Method for developing depleted and / or exhausted oil reservoirs with medium-viscosity oil using sub- and / or supercritical water

Abstract

FIELD: oil industry.SUBSTANCE: invention relates to a method for developing depleted and / or exhausted oil reservoirs with medium-viscosity oil. The method includes injecting a displacing agent into the formation through injection wells and extracting the product through production wells. A system of injection and production wells is formed on the deposit site, ensuring the area coverage of the inter-well space by the impact. Water in a subcritical and / or supercritical state is used as a displacing agent, which is injected at a temperature and pressure that ensures the formation of a stable high-temperature impact zone in the near-wellbore zone and / or interwell space and the initiation of intra-formational high-temperature processes. The impact is carried out in a cyclic mode or in a continuous injection mode with simultaneous production of products.EFFECT: increasing the efficiency of involving residual oil reserves in the production of depleted objects due to the formation of a stable high-temperature impact zone in the interwell space, increasing the mobility of the oil and intensifying the displacement of residual oil while ensuring the area coverage of the deposit area.12 cl, 4 dwg

Description

[0001] Technical field

[0002] The invention relates to the oil producing industry, in particular to technologies for developing oil fields at a late stage of operation and to methods for increasing oil recovery based on pumping displacing agents through injection wells and extracting products through production wells.

[0003] More specifically, the invention relates to methods for thermochemical action on depleted oil reservoirs with medium-viscosity oil, which provide for the area coverage of a section of the reservoir with a high-temperature agent and the use of water in a subcritical and / or supercritical state to initiate in-situ high-temperature processes aimed at increasing the oil recovery factor (including in-situ conversion and distillation of residual oil).

[0004] State of the art

[0005] Further in the text, the applicant provides terms necessary to facilitate a clear understanding of the essence of the declared materials and to eliminate contradictions and / or controversial interpretations when performing an examination on the merits.

[0006] Supercritical water (SCW) is a state of water in which it is under pressure and temperature exceeding its critical values ​​(critical points of water: temperature 374°C and pressure 22.1 MPa). In this state, water becomes a supercritical fluid, which does not distinguish between liquid and gas. [Al-Muntaser AA et al., Hydrothermal upgrading of heavy oil in the presence of water at sub-critical, near-critical, and supercritical conditions. Journal of Petroleum Science and Engineering, 184, 106-592.]

[0007] Subcritical water is a range of temperatures and pressures near the critical point of water, at which its physicochemical properties (density, dissolving power, permittivity, viscosity) change sharply, which affects the intensity of heat and mass transfer and the course of in-situ processes. [Al-Muntaser AA et al., Hydrothermal upgrading of heavy oil in the presence of water at sub-critical, near-critical and supercritical conditions. Journal of Petroleum Science and Engineering, 184, 106-592.].

[0008] Depleted (depleted) oil reservoir - an oil reservoir (development object) that is in a late stage of development, characterized by significant depletion of recoverable oil reserves and / or a high proportion of recovered oil relative to the initial recoverable reserves, as well as, as a rule, increased water cut of the extracted product and an altered fluid filtration regime in the interwell space due to long-term operation and flooding.

[0009] Medium-viscous oil is oil characterized by a dynamic viscosity under reservoir conditions in the range in which fluidity and the possibility of filtration in a porous medium are maintained, but at the same time, increased hydrodynamic resistance and a decrease in the efficiency of traditional water and / or thermal displacement are observed; in the context of the present invention, medium-viscosity oil is understood to mean oil with a dynamic viscosity under reservoir conditions from 10 to 500 mPa⋅s.

[0010] Thermochemical impact (TCI) is a complex impact on a formation, including the thermal effect of a high-temperature agent and the initiation of thermochemical processes of transformation of oil components and / or their interaction with the aqueous phase and rock, leading to an increase in oil mobility and / or oil recovery.

[0011] High-temperature agent - a displacing agent injected into a formation at temperatures significantly exceeding the formation temperature, providing heating of the porous medium and initiation of high-temperature processes; in the present invention, the high-temperature agent is water in a subcritical and / or supercritical state.

[0012] Area coverage of impact - the distribution of the high-temperature impact zone within the selected section of the reservoir, ensured by a system of injection and production wells and an injection mode in which the high-temperature agent impacts a significant part of the area of ​​the interwell space (as opposed to a local impact limited to the bottomhole zone).

[0013] High-temperature impact zone - the volume of the formation in the near-wellbore zone and / or interwell space in which the temperature and pressure created by the injection of the agent ensure the occurrence of thermochemical processes and a change in the properties of oil and / or rock compared to the initial state.

