RU2768785C1 - Method for restoring destroyed oil fields - Google Patents

Abstract

FIELD: oil industry.SUBSTANCE: invention relates to a method for restoring destroyed oil fields. According to the method, the geological and technological state of the deposit is analyzed, the system of drainage channels formed during the development of the productive reservoir between the injection and production wells along the restored section of the deposit is filled with a liquid working agent based on an aqueous cement solution with an added composition of fillers-additives selected according to the results of the analysis. The presence of a hydrodynamic connection between the injection and production wells in the field being restored is determined. Two days before the start of restoration work, oil production is stopped, all injection and production wells are stopped, and hydrodynamic processes in the subsurface are stabilized. In the injection well, tubing is installed 15 m above the perforation interval of the object being restored, technical means are installed and tied with technological pipelines with the injection well for the preparation and injection into the injection well of a working agent based on the aqueous cement solution with added fillers-additives prepared from sand and/or dredge, finely ground wood flour and sodium gluconate, the injection line is pressed to one and a half times the expected working injection pressure, from the dry part of the working agent using a cement mixing machine, a working agent is produced and simultaneously pumped into the injection well non-stop by a cementing unit. To maximize the coverage of the destruction zone, the first half of the working agent is pumped with a density of 1500-1600 kg/m3, the second with a density of 1600-1700 kg/m3, during the injection process, the density of the working agent injected into the well is controlled by sampling it every 5 tons of dry agent used, while monitoring the flow of the working agent into the producing well by sampling, when signs inherent in the selected sample of the working agent characterizing changes in the physical parameters of the liquid: specific gravity and/or electrical conductivity, the process of pumping the working agent into the injection well is stopped.EFFECT: injection and production wells are closed in anticipation of the solidification of the working agent in the drainage channels until the restoration of the destroyed sections of the field.3 cl, 4 dwg

Description

The present invention relates to the field of mining, namely, to the extraction of hydrocarbons by a hydrodynamic method through production wells. It can be used to develop flooded fields with hard-to-recover oil reserves.

Definitions, terms, phrases and their abbreviations used in the text:

- enclosing or productive deposits (layers) - rocks containing oil or other minerals;

- oil pillar (unrecovered oil) - an area in the depleted part of the deposit, in which oil remains unrecovered. The pillars can remain in separate interlayers, wedging out towards production (production) wells, as well as as a result of uneven advancement of the water-bearing contour (during the formation of flood tongues), when individual undeveloped sections of the reservoir are cut off by the advanced injected water. The formation of oil pillars leads to a decrease in the overall oil recovery factor [https://neft.academic.ru/418/%D0%A6%D0%B5%D0%BB%D0%B8%D0%BA%D0%B8%D0% BD%D0%B5%D1%84%D1%82%D0%B8];

- a destroyed field - an oil field, where in the course of many years of operation, the lithophysical structure of the enclosing deposits along their highly permeable directions between the injection and production wells has been destroyed by the hydrodynamic method;

- drainage channel (VSC) - a hydraulic structure formed in an operated facility between the injection and production (operational) wells in the course of many years of development of the field by the hydrodynamic method; VSK is formed as a result of gradual erosion and destruction of host deposits by water injected into the operating facility through an injection well through a reservoir pressure maintenance system; it is assumed that the minimum flow area of the VSK is not less than the diameter of the discharge pipe;

- lithophysical structure - a factor that determines the established physical form, hardness, porosity, permeability of the rock;

- working agent - an aqueous solution of cement with additional components - the initial state of the cement-wood stone;

- cement-wood stone (TsDK) - a working agent frozen in the drain channel, which has a design lithophysical characteristic;

- plasticizer - a special additive that improves the fluidity, plasticity of the working agent; some of them, for example, sodium gluconate, simultaneously act as cement setting retarders;

- gruss - terrigenous psephytic sedimentary rock formed as a result of mechanical destruction of rocks [ru.wikipedia.org>wiki];

- oil recovery factor (ORF) - the ratio of the volume of extracted oil to its recoverable reserves;

- abnormally high reservoir pressure (AHRP) - reservoir pressure exceeding hydrostatic pressure;

- well injectivity - a characteristic of an injection well, showing the possibility of injecting a working agent (water, gas, steam, etc.) into the reservoir; determined by the volume of the mixture injected into the reservoir per unit time [http://www.miningenc.ru/p/priemistost-skvazhiny/];

- maintenance of reservoir pressure - RPM;

- tubing - tubing;

- method of enhanced oil recovery - EOR.

As one of the options for field development, a hydrodynamic method is used to displace oil from a productive formation to production wells with the creation of a waterflooding front in the operated object. In the process of many years of development, the fields are gradually flooded, respectively, the rate of oil recovery is reduced.

In order to increase the level of production with increasing intensity, various methods (methods) of enhanced oil recovery (EOR) are used, for example, they are forcedly injected into the reservoir and fluid is withdrawn (FOL), hydraulic fracturing is carried out, the viscosity of the injected water is increased by adding various materials, including , polymer compounds, treat the flood front with surfactants. The use of EOR in flooded fields leads to only point successes, does not stop the decline in oil production. At the “final” stage of development in the predominant number of oil fields, the produced fluid consists of 95-99% water and, accordingly, 5-1% oil. The exploitation of such deposits turned out to be on the verge of profitability or unprofitability. Thus, in the current geological and technological conditions, the search for new technical solutions in the development of oil fields is relevant.

The content of the alleged invention is set out in the following two areas of a single problem: 1) analysis of field and geological materials of the object of application of the claimed method with the determination of its current geological and technological state, degree of destruction; 2) creation of an optimal method for restoring the destroyed sections of the deposit based on new information about its geological and technological state.

According to existing ideas, water injected into the reservoir through the reservoir pressure maintenance system (hereinafter referred to as RPM), simultaneously with the formation of a waterflooding front, is filtered through the most permeable deposits in an advanced mode to production wells without destroying their lithophysical structure. The currently used methods (methods) of enhanced oil recovery (EOR) of reservoirs are based on this definition.

