In the process of drilling oil and gas wells attract high-tech equipment with high power. The list of work performed depends on the characteristics of hydrocarbon deposits. Seams with natural raw materials can be located vertically, horizontally or obliquely, which directly affects the method of its extraction.

What is a well?

The wells are designed for the extraction of gas, water and other useful resources. It is a working in a rock having a cylindrical shape. Its length is much greater than its diameter. The well consists of several parts.

The beginning of a cylindrical recess in the rock is called the mouth, the walls - the trunk, the bottom - the bottom. The diameter of oil wells at the top rarely exceeds 900 mm, and at the bottom - more than 165 mm. By depth, they are divided into shallow (up to 1500 m), medium (up to 4500 m), deep (up to 6000 m), ultra-deep (from 6000 m).

Depending on the purpose of wells for the production of hydrocarbons, they are divided into the following varieties:

• operational. Directly used for hydrocarbon production;
• injection. Water is pumped in to maintain reservoir pressure, which makes it possible to extend the period of development of energy resources deposits;
• exploration. Allow to determine the resource of the identified horizons;
• special. Designed to determine geological characteristics territory, oil-bearing layer, for discharge of effluents into deep layers;
• structural search. Designed to determine the exact location of hydrocarbon deposits.

How is drilling done?

The technology of drilling an oil and gas well involves the following work:

• The process of drilling wells with various technical characteristics begins with the preparation of specialized equipment.
• Carry out the deepening of the wellbore. In the process, water is pumped, which allows you to drill more efficiently.
• So that the recess in the ground does not collapse, its walls are strengthened. For this purpose casing pipes are used. The space between their walls and the soil is concreted, which makes it possible to significantly strengthen the cylindrical surface of the trunk.
• At the final stage of the work, the development of the well is carried out. There is a bottom-hole zone, perforation, oil outflow.

Drilling methods

Various equipment can be used during the time, which determines the way the main work is carried out.

impact method

It implies the sequential destruction of rocks with the help of a chisel suspended on a rope. The working tool of the drilling rig also consists of a shock rod, a rope lock. They are connected via a transition block and a rope to the supporting mast. The main working tool makes movements using a drilling machine. To clear the recess in the ground from the remnants of the rock, the chisel is removed from time to time. A special liquid is injected inside, which is extracted with the help of a bailer to the outside along with small particles of soil.

Rotational way

This drilling technology has become very popular. The destruction of rocks occurs with the help of the rotation of the bit. It is subjected to an axial load, which implies a direct transmission of torque from the drive mechanism to the working tool. When a rotor is used. It transmits rotation through the pipe string. In conventional drilling, an electric drill, a screw motor, which are installed directly above the bit, are used as a drive mechanism.

Features of drilling horizontal wells

It is produced for the extraction of hydrocarbons in hard-to-reach places where it is impossible to do this in other ways. This method has great performance. It is actively used for the extraction of energy resources from the bottom of large reservoirs.

In the course of work, a trunk is created that tilts relative to the vertical axis at a certain angle. Horizontal drilling takes place in several stages:

1. Preparation of drilling equipment for work;
2. It is necessary to drill a well to determine the characteristics of the rock, the depth of oil-bearing layers, their placement relative to the vertical axis;
3. Creation of a solution, careful adjustment of its main characteristics;
4. Carrying out works on jamming;
5. mouth sealing;
6. Carrying out preparatory work for the geological and physical study of equipped shafts;
7. Preparation of the shaft for lowering the tester of existing rocks;
8. Explosion of shells, which allows roll selection;
9. Development of a freshly equipped well;
10. Delivery to the place of production of drilling complexes.

Drilling horizontal wells

Offshore well drilling methods

The technology of drilling wells in reservoirs differs from those applied on land. The easiest way to carry out the necessary operations is to install platforms on a pile foundation on which all equipment is placed. The device of this design occurs in shallow water. Also, the installation of drilling equipment can take place on artificially filled land.

When drilling wells, oil is usually obtained from different parts of the ocean or sea. Therefore, it is advisable to install mobile platforms. After completion of the working cycle, they move to the selected point and continue the process of hydrocarbon production. There are three types of drilling platforms.

