The development of oil fields is understood to mean the control of the movement of oil in deposits to oil producing wells by proper placement and sequential commissioning of the entire given stock of oil production and water-gas injection wells in order to maintain their intended modes of operation with uniform and economical consumption of reservoir energy.

A rational system for the development of deposits provides for the solution and implementation of the following measures.

· Allocation of production facilities in a multilayer field and determination of the order of their commissioning. Operational object - a productive formation or a group of formations developed by an independent grid of wells while ensuring the control and regulation of their process exploitation... Production facilities in a multilayer field are subdivided into

basic (basic) - more studied, highly productive and relatively large in terms of reserves oil layers.

Recoverable - less productive and with less reserves, the development of which is planned to be carried out by returning wells from the base object.

Determination of the grid of wells, placing them on operational facility and the procedure for putting wells into operation. The placement of wells on objects can be uniform on deposits with fixed oil-bearing contours in the presence of bottom water or in the absence of formation water at all. In fields with moving oil-bearing contours, wells at the facilities are placed in rows parallel to the oil-bearing contours.

Distances between wells and well rows are selected taking into account the geological structure of the production facility in order to cover the development of all areas of the productive strata, as well as for economic reasons. It is necessary to strive to drill out objects with a sparse grid so that there is no interference between oil producing wells. This will ensure high productivity for each well. However, due to the lithological heterogeneity of productive layers, it is possible to leave undeveloped pillars oil.

· Establishing the operating mode of oil producing and water injection wells is reduced to planning the rate of oil withdrawal and water injection into the reservoir to maintain reservoir pressure for a certain period of time. The flow rates and injectivity of wells can be very diverse and depend on the geological structure of the productive formations and the accepted operating modes of the deposits. Well operation modes change over time depending on the state of reservoir development (position of the oil-bearing contour, water cut, breakthrough gas to them, technical condition operational columns used equipment for lifting fluid from the formation to the surface, pumping a working agent into the formation (water, gas) to maintain reservoir pressure, etc.).

· Regulation of the balance of reservoir energy in oil deposits is carried out by influencing the reservoir as a whole. Currently, the main method of intensification mining oil - maintaining reservoir pressure by artificial waterflooding. In some fields, injection is also carried out gas v gas hat.

Waterflooding occurs:

Zakonturnoe,

Borderline,

· In-circuit.

In-line waterflooding is used in the development of relatively small deposits. Injection wells are located behind the oil-bearing contour at a distance of 200-100 m and more.

Surface waterflooding is used in fields with low permeability of productive formations in the water part of the reservoir. The distance between the injection wells and the oil-bearing contour is very small or they are located directly on the oil-bearing contour.

Intra-contour waterflooding is used in a large field by dividing it by rows of injection wells into separate operational objects that are further exploited as independent deposits. Injection wells are located, taking into account the geological structure of the fields, mainly in highly permeable areas. At the same time, the power sources for the edge sections of the fields are the pressure of the edge waters and the pressure of water on the artificial flooding line by rows of water injection wells located near the contour oil content or several moved away from it, as well as rows of water injection wells drilled in oil parts of the reservoir. These in-line water injection wells are also power sources for other individual oil areas of deposits.

Basic concepts and characteristics of development systems

The field development system is understood as a set of measures for the extraction of hydrocarbons from the subsoil and the management of this process. The development system determines the number of production facilities, methods of influencing the reservoirs and the rate of extraction of hydrocarbons from them, the location and density of the grid of production and injection wells, the sequence of putting blocks and areas of the reservoir into development, methods and modes of well operation, measures to control and regulate the development process, protection of subsoil and the environment.

Development systems are justified in technological design documents.

The operational object is understood as a productive formation, a part of a formation or a group of formations allocated for development with an independent well grid. The formations combined into one development object should have similar lithological characteristics and reservoir properties of the rocks of productive formations, physicochemical properties and composition of the fluids saturating them, the values ​​of the initial reduced formation pressures.