[0014] Intra-reservoir high-temperature processes are a set of processes initiated by the injection of a high-temperature agent, including hydrothermal transformation of high-molecular components of oil, redistribution of fractional composition, destruction of resin and asphaltene associates, as well as accompanying heat and mass transfer processes in a porous medium.

[0015] Thermochemical action mode (cyclic / continuous) - method of implementing agent injection:

[0016] a) the cyclic mode includes the stages of injection, holding (impregnation) and subsequent production;

[0017] b) Continuous mode includes continuous injection of agent with simultaneous production of products.

[0018] Hydrothermal conversion is one of the methods for modeling the processes of hydrocarbon generation (synthetic oil) and their subsequent transformation in the sedimentary strata in a water vapor environment using thermal methods of enhanced oil recovery [Kang, Zhiqin, et al. "A Review of In-Situ Shale Processing Technology." Applied Energy 269 (2020): 115121].

[0019] Hydrogenation is a chemical reaction involving the addition of gaseous hydrogen to saturate organic compounds. This reaction is generally possible in the presence of a catalyst in the reaction system [Maksimov, N.M. Hydrogenolysis and Hydrogenation of Middle Petroleum Distillate Components in the Presence of, 2011].

[0020] As of the filing date of this application, oil field development typically involves production stages based on the use of the natural energy of the reservoir (primary production) and subsequent stimulation of the reservoir through waterflooding (secondary production). As the energy potential is depleted and water cut increases, the effectiveness of these mechanisms decreases, while a significant proportion of residual oil reserves remains in the reservoir, due, among other things, to deteriorating sweep efficiency, increased viscosity and reduced oil mobility, and the development of uneven filtration flows. Involving these reserves in development requires technologies capable of purposefully modifying the properties of the oil and the conditions of its filtration in a porous medium.

[0021] Furthermore, when developing oil fields in the late stages of production, one of the key challenges is bringing residual oil reserves into production under conditions of high water cut, increasing heterogeneity of filtration flows, and declining efficiency of traditional waterflooding. Depleted oil reservoirs with medium-viscosity oil are characterized by deteriorating sweep efficiency, early breakthroughs through highly permeable channels and / or fractures, an increasing proportion of water in the produced product, and the limited effectiveness of localized bottomhole treatments. This collectively leads to reduced oil recovery rates and a decrease in the oil recovery factor.

[0022] To enhance oil recovery under such conditions, thermal and thermochemical methods are known. These methods involve injecting high-temperature agents and / or reagents into the formation, reducing oil viscosity and intensifying displacement processes. In recent years, scientific and patent literature has explored the use of water in subcritical / near-critical and supercritical states, which have increased enthalpy and altered physicochemical properties. This potentially allows for simultaneous improvement of heat and mass transfer efficiency and initiation of in-situ high-temperature processes for the conversion of oil components.

[0023] However, the applicability of the indicated approaches to developed objects with medium-viscosity oil, as well as the possibility of forming a stable zone of high-temperature impact in the interwell space with ensuring area coverage of the deposit area, require an analysis of known solutions, identification of their shortcomings and determination of the closest analogue (prototype) for subsequent substantiation of the distinctive features of the claimed method.

[0024] Methods for enhancing oil recovery and developing hydrocarbon reservoirs are known, based on the injection of displacing agents and / or thermal stimulation, including the use of high-temperature fluids. Scientific and technical literature and patent sources have shown that when injecting water in subcritical / near-critical and supercritical states, effects are possible due to a combination of thermal viscosity reduction, solvent-like effects, and in-situ reaction-driven transformations (aquathermolysis-like processes). However, limitations in the modes are also noted (in particular, the risk of coke formation / formation damage at excessive temperatures and exposure times).

[0025] Analog 1. A known method for developing high-viscosity oil and bitumen deposits involves creating a system of horizontal channels / collectors, injecting a heat transfer fluid into the formation, and extracting the product to the surface (patent RU 2330950 C1). A disadvantage of this solution, as applied to depleted formations with medium-viscosity oil, is its focus on high-viscosity / bituminous deposits and the structural and infrastructural tie-in to a specific formation drilling and heat transfer scheme. It does not address the task of initiating in-situ thermochemical processes with sub- / supercritical water and does not explicitly emphasize areal coverage through a system of injection and production wells.