Self-elevating

It is a pontoon. There is a cutout on the platform, above which the drilling rig is placed. Also on the pontoon is everything necessary equipment, power plant, storage and auxiliary premises, multi-storey cabin. When drilling, the columns are lowered, resting on the bottom, which leads to the rise of the platform above the water surface.

semi-submersible

They are used where the depth of oil production reaches 300-600 m. The semi-submersible platform floats on the surface of the water on huge pontoons. The fixation of the entire structure is carried out by massive anchors weighing about 15 tons.

Gravity

Mounted on a massive concrete base that rests on the seabed.

The listed methods of drilling wells for the extraction of useful hydrocarbons are actively used all over the world. They are constantly being improved, which allows them to increase their productivity.

Video: Fundamentals of oil and gas geology

1. Well construction design sequence. Factors taken into account in the design.

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

The design of a 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 the design of the well design include 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 with the allocation of zones of possible complications and indication of reservoir pressures and hydraulic fracturing pressure by intervals;

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

Design order well designs for oil and gas next.

1. Selectedbottom hole design. The design of the well in the interval of the productive formation should provide the best conditions for the flow of oil and gas into the well and the most efficient use of the reservoir energy of the oil and gas deposit.

2. The requirednumber of casing strings and depths of their descent. For this purpose, a graph of the change in the coefficient of anomaly of reservoir pressures k, and the absorption pressure index kabl is plotted.

3. The choice is substantiateddiameter of the production string and the diameters of casing strings and bits are coordinated. Diameters are calculated from bottom to top.

4. 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 ah depth over 3000 m; in a section with a length of at least 500 m from the shoe of the intermediate column in oil wells up to 3004) m deep (provided that all permeable and unstable rocks are covered with cement slurry).

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

All casing strings in wells constructed in water areas are cemented along the entire length.

2. Design steps for a hydraulic flushing program
wells with drilling fluids.

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

When drawing up a hydraulic program, it is assumed:

Eliminate fluid shows from the formation and loss of drilling mud;

To prevent erosion of the well walls and mechanical dispersion of the transported cuttings in order to exclude drilling fluid production;

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

Create conditions for maximum use of the jet effect;

Rationally use the hydraulic power of the pumping unit;

Exclude emergencies during shutdowns, circulation and start-up of drilling pumps.

The listed requirements for the hydraulic program are satisfied under the condition of formalization and solution of a multifactorial optimization problem. The well-known schemes for designing the flushing process of drilling wells are based on the calculations of hydraulic resistance in the system according to the given pump flow and indicators of the properties of drilling fluids.

Similar hydraulic calculations are carried out according to the following scheme. First, based on empirical recommendations, the velocity of the drilling fluid in the annulus is set and the required flow of mud pumps is calculated. According to the passport characteristics of mud pumps, the diameter of the bushings is selected that can provide the required flow. Then, according to the appropriate formulas, hydraulic losses in the system are determined without taking into account pressure losses in the bit. The area of ​​nozzles of jetting bits is selected based on the difference between the maximum passport discharge pressure (corresponding to the selected bushings) and the calculated pressure loss due to hydraulic resistance.

3. Principles for choosing a drilling method: main selection criteria, accounting
well depth, wellbore temperature, drilling complexity, design profile and other factors.

The choice of a drilling method, the development of more efficient methods for the destruction of 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 reservoir, its reservoir properties, the composition of the liquids and / or gases contained in it, the number of productive interlayers and the formation pressure anomaly coefficients.

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), the purpose and conditions of drilling, can be crucial.

The choice of well drilling method is also influenced by the intended purpose of drilling operations.

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 amount of work to develop the reservoir.

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 the BHA, rotary BHAs based on a downhole motor are much more technologically advanced and more reliable in operation, more stable on the design trajectory.

Dependence of the deflecting force on the bit on the curvature of the hole for a stabilizing BHA with two centralizers.

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

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

In the case of choosing a drilling method with downhole hydraulic motors, after calculating the axial weight on bit, it is necessary to select the type of downhole motor. This choice is made taking into account the specific torque on bit rotation, axial load on bit and mud density. Specifications of the selected downhole motor are taken into account when designing the RPM of the bit and the hydraulic well cleanout program.