On the basis of the sequence of putting individual objects into production drilling, the following field development systems can be distinguished.

Top-down development system. This system consists in the fact that each layer of a given field is first put into exploration and then into production mass drilling, but after the overlying layer has been mainly drilled (Fig. 10).

The top-down development system was organically linked to percussion drilling, in which isolation of one layer from another during drilling is achieved not by circulating mud, as in rotary drilling, but by running a special string of casing pipes to isolate each layer. With the percussion drilling technique, this development system was the most economical and, accordingly, the most widespread. Given the current state of science and technology, it does not allow effective use of the existing drilling technique and data from electrometric well surveys. In addition, it severely delays the pace of development and exploration and is currently not being applied.

Rice. 10. Scheme of development of oil fields.

a- according to the "top-down" system, b- according to the system "bottom up"

Bottom-up development system. This system consists in the fact that first of all, the lowest of the high-rate horizons (strata) is drilled out. The development horizon is called the reference horizon (Fig. 10).

The main advantages of this system are as follows:

1) simultaneously with exploration and drilling of the reference horizon, all overlying formations are studied by logging and coring, which greatly reduces the number of exploration wells, while the structure of the entire field is illuminated at once;

2) the percentage of unsuccessful wells decreases, since wells that fall outside the contour of the reservoir in the reference horizon can be returned by operation to the overlying horizons;

3) the rate of development of oil fields is significantly increasing;

4) the number of accidents during drilling associated with the escape of the circulating fluid into the reservoir formations is reduced, and clay formation in the formations is significantly reduced.

Development system by floors. The floor-by-floor system is usually used in the development of multilayer fields, in the section of which there are two or three or more productive strata that are sustained along the strike and remote along the section.

On the basis of the sequence of the development of deposits in rows and the commissioning of wells, the development systems are subdivided into phased and simultaneous (continuous).

In a staged system of reservoir development, first, two or three rows of wells are drilled closest to the row of injection wells, while leaving a significant part of the reservoir not drilled. Calculations and field development experience similarly show that drilling the fourth row of wells does not increase the total oil production due to well interference. Therefore, drilling of the fourth row starts when the first row of wells is watered and goes out of operation. The fifth row is drilled simultaneously with the exit from the second row of wells, etc.

Each replacement of an external row of wells with an internal one is called a development stage. Such a system of drilling in rows in the case of development from the contour to the roof resembles a creeping system of continuous drilling along the rise and differs from it in that not all wells are in operation at the same time, but not more than three rows.

With a simultaneous development system, the reservoir is covered by flooding simultaneously over the entire area.

Classification of reservoir development based on the impact on the reservoir

The current state of technology corresponds to the following division of methods for the development of oil deposits based on the impact on the reservoir:

1) development method without maintaining reservoir pressure;

2) a method of maintaining pressure by pumping water;

3) a method of maintaining pressure by pumping gas or air;

4) vacuum process;

5) compressor-circulation method for the development of condensate deposits;

6) in-situ combustion method;

7) the method of cyclic steam injection.

Development without reservoir pressure maintenance is used in cases where the pressure of the edge waters provides an elastic-water pressure regime in the reservoir during the entire operation period or when, for one reason or another, it is economically unprofitable to organize the injection of gas or water into the reservoir.

In cases where the formation water pressure cannot provide an elastic-water pressure regime, the development of a deposit without maintaining reservoir pressure will necessarily lead to the manifestation of the dissolved gas regime, and therefore to a low utilization rate of reserves. In these cases, it is necessary to artificially maintain reservoir pressure.

If it is assumed that the oil field will be developed during the main period under the dissolved gas regime, which is characterized by a slight movement of the water-oil section, i.e., with a weak activity of the marginal waters, then apply a uniform, geometrically correct location of wells on a square or triangular grid. In the same cases, when a certain movement of the oil-water and gas-oil sections is assumed, the wells are located taking into account the position of these sections.