[0026] Analog 2. A technical solution is known that involves generating and injecting a multicomponent thermal fluid containing supercritical water and CO2 into a reservoir (application CN106640007A, published May 10, 2017). According to the description, the thermal fluid is generated through a combination of fuel gasification stages in a supercritical water environment and subsequent "supercritical" combustion of the products, resulting in an injection flow for developing heavy oil deposits and reducing their viscosity. A disadvantage of the claimed method is its focus on the thermal fluid generation system and heavy oil deposits, whereas the claimed solution is structured as a method for developing a depleted formation with medium-viscosity oil with areal coverage of the deposit area and the initiation of in-situ high-temperature processes in the interwell space.

[0027] Analogue 3. A multi-stage method for extracting hydrocarbons from oil-kerogen-containing formations and a technological complex for its implementation are known (patent RU 2671880 C1, published 07.11.2018), which uses working agents based on water in subcritical, supercritical and "ultra-supercritical" states, as well as additional stages of low-temperature preparation of the bottomhole zone, acid / thermocatalytic effects, etc.; the description also mentions the possibility of circulating water through the formed high-temperature intra-formation zone after the extraction of hydrocarbons from the depleted formation (heat recovery).The disadvantage of this solution is its focus on low-permeability oil-kerogen-containing formations and extreme conditions, as well as the complexity of the technological complex and the lack of a formulation of the task of developing specifically depleted oil reservoirs with medium-viscosity oil with areal coverage of the impact due to the controlled injection of water in a subcritical and / or supercritical state through a system of injection and production wells.

[0028] Analogue 4. A known method for increasing the efficiency of hydrocarbon production (including from oil-kerogen-containing formations) and a technological complex implementing a cyclic sequence of thermochemical effects with the formation of a highly permeable "retort" in the near-wellbore zone and the injection of high-temperature water at ultra-high temperatures and pressures (patent RU 2726703 C1, published July 15, 2020). The disadvantage of this solution is its primary focus on the near-wellbore zone (local retort) and cyclic stimulation, rather than on areal interwell displacement / reservoir coverage; furthermore, the object and modes are oriented towards unconventional / kerogen systems and high-viscosity oils.

[0029] Analog 5. A known method for thermochemical treatment of an oil reservoir involves injecting a binary mixture (ammonium nitrate and sodium nitrite) with temperature and pressure control, with provision for injectivity determination, two-stage injection with a separating water pack, and mixture preparation immediately prior to injection (patent RU 2696714 C1, published 05.08.2019). A disadvantage of the claimed solution is that the effect is realized through exothermic reactions of reagents and relates primarily to localized treatment (stimulation) of the reservoir / bottomhole zone; the use of water in a subcritical and / or supercritical state as the main high-temperature displacing agent and the design of the method specifically for developing a depleted reservoir with areal coverage of the interwell space are not disclosed in this solution.

[0030] Prototype. The closest technical solution to the claimed one is a method for the combined treatment of formations containing hydrocarbons and / or solid organic matter, and a device for implementing the method (patent RU 2576267 C1, published February 27, 2016). This solution involves forming a working fluid based on water, primarily in a supercritical state, generating supercritical water on the surface, delivering it to the well via a thermally insulated pipeline, and feeding reactants (an organic compound and an oxidizer) into the reaction zone for exothermic heating / pressure increase and the formation of CO2 in a supercritical state, after which the working fluid is injected into the formation.

[0031] The disadvantages of the prototype in relation to the claimed solution are: orientation primarily towards deep-seated natural bitumen / heavy oils, low-permeability rocks and / or kerogen objects, significant connection to the device / infrastructure for the formation and delivery of the working agent and to the use of additional reagents for exothermic additional heating, the lack of formulation of the method specifically as the development of a depleted oil reservoir with medium-viscosity oil with ensuring areal coverage of the deposit area by exposure through a system of injection and production wells, oriented towards the interwell space and conditions of high water cut / heterogeneity, characteristic of the late stage of development.

[0032] Thus, the analysis of the state of the art shows the existence of solutions using thermochemical effects and / or water in a supercritical state, however, the known solutions are either focused on heavy / bituminous and oil-kerogen-containing objects and local (near-wellbore) effects, or focus on fluid generation systems, while not disclosing a method for developing depleted oil reservoirs with medium-viscosity oil, ensuring areal coverage of the deposit area and initiation of in-situ high-temperature processes during the injection of water in a subcritical and / or supercritical state under conditions characteristic of the late stage of development.

[0033] Disclosure of invention

[0034] The objective of the present invention is to create a method for developing depleted (depleted) oil reservoirs with medium-viscosity oil at a late stage of operation, ensuring an increase in the efficiency of involving residual oil reserves in production under conditions of high water cut and pronounced heterogeneity of reservoirs.