Question about choice of 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 proceeding to choice of drilling method for deepening the hole using gaseous agents, it should be borne in mind that their physical and mechanical properties introduce quite certain limitations, since some types of gaseous agents are not applicable for a number of drilling methods. On fig. 46 shows possible combinations of various types of gaseous agents with modern drilling techniques. As can be seen from the diagram, the most universal in terms of the use of gaseous agents are the methods of drilling with a rotor and an electric drill, the less universal is the turbine method, which is used only when using aerated liquids. [ 2 ]

The power-to-weight ratio of the PBU has less effect on choice of drilling methods and their varieties, than the power-to-weight ratio of the installation for drilling on land, since, in addition to the drilling equipment itself, the PBU is equipped with auxiliary equipment necessary for its operation and retention at the drilling point. In practice, drilling and auxiliary equipment work alternately. The minimum required power-to-weight ratio of the MODU is determined by the energy consumed auxiliary equipment, which is more than necessary for the drilling drive. [ 3 ]

Eighth, section technical project dedicated choice of 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-to-weight ratio of the equipment and does not affect choice of drilling method, as 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 base should be determined by calculation already at the initial stages of the hull design, since this determines the operating range of sea waves, in which normal and safe operation is possible, as well as choice of drilling method, systems and devices to reduce the impact of pitching on the workflow. Roll reduction can be achieved by rational selection of hull sizes, their mutual arrangement and the use of passive and active anti-roll means. [ 8 ]

The most common method of exploration and exploitation of groundwater remains the drilling of wells and wells. Choice of 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 their mineralization and aggressiveness in relation to concrete (cement) and iron. [ 9 ]

When drilling ultra-deep wells, the prevention of curvature of the wellbore is very important due to the negative consequences of the curvature of the well when it is deepened. 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 choice of drilling method is profitability - the cost of 1 m of penetration. [ 11 ]

Thus, the speed of rotary drilling with mud washing exceeds the speed of percussion drilling by 3–5 times. Therefore, the decisive factor in choice of drilling method it should be 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. Designing the technology of these processes includes choice of drilling method, type of rock breaking tool and drilling modes, design of the drill string and the layout of its bottom, hydraulic deepening program and indicators of drilling fluid properties, types of drilling fluids and the required quantities of chemicals and materials to maintain their properties. The adoption of design decisions determines the choice of the type of drilling rig, which, in addition, depends on the design of the casing strings and the geographic conditions of drilling. [ 13 ]

The application of the results of solving the problem creates a wide opportunity to conduct a deep, extensive analysis of the development of bits in a large number of objects with a wide variety of drilling conditions. At the same time, it is also possible to prepare recommendations for choice of drilling methods, downhole motors, drilling pumps and drilling fluid. [ 14 ]

In the practice of constructing wells for water, the following drilling methods have become widespread: rotary with direct flushing, rotary with reverse flushing, rotary with air purge, and shock-rope. The conditions for the use of various drilling methods are determined by the actual technical and technological features of drilling rigs, as well as the quality of well construction work. It should be noted that when choice of well drilling method on water, it is necessary to take into account not only the speed of drilling wells and the manufacturability of the method, but also the provision of such parameters of the opening of the aquifer, in which the deformation of rocks in the bottomhole zone is observed to a minimum degree and its permeability does not decrease in comparison with the formation one. [ 1 ]

It is much more difficult to choose a drilling method for deepening a vertical wellbore. If, when drilling out an interval selected based on the practice of drilling with drilling fluids, a curvature of the vertical hole 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 an electric drill with a bit rotation speed of up to 325 rpm. As the hardness of rocks increases, the drilling methods are arranged in the following sequence: displacement engine, rotary drilling and rotary percussion drilling. [ 2 ]

From the point of view of increasing the speed and reducing the cost of constructing wells with PDR, the method of drilling with core hydrotransport is interesting. This method, with the exclusion of the above limitations of its application, can be used in the exploration of placers with PBU at the prospecting and prospecting and appraisal stages. exploration work. The cost of drilling equipment, regardless of drilling methods, does not exceed 10% total cost PBU. Therefore, a change in the cost of only drilling equipment does not have a significant impact on the cost of manufacture and maintenance of the MODU and on choice of drilling method. An increase in the cost of a drilling rig is justified only if it improves working conditions, increases the safety and speed of drilling, reduces the number of downtime due to weather conditions, and extends the drilling season. [ 3 ]

4. Selection of the type of bit and drilling mode: selection criteria, methods of obtaining information and its processing to establish optimal modes, control the magnitude of parameters.