The water injection pressure maintenance method aims to keep the reservoir pressure above bubble point pressure. This will ensure the development of the deposit with a hard water pressure regime. The latter makes it possible to develop a deposit before extracting 40-50% of reserves, mainly by the fountain method with a high rate of fluid withdrawal, and ultimately to obtain a high utilization rate of reserves - 60-70%.

Development systems with reservoir pressure maintenance, in turn, are subdivided into systems with perimeter, perimeter and intra-perimeter stimulation.

The method of maintaining pressure, in which water is pumped into the formation zone, is called zone waterflooding. It is rational to use in-line waterflooding when developing relatively narrow reservoirs (no more than 3-4 km wide), on which from three to five rows of production wells are located.

When developing large deposits, when water injection into the aquifer area will not be able to provide the specified rates of production and to cover the influence of the wells located inside the reservoir, it is advisable to use in-circuit waterflooding. Earlier, at the dawn of the development of methods of maintaining pressure by pumping water, a phased development system was used, which was a creeping system of development by rise or fall. In both cases, a conserved part of the deposit was formed, which is extremely undesirable. That's why when developing large deposits at present use in-circuit waterflooding.

Systems with intra-circuit impact are divided into in-line, areal, focal, selective, central.

In-circuit waterflooding also used in the development of lithological deposits, the boundaries of which are determined by the replacement of sandstones with clays. In these cases, water is pumped along the axis of the reservoir. Such waterflooding is called in-loop along the axis. If the injection is carried out in the center of a lithologically limited reservoir through one well, waterflooding is called focal. Practice has shown the effectiveness of such flooding of lithological objects consisting of a large number of lenticular deposits.

Over time, during focal flooding, adjacent production wells begin to flood, and after full flooding, they are transferred to water injection. Gradually, focal waterflooding turns into a central one.

Central waterflooding is called waterflooding, which is performed through three to four wells located in the center of the reservoir.

As a rule, central waterflooding through several wells immediately at the beginning of development is never carried out in practice.

In the practice of developing large reservoirs, both boundary waterflooding, intracontour waterflooding and focal waterflooding are used simultaneously.

When developing large platform-type oil deposits in Western Siberia, in-line development systems are used. A variety of them are block systems. With these systems, in the fields, usually in a direction transverse to their strike, rows of production and injection wells are located. In practice, three-row and five-row wells are used, which are, respectively, an alternation of three rows of production and one row of injection wells, five rows of production and one row of injection wells. With a larger number of rows (seven to nine), the central rows of wells will not be provided with the injection impact due to their interference with the wells of the outer rows.

The number of rows in in-line systems is odd due to the need to lay a central row of wells, to which it is supposed to pull the oil-water section when it is moved in the course of reservoir development. Therefore, the central row of wells in these systems is often referred to as the collapse row.

The distance between the rows of wells usually varies within 400 - 600 m (less often up to 800 m), between the wells in the rows - within 300 - 600 m.

With a three-row system, the reservoir is cut by rows of injection wells into a row of transverse strips with a width equal to four times the distance between the rows of wells. In a five-row system, the stripe width is equal to six times the distance between the rows. These development systems provide very fast drilling out of the reservoir. With these systems, at the beginning of the development of the reservoir, the lithological features of the reservoir are not taken into account.

Systems with areal wells. Let us consider the most commonly used in practice oil field development systems with areal wells: five-point, seven-point and nine-point.

Five-point inverted system (Fig. 11). The element of the system is a square with producers in the corners and an injection well in the center. For this system, the ratio of injection and production wells is 1/1.

Rice. 11. Location of wells with a five-spot inverted development system

Seven-point inverted system (Fig. 12). The system element is a hexagon with production wells in the corners and an injection well in the center. The production wells are located in the corners of the hexagon and the injection wells are located in the center. The ratio is 1/2, that is, there are two producing wells for one injection well.

