sensors for measuring gas content

Geological module

The geological module of the station ensures the study of drill cuttings, core and formation fluid during the drilling of a well, registration and processing of the resulting data.

Research carried out by GTI station operators allows us to solve the following: main geological tasks:

lithological division of the section;

isolation of reservoirs;

assessment of the nature of reservoir saturation.

To quickly and efficiently solve these problems, the most optimal list of instruments and equipment was determined and, based on this, a set of geological instruments was developed (Fig. 8).

Rice. 8. Equipment and instruments of the geological module of the station

Microprocessor carbon meter KM-1A designed to determine the mineral composition of rocks in carbonate sections using cuttings and core. This device allows you to determine the percentage of calcite, dolomite and insoluble residue in the studied rock sample. The device has a built-in microprocessor that calculates the percentage of calcite and dolomite, the values of which are displayed on a digital display or on a monitor screen. A modification of the carbonate meter has been developed that makes it possible to determine the content of the mineral siderite in the rock (density 3.94 g/cm 3), which affects the density of carbonate rocks and cement of terrigenous rocks, which can significantly reduce porosity values.

Sludge density meter PSH-1 designed for express measurement of density and assessment of the total porosity of rocks from cuttings and cores. The measuring principle of the device is hydrometric, based on weighing the sample of sludge under study in air and water. Using the PSh-1 density meter, you can measure the density of rocks with a density of 1.1-3 g/cm³ .

Installation PP-3 designed to identify reservoir rocks and study the reservoir properties of rocks. This device allows you to determine volumetric, mineralogical density and total porosity. The measuring principle of the device is thermogravimetric, based on high-precision measurement of the weight of the studied rock sample, previously saturated with water, and continuous monitoring of changes in the weight of this sample as moisture evaporates when heated. Based on the time of moisture evaporation, one can judge the permeability of the rock under study.

Liquid distillation unit UJ-2 intended for assessment of the nature of saturation of rock reservoirs based on cuttings and cores, filtration and density properties, and also makes it possible to determine residual oil-water saturation based on core and drill cuttings directly at the drilling site thanks to the use of a new approach in the distillate cooling system. The installation uses a condensate cooling system based on a Peltier thermoelectric element instead of the water heat exchangers used in similar devices. This reduces condensate losses by providing controlled cooling. The principle of operation of the installation is based on the displacement of formation fluids from the pores of rock samples due to excess pressure arising during thermostated controlled heating from 90 to 200 ºС ( 3 ºС), condensation of vapors in a heat exchanger and separation of the condensate formed during the distillation process by density into oil and water.

Thermal desorption and pyrolysis unit allows you to determine the presence of free and sorbed hydrocarbons from small samples of rocks (sludge, core pieces), as well as assess the presence and degree of transformation of organic matter, and, based on the interpretation of the data obtained, identify intervals of reservoirs and caps of producing deposits in well sections, as well as assess the nature saturation of collectors.

IR spectrometer created for determining the presence and quantitative assessment of the hydrocarbon present in the studied rock (gas condensate, light oil, heavy oil, bitumen, etc.) in order to assess the nature of reservoir saturation.

Luminoscope LU-1M with a remote UV illuminator and a photography device is designed for examining drill cuttings and core samples under ultraviolet illumination in order to determine the presence of bituminous substances in the rock, as well as for their quantitative assessment. The measuring principle of the device is based on the property of bitumen, when irradiated with ultraviolet rays, to emit a “cold” glow, the intensity and color of which make it possible to visually determine the presence, qualitative and quantitative composition of bitumen in the studied rock in order to assess the nature of reservoir saturation. The device for photographing hoods is intended for documenting the results of luminescent analysis and helps eliminate the subjective factor when assessing the results of the analysis. A remote illuminator allows for preliminary inspection of large cores at the drilling rig in order to identify the presence of bitumens.

Sludge dryer OSH-1 designed for express drying of sludge samples under the influence of heat flow. The dehumidifier has a built-in adjustable timer and several modes for adjusting the intensity and temperature of the air flow.

The technical and information capabilities of the described GTI station meet modern requirements and allow the implementation of new technologies for information support for the construction of oil and gas wells.

Mining and geological characteristics of the section that influence the occurrence, prevention and elimination of complications.

Complications during the drilling process arise for the following reasons: difficult mining and geological conditions; poor awareness of them; low drilling speed, for example, due to long downtime, poor technological solutions included in the technical design for the construction of a well.

When drilling is complicated, accidents occur more often.

It is necessary to know the mining and geological characteristics in order to correctly draw up a project for the construction of a well, and to prevent and deal with complications during the implementation of the project.

Reservoir pressure (Ppl) - fluid pressure in rocks with open porosity. This is the name given to rocks in which voids communicate with each other. In this case, the formation fluid can flow according to the laws of hydromechanics. Such rocks include cement rocks, sandstones, and reservoirs of productive horizons.

Pore pressure (Ppor) is the pressure in closed voids, that is, the fluid pressure in the pore space in which the pores do not communicate with each other. Clays, salt rocks, and reservoir seals have these properties.

Rock pressure (Rg) – hydrostatic (geostatic) pressure at the considered depth from the overlying GB strata.

The static level of formation fluid in a well, determined by the equality of the pressure of this column with formation pressure. The level can be below the surface of the earth (the well will absorb), coincide with the surface (there is equilibrium) or be above the surface (the well will flow) Rpl = rgz.

The dynamic level of liquid in the well is set above the static level when adding to the well and below it when withdrawing liquid, for example, when pumping with a submersible pump.

Depression P=Psq-Rpl<0 – давление в скважине меньше пластового. Наличие депрессии – необходимое условие для притока пластового флюида.

Repression Р=Рсв-Рпл>0 – the pressure in the well is not greater than the formation pressure. Absorption takes place.

Anomaly coefficient of reservoir pressure Ka=Рпл/rвgzпл (1), where zpl is the depth of the roof of the formation under consideration, rв is the density of water, g is the acceleration of gravity. Ka<1=>ANPD; Ka>1=>AVPD.

Absorption or hydraulic fracturing pressure Рп is the pressure at which absorption of all phases of the flushing or cementing fluid occurs. The value of Pp is determined empirically based on observation data during the drilling process, or using special studies in the well. The data obtained is used when drilling other similar wells.

Combined graph of pressures during complications. Selection of the first well design option.

Combined pressure graph. Selection of the first well design option.

In order to correctly draw up a technical project for the construction of wells, it is necessary to accurately know the distribution of formation (pore) pressures and absorption (hydraulic fracturing) pressures along the depth or, what is the same, the distribution of Ka and Kp (in dimensionless form). The distribution of Ka and Kp is presented on a combined pressure graph.

Distribution of Ka and Kp over depth z.

· Well design (1st option), which is then specified.

From this graph it is clear that we have three depth intervals with compatible drilling conditions, that is, those in which fluid with the same density can be used.

It is especially difficult to drill when Ka=Kp. Drilling becomes extremely difficult at the value Ka=Kp<1. В этих случаях обычно бурят на поглощение или применяют промывку аэрированной жидкостью.

After opening the absorbing interval, insulation work is carried out, thanks to which the Kp (artificially) increases, making it possible to carry out, for example, cementing of the column.

Well circulation system diagram

Diagram of the circulation system of wells and diagram of the pressure distribution in it.

Diagram: 1. Bit, 2. Downhole motor, 3. Drill collar, 4. BT, 5. Tool joint, 6. Square, 7. Swivel, 8. Drilling sleeve, 9. Riser, 10. Pressure pipeline (manifold), 11 . Pump, 12. Suction pipe, 13. Trough system, 14. Vibrating sieve.

1. Hydrostatic pressure distribution line.

2. Line of hydraulic pressure distribution in the gearbox.

3. Line of hydraulic pressure distribution in the BT.

The pressure of the flushing fluid on the formation should always be inside the shaded area between Ppl and Pp.