At the same time, studies are known that confirm the destruction of the developed objects [Khisamutdinov N.I., Gilmanova R.Kh., Vladimirov N.V., Akhmetov N.Z., Abdulmazitov R.G., Sarvaretdinov R.G. Development of oil reservoirs at a late stage. Volume 1. Geology and development of a deposit at a late stage. - M.: OAO VNIIOENG. - 2004. - 252 p. - P. 104, p. 3], where, based on field geophysical methods of well research, the conclusion was made: "... after 30-50 years of development, the current formation porosity increases, which confirms the assumption of the destruction of reservoirs as a result of technogenic impact in the process of developing an oil field" .

Known article [Zapivalov N.P. (2020). Oil of the 21st century: a new paradigm. Georesources, Special issue. pp. 15-18. DOI https//doi.org/10.18599/grs.2020.SI.15-18], where the author notes: “Extreme (forced) development of easily accessible oil reserves (EOR Enhanced Oil Recovery) with prolonged use leads to rapid depletion and destruction of deposits ".

The main cause of destructive phenomena in the developed deposits is the forced injection of water into the reservoir, followed by the withdrawal of fluid from the reservoir and hydraulic fracturing of the exploited deposits from the beginning of the development of the oil field. This accelerates the narrowly directed advancing penetration of water to production wells along fractures and highly permeable interlayers. As a result, the enclosing deposits between the injection and production wells during 10-20 years of field operation, depending on the geological and technological conditions of development, are gradually eroded and destroyed, forming a system of drain channels (hereinafter referred to as VSK) [Mustafin I.A. Geological and technological results of the hydrodynamic method of developing oil fields in the Russian Federation on the example of the supergiants Romashkino and Samotlor. - Kazan: Folio. - 2018. - 88 p.].

With the formation of the VSC system, the water injected into the reservoir through the reservoir pressure maintenance systems and drain channels directly flows from the injection to the production well, without performing the expected work of displacing oil from productive deposits. With such a water flow through the VSC, there is a decrease in the technical hydraulic pressure on the waterflooding front, which is an adequate reason for reducing the rate of its advance along the reservoir up to a complete stop. [Mustafin I.A. Some results of in-loop flooding of oil fields. //Innovative technologies in geology and development of hydrocarbons: materials of the International Scientific and Practical Conference. - Kazan, September 9-11, 2009 - S. 294-295]. Under such conditions, individual sections of the reservoir with relatively low permeability remain unaffected by the flooding process in the form of unrecovered oil in the flooded oil field. The remaining intact oil reserves are moving into the category of hard-to-recover. For example, in the Romashkinskoye field, the share of hard-to-recover oil reserves increased from 30 to 80% compared to the original [Oil and gas potential of the Republic of Tatarstan. Geology and development of oil fields. In 2 volumes. Ed. Muslimov R. X. Kazan: FEN, - 2007, - 316 p.].

There are three periods of dynamic activity of injected water in the gradual process of long-term erosion of productive deposits, established by the method of applied logic and the principle of actualism, which correspond to the three hydrodynamic stages of oil field development [Mustafin I.A. Geological and technological results of the hydrodynamic method of developing oil fields in the Russian Federation on the example of the supergiants Romashkino and Samotlor. - Kazan: Ed. "Folio". - 2018. - 88 p. - S. 28-29] (see further Fig. 1 of the present description), where:

I - the stage of injected water filtration, II - the stage of washing out pelito-aleurite fractions from the enclosing deposits, III - the stage of destruction of the enclosing deposits;

A - the time of appearance of the first volumes of water in production wells;

B - time of maximum annual oil production;

C - the time of increasing water in the produced fluid up to 80%;

_ - the time of destruction (collapse) of the exploited deposits of the deposit and the formation of a system of drainage channels (indicated by a thick line).

The first (I) hydrodynamic stage of oil field development, lasting from the start of operation to time A, is characterized by:

- growth near the injection well of technogenic anomalously high formation pressure (AHRP) in the developed object;

- creation of a waterflooding front that displaces oil to production wells;

- an increase in the volume of produced anhydrous oil;

- the onset of time A.

The determining factor for allocating time A is the appearance of the first volumes of water (up to 1%) in the produced oil. For example, at the Romashkinskoye field (Republic of Tatarstan, Russian Federation), time A was reached 8 years after the start of production.

The second (II) hydrodynamic stage, lasting from time A to time B, is characterized by:

- intensive transformation of the activity of underground technogenic hydrodynamics around time B;

- deterioration of geological and technological conditions for creating and maintaining a waterflooding front;

- a progressive increase in the volume of injected water and produced water-oil emulsion and a corresponding increase in the washing out of solid fractions from the enclosing deposits; for example, at the Romashkinskoye field, the proportion of water in the produced fluid at time level B increased to 40%;

- formation of a point (section) of depression of technogenic anomalously high formation pressure (AHRP) near time (sign) B, as a result of the advance injected water reaching the radius of influence of the production well, where the process of destruction (collapse) of the lithophysical structure of the enclosing deposits begins, the formation of separate drain channels ( Fig. 1, Fig. 2);

- formation of a system of drainage channels VSK by connecting individual channels in the last quarter of the stage, as a man-made hydrodynamic structure between the injection and production wells in the subsoil.

The third (III) hydrodynamic stage, lasting from time B to infinity, is characterized by:

- a sharp increase in the proportion of water in the produced fluid from 40% in time B to 80% by time C, then gradually reaching 90-99%;

- lack of geological and technological conditions for creating a waterflooding front due to the active circulation of injected water in a direct-flow way through reservoir pressure maintenance systems (hereinafter referred to as RPM) and drain channels.

- a significant reduction in the volume of oil produced, followed by an irreversible decrease in it despite the progressive volume of injected water;

- destruction (collapse) of exploited deposits along previously developed channels for the penetration of advanced water, mass construction and integration of drain channels into a single system of VSC.