[0035] An additional objective of the invention is to ensure the formation and maintenance in the interwell space of a stable high-temperature impact zone with areal coverage of a section of the deposit by pumping water in a subcritical and / or supercritical state and selecting the impact mode (cyclic and / or continuous), which makes it possible to intensify the displacement processes and create conditions for intra-formational high-temperature processes aimed at reducing the viscosity and increasing the mobility of the oil.

[0036] The technical result achieved by implementing the claimed method consists in increasing the efficiency of developing depleted (depleted) oil formations with medium-viscosity oil at a late stage of operation by ensuring area coverage by the effect and the formation in the interwell space of a stable zone of high-temperature effect when injecting water in a subcritical and / or supercritical state.

[0037] The specified technical result is expressed, in particular, in the creation of conditions for the intensification of the displacement of residual oil and an increase in its mobility due to a decrease in the viscosity of the oil and a change in its structural-group and / or fractional composition as a result of intra-formational high-temperature processes initiated by a high-temperature agent, as well as in increasing the efficiency of involving residual oil reserves in the development of heterogeneous reservoirs with high water cut.

[0038] Additionally, the technical result is manifested in an increase in the technological controllability of the impact process due to the possibility of implementing the method in a cyclic mode (injection - holding - production) and / or in a continuous injection mode with simultaneous production, which makes it possible to adapt the impact parameters to the geological and physical conditions of a specific section of the deposit.

[0039] The invention relates to methods for developing depleted (depleted) oil reservoirs with medium-viscosity oil at a late stage of operation and is implemented by injecting a high-temperature displacing agent through a system of injection wells with simultaneous / subsequent extraction of products through production wells.

[0040] A method for developing exhausted (depleted) oil formations with medium-viscosity oil includes injecting a displacing agent into the formation through an injection well and extracting products through a production well, characterized in that a system of injection and production wells is formed in the reservoir section, ensuring area coverage of the interwell space by the action, and water in a subcritical and / or supercritical state is used as a displacing agent, which is injected at a temperature and pressure that ensure the formation in the bottomhole zone and / or interwell space of a stable zone of high-temperature action and the initiation of intra-formational high-temperature processes, wherein the action is carried out in a cyclic mode or in a continuous injection mode with simultaneous production of products.

[0041] An embodiment is possible, according to which the impact is carried out in a cyclic mode, including the stages of pumping water in a subcritical and / or supercritical state, maintaining (impregnating) the formation under conditions of elevated temperature and pressure and subsequent production of products, after which the cycle is repeated.

[0042] An embodiment is possible, according to which the impact is carried out in the mode of continuous injection of water in a subcritical and / or supercritical state with simultaneous production of products through production wells.

[0043] An embodiment is possible in which water is pumped in a subcritical state at a temperature below the critical temperature of water (T < 374°C) and a pressure that ensures that the water is predominantly in the liquid phase at a given temperature.

[0044] An embodiment is possible in which water is pumped in a supercritical state at a temperature above the critical temperature of water (T> 374°C) and a pressure above the critical pressure of water (P> 22.1 MPa).

[0045] An embodiment is possible, according to which the temperature and pressure parameters of the injected water are selected in such a way as to ensure a subcritical and / or supercritical state of water in the bottomhole zone of the injection well and / or in the high-temperature impact zone in the interwell space.

[0046] An embodiment is possible, according to which a system of injection and production wells is formed according to an area development scheme, including at least one injection well and at least one production well within the impact area.

[0047] An implementation option is possible, according to which the impact is carried out at a late stage of development with increased water cut of the extracted product, typical for developed objects.

[0048] An embodiment is possible, according to which the impact is carried out on formations with medium-viscosity oil, the dynamic viscosity of which under formation conditions is from 10 to 500 mPa⋅s.

[0049] An embodiment is possible, according to which reagents and / or a catalytically active component in the form of a water-soluble and / or oil-soluble precursor of transition metal compounds are additionally introduced into the injected water.

[0050] An embodiment is possible in which compounds of nickel, iron, cobalt and / or molybdenum are used as transition metal compounds.

[0051] An embodiment is possible, according to which the supply of water in a subcritical and / or supercritical state is carried out with control and regulation of the temperature and pressure at the mouth of the injection well and / or on the surface in the water preparation unit.

[0052] The technical result specified in the section is achieved by the fact that in the claimed method, water in a subcritical and / or supercritical state is used as a high-temperature displacing agent, which is pumped into the formation at a temperature and pressure that ensure the formation in the near-wellbore zone and / or interwell space of a stable high-temperature impact zone and the initiation of intra-formation high-temperature processes that contribute to an increase in the mobility of oil and the efficiency of displacement of residual oil.