The choice of the bit is made on the basis of knowledge of the rocks (g/p) that make up this interval, i.e. according to the category of hardness and according to the category of abrasiveness g / p.

In the process of drilling an exploratory and sometimes a production well, rocks are periodically selected in the form of intact pillars (cores) for compiling a stratigraphic section, studying the lithological characteristics of the passed rocks, identifying the content of oil and gas 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 body of the drill head with a thread.

Rice. 2.7. Scheme of the core bit device: 1 - drill head; 2 - core; 3 - soil carrier; 4 - body of the core set; 5 - ball valve

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

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

Pd [kN] – weight on the bit, n [rpm] – bit rotation frequency, Q [l/s] – flow rate (feed) of ind. well, H [m] - penetration per bit, Vm [m / h] - mech. penetration rate, Vav=H/tB – average,

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

In the design process, we use inf. obtained by drilling wells. in this

region, in analog. cond., data on goelog. section wells., recommendations of the manufacturer drill. instr., working 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 bottom hole does not collapse during drilling. This creates conditions for the formation of core 2. There are four-, six- and further eight-cone drill heads designed for drilling with coring in various rocks. The arrangement of rock-cutting elements in diamond and hard-alloy drill heads also makes it possible to destroy rock only along the periphery of the bottom hole.

When the well is deepened, the resulting rock column enters the core set, which consists of a body 4 and a core barrel (ground carrier) 3. The body of the core set serves to connect the drill head to the drill string, place the soil carrier and protect it from mechanical damage, as well as to pass flushing fluid between him and the soil carrier. The gruntonoska is designed to receive the core, save it during drilling and when lifting to the surface. To perform these functions, core breakers and core holders are installed in the lower part of the soil carrier, and at the top - a ball valve 5, which passes through itself the liquid displaced from the soil carrier when it is filled with a core.

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

Core barrels with a removable dredger allow you to lift the dredger with a 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 a 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 coring continues.

Core bits with a removable soil carrier are used in turbine drilling, and with a fixed one - in rotary drilling.

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

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

6. Schematic diagram of one-stage cementing. Pressure change in the cementing pumps involved in this process.

FEDERAL AGENCY FOR EDUCATION

GOUVPO "UDMURT STATE UNIVERSITY"

Department of Economics, Management of Oil and gas industry

Course work

On the topic "Drilling oil and gas wells"

Head Borkhovich S. Yu.

Questions to control work

1. Well drilling methods

1.1Percussive drilling

1.2 Rotary drilling

2. Drill string. Main elements. Load distribution along the length of the drill string

2.2 Drill string composition

3. Appointment of drilling fluids. Technological requirements and restrictions on the properties of drilling fluids

3.1 Mud functions

3.2 Drilling fluid requirements

4. Factors affecting the quality of well cementing

5. Types of drill bits and their purpose

5.1 Types of solid drill bits

5.2 Cone bits

5.3 Paddle bits

5.4 Milling bits

5.5 ISM bits

Literature

Questions for the test

Well drilling methods

Drill column. Main elements. Load distribution along the length of the drill string

Appointment of drilling fluids. Technological requirements and restrictions on the properties of drilling fluids

Factors affecting the quality of well cementing

Types of drill bits and their purpose

1 . Well drilling methods

There are different ways of drilling, but mechanical drilling has received industrial distribution. It is divided into shock and rotational.

1.1 Hammer drilling

When percussive drilling the drilling tool includes: bit (1); shock rods (2); rope lock (3); A mast (12) is installed on the surface; block (5); pull roller balancer (7); auxiliary roller (8); drilling rig drum (11); rope (4); gears (10); connecting rod (9); balancing frame (6). When the gears rotate, making movements, raising and lowering the balancing frame. When the frame is lowered, the draw roller raises the drilling tool above the bottom of the well. When the frame is raised, the rope is released, the chisel falls into the face, thereby destroying the rock. In order to prevent the collapse of the walls of the well, a casing string is lowered into it. This drilling method is applicable to shallow depths when drilling water wells. At the moment, the impact method for drilling wells is not used.

1.2 Rotary drilling

Rotary drilling. Oil and gas wells are drilled using the rotary drilling method. With such drilling, the destruction of the rock occurs due to the rotation of the bit. The rotation of the bit is given by the rotor located at the wellhead through the drill pipe string. This is called the rotary method. Also, the torque is sometimes created with the help of an engine (turbodrill, electric drill, screw downhole motor), then this method will be called drilling with a downhole motor.