In connection with the above-described change in the current geological and technological characteristics of oil fields, according to the proposed invention, a method for increasing oil recovery is used, corresponding to the new conditions that have arisen. For example, they restore destroyed areas of productive deposits, while maintaining/improving their natural lithophysical properties. The essence of this improvement lies in the alignment of the lithophysical properties of the restored deposits and adjacent pillars with hard-to-recover oil reserves. For example, for a CFM installed in the depths, by analogy with pillars, a lower permeability and an increased hardness are selected than for previously destroyed - eroded highly permeable deposits of the restored object. In this way, a single hydrodynamic development object is created at the field.

Studies of the prior art by the applicant identified analogues of the proposed invention. When describing analogues, the terminology of their (analogues) descriptions is used.

Known invention "Method of developing an oil deposit" [Russian patent RU 2652243. IPC E21V 43/20 (2006.01); SPK E21B 43/20 (2018.08). Priority from 04/26/2017. Published on 25.04.2018. Bull. No. 12. Description of the invention to the patent]. In its essence, the “Method of developing an oil deposit” includes the extraction of oil through production wells and the injection of a working agent through injection wells in a cyclic mode with injection by a fixed cycle of injection and downtime by days, differs in that the average daily volume of injected water in the reservoir is determined during stationary waterflooding , water is pumped into injection wells at a pressure 10-15% less than the hydraulic fracturing pressure and in a volume three times greater than a certain average daily volume of water, and the injection is carried out during the day in combination with three days of downtime, while in production wells , hydrodynamically connected with the used injection wells for the injection time, reduce production by 70% or more up to a complete stop.

The disadvantage of using the known method for the development of destroyed fields is its low efficiency - only a very limited amount of oil is washed out, namely, a limited amount of oil accumulated in the volumes of the drainage canal system (hereinafter referred to as VSK). The reason for the low efficiency of the known method is the formation of the VSC system [Mustafin I.A. Geological and technological results of the hydrodynamic method of developing oil fields in the Russian Federation on the example of the supergiants Romashkino and Samotlor. - Kazan: Ed. "Folio". - 2018. - 88 p.] in developed deposits. After the formation of the VSC system, the water injected into the reservoir in a direct flow through the drain channels flows to the production wells without the formation of a waterflood front - the main (only) factor displacing oil to the production wells. For this reason, the use of the known method does not contribute to the optimal displacement of oil from the destroyed fields. The disadvantage significantly limits the scope of the known method according to patent RU 2652243.

Known invention "Method of increasing oil recovery of production wells" [Russian patent RU 2483201. IPC E21V 43/20 (2006.01). Priority from 21.10.2011. Published on 05/27/2013. Bull. No. 15. Description of the invention to the patent]. In essence, the well-known method of increasing oil recovery of production wells is based on the periodic injection of a working agent into injection wells, which are used as part of the production wells at a late stage of development of the deposit by transferring them to injection wells, differs in that the injection of the working agent is carried out at a gradual, during several months, an increase in pressure, excluding its breakthrough into neighboring wells and up to a value exceeding twice the formation pressure at the time of transfer of production wells to injection wells, and after the volume of the injected working agent becomes equal to the volume of fluid extracted from the production well for the entire period development before the transfer of production wells to injection wells, abruptly, from the condition of closing of cracks in the reservoir layers, the injection of the working agent into the injection wells is stopped, while the bottom water formed during the operation of the production wells is used as the working agent.

The disadvantage of this method when applied to destroyed fields is its inability to create/ensure the continuity (continuity) of the waterflooding front in the operated object, as the main operating factor in the displacement of oil to production wells. Therefore, in a known way, only the amount of oil that seeps into the VSC system from the surrounding productive deposits is washed onto the day surface, and oil remains remain in the productive formation. The disadvantage significantly limits the scope of the known method according to patent RU 2483201.

It is known to use aqueous solutions with various solid fillers as a way to isolate the absorption of solutions during drilling of oil wells.

Known "Method of isolation of layers with cement-silicate solutions" according to an application for a patent of the Russian Federation [application RU 2012151072. IPC E21B 33/138 (2006.01); C09K 8/467(2006.01). Priority from 28.11.2012. Published on 06/10/2014. Bull. No. 16. Text of the claims]. In essence, the method of isolating formations with cement-silicate mortars includes injecting a cement mortar with a setting accelerator into the near-wellbore zone, characterized in that plugging is carried out by cyclic sequentially alternating injection of sodium silicate solutions into the well (mass fraction from 20 to 45%, silicate module more than 2, 5) with a filler - wood flour (mass fraction not more than 3%) and cement mixed with an aqueous solution of sodium silicate (mass fraction not more than 5%) in a ratio to cement equal to 0.5, and the solutions of sodium silicate and cement are separated during injection buffer - fresh water in a volume of 10 to 15% of the volume of technological pipes lowered into the well, and the volume ratio of the cement slurry to the sodium silicate solution is from 0.3 to 0.7. In the technical solution according to the application RU 2012151072, wood flour particles soaked in liquid glass (silicate) are additional nuclei for structuring and accelerating the setting of the cement mortar.

The disadvantage of this method, when used to restore the destroyed sections of oil fields, is the impending deaf hard isolation of productive formations with clogging of the paths of oil advancement to production wells, which significantly limits or completely closes the possibility of exploiting individual sections of the field. The disadvantage significantly limits the scope of the known method according to the application RU 2012151072.

The invention "Method of developing oil deposits" is known [Russian patent RU 2383722. IPC E21B 43/20(2006.01). Priority from 18.02.2008. Published on 03/10/2010. Bull. No. 7. Description of the invention to the patent]. In essence, the “Method for developing oil deposits” includes flooding a productive formation through injection wells and extracting oil to the surface through production wells, leveling the movement of the waterflooding front in the formation and isolating the inflow of water in production wells, determining during the development of a field production wells that are flooded to the established limit values, and installation through watertight screens selected from among them, differs in that the maximum watered production wells are stopped and put into idle ones, and for the installation of watertight screens, those idle production wells are selected that are on the path of filtration flows from injection to production wells, at the same time, the path of movement of filtration flows is determined by pumping an individual tracer agent into each idle production well with a continuous mode of pumping water into injection wells. Based on the research results, the type, volume and structural-mechanical properties of insulating compositions for waterproof screens are determined. Chemical indicators are used as tracers: fluorescein, ammonium nitrate, urea, thiocyanate.