[0053] The essential features of the claimed method are:

[0054] • formation (selection / organization) of a section of a deposit with the placement of a system of injection and production wells on it, ensuring area coverage of the impact (interwell impact, and not just local treatment of the bottomhole zone);

[0055] • preparation of water on the surface to the parameters of a subcritical and / or supercritical state (heating and increasing pressure) and its supply to the formation through an injection well;

[0056] • maintaining injection parameters that ensure the occurrence of thermochemical action in a porous medium and the creation of conditions for intra-formational high-temperature processes;

[0057] • the possibility of implementing the impact in a cyclic mode (injection - holding - production) and / or in a continuous injection mode with simultaneous production, with the selection of the mode for the geological and physical conditions and the stage of depletion of the object.

[0058] In preferred embodiments of the method:

[0059] • in subcritical mode, water is pumped at a temperature below the critical temperature (T < 374°C) at a pressure that ensures that the water is predominantly in the liquid phase at a given temperature and its stable supply to the formation;

[0060] • in supercritical mode, water is pumped at a temperature and pressure above critical values ​​(T> 374°C and P> 22.1 MPa), ensuring that it remains in a supercritical state in the near-wellbore zone and / or in the impact zone;

[0061] • the implementation of subcritical conditions (near the critical parameters of water) is allowed, in which the physicochemical properties of water change significantly, affecting heat and mass transfer and the nature of intra-reservoir processes.

[0062] The formation and maintenance of a high-temperature impact zone in the interwellbore space enhances heat and mass transfer, reduces oil viscosity through thermal stimulation, and creates conditions for in-situ high-temperature processes, including hydrothermal transformation of high-molecular oil components, redistribution of fractional / group composition, and weakening of associative interactions between resin-asphaltene components. These factors, taken together, lead to increased oil mobility and improved residual oil displacement efficiency under conditions typical of depleted reservoirs (high water cut, heterogeneity, and the presence of highly permeable channels and / or fractures).

[0063] In one embodiment of the method, a reagent composition / catalytically active component (in the form of a water-soluble and / or oil-soluble precursor of transition metal compounds) is additionally introduced into the injected water. This component enhances the thermochemical processes that transform oil components in the high-temperature impact zone. This embodiment is considered an optional implementation of the method and is used when intensification of in-situ processes is necessary, taking into account the geological and physical conditions of the development site.

[0064] The claimed method is intended for use on depleted oil reservoirs with medium-viscosity oil and provides a technologically controlled effect due to the selection of water parameters (subcritical and / or supercritical state), the configuration of the well system and the implementation mode (cyclic / continuous), which makes it possible to adapt the process to the heterogeneity of the reservoir and the conditions of the late stage of development.

[0065] The implementation of the claimed method for developing depleted (depleted) oil reservoirs with medium-viscosity oil includes preparatory measures and subsequent implementation of thermochemical action by pumping water in a subcritical and / or supercritical state through injection wells with the withdrawal of products through production wells.

[0066] 1. Preparatory stage

[0067] 1.1. Selecting the impact area

[0068] Select a reservoir section at a late stage of development characterized by depletion, increased water cut, and reduced efficiency of traditional waterflooding. Based on available geological and technical data, the reservoir structure (heterogeneity, presence of highly permeable intervals / fractures), oil parameters (viscosity at reservoir conditions), reservoir conditions (temperature, pressure), and the current development system are determined.

[0069] 1.2. Formation of a well system

[0070] A system of injection and production wells is created at the selected site, ensuring areal coverage of the interwellbore impact. Examples include waterflooding schemes with one or more injection wells and surrounding production wells (five-spot, seven-spot, linear, and others), with the specific scheme selected based on the site's geology and infrastructure constraints.

[0071] 1.3. Equipment preparation

[0072] A surface water treatment unit is installed, including heating and pressure boosting units that convert water to a subcritical and / or supercritical state, as well as temperature and pressure control units. Design solutions (including pipeline and / or tubing insulation) are selected taking into account the requirements for maintaining the temperature regime along the path from the surface equipment to the bottomhole zone of the injection well.

[0073] 2. Implementation of the method: pumping water in a subcritical and / or supercritical state

[0074] 2.1. General conditions for downloading

[0075] Water is injected into the injection well at subcritical, near-critical, and / or supercritical temperature and pressure parameters. The temperature and pressure are selected to ensure the formation of a high-temperature impact zone in the near-wellbore zone and / or interwellbore space, extending into the reservoir volume sufficient to achieve areal coverage of the reservoir section.