Turbodrill- This is a hydraulic turbine driven by a flushing fluid pumped into the well by pumps.

electric drill- is an electric motor electricity it is supplied to it is supplied by cable from the surface. Well drilling is carried out using a drilling rig.

1-chisel; 2 - near-bit drill collar; 3.8 - sub; 4 - centralizer; 5 - sleeve sub; 6.7 - drill collars; 9 - safety ring; 10 - drill pipes; 11 - safety sub; 12.23 - rod subs, lower and upper; 13 - leading pipe; 14 - reducer; 15 - winch; 16 - swivel sub; 17 - hook; 18 - crown block; 19 - tower; 20 - traveling block; 21 - swivel; 22 - hose; 24 - riser; 25 - rotor; 26 - sludge separator; 27 - mud pump

The destruction is carried out with the help of a bit, lowered on drill pipes, to the bottom. The rotational movement is imparted by means of a downhole motor through the drill pipe string. After lowering the drill pipes with a bit, two inserts are inserted into the hole of the rotor shaft, and two clamps are inserted inside them, which form a square section hole. In this hole there is also a leading pipe, also of a square section. It perceives the torque from the rotor table and moves freely along the rotor axis. All tripping operations and holding the weight of the drill pipe string are carried out by a lifting mechanism.

2 Drill string. Main elements. Load distribution along the length of the drill string

2.1 Purpose of the drill string

The drill string is a link between the drilling equipment located on the day surface and the downhole tool (drill bit, formation tester, fishing tool, etc.) used at the given time to perform any technological operation in the wellbore.

The functions performed by the drill string are determined by the work carried out in the well. The main ones are the following.

In the process of mechanical drilling, the drill string:

· is a channel for bringing to the bottom of the energy required to rotate the bit: mechanical - in rotary drilling; hydraulic – when drilling with hydraulic downhole motors (turbodrill, screw downhole motor); electric - when drilling with electric drills (through a cable located inside the pipes);

· perceives and transmits to the well walls (at a small current depth of the well also to the rotor) reactive torque when drilling with downhole motors;

is a channel for the circular circulation of the working agent (liquid, gas-liquid mixture, gas); usually, the working agent moves down to the bottom hole through the tubular space, captures the destroyed rock (sludge), and then moves upward through the annulus to the wellhead (direct flushing);

serves to create (by the weight of the lower part of the string) or transfer (with the forced feed of the tool) the axial load on the bit, simultaneously absorbing dynamic loads from the operating bit, partially extinguishing and reflecting them back to the bit and partially passing them higher;

· it can serve as a communication channel for receiving information from the bottomhole or transferring control action to the downhole tool.

· During tripping operations, the drill string is used for lowering and lifting the bit, downhole motors, various downhole assemblies;

· for the passage of downhole instrumentation;

for working out the wellbore, carrying out intermediate washings with

to remove sludge plugs, etc.

When eliminating complications and accidents, as well as conducting research in a well and testing formations, the drill string serves:

· for injection and blowing plugging materials into the reservoir;

· for descent and installation of packers for the purpose of hydrodynamic studies of formations by selection or injection of fluid;

for descent and installation of overlappers in order to isolate absorption zones,

· strengthening of areas of shedding or collapses, installation of cement bridges, etc.;

· for descent of the fishing tool and work with it.

When drilling with coring (rock sample) with a removable core barrel, the drill string serves as a channel through which the core barrel is lowered and raised.

2.2 Drill string composition

The drill string (with the exception of the continuous pipes that have appeared recently) is made up of drill pipes using a threaded connection. The connection of pipes to each other is usually carried out using special connecting elements - drill joints, although toolless drill pipes can also be used. When lifting the drill string (in order to replace a worn bit or when performing other technological operations), the drill string is each time disassembled into shorter links with the latter installed inside the derrick on a special platform - a candlestick or (in rare cases) on racks outside the derrick, and when descending, she again gathers in a long column.

It would be inconvenient and irrational to assemble and disassemble the drill string with its disassembly into separate (single) pipes. Therefore, individual pipes are preliminarily (when building up the tool) assembled into so-called drill stands, which are not further dismantled (while drilling is being carried out with this drill string).