The disadvantage of this known method is that in the presence of an established system of drainage channels (VSC) man-made waterproof screen will be bypassed by injected water through other branches of the established system of VSC. At the same time, the possible installation of watertight screens in the enclosing sediments significantly complicates the development of fields, since it permanently closes the paths of hydrocarbon movement in the exploited area and decommissions certain sections of the field. This reduces the oil recovery factor for the field. The disadvantages significantly limit the scope of the known method according to patent RU 2383722.

Known invention "Method of isolating zones of catastrophic loss of drilling mud when drilling oil and gas wells" [patent of Russia RU 2270327. IPC E21B 33/13 (2000.01). Priority from 22.07.2004. Published on 02/20/2006. Bull. No. 5. Description of the invention to the patent]. The essence of this technical solution lies in the method of isolating the zones of catastrophic absorption of the drilling fluid in the well, including determining the interval of the isolated absorbing formation, lowering the drill string to the absorption zone and pumping into the well with the help of a cementing unit a hardening cementing slurry-carrier with a filler of fibrous material introduced into the cement slurry carrier in the process of pumping it into the well through a funnel installed at the upper end of the drill string, characterized in that before the preparation of the carrier slurry, the fitting of the mixer pot of the cement mixing machine, through which mixing water is supplied under pressure by the jet pump of the cementing unit CA -320M, is replaced with a fitting with a smaller diameter of 8-9 mm, which ensures the preparation and injection of a carrier solution from cement or gel cement, or clay solution into the well, in a volume of 7-8 m ³ in one hour, and the input of a filler, which is use tons of cord fiber, cotton production waste - uluk, is produced at the rate of 25-50 kg per 1 m ³ of the carrier solution, and after the cement mixture supply is stopped, the funnel is disconnected from the drill pipe string and a sealing head is installed instead of it, after which the cement mixture is forced into the absorbing layer under pressure.

The disadvantage of the known method when it is used to restore the destroyed sections of the productive formation is that the cement carrier solution injected into the well tightly clogs the pores and cracks of productive deposits, and in the case of using the gel cement or clay carrier solution, the isolation of the aquifer is short-term or does not occur at all, since the insulating material is eroded and carried away by the flow of injected water in the VSC system. The disadvantage significantly limits the scope of the known method according to patent RU 2270327.

The closest in essence to the claimed technical solution - the prototype is the invention "Method of developing an oil deposit" [Russian patent RU 2530007. IPC E21V 43/20 (2006.01); C09K 8/508 (2006.01). Priority from 07.11.2012. Published 10.10.2014. Bull. No. 28. Description of the invention to the patent]. In essence, the "Method of developing an oil deposit", including the selection of products through production wells, the injection of a working agent and a polymer-dispersed system through injection wells, differs in that the properties of the deposit are analyzed and the deposit is isolated with a porosity of productive formations of more than 5%, the density of mineralized water is determined in near-wellbore zone, changed as a result of injection ^of a working agent, at a density of mineralized water up to 1020 kg/m 100%, with a density of mineralized water from 1020 to 1100 kg/m ³ the polymer concentration is increased by at least 30%, with a density of mineralized water over 1100 kg/m ³ the polymer concentration is increased by at least 60% of the polymer concentration determined with water density up to 1020 kg/m ³ , while in the composition of the polymer-dispersed system using a dispersed phase with a particle size of not more than 90% of the size of the pores or cracks in the reservoir.

The disadvantage of using the prototype in the conditions of the "final" stage (the third hydrodynamic stage of development, Fig. 1) of destroyed oil fields are:

- the lack of a description of the degree of acceptability of the known method in the conditions of destroyed fields, when the injected water flows in a direct flow through the systems for maintaining reservoir pressure of the RPM and drainage channels of the VSK;

- the absence of geological and technological characteristics of the object of application introduces an element of incompleteness and uncertainty in the goal, makes it difficult to determine the optimal concentration of the polymer dispersed system (PDS) in the working agent, which, in turn, reduces the quality of the expected results;

- unpredictability of the expected/actual physical properties of the injected volume of PDS in reservoir conditions, casting doubt on the quality of the technical solution and the duration of the effect of increasing the volume of oil produced;

- the use of expensive polymeric materials unusual for the environment, moreover, in the presence of known and available natural materials, which is an undesirable factor, especially in large-scale projects.

The disadvantages significantly limit the scope of the prototype according to patent RU 2530007, make the prototype unsuitable for the recovery of oil fields destroyed by drainage channels.

The purpose of the proposed invention is to increase oil recovery from destroyed reservoirs of productive deposits operated with low productivity in conditions of high water cut in fields with hard-to-recover oil reserves, that is, in the conditions of the third (“final”) stage of field development.

The objectives are achieved by closing (plugging) the drainage channels of the VSC by the claimed method of restoring the destroyed productive deposits of the field between injection and production wells and by combining disparate pillars of oil into a single hydrodynamic object. To do this, perform an analysis of the geological and technological state of the field, determine the hydrodynamic relationship between injection and production wells. Formed during the development of a productive formation, the system of drainage channels of the VSC between the injection and production wells having a hydrodynamic connection throughout the field is alternately filled with a liquid working agent based on a cement mortar with fillers.