[0076] 2.2. Subcritical mode

[0077] In subcritical mode, water is injected at a temperature below the critical temperature (T < 374°C) at a pressure that ensures the water remains predominantly in the liquid phase and its stable delivery to the formation. Temperature and pressure are selected based on formation conditions, permissible process limitations, and the required penetration depth of the high-temperature impact zone.

[0078] 2.3. Supercritical mode

[0079] In supercritical mode, water is injected at a temperature and pressure above critical values ​​(T > 374°C and P > 22.1 MPa), ensuring its supercritical state in the near-wellbore zone and / or in the impact zone. The mode parameters are selected to maintain the required thermodynamic conditions of the water en route to the impact zone and to ensure process controllability.

[0080] 3. Modes of implementation of influence

[0081] 3.1. Cyclic mode (injection - holding - production)

[0082] In cyclic mode, the process includes the following stages:

[0083] • injection of water in a subcritical and / or supercritical state into a formation through an injection well for a specified time and / or until a specified injection volume is reached;

[0084] • holding (impregnation) - stop pumping and hold the formation under conditions of elevated temperature and pressure to develop a high-temperature impact zone and initiate intra-formational high-temperature processes;

[0085] • production - the product is extracted through production wells until the specified technological criteria are reached (for example, oil flow rate / water cut / product temperature), after which the cycle is repeated.

[0086] 3.2. Continuous download mode

[0087] In continuous injection mode, water in a subcritical and / or supercritical state is continuously injected through injection wells while simultaneously withdrawing product through production wells. If necessary, the injection temperature, pressure, and flow rate parameters are adjusted to ensure the required stability of the high-temperature impact zone and process control.

[0088] 4. Additional option: introduction of reagents / catalytically active components (optional)

[0089] In one embodiment of the method, a reagent composition and / or a catalytically active component in the form of a water-soluble and / or oil-soluble precursor of transition metal compounds is introduced into the injected water. This additive enhances the thermochemical processes of oil component conversion in the high-temperature impact zone. The specific composition and concentration of the additive are selected taking into account the geological and physical conditions of the development site and process constraints. Preferred transition metal compounds are nickel, iron, cobalt, and / or molybdenum compounds, in particular molybdenum oleate, nickel tallate as a precursor, and nickel oxides and sulfides.

[0090] 5. Process control and management

[0091] During the implementation of the method, injection parameters (temperature, pressure, flow rate) and production parameters (oil and liquid flow rate, water cut, product temperature, etc.) are monitored. Based on the monitoring results, adjustments to the injection mode (transition between subcritical / near-critical / supercritical water states, changing the duration of the injection / holding / production stages in cyclic mode, changing the parameters of continuous injection) are permitted to achieve the required stability of the high-temperature impact zone and ensure areal coverage of the reservoir area.

[0092] Examples of the use of transition metal compounds as reagents and / or catalytically active components that reduce oil viscosity and / or ensure increased oil production.

[0093] Below are examples of laboratory and pilot field work published in scientific and technical sources, demonstrating (according to the authors) the achievability of viscosity reduction and / or production enhancement effects with in-situ high-temperature stimulation under various conditions. These examples are provided solely for illustrative purposes and do not limit the scope of legal protection for the claimed technical solution.

[0094] It should be noted that in the cited sources, steam and / or a high-temperature aqueous medium served as the working agent; in the claimed method, water in a subcritical and / or supercritical state is used as a high-temperature displacing agent, which represents a higher-temperature modification of hydrothermal action, aimed at forming a high-temperature action zone and intensifying in-situ processes.

[0095] Example 1. According to Wen Shoubin et al. (A Study on Catalytic Aquathermolysis of Heavy Crude Oil During Steam Stimulation, International Symposium on Oilfield Chemistry, Houston, Texas, USA, SPE-106180-MS, 2007), laboratory and subsequent pilot field tests of the technology of catalytic aquathermolysis processing of heavy oil from the Liaohe field were carried out using an oil-soluble catalyst - molybdenum oleate. Laboratory conditions: 240 °C, 24 h, 0.5 wt. % catalyst solution; according to the authors, a viscosity reduction of more than 90% was achieved. Pilot field tests on the Qi-40 and Qi-108 blocks under puff-and-huff conditions resulted in reduced viscosity and increased production, as well as improved production decline rates over the cycles when compared to the baseline conditions without catalytic treatment.