Through each threaded connection BC, liquid tries to flow from the pipe into the annulus (during circulation). This trend is caused by the pressure difference in the pipes and gearbox. When leakage occurs, the threaded connection is destroyed. All other things being equal, the organic disadvantage of drilling with a hydraulic downhole motor is the increased pressure drop at each threaded connection, since in a downhole motor

The circulation system serves to supply drilling fluid from the wellhead to receiving tanks, clean up drill cuttings and degass.

The figure shows a simplified diagram of the circulation system TsS100E: 1 – topping pipeline; 2 – solution pipeline; 3 – cleaning block; 4 – receiving block; 5 – electrical equipment control cabinet.

A simplified design of the circulation system is a gutter system, which consists of a trough for the movement of the solution, a floor near the gutter for walking and cleaning the gutters, railings and a base.

The gutters can be made of wood from 40 mm boards and metal from 3-4 mm sheet iron. Width – 700-800 mm, height – 400-500 mm. Rectangular and semicircular gutters are used. In order to reduce the flow rate of the solution and the loss of sludge from it, partitions and differences in height of 15-18 cm are installed in the gutters. At the bottom of the trench in these places, hatches with valves are installed through which the settled rock is removed. The total length of the trough system depends on the parameters of the solutions used, drilling conditions and technology, as well as on the mechanisms used to clean and degas the solutions. The length, as a rule, can be in the range of 20-50 m.

When using sets of mechanisms for cleaning and degassing the solution (vibrating screens, sand separators, sludge separators, degassers, centrifuges), the trough system is used only to supply the solution from the well to the mechanism and receiving tanks. In this case, the length of the trench system depends only on the location of the mechanisms and containers in relation to the well.

In most cases, the gutter system is mounted on metal bases in sections with a length of 8-10 m and a height of up to 1 m. Such sections are installed on steel telescopic stands that regulate the installation height of the gutters; this makes dismantling the gutter system easier in winter. Thus, if drilled rock accumulates and freezes under the gutters, the gutters along with the bases can be removed from the racks. Install a gutter system with a slope towards the movement of the solution; The gutter system is connected to the wellhead by a pipe or trench of a smaller cross-section and with a large slope to increase the speed of movement of the solution and reduce the loss of cuttings in this area.

In modern well drilling technology, special requirements are placed on drilling fluids, according to which the equipment for cleaning the fluid must ensure high-quality cleaning of the solution from the solid phase, mix and cool it, and also remove gases from the solution that entered it from gas-saturated formations during drilling. In connection with these requirements, modern drilling rigs are equipped with circulation systems with a certain set of standardized mechanisms - containers, cleaning devices and preparation of drilling fluids.

The circulation system mechanisms provide three-stage cleaning of the drilling fluid. From the well, the solution enters the vibrating sieve in the first stage of coarse cleaning and is collected in the settling tank of the tank, where coarse sand is deposited. From the settling tank, the solution passes into the circulation system compartment and is supplied by a centrifugal slurry pump to the degasser if it is necessary to degas the solution, and then to the sand separator, where the second stage of cleaning from rocks up to 0.074-0.08 mm in size takes place. After this, the solution is fed to the desilter - the third stage of purification, where rock particles up to 0.03 mm are removed. Sand and silt are dumped into a container, from where it is fed into a centrifuge for additional separation of the solution from the rock. The purified solution from the third stage enters the receiving tanks - the receiving unit of the drilling pumps for supplying it to the well.

The circulation system equipment is assembled at the plant into the following units:

solution purification unit;

intermediate block (one or two);

receiving block.

The base for assembling the blocks are rectangular containers installed on sled bases.

Hydraulic pressure of clay and cement mortars after stopping circulation.

Takeovers. The reasons for their occurrence.

Byabsorption of drilling or grouting fluids is a type of complication that is manifested by the escape of fluid from the well into the rock formation. Unlike filtration, absorption is characterized by the fact that all phases of the liquid enter the GP. And when filtering, only a few. In practice, losses are also defined as the daily loss of drilling fluid into the formation in a volume exceeding the natural loss due to filtration and cuttings. Each region has its own standard. Usually a few m3 per day is allowed. Absorptions are the most common type of complications, especially in the Ural-Volga region of eastern and southeastern Siberia. Loss occurs in sections in which there are usually fractured GPs, the greatest deformations of rocks are located and their erosion is caused by tectonic processes. For example, in Tatarstan, 14% of calendar time is spent annually on combating takeovers, which exceeds the time spent on fur. drilling As a result of losses, well drilling conditions deteriorate:

1.The risk of tool sticking increases, because The speed of the upward flow of the drilling fluid above the absorption zone decreases sharply; if large particles of cuttings do not go into the formation, then they accumulate in the barrel, causing tightening and sticking of the tool. The likelihood of the tool getting stuck by settling sludge especially increases after stopping the pumps (circulation).

2. Scree collapses in unstable rocks intensify. GNVP may arise from fluid-containing horizons existing in the section. The reason is a decrease in the pressure of the liquid column. In the presence of two or more simultaneously exposed layers with different coefficients. Ka and Kp, cross-flows may occur between them, complicating insulation work and subsequent cementing of the well.

A lot of time and material resources (inert fillers, backfill materials) are wasted on insulation, downtime and accidents causing absorption.

Reasons for acquisitions

The qualitative role of the factors that determine the amount of solution loss into the loss zone can be traced by considering the flow of a viscous fluid in a circular porous layer or a circular gap. We obtain the formula for calculating the flow rate of absorbed liquid in a porous circular formation by solving the system of equations:

1.Equation of motion (In Darcy form)

V=K/M*(dP/dr): (1) where V, P, r, M are, respectively, flow velocity, current pressure, formation radius, viscosity.

2. Equation of conservation of mass (continuity)

V=Q/F (2) where Q, F=2πrh, h – respectively, the liquid absorption flow rate, the area variable along the radius, the thickness of the absorption zone.

3. Equation of state

ρ=const (3) solving this system of equations: 2 and 3 in 1 we get:

Q=(K/M)*2π rH(dP/dr)

Q= (2π HK(PWith-Ppl))/Mln (rk/rc) (4)formula Dupiy

A similar Boussenesco formula (4) can be obtained for m circular cracks (slots) equally open and equally spaced from each other.

Q= [(πδ3(Pс-Ppl))/6Mln (rk/rc) ] *m (5)

δ- opening (height) of the slit;

m is the number of cracks (slits);

M is the effective viscosity.

It is clear that to reduce the consumption of absorbed liquid according to formulas (4) and (5), it is necessary to increase the parameters in the denominators and decrease them in the numerator.

According to (4) and (5)

Q=£(H (or m), Ppl, rk, Pc, rc, M, K, (or δ)) (6)

The parameters included in function (6) according to their origin at the time of opening of the absorption zone can be divided into 3 groups.

1.group – geological parameters;

2. group – technological parameters;

3. group – mixed.

This division is conditional, since during operation, i.e. technological impact (liquid withdrawal, flooding, etc.) on the reservoir also changes Ppl, rk

Absorption in rocks with closed fractures. Features of indicator curves. Hydraulic fracturing and its prevention.

Features of indicator curves.

Next we will consider straight line 2.

An approximate indicator curve for rocks with artificially opened closed cracks can be described by the following formula: Рс = Рb + Рпл+ 1/А*Q+BQ2 (1)

For rocks with naturally open fractures, the indicator curve is a special case of formula (1)

Рс-Рл= ΔР=1/А*Q=А*ΔР

Thus, in rocks with open fractures, absorption will begin at any values of repression, and in rocks with closed fractures - only after creating a pressure in the well equal to the hydraulic fracturing pressure Рс*. The main measure to combat losses in rocks with closed fractures (clay, salt) is to prevent hydraulic fracturing.

Assessing the effectiveness of work to eliminate takeovers.