At the beginning of work on the restored section of the field, repair and isolation work is carried out at the injection and production wells surrounding it, the presence of a hydrodynamic connection between the injection and production wells in the restored work area is determined, two days before the start of restoration work, oil production is stopped, all injection and production wells, stabilize hydrodynamic processes in the subsoil, lift submersible pumps from production wells to the day surface, having a hydrodynamic connection with the injection well, through which the working agent will be injected. In the injection well, the open end of the tubing tubing is installed 15 m above the perforation interval of the object being restored, the technical means for preparing and pumping the working agent into the injection well are installed and tied with technological pipelines to the injection well, the injection line is pressurized to 1.5 times the operating pressure, and preparation of the dry part of the working agent from cement and added fillers, from the dry part of the working agent using a cement mixing machine, they are produced and the cementing unit is continuously pumped into the injection well with a water-based solution - a working agent, in order to better cover the zone of destruction of the exploited deposits, conventionally, the first half of the working agent is pumped with a density of 1500-1600 kg / m ³ , the second - with a density of 1600-1700 kg / m ³ , in case it is necessary to increase the injectivity of the injection well, a decrease in the density of the working agent below 1500 kg/m ³ , while every 5 tons of used dry agent a sample of the working agent is taken, the change in the specific gravity or electrical conductivity of the liquid entering the production well is monitored, when signs inherent in the working agent appear in this liquid, the injection process into the injection well is stopped, Tubing tubing in the injection well is lowered 15 m below the perforation interval of the restored reservoir, the residual working agent is flushed back into the gutter system, the tubing is raised 300 m above the perforation interval, the injection well is closed in anticipation of the hardening of the working agent in the water waste channels of the VSC , the development of the field is resumed after the restoration of all its destroyed sections and reservoir pressure.

The method differs in that it is alternately used in relation to all injection and production wells in the field being restored, having a hydrodynamic connection between themselves through a system of drainage channels. The VSC system in exploited deposits is formed when the water cut of the produced fluid, depending on the conditions of field development, reaches (according to statistics) 30% or more. The degree of water cut of the produced fluid in a production well is a relative indicator of the level of injectivity in a hydrodynamically unified injection well.

The method is characterized in that the dry part of the working agent consists of cement in the amount of 99.7-99.9% and wood flour up to 0.3%, sodium glucanate up to 0.25% of the total weight, used when the water cut of the produced liquid is 30-40 % (characterizes the relatively low injectivity of the injection well).

The method is characterized in that the dry part of the working agent consists of cement in the amount of 30.0%, river sand up to 70%, wood flour from 0.1 to 0.2%, sodium gluconate up to 0.25% of the total weight, used when the water cut of the produced fluid is 40-50% (characterizes a relatively average injectivity of an injection well) or 50-99% (characterizes a relatively high injectivity of an injection well).

The method is characterized in that the dry part of the working agent consists of cement in the amount of 30.0%, river sand from 20.0 to 50.0%, gravel (fine gravel) from 20.0 to 50.0%, wood flour from 0 ,1 to 0.2%, sodium gluconate up to 0.25% of the total weight, is used when the water cut of the produced fluid is 50-99% (characterizes the relatively high injectivity of the injection well), a concrete pump is used for injection.

The technical result of the implementation of the claimed method is the restored areas of the exploited deposits of the oil field in the volume of the system of drainage channels, filled with a working agent - an aqueous solution of cement with fillers. Hardening in the subsoil, the working agent acquires the configuration of drain channels - destroyed areas of the deposit, closes (plugs) the VSC system with a material with similar primary / improved lithophysical characteristics (porosity, permeability, hardness). Closing the drainage channels stops the unimpeded flow of water injected through the injection well to the production well, and helps to restore the waterflooding front. The movement of the restored hydrodynamic flooding front ensures the displacement of previously difficult-to-recover or non-recoverable oil from the pillars to the production well, and the resumption of profitable development of flooded fields.

The essence of the claimed technical solution is a method for restoring destroyed oil fields, including the study of the geological and technological characteristics of the object of action, hydrodynamic connections between injection and production wells, the search for lithophysical properties of destroyed deposits in the restored section of the field based on the results of core analyzes performed at the stage of exploration and early production drilling , characterized in that they stop production work on oil production at the site, prepare the dry part of the working agent based on cement with added components. A method characterized in that, depending on the injectivity of the injection well, the design lithophysical properties of the deposits to be restored, and the methods of using the working agent in the dry part, the following components are used:

1) cement. The content of cement is from 30.0 to 99.9% by weight of the dry part of the working agent. In this case, for example, Portland cement grade M400 GOST 31108-2003 is used;

2) sand. The sand content is from 0.0 to 70.0% by weight of the dry part of the working agent. By changing the concentration of sand in the working agent, natural or increased hardness of the cement-wood stone (CDC) is achieved, for example, an increase in the proportion of sand increases the hardness of the CFC and vice versa. In this case, for example, river sand is used according to GOST 8736 - 2014, the sand group is fine, fineness modulus (Mk) = 1.5-2.0 mm;

3) gruss (small gravel). The grus content is from 0.0 to 50.0% by weight of the dry part of the working agent. By changing the grus concentration in the working agent, a natural/improved (increased) hardness of the cement-wood stone is achieved, for example, an increase in the proportion of grus increases the hardness of the cement-wood stone of the CFM and vice versa. In this case, for example, gruss is used according to GOST 8267-93. The grit group is small, fineness modulus (MK)=2.0-10.0 mm;

4) finely ground porous materials, for example, wood flour. The content of wood flour is from 0.0 to 7.0% by weight of the dry part of the working agent. By changing the concentration of porous materials in the working agent, the permeability of the designed cement-wood stone of the CFA is regulated, for example, an increase in the proportion of wood flour increases the permeability of the CFA and vice versa. In this case, for example, wood flour according to GOST 16361-87 grade 180 or 200 with a predominant particle size of less than 0.17 mm, a standard humidity of 8%, a standard density of 100 to 140 kg/m ³ is used;

5) air. In the process of injection into the injection well, the working agent is aerated in a cement barrel (tank), enriched with air from 1.0 to 15.0% of the volume of the working agent; rarely used as a substitute for wood flour in order to increase the permeability of the CDC;

6) special additives. They improve the plasticity, mobility, stackability of the working agent, prolong its setting time, some of them, for example, sodium gluconate, simultaneously perform both of the above functions, use sodium gluconate in an amount of up to 0.25% by weight of the working agent.