[0096] Example 2. According to Dong Long et al. (Laboratory Experiment Research and Field Tests on Catalyst of Aquathermolysis of Heavy Oils, Advanced Materials Research Vol. 773, pp. 298-303, 2013), aerosol, oil-soluble, and water-soluble nickel catalysts were studied for aquathermolysis processing of heavy oils. The laboratory part showed an increase in gas formation relative to the non-catalytic mode by 49%, 41%, and 21%, respectively. For a combined composition of nickel catalysts (ratio 1:1:2), according to the authors, an increase in oil recovery by 8.5%, a decrease in the viscosity of model oil by 89.6%, and a decrease in the average relative molecular weight by 23% with a decrease in the content of resins and asphaltenes were noted. Based on the results of pilot field tests, an increase in production for each well of 81.2-226.1 tons per cycle of action compared to the previous cycle is reported.

[0097] Example 3. According to Vakhin A. et al. (Improvement of CSS Method for Extra-Heavy Oil Recovery in Shallow Reservoirs by Simultaneous Injection of in-Situ Upgrading Catalysts and Solvent: Laboratory Study, Simulation and Field Application, SPE EOR Conference at O&G West Asia, Muscat, Oman, SPE-200082-MS, 2022), an approach to increasing the efficiency of cyclic steam stimulation (CSS) for extra-heavy oil is proposed through the combined supply of steam, catalyst solution, and solvent; the injection volumes and conditions were selected based on laboratory studies and modeling (tNavigator / STARS). Pilot tests included the following stages: preliminary injection (warm-up), injection of catalyst solution and solvent, subsequent injection, imbibition, and production.Analysis of samples after six months of testing revealed an early viscosity reduction due to solvent dilution and a later onset of the rock-adsorbed catalyst effect; a significant degree of conversion of resins and asphaltenes into lighter fractions was established.

[0098] Example 4. According to Vakhin AV et al. (Industrial Application of Nickel Tallate Catalyst During Cyclic Steam Stimulation in Boca De Jaruco Reservoir, SPE Russian Petroleum Technology Conference, Virtual, SPE-206419-MS, 2021), a nickel catalyst precursor (nickel tallate) has been developed for in-situ upgrading of heavy oil under hydrothermal conditions. Under laboratory conditions at 300°C and 90 bar, a decrease in asphaltene content from 22% to 7 wt. % and a 3-fold decrease in viscosity were shown. A technology for industrial production of the precursor has been developed; the first pilot batch weighing 12 tons has been obtained. The CSS technology has been modified to deliver the catalytic composition to the productive intervals of the carbonate bituminous formation of the Boca de Jaruco field (Cuba); active forms of the catalyst are nanodispersed mixed oxides and sulfides of nickel.The authors report an increase in cumulative production and incremental oil recovery relative to the previous cycle (without catalyst) of up to 170% (the effect continues to develop); based on the analysis of more than 200 samples, a decision was made to expand the industrial application of the technology.

[0099] These examples demonstrate that with in-situ high-temperature stimulation (including cyclic injection-hold-production modes) and the use of additional catalytic systems, significant viscosity reduction and production enhancement effects are achievable, confirming the feasibility of this approach to forming a high-temperature stimulation zone and intensifying in-situ processes. In the proposed method, similar mechanisms are implemented by injecting water in a subcritical and / or supercritical state, with the option of selecting cyclic or continuous operation depending on the conditions of the depleted reservoir.

[0100] Brief description of drawings

[0101] The claimed technical solution is explained in Fig. 1 - Fig. 4.

[0102] Fig. 1 shows a diagram of the implementation of the claimed method for developing depleted (depleted) oil reservoirs with medium-viscosity oil using water in a subcritical and / or supercritical state, including a system of injection and production wells, the direction of injection and product withdrawal flows, as well as a high-temperature (thermochemical) impact zone formed in the interwell space with areal coverage of a section of the deposit.

[0103] Fig. 2 shows a diagram of a cyclic mode of thermochemical action on a formation, including successive stages of pumping water in a subcritical and / or supercritical state, holding (impregnation) of the formation and subsequent production of products.

[0104] Fig. 3 shows a diagram of a continuous mode of thermochemical action on a formation, which provides for the constant injection of water in a subcritical and / or supercritical state through an injection well with the simultaneous production of products through a production well (or a system of production wells) with the formation of a stable zone of high-temperature action in the interwell space.

[0105] Fig. 4 shows a diagram of the phase state of water in pressure-temperature coordinates indicating the critical point and areas of subcritical and supercritical conditions, used to select the parameters for pumping water and ensure that it is in a subcritical and / or supercritical state when implementing the claimed method.