A stand with a length of 24-26 m (at a drilling depth of 5000 m or more, drilling stands with a length of 36-38 m can be used with a drilling rig 53-64 m high) is made up of two, three or four pipes when using pipes with a length of 12, 8 and m, respectively In the latter case, for the sake of convenience, two 6-meter pipes are pre-connected using a coupling into a two-pipe (elbow), which is not further disassembled.

As part of the drill string directly above the bit or above the downhole motor, drill collars (DCs) are always provided, which, having a mass and rigidity many times greater than conventional drill pipes, allow you to create the necessary load on the bit and provide sufficient rigidity of the bottom of the tool during avoiding its longitudinal bending and uncontrolled curvature of the wellbore. Drill collars are also used to control vibrations of the bottom of the drill string in combination with its other elements.

The composition of the drill string usually includes centralizers, calibrators, stabilizers, filters, often - metal sludge traps, check valves, sometimes - special mechanisms and devices, such as reamers, flywheels, downhole feed mechanisms, waveguides, resonators, shock absorbers of longitudinal and torsional vibrations, tread rings with the corresponding purpose.

To control the curvature of the wellbore in a given direction or, on the contrary, to straighten an already deviated wellbore, deflectors are included in the drill string, and special, often quite complex, layouts of the lower part of the drill string are used to maintain the straight direction of the wellbore.

Vladimir Khomutko

Reading time: 3 minutes

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Methods for drilling oil and gas wells

The well is a vertical or inclined mine working of a circular cross section, the construction of which takes place without access to the interior of the working of a person. The length of such a working is several times greater than its diameter.

How oil wells are drilled

The main elements of any well are:

• mouth (uppermost part);
• trunk (intermediate part);
• bottomhole (the lowest part located in the reservoir).

The distance between the mouth and the bottom along the axis of the working shaft is called the length of the well, and the same distance, but taken along the vertical projection of the axis, is called its depth.

Derrick

In other words, the length and depth of a vertical well are the same, but an inclined one is not.

Drilling oil and gas wells, as a rule. occurs with a gradual decrease in the diameter of the trunk after a certain section has been drilled. The initial diameter of such a working, as a rule, is not more than 900 millimeters, and the diameter in the face area is from 75 millimeters or more.

The process of deepening such a mine working is the destruction of rocks either over the entire area of ​​the face (the so-called continuous drilling) or along its periphery (core drilling). In the second case, a piece of cylindrical rock, called a core, remains in the mine shaft. Cores are periodically retrieved from the well to study the composition of the passed rocks. The specialty of a person who is engaged in drilling is called a driller.

Many of you are interested in the question: “How are wells drilled?”

Methods of deepening mine workings according to the criterion of the nature of the impact on passable rocks are divided into:

• mechanical;
• thermal;
• physical and chemical;
• electrical and so on.

In the industrial development of deposits, only mechanical methods are used. All other listed techniques are at the stage of experimental verification of effectiveness.

Mechanical methods are rotational and impact.

The impact method involves the mechanical destruction of the rock with the help of a special tool suspended on a rope, which is called a chisel. In addition, the composition of such a drilling device includes a rope lock and a shock rod. The device is suspended on a rope thrown over a block, which is placed on a mast, and a special drilling machine gives this tool a reciprocating motion.

As the depth of the trunk increases, the rope is gradually lengthened. The cylindrical shape of the barrel is formed by turning the bit during operation.

To clean the bottomhole from the drilled rock, the tool must be periodically raised to the surface. Instead, a special device called a bailer is lowered. It looks like a long bucket, equipped with a valve at the bottom.

The bailer is immersed in the liquid (either reservoir or surface supplied) and the valve opens. A mixture of liquid and pieces of destroyed rock enters the “bucket”, after which all this is removed to the surface (as soon as the bailer is lifted, the valve immediately closes). After the end of the bottomhole cleaning, the drilling tool is lowered into the shaft again, and the process is repeated again and again.

To prevent the walls from collapsing, a special pipe, called a casing, is lowered into it. From such pipes, as the mine working deepens, a whole pipe string is formed.

Well drilling bit

In Russia, at the moment, the shock method is not used in practice.

The rotary method involves the deepening of the tool into the rock mass due to the simultaneous impact on the bit of torque and vertical load. The vertical load drives the bit into the rock being drilled, and the torque allows the tool to shear, abrade and crush the rock.