The effectiveness of insulation work is characterized by the injectivity (A) of the absorption zone, which can be achieved during insulation work. If the resulting injectivity A is below a certain technologically permissible value of injectivity Aq, which is characterized for each region, then the insulation work can be considered successful. Thus, the isolation condition can be written in the form A≤Aq (1) A=Q/Pc- P* (2) For rocks with artificially opened cracks P* = Pb+Ppl+Pp (3) where Pb is the lateral pressure of the rock, Рр - tensile strength g.p. In the particular case, Рb and Рр = 0 for rocks with natural open cracks A = Q/Pc - Рpl (4), if the slightest absorption is not allowed, then Q = 0 and A→0,

then Rs<Р* (5) Для зоны с открытыми трещинами формула (5) заменяется Рс=Рпл= Рпогл (6). Если давление в скважине определяется гидростатикой Рс = ρqL то (5 и 6) в привычных обозначениях примет вид: ρо≤Кп (7) и ρо= Ка=Кп (8). На практике трудно определить давление поглощения Р* , поэтому в ряде районов, например в Татарии оценка эффективности изоляционных работ проводят не по индексу давления поглощения Кп а по дополнительной приемистости Аq. В Татарии допустимые приемистости по тех. воде принято Аq≤ 4 м3/ч*МПа. Значение Аq свое для каждого района и различных поглощаемых жидкостей. Для воды оно принимается обычно более, а при растворе с наполнителем Аq берется меньше. Согласно 2 и 4 А=f (Q; Рс) (9). Т.е все способы борьбы с поглощениями основаны на воздействии на две управляемые величины (2 и 4) , т.е. на Q и Рс.

Methods to combat losses during the opening of the loss zone.

Traditional methods of preventing losses are based on reducing pressure drops across the absorption layer or changing the a/t) of the filtered liquid. If, instead of reducing the pressure drop across the formation, the viscosity is increased by adding plugging materials, bentonite or other substances, the absorption rate will change in inverse proportion to the increase in viscosity, as follows from formula (2.86). In practice, if you adjust the solution parameters, the viscosity can only be changed within relatively narrow limits. Preventing lost losses by switching to flushing with a solution with increased viscosity is only possible if scientifically based requirements for these fluids are developed, taking into account the peculiarities of their flow in the formation. Improving methods for preventing losses, based on reducing pressure drops on absorption formations, is inextricably linked with the in-depth study and development of methods for drilling wells in equilibrium in the well-formation system. The drilling fluid, penetrating into the absorption formation to a certain depth and thickening in the absorption channels, creates an additional obstacle to the movement of the drilling fluid from the wellbore into the formation. The property of a solution to create resistance to fluid movement inside the formation is used when carrying out preventive measures to prevent losses. The strength of such resistance depends on the structural and mechanical properties of the solution, the size and shape of the channels, as well as on the depth of penetration of the solution into the formation.

To formulate the requirements for the rheological properties of drilling fluids when passing through absorption layers, consider the curves (Fig. 2.16) reflecting the dependence of shear stress and deformation rate de/df for some models of non-Newtonian fluid. Straight 1 corresponds to the model of a viscoplastic medium, which is characterized by the ultimate shear stress m0. Curve 2 characterizes the behavior of pseudoplastic liquids, in which, with increasing shear rate, the rate of stress growth slows down, and the curves flatten out. Straight line 3 reflects the rheological properties of a viscous fluid (Newtonian). Curve 4 characterizes the behavior of viscoelastic and dilatant fluids, in which the shear stress increases sharply with increasing strain rate. Viscoelastic liquids, in particular, include weak solutions of some polymers (polyethylene oxide, guar gum, polyacrylamide, etc.) in water, which exhibit the property of sharply reducing (by 2-3 times) hydrodynamic resistance when flowing liquids with high Reynolds numbers (Toms effect). At the same time, the viscosity of these liquids when moving through absorbing channels will be high due to high shear rates in the channels. Drilling with flushing with aerated drilling fluids is one of the radical measures in a set of measures and methods designed to prevent and eliminate losses when drilling deep wells. Aeration of the drilling fluid reduces hydrostatic pressure, thereby facilitating its return in sufficient quantities to the surface and, accordingly, normal cleaning of the wellbore, as well as the selection of representative samples of passable rocks and formation fluids. Technical and economic indicators when drilling wells with bottom-hole flushing with an aerated solution are higher compared to indicators when water or other flushing fluids are used as a drilling fluid. The quality of opening productive formations also improves significantly, especially in fields where these formations have abnormally low pressures.

An effective measure to prevent loss of drilling fluid is the introduction of fillers into the circulating drilling fluid. The purpose of their use is to create tampons in absorption channels. These plugs serve as a basis for the deposition of filter cake and isolation of absorption layers. V.F. Rogers believes that the plugging agent can be almost any material that consists of particles of a small enough size that, when introduced into the drilling fluid, it can be pumped by mud pumps. In the USA, more than one hundred types of fillers and their combinations are used to plug absorption channels. Wood shavings or bast, fish scales, hay, rubber waste, gutta-percha leaves, cotton, cotton bolls, sugar cane fibers, nutshells, granulated plastics, perlite, expanded clay, textile fibers, bitumen, mica, asbestos, chopped are used as sealing agents. paper, moss, chopped hemp, cellulose flakes, leather, wheat bran, beans, peas, rice, chicken feathers, lumps of clay, sponge, coke, stone, etc. These materials can be used separately and in combinations manufactured by industry or compiled before use . It is very difficult to determine the suitability of each closure material in the laboratory due to the unknown size of the holes to be sealed.

In foreign practice, special attention is paid to ensuring “dense” packaging of fillers. They adhere to the opinion of Furnas, according to which the most dense packing of particles meets the condition of their size distribution according to the law of geometric progression; When eliminating lost circulation, the greatest effect can be obtained with a maximum compacted plug, especially in the case of instant loss of drilling fluid.

Based on their quality characteristics, fillers are divided into fibrous, lamellar and granular. Fibrous materials are of plant, animal, and mineral origin. This also includes synthetic materials. The type and size of fiber significantly affect the quality of work. The stability of the fibers when circulating in the drilling fluid is important. The materials give good results when plugging sand and gravel layers with grains up to 25 mm in diameter, as well as when plugging cracks in coarse-grained (up to 3 mm) and fine-grained (up to 0.5 mm) rocks.

Plate materials are suitable for plugging coarse gravel layers and cracks up to 2.5 mm in size. These include: cellophane, mica, husks, cotton seeds, etc.

Granular materials: perlite, crushed rubber, pieces of plastic, nut shells, etc. Most of them effectively clog gravel layers with grains up to 25 mm in diameter. Perlite gives good results in gravel layers with a grain diameter of up to 9-12 mm. Walnut shells measuring 2.5 mm or less clog cracks up to 3 mm in size, and larger (up to 5 mm) and crushed rubber clog cracks up to 6 mm in size, i.e. they can clog 2 times more cracks than when using fibrous or plate materials.

In the absence of data on the sizes of grains and cracks of the absorbing horizon, mixtures of fibrous with lamellar or granular materials, cellophane with mica, fibrous with scaly and granular materials are used, as well as when mixing granular materials: perlite with rubber or nut shells. The best mixture for eliminating absorption at low pressures is a highly colloidal clay solution with additions of fibrous materials and mica leaves. Fibrous materials, deposited on the borehole wall, form a network. Mica leaves strengthen this network and clog larger channels in the rock, and on top of all this a thin and dense clay crust forms.

Gas-water-oil shows. Their reasons. Signs of influx of formation fluids. Classification and recognition of types of manifestations.

During absorption, the fluid (flushing or plugging fluid) flows from the well into the formation, and during development, on the contrary, from the formation into the well. Reasons for influx: 1) influx of fluid containing formations into the well from the drilled rock. In this case, the pressure in the well is not necessarily higher and lower compared to the reservoir; 2) if the pressure in the well is lower than the formation pressure, i.e. there is depression on the formation, the main reasons for the occurrence of depression, i.e. a decrease in pressure on the formation in the well are the following: 1) not filling the well with flushing fluid when lifting the tool. A device for automatic filling into the well is required; 2) a decrease in the density of the washing liquid due to its foaming (carbonation) when the liquid comes into contact with air on the surface in the gutter system, as well as due to the treatment of the liquid with surfactants. Degassing is required (mechanical, chemical); 3) drilling a well in incompatible conditions. There are two layers in the diagram. The first layer is characterized by Ka1 and Kp1; for the second Ka2 and Kn2. first layer must drill with a solution of ρ0.1 (between Ka1 and Kp1), second layer ρ0.2 (Fig.)