The chemical composition of the main component of the working agent (CaO, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MgO and other oxidants) and restored sandy-silt-clay deposits (SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MgO and other oxidants) in the fields of the oil and gas provinces of the country, according to [https://poznayka.org/s19660t1.html], they are overwhelmingly identical. Identity allows us to assert that, according to the claimed method, the frozen working agent does not violate the requirements of ecology and corresponds to the geological and technical conditions for the operation of the restored oil field.

The type and concentration of the working agent components used are determined empirically in laboratory conditions, the dry part of the working agent is prepared from cement and added fillers, the dry part of the working agent is produced using a cement mixing machine and a cementing unit is continuously pumped into the injection well with a water-based solution - working agent, while in order to maximize the coverage of the destroyed areas, the conditional first half of the working agent is pumped with a density of 1500-1600 kg/m ³ , the second - with a density of 1600-1700 kg/m ³ , if it is necessary to increase the injectivity of the well, it is necessary to pump the working agent with a density below 1500 kg/m ³ , while every five tons of the used dry part of the working agent, a sample of the working agent is taken, injection is performed until the working agent appears in one of the production wells or up to the maximum design injection pressure at the wellhead of the injection well, after which the process pumping of the working agent is stopped, the well is closed for hardening of the working agent, the development of the field is resumed after the restoration of all its destroyed sections and reservoir pressure.

The implementation of the proposed invention is shown on the example of one pair of wells in the Abdrakhmanovskaya area, which is one of the central areas of the Romashkino oil field - along injection well No. 23508 and production well No. 3378. The geological and technological state of the object of action and the method of restoration work are illustrated by the figures - Fig. 1, Fig. 2, Fig. 3, Fig. 4.

On FIG. 1 shows the hydrodynamic stages of the development of an oil field, where: I - the stage of filtration of injected water, II - the stage of washing out pelito-aleurite fractions from the enclosing deposits, III - the stage of destruction of the enclosing deposits;

A - the time of appearance of the first volumes of water in production wells;

B - time of maximum annual oil production;

C - the time of increasing water in the produced fluid up to 80%;

_ - time of destruction (collapse) of exploited deposits of the field and

formation of a system of drainage channels between times (signs) B and C (indicated by a thick line).

On FIG. 2 on the section along the line of wells No. 1 and 2 shows the scheme of the destruction of the exploited reservoir, where:

1 - injection well; 2 - production well; 3 - object of operation;

4 - directional water with technogenic abnormally high reservoir pressure (AHRP);

5 - the starting point of the depression of the AVPD; 6 - the end point of depression AVPD;

7 - deposits under pressure below the initial formation pressure.

On FIG. 3, a schematic cross-section through the VSC shows the object of using the claimed method for restoring destroyed oil fields, where:

3 - object of operation; 8 - zone outside the front of waterflooding;

9 - zone of repeatedly washed deposits;

10 - drainage channel VSK, which according to the claimed method is filled with a working agent.

On FIG. 4 shows a piping diagram of an injection well with technical means, where: 11 - wellhead, 12 - annular valve, 13 - check valve, 14 - hydraulic vacuum mixing device, 15 - cement tank, 16 - mixing plant, 17 - cementing unit, 18 - connection to the RPM system, 19 - tee, 20 - gutter system, 21-22 - on-duty cementing and grouting units.

The Romashkinskoye field is located in the Republic of Tatarstan of the Russian Federation, discovered in 1948, has been developed for more than 70 years. The industrial development of the field, which began in 1953, is continued by the oil company PJSC Tatneft (Almetyevsk, Republic of Tatarstan). The field with balance oil reserves of 5 billion tons and dimensions of 65 × 75 km, according to the international classification, belongs to the supergiants; it is multi-layer, oil-bearing capacity was established in 22 layers of the Devonian and Carboniferous, the main oil reserves accumulated in the horizons D0 and D1 of the Devonian; the absolute mark of the roof of the D ₁ formation varies from 1430 to 1463 m.

Horizon D ₀ -D ₁ on the Abdrakhmanovskaya area is represented by fine-grained sandstone with a median grain size ranging from 0.1-0.2 mm to 1.5-2.0 mm, a group of fine sand, coarse-grained silt with a median grain size of 0, 05 to 0.01 mm. The cementing agent is clay. The porosity of highly productive formations (sandstones) is more than 16%, the permeability is more than 100 mD. Akishev. The structure of the terrigenous Devonian in the east of Tataria and some regularities in the distribution of oil deposits in it. Proceedings of TatNIPIneft, vol. VI. - L.: 1964. - S. 16-30].

Initially, the deposit was exploited by the flowing method. After lowering the initial abnormally high reservoir pressure (hereinafter referred to as AHRP) to hydrostatic, they switched to a hydrodynamic development method with in-loop waterflooding, dividing the field with rows of injection wells into 21 independent areas. The maximum level of oil production of 81.5 million tons was reached in 1970. Production at the level of about 80 million tons was maintained for 6 years and is gradually decreasing. In 2018, 15.49 million tons of oil were produced. To date, the estimated depletion of the Romashkinskoye field is about 90%. The exploited layers are flooded up to 95-99%. Accordingly, in the liquid extracted to the surface, the oil content decreased to 5 - 1%, depending on the well.

Since the beginning of the development of the Abdrakhmanovskaya area of the Romashkinskoye oil field, more than 90% of the initial recoverable reserves have been produced along the D ₀ -D ₁ horizons. During development, the water cut of these reservoirs reached more than 95%. In the horizon D ₀ -D ₁ on the Abdrakhmanovskaya area, long-term industrial work was carried out to increase the injection pressure to 0.70-0.75 from the vertical mountain pressure at the bottoms of injection wells, i.e. 1.3-1.6 times the initial formation pressure [Khisamov R.S. Features of the geological structure and development of multilayer oil fields. - Kazan: Ed. "Monitoring", 1996. - 288 p. - S. 46]. These data mean that at an initial formation pressure of 17.5 MPa, the pressure at the bottom of the injection wells rose to 28.0 MPa. In various years of development of productive formations, the pressure at the mouth of injection wells at the Romashkino oil field varied from 10.0 to 35.0 MPa [Khisamov R.S. Features of the geological structure and development of multilayer oil fields. - Kazan: - Monitoring, 1996. - 288 p. - S. 204, Tab. 4.19].