Depending on where the unit's engine is located, rotary drilling is divided into rotary drilling (the engine is located on the surface and rotates the bit through a tubular string made up of special drill pipes) and downhole drilling (the engine is located in the bottom hole and is placed directly above the bit).

In the rotary method, the motor rotates the rotor, which, in turn, rotates the drill string, at the end of which the bit is attached. In the downhole method, the motor rotates the bit itself, while the drill string and the body of the motor itself remain stationary.

For rotary drilling method characteristic feature is the use of continuous flushing of the borehole with either water or specially prepared drilling fluids. For this purpose, special mud pumps are used, the operation of which is provided by engines of various types. It is these pumping units that pump the flushing fluid through the riser pipeline, which is mounted, as a rule, in the right corner of the drilling rig. Further, by means of a flexible drill hose and a swivel, the fluid is fed directly into the drill string itself.

Reaching the level of the bit, this flushing fluid enters the rock through the holes that are in this tool, and then through the annular free space that remains between the wall of the wellbore and the drill string. rises up, washing out pieces of drilled rock. Further, with the help of a system of gutters and special cleaning devices, this liquid is cleaned of cuttings, after which it enters a tank located on the mud pump. After that, it can be reused.

Vladimir Khomutko

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What is an oil well?

It is difficult to imagine modern life without oil products. They are made from oil, which is extracted with the help of special mine workings. Many of us have heard the term "oil well", but hardly everyone knows what it actually is. Let's try to figure out what this building is, and what they are.

A well is a cylindrical mine working, whose diameter is many times less than the total length of its shaft (depth).

In addition to the well, there are also such mine workings as a well and a mine. How do they differ from our definition? In fact, everything is quite simple. A person can get into a mine or a well, but not into a well. Thus, an additional definition of this structure is as follows - a mine working, the scheme and shape of which excludes human access to it.

The upper part of such a working is called the mouth, and the lower part is called the face. The walls going down form the so-called trunk.

Everyone knows that wells are made by drilling. However, to say that they are just Buryats would be wrong. These capital structures, complex in their structure, are more likely to be built underground, in connection with which they are classified as fixed assets of the organization, and the costs of drilling and equipping them are capital investments.

Construction of oil and gas wells

The design of the well is selected at the design stage and must meet the following requirements:

• the design should provide the possibility of free access to the bottom of geophysical instruments and downhole equipment;
• the design must prevent the collapse of the walls of the trunk;
• it must also provide reliable separation from each other of all passable layers and prevent fluids from flowing from layer to layer;
• if necessary, the design of this working should make it possible to seal its mouth in case of such a need.

Construction and installation of oil and gas wells is carried out as follows:

1. The first step is to drill the initial hole of a large diameter. Its depth is about 30 meters. Then a metal pipe, which is called a direction, is lowered into the drilled hole, and the space surrounding it is lined with special casing pipes and cemented. The task of the direction is to prevent the erosion of the upper soil layer in the process of further drilling.
2. Further, to a depth of 500 to 800 meters, a shaft of a smaller diameter is drilled, into which a string of pipes, called a conductor, is lowered. The space between the walls of the pipe and the rock is also filled with cement mortar to the full depth.
3. Only after the arrangement of the direction and the conductor, the well is drilled to the depth specified by the project, and a string of pipes of an even smaller diameter is lowered into it. This column is called operational. If the formation depth is large, then it is possible to use the so-called intermediate tubing strings. The entire space between the wellbore and the surrounding rock is filled with cement.

What is the main purpose of a conductor? The fact is that at depths of up to 500 meters there is an active zone of fresh waters, and below this depth (depending on the region of development) a zone with difficult water exchange begins, in which there is a lot of salt water and other mobile fluids (including gases and oil). ). So, the main task of the conductor is additional protection, which prevents salinization of surface fresh water and does not allow harmful substances that are concentrated in the lower layers to penetrate into them.

What are wells?

Depending on the geological conditions in which oil fields are located, different types of such workings are drilled.

Main types of wells:

• vertical;
• obliquely directed;
• horizontal;
• multilateral or multilateral.

A well is called vertical if the angle of deviation of the wellbore from the vertical is not more than five degrees.

If this angle is more than five degrees, then this is already an obliquely directed type.