It is impossible to open the second layer with a solution with the density for the first layer, since it will be absorbed in the second layer; 4) sharp fluctuations in hydrodynamic pressure during pump stops, special work and other works, aggravated by an increase in static shear stress and the presence of seals on the column;

5) underestimated density of the reservoir adopted in the technical design due to poor knowledge of the actual distribution of reservoir pressure (Ka), i.e. the geology of the area. These reasons apply more to exploratory wells; 6) low level of operational clarification of reservoir pressures by predicting them during well deepening. Not using methods for predicting d-exponent, σ (sigma)-exponent, etc.; 7) loss of weight material from the drilling fluid and a decrease in hydraulic pressure. Signs of formation fluid entry are: 1) an increase in the level of circulating fluid in the pump receiving tank. Need a level gauge; 2) gas is released from the solution leaving the well at the mouth, and boiling of the solution is observed; 3) after circulation stops, the solution continues to flow out of the well (the well overflows); 4) the pressure rises sharply when the formation is suddenly opened with high pressure. When oil enters from the formations, its film remains on the walls of the gutters or flows over the solution in the gutters. When formation water enters, the properties of the fluid change. Its density usually falls, the viscosity may decrease, or it may increase (after the entry of salt water). Water loss usually increases, pH changes, and electrical resistance usually decreases.

Classification of fluid influx. It is carried out according to the complexity of the measures necessary for their elimination. They are divided into three groups: 1) manifestation - non-hazardous entry of formation fluids that do not disrupt the drilling process and the adopted work technology; 2) blowout - the influx of fluids that can be eliminated only through a special targeted change in drilling technology using the tools and equipment available at the drilling rig; 3) fountain - entry of fluid, the elimination of which requires the use of additional means and equipment (except for those available at the rig) and which is associated with the occurrence of pressures in the well-reservoir system that threaten the integrity of the well. , wellhead equipment and formations in the unsecured part of the well.

Installation of cement bridges. Features of the choice of formulation and preparation of cement mortar for the installation of bridges.

One of the serious varieties of cementing process technology is the installation of cement bridges for various purposes. Improving the quality of cement bridges and the efficiency of their operation is an integral part of improving the processes of drilling, completion and operation of wells. The quality of bridges and their durability also determine the reliability of environmental protection. At the same time, field data indicate that there are often cases of installation of low-strength and leaky bridges, premature setting of cement mortar, stuck column pipes, etc. These complications are caused not only and not so much by the properties of the grouting materials used, but by the specifics of the work itself when installing bridges.

In deep, high-temperature wells, during the above-mentioned work, accidents quite often occur due to intense thickening and setting of a mixture of clay and cement mortars. In some cases, bridges are found to be leaky or not strong enough. The successful installation of bridges depends on many natural and technical factors that determine the formation of cement stone, as well as its contact and “adhesion” with rocks and pipe metal. Therefore, an assessment of the bearing capacity of the bridge as an engineering structure and a study of the conditions existing in the well are mandatory when carrying out these works.

The purpose of installing bridges is to obtain a stable water-gas-oil-tight layer of cement stone of a certain strength for moving to the overlying horizon, drilling a new shaft, strengthening the unstable and cavernous part of the wellbore, testing the horizon using a formation tester, major repairs and conservation or abandonment of wells.

Based on the nature of the operating loads, two categories of bridges can be distinguished:

1) experiencing liquid or gas pressure and 2) experiencing load from the weight of the tool during drilling of the second hole, the use of a formation tester or in other cases (bridges in this category must, in addition to gas-water tightness, have very high mechanical strength).

Analysis of field data shows that bridges can be subject to pressures of up to 85 MPa, axial loads of up to 2100 kN, and shear stresses of up to 30 MPa per 1 m of bridge length. Such significant loads arise when testing wells with the help of formation testers and during other types of work.

The load-bearing capacity of cement bridges largely depends on their height, the presence (or absence) and condition of mudcake or drilling fluid residues on the column. When removing the loose part of the clay cake, the shear stress is 0.15-0.2 MPa. In this case, even when maximum loads occur, a bridge height of 18-25 m is sufficient. The presence of a 1-2 mm thick layer of drilling (clay) mud on the walls of the column leads to a decrease in shear stress and an increase in the required height to 180-250 m. In this regard the height of the bridge should be calculated using the formula Nm ≥ Ho – Qm/pDc [τm] (1) where H0 is the installation depth of the lower part of the bridge; QM is the axial load on the bridge caused by the pressure drop and unloading of the pipe string or formation tester; Dс - well diameter; [τm] is the specific load-bearing capacity of the bridge, the values of which are determined both by the adhesive properties of the backfill material and by the method of installing the bridge. The tightness of the bridge also depends on its height and the condition of the contact surface, since the pressure at which water breakthrough occurs is directly proportional to the length and inversely proportional to the thickness of the crust. If there is a clay cake with a shear stress of 6.8-4.6 MPa and a thickness of 3-12 mm between the casing and the cement stone, the water breakthrough pressure gradient is 1.8 and 0.6 MPa per 1 m, respectively. In the absence of a cake, water breakthrough occurs at a pressure gradient of more than 7.0 MPa per 1 m.

Consequently, the tightness of the bridge also largely depends on the conditions and method of its installation. In this regard, the height of the cement bridge should also be determined from the expression

Nm ≥ But – Рм/[∆р] (2) where Рм is the maximum value of the pressure difference acting on the bridge during its operation; [∆р] - permissible pressure gradient of fluid breakthrough along the contact zone of the bridge with the well wall; this value is also determined mainly depending on the method of installing the bridge and on the backfill materials used. From the values of the height of cement bridges determined by formulas (1) and (2), the larger one is selected.

The installation of a bridge has much in common with the process of cementing columns and has features that boil down to the following:

1) a small amount of cementing materials is used;

2) the lower part of the filling pipes is not equipped with anything, a stop ring is not installed;

3) rubber separating plugs are not used;

4) in many cases, backwashing of wells is carried out to “cut off” the roof of the bridge;

5) the bridge is not limited by anything from below and can spread under the influence of the difference in the densities of the cement and drilling fluids.

Installing a bridge is a simple operation in concept and method of implementation, which in deep wells is significantly complicated by factors such as temperature, pressure, gas and oil shows, etc. The length, diameter and configuration of the filling pipes, the rheological properties of cement and drilling fluids, are also important. cleanliness of the wellbore and modes of movement of downward and upward flows. The installation of a bridge in the uncased part of the well is significantly influenced by the cavernous nature of the wellbore.

Cement bridges must be strong enough. Practice shows that if, during strength testing, the bridge does not collapse when a specific axial load of 3.0-6.0 MPa is placed on it and simultaneous flushing, then its strength properties satisfy the conditions of both drilling a new shaft and loading from the weight of a pipe string or formation tester.

When installing bridges for drilling a new shaft, they are subject to an additional height requirement. This is due to the fact that the strength of the upper part (H1) of the bridge must ensure the possibility of drilling a new shaft with an acceptable intensity of curvature, and the lower part (H0) - reliable isolation of the old shaft. Nm=H1+No = (2Dс* Rc)0.5+ No(3)

where Rc is the radius of curvature of the trunk.

Analysis of available data shows that obtaining reliable bridges in deep wells depends on a complex of simultaneously acting factors, which can be divided into three groups.

The first group is natural factors: temperature, pressure and geological conditions (vugginess, fracturing, the action of aggressive waters, water and gas shows and absorption).