Rice. 12. Location of wells in a seven-spot inverted development system

1 - conditional oil-bearing contour, 2 and 3 - injection and production wells, respectively

Nine-point inverted system (Fig. 13). The ratio of injection and production wells is 1/3.

Rice. 13. Location of wells with a nine-spot reverse development system

1 - conditional oil-bearing contour, 2 and 3 - injection and production wells, respectively

The most intensive of the considered systems with areal wells is five-spot, the least intense is nine-spot. It is considered that all areal systems are "rigid", since it is not allowed to use other injection wells to displace oil from this element without violating the geometric ordering of wells and flows of substances moving in the formation, if the injection well belonging to this element cannot be operated for those or for other reasons.

Indeed, if, for example, in block development systems (especially in three-row and five-row) any injection well cannot be operated, then it can be replaced by an adjacent one in the row. If the injection well of one of the elements of the system with an areal arrangement of wells is out of order or does not accept the agent injected into the formation, then it is necessary either to drill another such well (focus) at some point of the element, or to carry out the process of displacing oil from the formation due to more intensive injection working agent into injection wells of neighboring elements. In this case, the ordering of flows in the elements is greatly disturbed.

At the same time, when using a system with an areal location of wells, an important advantage is obtained in comparison with an in-line one, which consists in the possibility of a more dispersed impact on the formation. This is especially important during the development of highly heterogeneous formations in area. When using in-line systems to develop highly heterogeneous formations, the injection of water or other agents into the formation is concentrated in separate rows. In the case of systems with areal wells, injection wells are more dispersed over the area, which makes it possible to expose individual sections of the formation to greater impact. At the same time, as already noted, in-line systems, due to their greater flexibility compared to systems with areal wells, have the advantage of increasing the vertical sweep of the reservoir. Thus, in-line systems are preferred when developing highly heterogeneous formations along the vertical section.

At a later stage of development, the formation is largely occupied by an oil-displacing agent (for example, water). However, water, moving from injection wells to producing wells, leaves in the formation some zones with high oil saturation, close to the initial oil saturation of the formation, that is, the so-called pillars of oil. In fig. 14 shows pillars of oil in an element of a five-spot development system. To extract oil from them, in principle, it is possible to drill wells from the reserve ones, as a result of which a nine-point system is obtained.

In addition to those mentioned, the following development systems are known: a system with a battery (ring) arrangement of wells (Fig. 15), which can be used in rare cases in circular formations in plan; system for barrier flooding used in the development of oil and gas deposits; mixed systems - a combination of the described development systems, sometimes with a special arrangement of wells, are used in the development of large oil fields and fields with complex geological and physical properties.

Rice. 14. Element of the five-point system, which can be transformed into an element of the nine-point system of well placement

1 - "quarter" of the main production wells of the five-spot element (corner wells), 2 - pillars of oil (stagnant zones), 3 - additionally drilled production wells (side wells), 4 - the flooded area of ​​the element, 5 - injection well

Rice. 15. Scheme of battery well location

1 - injection wells, 2 - conditional oil-bearing contour, 3 and 4 - production wells, respectively, of the first battery with a radius R 1 and the second battery with a radius R 2

In addition, they use selective pressure systems used to regulate the development of oil fields with a partial change in the pre-existing system.

In the case of application of methods of influence in the development of depleted deposits, they are called secondary. If they are used from the very beginning of the development of the reservoir, they are called primary. The vacuum process is a typical secondary process and is never applied from the outset.

The pressure maintenance method by gas injection is usually used in reservoirs that have a gas cap. Maintaining pressure by injecting gas aims to maintain the energy resources of the formation during operation. For this, from the very beginning of operation, gas is pumped into the roof of the structure through injection wells located along the long axis of the structure. In addition, gas injection is sometimes used for areal gas displacement of oil (Marietta method).

Thermal action on the reservoir is carried out by pumping hot water into the reservoir through injection wells. Hot water injection is used for waterflooding of formations containing highly paraffinic oil and having a temperature of about 100 ° C. Injection of cold water into such a formation leads to the cooling of the formation, to the precipitation of paraffin, which clogs the pores of the formation.