The high pressure used since the beginning of the development of the Abdrakhmanovskaya area in the reservoir pressure maintenance system (hereinafter referred to as RPM) led to hydraulic fracturing. Frequent change in RPM intensity in a wide range from low to high and vice versa, forced withdrawal and injection of liquid actively drained the exploited objects, contributed to the accelerated washing out of solid fractions, the destruction of their lithophysical structure and the formation of drainage channels (DSC) in directions with high permeability and fracturing.

An example of the geological and technological state of the object of action and the method of restoration work are illustrated by the figures - Fig. 1, Fig. 2, Fig. 3, Fig. 4.

The alleged invention is carried out in stages, for example, in the following way:

I stage. The geological and technological state of the object of application of the claimed method for restoring a destroyed oil field is analyzed. In the geological funds of the customer, they search for the results of the analysis of the core from the destroyed sections of the field, performed at the stage of drilling exploration and first production wells, establish the design lithophysical properties of the recovered deposits,

II stage. Produce field preparation.

1. At the injection and production wells surrounding it, repair and insulation work is performed, the presence of a hydrodynamic connection between the injection and production wells at the work site is determined.

2. In the area to be restored, the operation of all injection and production wells is stopped, for example, for 48 hours and the hydrodynamic processes in the subsoil are stabilized before starting work.

3. Submersible pumps are raised to the day surface from production wells having hydrodynamic connection with the injection well, through which the working agent will be injected.

4. In the injection well, the open end of the tubing (hereinafter referred to as tubing) is installed 15 m above the perforation interval of the restored object.

5. Arrange special equipment, tie these technical means with the wellhead according to Fig. 4, where: 11 - wellhead, 12 - annular valve, 13 - check valve, 14 - hydraulic vacuum mixing device, 15 - cement tank, 16 - mixing plant, 17 - cementing unit, 18 - connection to the pressure maintenance system, 19 - tee , 20 - gutter system, 21-22 - on-duty cementing and grouting units.

6. Pressurize the discharge line to 1.5 times (one and a half times) working pressure.

III stage. The dry part of the working agent is prepared.

Empirically, for example, in laboratory conditions, the components (components) of the dry part of the working agent are selected, ensuring the achievement of the natural properties of the lithophysical parameters of the deposits of the restored area of the deposit, the combination and concentration of the components (materials). The duration of the solidification time of the aqueous solution of the working agent with the selected composition of the components (working agent) is determined.

The lithophysical properties of the rock of the recoverable reservoir D ₀ -D ₁ obtained by analyzing archival materials between injection well No. 23508 and production well No. 3378 of the Abdrakhmanovskaya area are as follows: porosity 15-20%, permeability 0.2 μm ² , hardness - cemented sandstone. Similar lithophysical properties of cement-wood stone for a restored productive formation are ensured by the use of an aqueous solution of a working agent of the following composition: cement grade M 400 GOST 31108-2003 - 30%, fine-grained river sand grade 300 GOST 8736-2014 - 69.8%, wood grade flour 200 GOST 16361-87 - 0.1%, sodium gluconate - 0.1% by weight of the dry working agent. For example, in terms of weight, to make up 9,000 tons of dry working agent, the following are used: cement - 2.700 tons, sand - 6.282 tons, wood flour - 0.009 tons, sodium gluconate - 0.009 tons.

For restored areas of the deposit with other lithophysical properties of the rock, providing reliable blockage of the water drain channels of the VSC and the necessary hardness, the permeability of the cement-wood stone (hereinafter referred to as the CDC) is regulated in a wide range by selecting components in the laboratory, for example, permeability from 0.01 up to 2.00 µm ² , the hardness of strongly cemented sandstone.

To significantly extend the life of the field, the components of the working agent are selected to provide increased hardness and reduced permeability compared to the natural lithophysical parameters of the recoverable productive deposits.

, например - вдвое, количестве от предполагаемого расхода. Например, в настоящем примере сухую часть рабочего агента - в количестве 18 тонн. Подготовленную сухую часть рабочего агента в 18 тонн в двух цементосмесительных машинах 2СМН-20, доставляют на участок работ и обвязывают с устьем скважины (Фиг. 4).The components of the dry part of the working agent, selected empirically, are thoroughly mixed, for example, in the conditions of a plugging company, until a uniform distribution of the selected components over the entire volume of the dry mass is achieved. To ensure the continuity of the recovery process, the dry part of the working agent is prepared in

, for example - twice the amount of the estimated expense. For example, in the present example, the dry part of the working agent is in the amount of 18 tons. The prepared dry part of the working agent of 18 tons in two 2SMN-20 cement mixing machines is delivered to the work site and tied to the wellhead (Fig. 4).

From the dry part of the working agent, using a cement mixing machine, a water-based solution - a working agent - is continuously pumped into the injection well by a cementing unit. In order to maximize the coverage of the destroyed sections of the formation, the conditional first half of the mass of the working agent is pumped with a density of 1500-1600 kg/m ³ , the second half - with a density of 1600-1700 kg/m ³ . Depending on the injectivity of the well, the density of the working agent is adjusted, for example, if it is necessary to increase the injectivity of the injection well, the density of the working agent is reduced below 1500 kg/m ³ , while every 5 tons of dry agent used, a sample of the injected working agent is taken.

The time of possible receipt of the working agent in the production well is determined by known geophysical methods, controlling the change in the specific gravity or electrical conductivity of the fluid in the production well. Changes in the physical parameters of the fluid in production well No. 3378 or an increase in pressure at the mouth of injection well No. 23508 to the maximum design level indicate the need to complete the process of pumping the working agent into the injection well.