The second group is technological factors: the speed of flow of cement and drilling fluids in pipes and the annular space, the rheological properties of the solutions, the chemical and mineralogical composition of the cementitious material, the physical and mechanical properties of the cement mortar and stone, the contraction effect of well cement, the compressibility of the drilling fluid, heterogeneity of densities , coagulation of drilling fluid when mixed with cement (formation of high-viscosity pastes), the size of the annular gap and the eccentricity of the location of pipes in the well, the time of contact of the buffer fluid and cement solution with the mud cake.

The third group is subjective factors: the use of cementing materials that are unacceptable for the given conditions; incorrect selection of solution formulation in the laboratory; insufficient preparation of the wellbore and the use of drilling fluid with high values of viscosity, viscosity and fluid loss; errors in determining the amount of displacement fluid, the location of the pouring tool, the dosage of reagents for mixing the cement slurry in the well; the use of an insufficient number of cementing units; use of insufficient amount of cement; low degree of organization of the bridge installation process.

An increase in temperature and pressure contributes to the intense acceleration of all chemical reactions, causing rapid thickening (loss of pumpability) and setting of grouting solutions, which, after short-term stops in circulation, are sometimes impossible to push through.

Until now, the main method of installing cement bridges has been pumping cement slurry into a well at a designed depth interval along a pipe string lowered to the level of the bottom level of the bridge and then raising this column above the cementing zone. As a rule, work is carried out without dividing plugs and means of controlling their movement. The process is controlled by the volume of displacement fluid, calculated from the condition of equal levels of cement slurry in the pipe string and the annular space, and the volume of cement slurry is taken equal to the volume of the well in the bridge installation interval. The effectiveness of the method is low.

First of all, it should be noted that the cementitious materials used for cementing casing strings are suitable for installing durable and airtight bridges. Poor installation of bridges or their absence at all, premature setting of the binder solution and other factors are to a certain extent due to incorrect selection of the binder solution formulation according to the thickening (setting) time frame or deviations from the recipe selected in the laboratory that were made when preparing the binder solution.

It has been established that in order to reduce the likelihood of complications, the setting time, and at high temperatures and pressures, the thickening time, should exceed the duration of work on installing bridges by at least 25%. In a number of cases, when selecting recipes for binder solutions, the specifics of bridge installation work, which consists in stopping the circulation to lift the filling pipe column and seal the mouth, are not taken into account.

Under conditions of high temperatures and pressure, the shear resistance of cement mortar, even after short-term stops (10-20 minutes) of circulation, can increase sharply. Therefore, circulation cannot be restored and in most cases the column of filling pipes becomes stuck. As a result, when selecting a cement mortar formulation, it is necessary to study the dynamics of its thickening using a consistometer (CC) using a program that simulates the process of installing a bridge. The thickening time of the cement mortar Tzag corresponds to the condition

Tzag>T1+T2+T3+1.5(T4+T5+T6)+1.2T7 where T1, T2, T3 are the time spent, respectively, on preparing, pumping and forcing cement mortar into the well; T4, T5, T6 - time spent on lifting the column of filling pipes to the bridge cutting site, sealing the mouth and carrying out preparatory work for cutting the bridge; Tt is the time required to cut the bridge.

According to a similar program, it is necessary to study mixtures of cement slurry with drilling fluid in a ratio of 3:1, 1:1 and 1:3 when installing cement bridges in wells with high temperatures and pressures. The success of installing a cement bridge largely depends on the exact adherence to the recipe selected in the laboratory when preparing the cement mortar. The main conditions here are maintaining the selected content of chemical reagents and mixing fluid and water-cement ratio. To obtain the most homogeneous cement slurry, it should be prepared using a settling tank.

Complications and accidents when drilling oil and gas wells in permafrost conditions and measures to prevent them .

When drilling in permafrost intervals, as a result of the combined physicochemical impact and erosion on the well walls, sandy-clay deposits cemented by ice are destroyed and are easily washed away by the flow of drilling fluid. This leads to intense cavern formation and associated landslides and rock slides.

Rocks with low ice content and weakly compacted rocks are most intensively destroyed. The heat capacity of such rocks is low, and therefore their destruction occurs much faster than rocks with high ice content.

Among the frozen rocks there are interlayers of thawed rocks, many of which are prone to absorption of drilling fluid at pressures slightly exceeding the hydrostatic pressure of the water column in the well. Loss in such formations can be very intense and require special measures to prevent or eliminate them.

In permafrost sections, Quaternary rocks are usually the most unstable in the range of 0 - 200 m. With traditional drilling technology, the actual volume of the trunk in them can exceed the nominal volume by 3 - 4 times. As a result of severe cavities. which is accompanied by the appearance of ledges, sludge sliding and rock falls, the conductors in many wells were not lowered to the designed depth.

As a result of the destruction of permafrost, in a number of cases, subsidence of the conductor and direction was observed, and sometimes entire craters formed around the wellhead, preventing drilling operations.

In the permafrost zone, it is difficult to ensure cementation and fastening of the barrel due to the creation of stagnant zones of drilling fluid in large caverns, from where it cannot be displaced by cement slurry. Cementation is often one-sided, and the cement ring is not continuous. This creates favorable conditions for interlayer flows and the formation of griffins, which cause collapse of columns during reverse freezing of rocks in the case of long-term “interlayers” of the well.

The destruction processes of permafrost are quite complex and little studied. 1 The drilling fluid circulating in the well thermo- and hydrodynamically interacts with both rock and ice, and this interaction can be significantly enhanced by physicochemical processes (for example, dissolution), which do not stop even at subzero temperatures.

At present, the presence of osmotic processes in the system rock (ice) - crust on the well wall - flushing fluid in the wellbore can be considered proven. These processes are spontaneous and directed in the direction opposite to the potential gradient (temperature, pressure, concentration), i.e. strive to equalize concentrations, temperatures, pressures. The role of a semi-permeable partition can be performed by both the filter cake and the near-wellbore race layer of the rock itself. And in addition to ice as a cementing substance, frozen rock may contain non-freezing pore water with varying degrees of mineralization. The amount of non-freezing water in MMG1 depends on temperature, material composition, salinity and can be estimated using the empirical formula

w = aT~ b .

1pa = 0.2618 + 0.55191nS;

1p(- b)= 0.3711 + 0.264S:

S is the specific surface area of the rock. m a / p G - rock temperature, "C.

Due to the presence of flushing drilling fluid in the open wellbore, and in the permafrost - pore fluid with a certain degree of mineralization, a process of spontaneous equalization of iodine concentrations occurs under the influence of osmotic pressure. As a result, destruction of frozen rock may occur. If the drilling fluid has an increased concentration of some dissolved salt compared to pore water, then phase transformations associated with a decrease in the melting temperature of ice will begin at the ice-liquid interface, i.e. the process of its destruction will begin. And since the stability of the well wall depends mainly on ice, as a cementing substance for the rock, then under these conditions the stability of the permafrost that patches the well wall will be lost, which can cause screes, collapses, the formation of cavities and sludge plugs, landings and tightening during hoisting operations, stopping casing strings lowered into the well, absorption of drilling flushing and cementing solutions.

If the degree of mineralization of drilling fluid and pore water of permafrost is the same, then the well-rock system will be in isotonic equilibrium, and destruction of permafrost under physicochemical influence is unlikely.

As the degree of salinity of the flushing agent increases, conditions arise under which pore water with less salinity will move from the rock to the well. Due to the loss of immobilized water, the mechanical strength of the ice will decrease, the ice may collapse, which will lead to the formation of a cavern in the borehole of the well being drilled. This process is intensified by the erosive effect of the circulating flushing agent.

The destruction of ice by salty washing liquid has been noted in the works of many researchers. Experiments conducted at the Leningrad Mining Institute showed that with increasing salt concentration in the liquid washing the ice, the destruction of ice intensifies. So. When the circulating water contained 23 and 100 kg/m NaCl, the intensity of ice destruction at a temperature of minus 1 °C was 0.0163 and 0.0882 kg/h, respectively.

The process of ice destruction is also influenced by the duration of exposure to the salty washing liquid. Thus, when ice is exposed to a 3% NaCl solution, the weight loss of an ice sample with a temperature of minus 1 °C will be: after 0.5 h 0.62 p after 1.0 h 0.96 g: after 1.5 h 1.96 g.