In the case when the impact on the reservoir by means of water injection is carried out after the development of the reservoir in the dissolved gas mode, two main stages can be distinguished: a) the period of waterless production, when the injected water goes to fill the drained voids occupied by low pressure gas, and to replace displaced residual oil; b) a period of progressive watering of production wells.

By the moment of water breakthrough into production wells, all pore space in the reservoir will be occupied by the liquid phase, therefore, the further waterflooding process will be steady: the amount of fluid produced per day will be equal to the daily volume of injected water.

Generalization of materials carried out American researchers, showed that the oil recovery factor under the dissolved gas regime is on average 20% of the geological reserves. The use of areal flooding at the last stage of development increases it to 40%. At the same time, the application of waterflooding at the very beginning of development increases the recovery factor from 60 to 85%. According to the calculations of American specialists, the final oil recovery of about 80% of the geological reserves is expected at the East Texas field.

You can specify four more parameters that characterize this or that development system.

1. The parameter of the density of the grid of wells S c, equal to the oil-bearing area per one well, regardless of whether the well is a production or injection well.
If the oil-bearing area of ​​the field is S, and the number of wells in the field is n, then S c = S / n. Dimension - m2 / well. In some cases, the parameter S sd is used, which is equal to the oil-bearing area per one production well.

2. Parameter А.B. Krylov N cr, equal to the ratio of recoverable oil reserves N to the total number of wells in the field N cr = N / n. Dimension of parameter = t / well.

3. A parameter equal to the ratio of the number of injection wells n n to the number of producing wells n d = n n / n d. The parameter is dimensionless. The parameter for a three-row system is approximately 1/3, and for a five-row system ~ 1/5.

4. Parameter p, equal to the ratio of the number of reserve wells drilled in addition to the fixed stock of wells in the field to the total number of wells. Reserve wells are drilled in order to involve in the development of parts of the reservoir that are not covered by development as a result of previously unknown features of the geological structure of this reservoir, as well as physical
properties of oil and its containing rocks (lithological heterogeneity, tectonic disturbances, non-Newtonian properties of oil, etc.).

If the number of wells of the main stock in the field is n, and the number of reserve wells is n p, then p = n p / n. The parameter p is dimensionless.

Generally speaking, the well grid density parameter S with can vary over a very wide range for development systems without stimulating the formation. So, in the development of super-viscous oil fields (with a viscosity of several thousand 10 -3 Pa * s), it can be 1 - 2 * 10 4 m 2 / well. Oil fields with low-permeability reservoirs (hundredths of a micron 2) are developed at S c = 10 - 20 * 10 4 m 2 / well. Of course,
the development of both high-viscosity oil fields and fields with low-permeability reservoirs at the indicated S c values ​​can be economically feasible with significant reservoir thicknesses, i.e., with high values ​​of the A.I. Krylov parameter or at shallow depths of the developed reservoirs, i.e. ... at low cost of wells. For the development of conventional reservoirs S c = 25 - 64 * 10 4 m 2 / well.

When developing fields with highly productive fractured reservoirs, S c can be equal to 70 - 100 * 10 4 m 2 / well and more. The parameter N cr also varies within a fairly wide range. In some cases it can be equal to several tens of thousands of tons of oil per well, in others it can reach up to a million tons of oil per well.

For oil field development systems without impacting the reservoir, the parameter is naturally equal to zero, and the parameter p can be, in principle, 0.1 - 0.2, although reserve wells are mainly provided for the system with impact on oil reservoirs.

For one and the same field, there are many systems that differ in the number of producing wells, in their location on the structure, in the method of influencing productive strata, etc., therefore, there is a need to formulate the concept of a rational development system. The following basic provisions are accepted as criteria for a rational development system.

· A rational development system should ensure the least degree of interaction between wells.