A well is called horizontal if the angle of deviation from the vertical of its wellbore is approximately equal to 90 degrees. However, there are some nuances to this definition. Since “straight lines” are rarely found in wildlife, and the developed reservoirs most often lie with some slope, then from a practical point of view, drilling strictly horizontal wells, as a rule, does not make sense.

It is easier and more efficient to direct the trunk along the optimal trajectory of occurrence. Based on this, it is possible to define the horizontal type of such workings as a well, which has an extended shaft, drilled as close as possible to the direction of the target productive formation, while maintaining the optimal azimuth.

Wells with two or more wellbores are called multilateral or multilateral wells. Their difference from each other is in the location of the branching point, in which additional ones depart from the main table. If this point is located above the level of the productive horizon, then this type of development is called multilateral. If this point is located within the productive horizon, then this is a multilateral type of well.

Simply put, if the main wellbore is drilled to the reservoir under development, and additional offshoots are drilled inside it, then this is a multilateral type (the productive reservoir breaks through at one point). All other workings with several shafts are referred to as multilateral (several points of formation penetration). Also, this type of wells is typical in cases where the layers are located at different horizons.

In addition, there are cluster wells. In this case, several trunks diverge at different angles and to different depths, and their mouths are close to each other (like a bush planted upside down).

This classification provides for the following categories of such mine workings:

Exploratory drilling is carried out in areas whose oil or gas content has already been established in order to clarify the volumes of discovered hydrocarbon deposits and to clarify the initial parameters of the field, which are necessary when designing a field development method, therefore special attention is paid to exploration.

Production drilling creates workings of the following types:

• main (producing and injection);
• reserve;
• control;
• appraisal;
• duplicating;
• wells for special purposes (absorption, water intake, and so on).

The extraction of raw materials itself is carried out through mining workings, which are pumping, gas lift and fountain.

The purpose of injection wells is to influence the reservoir under development by injecting steam, gas or water into it, as well as other working media. They are intra-contour, near-contour and contour.

Reserves are necessary for the development of separate and stagnant zones, as well as wedging zones that are not included in the contour of the main wells.

The control ones are needed to monitor the current position of the zones of contact between the extracted resource and water and other changes in the reservoir under development. In addition, they control the pressure in productive formations.

Estimated ones are needed for a preliminary assessment of deposits being prepared for development. They help to determine the boundaries and sizes of reserves, as well as other necessary preliminary parameters.

Duplicating ones are used during the replacement of wells of the main stock that are being liquidated due to physical wear or accidents.

Technical water is extracted through special ones, commercial water is discharged, open fountains are eliminated with their help, and so on.

The process of drilling an oil well, according to the nature of its impact on rocks, is:

• mechanical;
• thermal;
• physical and chemical;
• electric and so on.

Oil well construction

Industrial development of deposits implies the use of only mechanical methods that use different drilling modes. All other drilling methods are under experimental development.

Mechanical drilling methods are divided into rotary and percussion.

The impact method is the mechanical destruction of rock, which is performed by a special tool suspended on a rope - a chisel. The structure of such a drilling complex also includes a rope lock and a shock rod. This device is suspended on a rope, which is thrown over a block mounted on a drilling mast. The reciprocating movement of the bit is provided by a special drilling machine. The barrel acquires a cylindrical shape due to the rotation of the bit during operation.

The bottomhole is cleaned from the destroyed rock using a bailer, which resembles a long bucket with a valve on the bottom. The tool is removed from the barrel, the bailer is lowered, its valve is opened in the bottomhole. The bucket is filled with liquid with pieces of rock, the valve closes, and the full bailer raises to the surface. Everything, you can continue drilling.

In Russia, percussive drilling is practically not used at the moment.

The rotational method is based on immersing the bit into the rock mass by simultaneously exposing the tool to both vertical load and torque. The vertical load allows the bit to sink into the rock, and then, with the help of torque, the bit shears, wears and crushes the rock.

According to the way the power unit is located, rotary drilling is divided into rotary and downhole drilling. In the first case, the engine is on the surface, and the torque is transmitted to the bottom by the drill pipe strings. In the second case, the engine is placed immediately behind the bit, and the drill string does not rotate (only the bit rotates).

The deepest well in the world is the Kola Superdeep (SG-3). Its depth is 12,262 meters. It was drilled in the Murmansk region to study the deep structure of the Earth.