As the near-well zone of the permafrost melts, part of its burrow space is released, into which the flushing fluid or its dispersion medium can also be filtered. This process may turn out to be another physical and chemical factor contributing to the destruction of permafrost. It can be accompanied by osmotic flow of fluid from wells into the rock if the concentration of some soluble salt in the permafrost fluid is greater than in the fluid. filling the wellbore.

Therefore, in order to minimize the negative impact of physical and chemical processes on the condition of the wellbore of a well drilled in permafrost, it is necessary, first of all, to ensure an equilibrium concentration of the components of the drilling mud and pore fluid in permafrost on the well wall.

Unfortunately, this requirement is not always feasible in practice. Therefore, they often resort to protecting permafrost-cementing ice from the physicochemical effects of drilling fluid by films of viscous liquids, which cover not only the ice surface exposed by the well, but also the pore space partially adjacent to the well. thereby breaking the direct contact of the mineralized liquid with ice.

As AV Maramzin and AA Ryazanov point out, during the transition from flushing wells with salt water to flushing with a more viscous clay solution, the intensity of ice destruction decreased by 3.5 - 4 times at the same concentration of NaCl in them. It decreased even more when the drilling fluid was treated with protective colloids (CMC, SSB). The positive role of additives to the drilling fluid, highly colloidal bentonite clay powder and hypane, was also confirmed.

Thus, to prevent cavern formation, destruction of the wellhead zone, slides and landslides when drilling wells in permafrost. The drilling fluid must meet the following basic requirements:

have a low filtration rate:

have the ability to create a dense, impenetrable film on the surface of ice in permafrost:

have low erosion ability; have a low specific heat capacity;

form a filtrate that does not create true solutions with the rock liquid;

be hydrophobic to the ice surface.

Subject: Drilling oil and gas wells.

Plan: 1. General information about oil and gas operations.

2. Methods of drilling wells.

3. Classification of wells.

1. General information about oil and gas operations.

Well drilling is the process of constructing a directional mine opening of large length and small (compared to the length) diameter. The beginning of a well on the surface of the earth is called the mouth, the bottom is called the bottom. This process - drilling - is common in various sectors of the national economy.

Goals and objectives of drilling

Oil and gas are produced using wells, the main construction processes of which are drilling and casing. It is necessary to carry out high-quality construction of wells in ever-increasing volumes with a multiple reduction in the timing of their installation, as well as with a reduction in labor and energy intensity and capital costs.

Drilling wells is the only method of effective development, increment of production and reserves of oil and gas.

The cycle of construction of oil and gas wells before putting them into operation consists of the following sequential links:

sinking a wellbore, the implementation of which is only possible when two types of work are carried out in parallel - deepening the face through local destruction of rock and cleaning the shaft from destroyed (drilled) rock;

isolation of layers, consisting of successive works of two types - securing the walls of the barrel with casing pipes connected into a casing string, and sealing (cementing, plugging) the annular space;

development of a well as a production facility.

2. Methods of drilling wells.

Common methods of rotary drilling - rotary, turbine and electric drilling - involve the rotation of a rock-destroying working tool - a bit. The destroyed rock is removed from the well by drilling fluid, foam or gas pumped into the pipe string and exiting through the annulus.

Rotary drilling

In rotary drilling, the bit rotates along with the entire drill string; rotation is transmitted through a working pipe from a rotor connected to the power plant by a transmission system. The weight on bit is created by part of the weight of the drill pipes.

In rotary drilling, the maximum torque of the string depends on the resistance of the rock to the rotation of the bit, the frictional resistance of the string and the rotating fluid on the well wall, as well as on the inertial effect of elastic torsional vibrations.

In world drilling practice, the most common is the rotary method: almost 100% of the volume of drilling work in the USA and Canada is carried out using this method. In recent years, there has been a tendency to increase the volume of rotary drilling in Russia, even in the eastern regions. The main advantages of rotary drilling over turbine drilling are the independence of regulation of drilling mode parameters, the ability to trigger large pressure drops at the bit, a significant increase in penetration per bit trip due to lower frequencies of its rotation, etc.

Turbine drilling

In turbine drilling, the bit is connected to the turbine shaft of the turbodrill, which is driven into rotation by the movement of fluid under pressure through a system of rotors and stators. The load is created by part of the weight of the drill pipes.

The greatest torque is due to the resistance of the rock to the rotation of the bit. The maximum torque, determined by the calculation of the turbine (the value of its braking torque), does not depend on the depth of the well, the speed of rotation of the bit, the axial load on it and the mechanical properties of the drilled rocks. The power transfer coefficient from the energy source to the destructive tool in turbine drilling is higher than in rotary drilling.

However, during turbine drilling it is impossible to independently regulate the parameters of the drilling mode, and at the same time, the energy costs per 1 m of penetration, the costs of depreciation of turbo drills and the maintenance of workshops for their repair are high.

The turbine drilling method has become widespread in Russia thanks to the work of VNIIBT.

Drilling with screw (displacement) motors

The working parts of the engines are created on the basis of a multi-start screw mechanism, which makes it possible to obtain the required rotation speed with increased torque compared to turbodrills.

The downhole motor consists of two sections - motor and spindle.

The working bodies of the motor section are the stator and the rotor, which are a screw mechanism. This section also includes a double joint. The stator is connected to the drill pipe string using a sub. Torque is transmitted from the rotor to the spindle output shaft via a double-joint connection.

The spindle section is designed to transmit the axial load to the face, absorb the hydraulic load acting on the motor rotor, and seal the lower part of the shaft, which helps create a pressure drop.

In screw motors, torque depends on the pressure drop across the motor. As the shaft is loaded, the torque developed by the engine increases, and the pressure drop in the engine also increases. The performance characteristics of the screw engine with the requirements for efficient bit processing allows us to obtain an engine with an output shaft rotation speed in the range of 80-120 rpm with increased torque. This feature of screw (displacement) engines makes them promising for implementation in drilling practice.

Electric drilling

When using electric drills, the rotation of the bit is carried out by an electric (three-phase) AC motor. Energy is supplied to it from the surface through a cable located inside the drill string. The drilling fluid circulates in the same way as with the rotary drilling method. The cable is inserted into the pipe string through a current collector located above the swivel. The electric drill is attached to the lower end of the drill string, and the bit is attached to the shaft of the electric drill. The advantage of an electric motor over a hydraulic one is that the electric drill’s rotation speed, torque and other parameters do not depend on the amount of fluid supplied, its physical properties and the depth of the well, and the ability to control the process of engine operation from the surface. Disadvantages include the difficulty of supplying energy to the electric motor, especially at high pressure, and the need to seal the electric motor from drilling fluid.

Promising directions in the development of drilling methods in world practice

In domestic and foreign practice, research and development activities are carried out

work in the field of creating new drilling methods, technologies, and equipment.

These include deepening in rocks using explosions, destruction of rocks using ultrasound, erosion, using a laser, vibration, etc.

Some of these methods have been developed and are used, albeit to a small extent, often at the experimental stage.

Hydromechanical The method of rock destruction during well deepening is increasingly used in experimental and field conditions. S.S. Shavlovsky carried out a classification of water jets that can be used when drilling wells. The basis of the classification is the developed pressure, the working length of the jets and the degree of their impact on rocks of different composition, cementation and strength, depending on the diameter of the nozzle, the initial pressure of the jet and water flow. The use of water jets allows, in comparison with mechanical methods, to increase the technical and economic indicators of drilling a well.

At the VII International Symposium (Canada, 1984), the results of work on the use of water jets in drilling were presented. Its capabilities are associated with continuous, pulsating or intermittent fluid supply, the presence or absence of abrasive material and the technical and technological features of the method.

Erosive drilling provides deepening speeds 4-20 times higher than with rotary drilling (under similar conditions). This is explained, first of all, by a significant increase in the power supplied to the face compared to other methods.