The minimum interaction between the wells is achieved by increasing the distance between them. On the other hand, as the distance between the wells increases, their total number in the field decreases, which leads to a decrease in the total well production rate. In addition, in the conditions of a heterogeneous reservoir, an increase in the distance between wells can lead to the fact that some of the oil-saturated lenses, half-lenses or interlayers will not be covered by the wells and they will not be involved in development. Thus, the smallest interaction between wells cannot serve as the only overarching criterion for the rationality of a development system.

· A rational system should provide the highest oil recovery factor.

Maximum oil recovery can be achieved with full coverage of the oil-producing formation by the displacement process. This condition, especially in heterogeneous formations, can be met by tighter well placement. In addition, since the highest coefficients are achieved in a water-driven regime, and natural water inflows often do not provide high rates of development, there is a need to create an artificial water-driven regime by pumping water or gas into the reservoir.

· A rational development system should ensure the minimum cost of oil.

Of the several development options considered in the design process, an option is selected that provides the highest oil recovery. The above criteria, although they correctly determine the benchmarks for choosing a development system, nevertheless, none of them can be taken as decisive, since they do not take into account the need for oil production. Therefore, the concept of a rational development system in its final form is formulated as follows: a rational development system should provide a given oil production at minimum costs and possibly high oil recovery factors.

Development design consists in the selection of such an option that would meet the requirements of a rational development system.

Starting the development design, the initial geological and physical data on the oil-producing reservoir and the properties of the liquids and gases saturating it are consistently determined; hydrodynamic calculations are performed to establish technological development indicators for several options, which differ in the number of wells, the method of impact on productive formations, well operation conditions, etc.; the economic efficiency of development options is calculated; economic and technological indicators of development are analyzed and a variant of a rational development system is selected.

The introduction of a rational development system allows achieving high technical and economic indicators in field development.

Since field development begins with the withdrawal of oil from the first exploration wells, it can be noted that the development system is dynamic and must be continuously improved over time.

Development is carried out on the basis of a trial operation project, a technological scheme of industrial or pilot-industrial development, a development project. In the development project, on the basis of exploration and trial operation data, the conditions under which the field will be exploited are determined: its geological structure, reservoir properties of rocks, physicochemical properties of fluids, saturation of rocks with water, gas, oil, reservoir pressures, temperatures, etc. Based on these data, with the help of hydrodynamic calculations, the technical indicators of reservoir exploitation for various options of the development system are established, an economic assessment of the options is made and the optimal one is selected.

Development systems envisage: selection of development objects, the sequence of putting objects into development, the rate of field drilling, methods of influencing productive strata in order to maximize oil recovery; the number, ratio, location and procedure for putting into operation production, injection, control and reserve wells; their mode of operation; methods of regulation of development processes; environmental protection measures. The development system adopted for a particular field predetermines the technical and economic indicators - the flow rate, its change over time, the oil recovery factor, capital investments, the cost of 1 ton of oil, etc. , effective environmental protection.

The main parameters characterizing the development system: the ratio of the oil-bearing area of ​​the field to the number of all injection and production wells (well grid density), the ratio of recoverable oil reserves of the field to the number of wells - recoverable reserves per well (development system efficiency), the ratio of the number of injection and production wells wells (intensity of reserves development); the ratio of the number of reserve wells drilled after the field was put into production with the aim of more complete oil recovery (reliability of the development system). The development system is also characterized by geometric parameters: the distance between the wells and the rows of wells, the strip width between the injection wells (with block-row development systems), etc. three-point) location of production wells; with moving oil-bearing contours, the location of the wells takes into account the shape of these contours. Systems for the development of oil fields without impact on the reservoir are rarely used; for the most part, the field is developed with waterflooding. The most widely used is block-row intra-contour waterflooding. Areal waterflooding systems are also created with a distance between wells of 400-800 m.