IV stage. After the injection of the working agent is completed, the following final works are performed: the tubing pipes are lowered 15 m below the perforation interval, the residual working agent is flushed back into the trough system, the tubing is raised 300 m above the perforation interval, the injection well is closed in anticipation of the solidification of the working agent and reservoir pressure recovery;

The described actions, with the appropriate options for the composition of the working agent, are performed with all injection and production wells of the field, where a system of drainage channels has formed. The VSC system, depending on the field development conditions, is formed when the gradually increasing water cut of the produced fluid reaches (according to statistics) 30% or more.

The operation of the deposit is resumed after the restoration of all its destroyed sections.

The results of the work carried out according to the proposed invention significantly transform the underground technogenic hydrodynamics and the geological and technological state of the destroyed, watered up to 95-99% oil fields. The essence of the transformations lies in the fact that by closing the system of drainage channels (VSC) throughout the field, according to the claimed method, the paths of the "idle" direct flow of injected water from injection to production wells are blocked. Thus, conditions are provided for returning the oil field to operation at the level of its current depletion, to its original/improved state in terms of the determining lithophysical and geological and technological parameters.

Restoration of destroyed deposits according to the claimed method allows:

1) stop the destruction of exploited deposits;

2) to redesign field development technologies based on the restored hydrodynamic, lithophysical parameters of productive deposits;

3) replace the current development method with another method, for example, replace in-loop flooding with out-of-loop flooding;

4) to resume the development of the field by the hydrodynamic method with the restored waterflooding front;

5) to resume and increase the volume of production by involving in the development of hard-to-recover reserves from whole oil, to increase the oil recovery factor;

6) significantly reduce the level of water cut in the produced product.

The described results of using the alleged invention show the feasibility of the stated goal of the technical solution - there is a real possibility of restoring destroyed, operated with low productivity in high water cut fields with hard-to-recover oil reserves.

The given examples of the use of the proposed invention show its usefulness for the restoration of destroyed and therefore operated with low productivity in conditions of high watering of fields with hard-to-recover oil reserves, that is, in the conditions of the “final” stage of field development. The use of the claimed technical solution contributes to the increase, in comparison with the prototype, the oil recovery factor, increase the profitability of operation in conditions of high water cut in fields with hard-to-recover oil reserves.

The proposed invention satisfies the criteria of novelty, since when determining the level of technology in the field of mining, no tool was found that has features that are identical (that is, they match in terms of the function they perform and the form of execution of these features) to all the features listed in the claims, including the purpose characteristic .

The claimed technical solution meets the criterion of an inventive step due to its non-obviousness, the absence in world practice of methods similar to the claimed technical solution for the recovery of oil fields, since in the field of oil field exploitation technologies no technical solutions have been identified that have features that coincide with the distinctive features of the claimed invention and the popularity of the influence has not been established distinctive features on the specified technical result.

The claimed technical solution can be implemented in the commercial operation of oil fields, including high-watering, long-term exploitation in the activities of oil producing organizations, through the use of well-known standard technical devices, materials and equipment. This corresponds to the criterion of "industrial applicability" for inventions.

Claims (3)

1. A method for restoring destroyed oil fields, including taking products through production wells, pumping a working agent through injection wells, determining natural lithophysical properties - hardness, porosity, permeability of a productive formation, determining, identifying a hydrodynamic connection between injection and production wells, characterized in that analyze the geological and technological state of the field, formed in the process of developing a productive formation, a system of drainage channels - VSC between the injection and production wells along the restored section of the field, fill it with a liquid working agent based on an aqueous solution of cement with an added composition of fillers-additives selected according to the results of the analysis, why, on the restored section of the field, on the injection and production wells surrounding it, repair and insulation work is performed, the presence of a hydrodynamic connection between the injection and production wells is determined two days before the start of restoration work, oil production is stopped, all injection and production wells are stopped, hydrodynamic processes in the subsoil are stabilized, submersible pumps are raised to the day surface from production wells that have a hydrodynamic connection with the injection well, through which the working agent will be injected, the open end of the tubing (tubing) is installed in the injection well 15 m above the perforation interval of the restored object, the technical means for preparing and pumping the working agent based on an aqueous solution of cement with added additive fillers prepared from sand and / or grit, finely ground wood flour and sodium gluconate, pressurize the injection line for one and a half times the expected work which injection pressure is produced from the dry part of the working agent using a cement mixing machine and at the same time the cementing unit continuously pumps the working agent into the injection well, in order to maximize coverage of the destruction zone, the first half of the working agent is pumped with a density of 1500-1600 kg / m ³ ‚ the second with a density 1600-1700 kg / m ³ during the injection process, the density of the working agent injected into the well is controlled by sampling it every 5 tons of the used dry agent, while monitoring the flow of the working agent into the production well by taking samples, when the samples inherent in the working agent appear in the selected sample agent of signs characterizing changes in the physical parameters of the fluid - specific gravity and / or electrical conductivity, the process of pumping the working agent into the injection well is stopped, tubing in the injection well is lowered 15 m below the perforation interval of the restored reservoir a, flushing flushes the residual working agent from the tubing into the gutter system, after which the tubing (tubing) is raised 300 m above the perforation interval, the injection and production wells are closed in anticipation of the hardening of the working agent in the drainage channels - VSC until all damaged areas are restored Place of Birth. 2. The method according to p. 1, characterized in that, according to the results of the analysis, the components of the working agent are selected based on an aqueous solution of cement with fillers-additives, which, after hardening of the working agent in the system of drain channels - VSK between the injection and production wells, form a closing, plugging VSK cement-wood stone with improved lithophysical properties - with greater hardness and lower porosity and permeability compared to destroyed deposits. 3. The method according to p. 1, characterized in that the individual composition of the working agent, selected according to the results of the analysis of the lithophysical properties of the destroyed deposits, is used in turn for all wells that have a hydrodynamic connection with each other through a system of drainage channels, restore the hydrodynamic unity of the development object, after restoration of all destroyed areas and reservoir pressure resume the operation of the field.

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