Its essence lies in the fact that an abrasive material - steel shot - is supplied to a specially designed bit along with the drilling fluid. The size of the granules is 0.42 - 0.48 mm, the concentration in the solution is 6%. Through the bit nozzles, this solution with shot is supplied to the face at high speed and the face is destroyed. Two filters are installed in series in the drill string, designed to screen out and retain particles whose size does not allow them to pass through the bit nozzles.

One filter is above the bit, the second is under the leading pipe, where cleaning can be carried out. Chemical processing of shot drilling fluid is more difficult than processing conventional drilling fluid, especially at elevated temperatures.

The peculiarity is that it is necessary to keep the shot suspended in solution and then generate this abrasive material.

After preliminary cleaning of the drilling fluid from gas and cuttings using hydrocyclones, the shot is collected and stored in a wet state. Then the solution is passed through fine hydrocyclones and a degasser and its lost properties are restored by chemical treatment. Part of the drilling fluid is mixed with shot and fed into the well, along the way mixing with ordinary drilling fluid (in the calculated ratio).

Lasers- optical quantum generators are one of the remarkable achievements of science and technology. They have found wide application in many fields of science and technology.

According to foreign data, it is currently possible to organize the production of continuous gas lasers with an output power of 100 kW and higher. The efficiency of gas lasers can reach 20 - 60%. The high power of lasers, provided that extremely high radiation densities are obtained, is sufficient to melt and evaporate any materials, including rocks. The rock also cracks and peels off.

The minimum power density of laser radiation sufficient to destroy rocks by melting has been experimentally established: for sandstones, siltstones and clays it is approximately 1.2-1.5 kW/cm 2 . The power density of effective destruction of oil-saturated rocks due to thermal processes of oil combustion, especially when air or oxygen is blown into the destruction zone, is lower and amounts to 0.7 - 0.9 kW/cm 2 .

It is estimated that for a well with a depth of 2000 m and a diameter of 20 cm, about 30 million kW of laser radiation energy must be spent. Drilling wells of this depth is not yet competitive with traditional mechanical drilling methods. However, there are theoretical prerequisites for increasing the efficiency of lasers: with an efficiency of 60%, energy and cost costs will be significantly reduced and its competitiveness will increase. When using a laser in the case of drilling wells with a depth of 100 - 200 m, the cost of work is relatively low. But in all cases, during laser drilling, the cross-sectional shape can be programmed, and the borehole wall will be formed from molten rock and will be a glassy mass, which makes it possible to increase the coefficient of displacement of drilling mud by cement. In some cases, it is obviously possible to do without securing wells.

Foreign companies offer several laser designs. They are based on a powerful laser housed in a sealed housing that can withstand high pressure. Temperature resistance has not yet been studied. According to these designs, laser radiation is transmitted to the face through a light-conducting fiber. As the rock is destroyed (melted), the laser drill is fed down; it can be equipped with a vibrator installed in the housing. When the projectile is pressed into the molten rock, the walls of the well can become compacted.

Japan has begun producing carbon dioxide gas lasers, which, when used in drilling, will significantly (up to 10 times) increase the penetration rate.

The well section when forming a trunk using this method can have an arbitrary shape. Using a developed program, the computer remotely sets the scanning mode of the laser beam, which allows you to program the size and shape of the wellbore.

Laser-thermal work is possible in the future in perforation work. Laser perforation will provide control over the process of destruction of the casing, cement stone and rock, and can also facilitate the penetration of channels to a significant depth, which will certainly increase the degree of perfection of formation penetration. However, melting of rocks, which is advisable when deepening a well, is unacceptable here, which must be taken into account when using this method in the future.

In domestic works there are proposals for the creation of laser plasma installations for thermal drilling of wells. However, transporting plasma to the bottom of the well is still difficult, although research is underway into the possibility of developing light guides (“fiber pipes”).

One of the most interesting methods of influencing rocks, which have the “universality” criterion, is the method of melting them using direct contact with a refractory tip - a penetrator. Significant advances in the creation of heat-resistant materials have made it possible to move the issue of rock melting into the realm of real design. Already at a temperature of approximately 1200-1300 °C, the melting method works

especially in loose soils, sands and sandstones, basalts and other crystalline basement rocks. In sedimentary rocks, excavation of clayey and carbonate rocks apparently requires higher temperatures.

The fusion drilling method makes it possible to obtain a fairly thick glass-ceramic crust with smooth internal walls on the walls of the well. The method has a high coefficient of energy input into the rock - up to 80-90%. In this case, the problem of removing the melt from the face can be solved, at least in principle. Emerging through outlet channels or simply flowing around a smooth penetrator, the melt solidifies and forms slurry, the size and shape of which can be controlled. The cuttings are carried away by a fluid that circulates above the drill string and cools its top.

The first projects and samples of thermal drills appeared in the 60s, and the most active theory and practice of rock melting began to develop in the mid-70s. The efficiency of the melting process is determined mainly by the temperature of the penetrator surface and the physical properties of rocks and depends little on the mechanical and strength properties. This circumstance determines a certain universality of the melting method in the sense of its applicability for sinking various rocks. The melting temperature range of these various polymineral multicomponent systems generally falls within the range of 1200-1500 °C at atmospheric pressure. In contrast to the mechanical method of destruction of rocks by melting, with increasing depth and temperature of the underlying rocks, its effectiveness increases.

As already mentioned, in parallel with the penetration, the walls of the well are secured and insulated as a result of the creation of an impenetrable glassy annular layer. It is not yet clear whether wear of the surface layer of the penetrator will occur, what its mechanism and intensity are. It is possible that fusion drilling, although at a low speed, can be carried out continuously within the interval determined by the well design. This design itself, due to the continuous fastening of the walls, can be significantly simplified, even in difficult geological conditions.

One can imagine technological procedures associated only with fastening and insulating the walls in series with the drilling of a shaft using conventional mechanical drilling. These procedures may only apply to in-

intervals that pose a danger due to the possibility of various complications.

From the point of view of technical implementation, it is necessary to provide a current conductor to the injection elements of the penetrator, similar to that used for electric drilling.

3. Classification of wells

Wells can be classified according to their purpose, the profile of the trunk and filter, the degree of perfection and design of the filter, the number of casing columns, location on the surface of the earth, etc.

Wells are distinguished by purpose: reference, parametric, structural-search, exploration, oil, gas, geothermal, artesian, injection, observation, special.

According to the profile of the wellbore and filter, there are: vertical, inclined, directional, horizontal.

Wells are classified according to the degree of perfection: super-perfect, perfect, imperfect in terms of the degree of opening of productive layers, imperfect in terms of the nature of opening of productive layers.

Based on the design of the filter, wells are classified into: unsupported, supported by a production casing, supported by an insert slot or mesh filter, supported by a gravel-sand filter.

Based on the number of columns in the well, wells are distinguished: single-column (production column only), multi-column (two-, three-, p-column).

Wells are classified according to their location on the earth's surface: onshore, offshore, and offshore.

The purpose of structural prospecting wells is to establish (clarify) tectonics, stratigraphy, lithology of the rock section, and assess possible productive horizons.

Exploration wells are used to identify productive formations, as well as to delineate developed oil and gas fields.

Extractive (exploitation) ones are intended for the extraction of oil and gas from the bowels of the earth. This category also includes injection, appraisal, observation and piezometric wells.

Injection pumps are necessary for injecting water, gas or steam into the reservoir in order to maintain reservoir pressure or treat the near-wellbore zone. These measures are aimed at extending the period of flowing oil production or increasing production efficiency.

The purpose of appraisal wells is to determine the initial water-oil saturation and residual oil saturation of the formation and conduct other studies.

Monitoring and observation wells serve to monitor the development object, study the nature of the movement of formation fluids and changes in gas-oil saturation of the formation.

Reference wells are drilled to study the geological structure of large regions in order to establish general patterns of occurrence of rocks and identify the possibility of the formation of oil and gas deposits in these rocks.