Along with the choice of a development system, the choice of an effective development technology is of great importance. The system and technology are in principle independent; different development technologies are used with the same system. The main technological indicators of the development process: current and cumulative production of oil, water, liquid; development rate, water cut of well production, reservoir pressure and temperature, as well as these parameters at characteristic points of the reservoir and well (at the bottom and the wellhead, at the boundaries of elements, etc.); gas factor in individual wells and for the field as a whole. These indicators change over time depending on the reservoir regimes (the nature of the appearance of in-situ forces driving oil to the bottom of the wells) and the development technology. An important indicator of the development of oil fields and the efficiency of the applied technology is the current and final value of oil recovery. Long-term development of oil fields under elastic conditions is possible only in some cases, because Usually, the reservoir pressure drops during development and a dissolved gas regime appears in the reservoir. The final oil recovery factor during development in this mode is small, rarely reaches (with good formation permeability and low oil viscosity) values ​​of 0.30-0.35. With the use of waterflooding technology, the final oil recovery factor increases to 0.55-0.6 (on average, 0.45-0.5). With an increased viscosity of oil (20-50.10 -3 Pa.s), it does not exceed 0.3-0.35, and with an oil viscosity of more than 100.10 -3 Pa.s - 0.1. Waterflooding under these conditions becomes ineffective. To increase the final value of the oil recovery factor, technologies are used based on physicochemical and thermal methods of stimulating the formation (see. Thermal methods of production). Physicochemical methods use oil displacement by solvents, high-pressure gas, surfactants, polymer and micellar-polymer solutions, solutions of acids and alkalis. The use of these technologies makes it possible to reduce the tension at the oil-displacing fluid contact, or eliminate it (displacing oil by solvents), improve the wettability of rocks with the displacing fluid, thicken the displacing fluid and thereby reduce the ratio of oil viscosity to fluid viscosity, making the process of displacing oil from formations more resilient and efficient. Physicochemical methods of reservoir stimulation increase oil recovery by 3-5% (surfactants), by 10-15% (polymer and micellar flooding), by 15-20% (carbon dioxide). The use of solvent displacement methods theoretically makes it possible to achieve full oil recovery. However, pilot work revealed a number of difficulties in the practical implementation of these methods of oil recovery: sorption of surfactants by the reservoir medium, change in their concentration, separation of compositions of substances (micellar-polymer flooding), extraction of only light hydrocarbons (carbon dioxide), reduction of the sweep efficiency (solvents and high-pressure gas), etc. Research is also being developed in the field of thermochemical methods of oil recovery under the combined action of heat and chemical reagents on the formation - thermal alkaline, thermopolymer flooding, the use of catalysts for in-situ reactions, etc. based on the introduction of bacteria into the oil reservoir, as a result of the vital activity of which substances are formed that improve the fluidity and facilitate the extraction of oil.

In the development of oil fields, 4 periods are distinguished: increasing, constant, sharply falling and slowly falling oil production (late stage).

At all stages of the development of oil fields, control, analysis and regulation of the development process are carried out without changing the development system or with its partial change. Regulation of the process of oil field development allows to increase the efficiency of oil displacement. Influencing the reservoir, they enhance or weaken filtration flows, change their direction, as a result of which previously not drained areas of the field are involved in development and an increase in the rate of oil extraction occurs, a decrease in associated water production and an increase in the final oil recovery factor. Methods for regulating the development of oil fields: increasing the productivity of wells by reducing the bottomhole pressure (switching to a mechanized method of operation, establishing a forced or optimal mode of well operation); shutdown of highly watered wells; increase in discharge pressure; additional production wells (reserve) or wells return from other horizons; transfer of the injection front; use of focal and selective waterflooding; insulation work; alignment of the inflow profile or well injectivity; impact on the bottomhole zone to stimulate the inflow (hydraulic fracturing, hydrosand-jet perforation, acidizing); application of physicochemical methods to enhance oil recovery (injection of sulfuric acid, surfactants, etc.). Development of shallow formations saturated with high-viscosity oil, in some cases, is carried out by the mine method (see).