Control questions:

1. How are wells classified?

2. What are the known methods of drilling wells?

3. What is laser drilling? ?

Literature

1. Bagramov R.A. Drilling machines and complexes: Textbook. for universities. - M.: Nedra, 1988. - 501 p.

2. Basarygin Yu.M., Bulatov A.I., Proselkov Yu.M. Well completion: Textbook. benefit for

universities - M: Nedra-Business Center LLC, 2000. - 670 p.

3. Basarygin Yu.M., Bulatov A.I., Proselkov Yu.M. Complications and accidents during oil drilling

and gas wells: Proc. for universities. - M.: Nedra-Business Center LLC, 2000. -679 p.

4. Basarygin Yu.M., Bulatov A.I., Proselkov Yu.M. Oil and gas drilling technology

wells: Proc. for universities. - M.: Nedra-Business Center LLC, 2001. - 679 p.

5. Boldenko D.F., Boldenko F.D., Gnoevykh A.N. Downhole screw motors. - M.: Nedra,

Zavgorodniy Ivan Alexandrovich

2nd year student, mechanical department, specialty “Drilling of oil and gas wells”, Astrakhan State Polytechnic College, Astrakhan

Email:

Kuznetsova Marina Ivanovna

teacher of special disciplines, Astrakhan State Polytechnic College, Astrakhan

Email:

Introduction. Since ancient times, humanity has been extracting oil; at first, primitive methods were used: using wells, collecting oil from the surface of reservoirs, processing limestone or sandstone soaked in oil. In 1859, mechanical drilling of oil wells appeared in the US state of Pennsylvania, and around the same time well drilling began in Russia. In 1864 and 1866, the first wells were drilled in the Kuban with a flow rate of 190 tons/day.

Initially, oil wells were drilled using a manual rod-rotary method, but soon they switched to drilling using a manual rod-percussion method. The shock-rod method has become widespread in the oil fields of Azerbaijan. The transition from the manual method to mechanical drilling of wells led to the need to mechanize drilling operations, a major contribution to the development of which was made by Russian mining engineers G.D. Romanovsky and S.G. Wojslaw. In 1901, for the first time in the United States, rotary drilling was used with flushing the bottom with a circulating flow of liquid (using drilling fluid), and the lifting of drilled rock with a circulating flow of water was invented by the French engineer Fauvelle back in 1848. From this moment on, the period of development and improvement of the rotary drilling method began. In 1902, the first well with a depth of 345 m was drilled in Russia using the rotary method in the Grozny region.

Today, the United States occupies a leading position in the oil industry, 2 million wells are drilled annually, a quarter of them turn out to be productive, Russia so far occupies only second place. In Russia and abroad the following are used: manual drilling (water extraction); mechanical; controlled spindle drilling (safe drilling system developed in England); explosive drilling technologies; thermal; physico-chemical, electric spark and other methods. In addition, many new technologies for drilling wells are being developed; for example, in the USA, the Colorado Mining Institute has developed a laser drilling technology based on burning rock.

Drilling technology. The mechanical drilling method is the most common; it is carried out using percussion, rotary and percussion-rotary drilling methods. With the impact drilling method, rock destruction occurs due to impacts of the rock-cutting tool on the bottom of the well. The destruction of rocks due to the rotation of a rock-cutting tool (chisel, crown) pressed to the bottom is called the rotational drilling method.

When drilling oil and gas wells in Russia, only the rotational drilling method is used. When using the rotary drilling method, a well is drilled with a rotating bit, while the drilled rock particles during the drilling process are carried to the surface by a continuously circulating stream of drilling fluid or air or gas injected into the well. Depending on the location of the engine, rotary drilling is divided into rotary drilling and turbo drilling. In rotary drilling, the rotator is located on the surface, causing the bit to rotate at the bottom using a string of drill pipes, the rotation speed is 20-200 rpm. When drilling with a downhole motor (turbo drill, screw drill or electric drill), torque is transmitted from a downhole motor installed above the bit.

The drilling process consists of the following main operations: lowering drill pipes with a bit into the well to the bottom and lifting drill pipes with a spent bit from the well and operating the bit at the bottom, i.e., destruction of the drilling rock. These operations are periodically interrupted to lower casing pipes into the well in order to protect the walls from collapses and separate oil (gas) and water horizons. At the same time, during the process of drilling wells, a number of auxiliary works are carried out: core sampling, preparation of drilling fluid (drilling fluid), logging, measuring curvature, well development in order to cause an influx of oil (gas) into the well, etc.

Figure 1 shows the technological diagram of the drilling rig.

Figure 1. Diagram of a drilling rig for rotary drilling: 1 - traveling rope; 2 - traveling block; 3 - tower; 4 - hook; 5 - drilling hose; 6 - leading pipe; 7 - gutters; 8 - mud pump; 9 - pump motor; 10 - pump piping; 11 - receiving tank (capacity); 12 - drill joint; 13 - drill pipe; 14 - hydraulic downhole motor; 15 - chisel; 16 - rotor; 17 - winch; 18 - winch and rotor motor; 19 - swivel

A drilling rig is a set of machines and mechanisms designed for drilling and securing wells. The drilling process is accompanied by lowering and raising the drill string, as well as maintaining it in weight. To reduce the load on the rope and reduce engine power, lifting equipment is used, consisting of a tower, a drilling drawworks and a traveling system. The traveling system consists of a fixed part of the crown block installed at the top of the tower canopy and a moving part of the traveling block, traveling rope, hook and slings. The traveling system is designed to convert the rotational movement of the winch drum into the translational movement of the hook. The drilling derrick is designed for raising and lowering the drill string and casing into the well, as well as for holding the drill string suspended during drilling and its uniform delivery and placement of the traveling system, drill pipes and part of the equipment in it. Hoisting operations are carried out using a drill winch. The drawworks consists of a base on which the winch shafts are fixed and connected to each other by gears, all shafts are connected to the gearbox, and the gearbox in turn is connected to the engine.

Land drilling equipment includes a receiving bridge designed to lay drill pipe and move equipment, tools, materials and spare parts along it. A system of devices for cleaning the flushing solution from drilled rock. And a number of auxiliary structures.

The drill string connects the drill bit (rock cutting tool) to the surface equipment, i.e., the drilling rig. The top pipe in a drill string is square and can be hexagonal or grooved. The drive tube passes through the hole in the rotor table. The rotor is placed in the center of the derrick. The leading pipe is connected at its upper end to a swivel designed to ensure rotation of the drill string suspended on a hook and supply flushing fluid through it. The lower part of the swivel is connected to the kelly and can rotate with the drill string. The top of the swivel is always stationary.

Let's consider the technology of the drilling process (Figure 1). A flexible hose 5 is connected to the hole of the stationary part of the swivel 19, through which the washing liquid is pumped into the well using drilling pumps 8. The washing liquid passes along the entire length of the drill string 13 and enters the hydraulic downhole motor 14, which causes the motor shaft to rotate, and then the liquid enters the bit 15. Coming out of the holes of the bit, the liquid washes the bottom, picks up particles of the drilled rock and, together with them, rises upward through the annular space between the walls of the well and the drill pipes and is sent to the pump intake. At the surface, the drilling fluid is cleaned of drilled rock using special equipment, after which it is again fed into the well.

The technological process of drilling largely depends on the drilling fluid, which, depending on the geological features of the field, is prepared on a water basis, on an oil basis, using a gaseous agent or air.

Conclusion. From the above it is clear that the technologies for the behavior of drilling processes are different, but the one suitable for the given conditions (depth of the well, the rock that composes it, pressure, etc.) must be selected based on geological and climatic conditions. Since, the further operational characteristics of the well, namely its flow rate and productivity, depend on the high-quality opening of the productive horizon in the field.

Bibliography:

1. Vadetsky Yu.V. Drilling oil and gas wells: a textbook for beginners. prof. education. M.: Publishing center "Academy", 2003. - 352 p. ISB# 5-7695-1119-2.

2. Vadetsky Yu.V. Driller's Handbook: textbook. guide for beginners prof. education. M.: Publishing center "Academy", 2008. - 416 p. ISB# 978-5-7695-2836-1.