Question 1. Give a definition to the concept of "oil and oil and gas fields".
Answer. Oil and oil and gas fields- These are industrial accumulations of hydrocarbons in the earth's crust, confined to one or more localized geological structures, i.e. structures located near the same geographical point. The hydrocarbon deposits included in the fields are usually located in strata or rock massifs with different distributions underground, often with different geological and physical properties. In many cases, individual oil and gas reservoirs are separated by significant strata of impermeable rocks or are located only in certain areas of the field.
Dictionary of oil and gas terms.

Question 2. Give a definition to the concept of "field development object".
Answer. Development object Is a geological formation (reservoir, massif, structure, aggregate of layers) artificially allocated within the developed field, containing commercial reserves of hydrocarbons, which are extracted from the subsoil using a certain group of wells.

Question 3. What are the main features of the development object?
Answer. The main features of the development object- the presence of commercial oil reserves in it and a certain group of wells inherent in this object, with the help of which it is developed.

Question 4. What types of development objects are subdivided?
Answer. Development objects sometimes subdivided into the following types: independent, i.e. currently under development, and returnable, i.e. one that will be developed by wells operating another object during this period.

Question 5. What is meant by a field development system?
Answer. The field development system is understood as a set of technological and technical measures aimed at extracting oil, gas, condensate and associated components from the reservoir, and managing this process.
Depending on the number, capacity, types and filtration characteristics of reservoirs, the depth of each of the productive layers, the degree of their hydrodynamic connectivity, etc. The field development system provides for the allocation of one, two or more development objects (operational objects) in its geological section. When two or more objects are identified in a field, a rational development system is justified for each of them.

Question 6. What system of field development is called rational?
Answer. A rational development system is called a development system that provides the most complete extraction of fluids from the reservoirs at the lowest cost. It provides for the observance of the rules for the protection of subsoil and the environment, takes into account the natural, production and economic characteristics of the area.

Question 7. What does the field development system include?
Answer. The development system includes a scheme and plan for drilling out deposits, taking into account measures to influence the formation.
Drilling scheme- This is the layout of the wells in the reservoir and the distance between the wells. Drilling plan provides for the volume, location and sequence of well drilling. Measures for stimulating the reservoir determine the stimulation system (location of reservoir pressure maintenance wells) and methods of enhanced oil recovery.
Abbreviations of names in the oil industry.

Question 8. What types of waterflooding are currently used?
Answer. The following types of waterflooding are currently used:
Zakonturnoye- injection wells are located outside the oil-bearing contour. It is used for small deposits with good reservoir properties.
Perimeter- injection wells are located at some distance from the oil-bearing contour within the water-oil part of the reservoir. The application conditions are the same as for the peripheral waterflooding, but with a significant width of the water-oil zone.
In-circuit waterflooding- has a number of varieties:
block flooding- the oil deposit is cut into strips (blocks) by rows of injection wells, within which rows of injection wells are placed, within which rows of production wells of the same direction are placed.
The width of the blocks is chosen from 4 to 1.5 km in accordance with the reservoir properties of the formation. The number of rows of production wells in block 3 (three-row) and 5 (five-row waterflooding).
The types of block flooding are:
axial flooding- for narrow elongated deposits;
central flooding- for small round-shaped deposits;
ring flooding- for large round deposits;
focal and selective waterflooding- to enhance the impact on poorly depleted areas of the deposit;
barrier flooding- it is used to isolate the gas cap from the oil part of the reservoir;
areal flooding- a kind of in-circuit waterflooding, in which, in conditions of a general uniform grid of wells, injection and production wells alternate in a strict pattern established by the development project document. This development system is more active than the above systems. Several variants of the shape of the grids and the mutual arrangement of injection and production wells are used, in which the development systems are characterized by different activity, i.e. different values ​​of the ratio of the number of injection and production wells. The most common are 5-point, 7-point and 9-point systems, the spacing between wells is 300, 400, 500, 600 and 700 meters.