[0106] Embodiments of the present invention

[0107] The claimed technical solution relates to methods for developing depleted (depleted) oil reservoirs with medium-viscosity oil at a late stage of operation and is aimed at increasing the efficiency of involving residual oil reserves in production under conditions of high water cut and reservoir heterogeneity due to the thermochemical effect of a high-temperature agent while ensuring areal coverage of the deposit area.

[0108] The essence of the claimed technical solution is that a system of injection and production wells is formed in a selected section of the reservoir, ensuring area coverage of the impact in the interwell space, after which a high-temperature agent is pumped into the formation through an injection well (or a group of injection wells) - water in a subcritical and / or supercritical state - at a temperature and pressure that ensure the formation of a stable zone of high-temperature (thermochemical) impact in the bottomhole zone and / or interwell space.

[0109] Injecting subcritical and / or supercritical water creates conditions for intensifying heat and mass transfer in a porous medium and initiating high-temperature in-situ processes, which reduce oil viscosity, increase its mobility, and improve the displacement of residual oil in the interwellbore space. Forming a high-temperature impact zone with areal coverage of a reservoir section ensures the transition from localized stimulation (limited to the bottomhole zone) to interwellbore stimulation, which is especially important for depleted reservoirs with pronounced heterogeneity of filtration flows, the presence of highly permeable channels and / or fractures, and high water cut.

[0110] The claimed method allows for implementation in various thermochemical impact modes, selected depending on the geological and physical conditions of the development site, the degree of depletion and the current water content:

[0111] a) a cyclic mode, including successive stages of pumping water in a subcritical and / or supercritical state, holding (impregnation) of the formation under conditions of elevated temperature and pressure and subsequent production of products, after which the cycle can be repeated; the specified embodiment is shown in Fig. 2;

[0112] b) a continuous mode, including the constant injection of water in a subcritical and / or supercritical state with the simultaneous production of products through production wells, with the maintenance of injection parameters that ensure the stability of the high-temperature impact zone in the interwell space; the specified embodiment is shown in Fig. 3.

[0113] The general scheme for implementing the claimed method with the placement of injection and production wells in the deposit area, the direction of injection and product withdrawal flows, as well as the formed high-temperature impact zone in the interwell space is shown in Fig. 1.

[0114] Water injection temperature, pressure, and flow rate parameters are selected to ensure subcritical, near-critical, and / or supercritical water conditions in the near-wellbore zone and / or impact zone, as well as process control requirements. If necessary, thermal insulation of equipment and / or pipeline sections is provided, as well as monitoring and regulation of injection and production parameters.

[0115] In one embodiment of the claimed technical solution, reagents and / or catalytically active components (in the form of water-soluble and / or oil-soluble precursors of transition metal compounds) are additionally introduced into the injected water to intensify in-situ high-temperature processes; however, this embodiment is optional and is used when it is necessary to enhance the thermochemical effect, taking into account the specific conditions of the development site.

[0116] Industrial applicability

[0117] The claimed technical solution is industrially applicable, since it can be implemented in the oil producing industry using known field equipment and standard technological operations used in injecting agents into the formation and extracting products through a system of injection and production wells.

[0118] To implement the method, standard elements of ground and well infrastructure are used: a water treatment unit, including units for heating and increasing pressure to subcritical and / or supercritical state parameters, piping, shut-off and control valves, temperature and pressure control devices, as well as standard equipment for injection and production wells (tubing, packer assemblies if necessary, means for controlling injection / production modes and product collection units).

[0119] The method can be implemented in depleted (depleted) oil reservoirs with medium-viscosity oil at a late stage of development, including in conditions of high water cut and reservoir heterogeneity. This method involves selecting a treatment site, forming a system of injection and production wells, setting injection regimes, and implementing thermochemical treatment in a cyclic or continuous mode. Injection parameters (temperature, pressure, flow rate, and duration of stages in a cyclic mode) are selected taking into account the geological and physical conditions of a specific facility, ensuring process controllability.

[0120] Thus, the claimed method can be reproduced and used in field conditions, and its implementation allows for increasing the efficiency of developing depleted objects by forming a high-temperature impact zone in the interwell space during the injection of water in a subcritical and / or supercritical state and ensuring area coverage of the deposit area.

Claims

1. A method for developing depleted and / or exhausted oil reservoirs with medium-viscosity oil, which includes injecting a displacing agent into the reservoir through an injection well and extracting product through a production well, characterized in that a system of injection and production wells is formed in a section of the reservoir, ensuring area coverage of the interwell space by the action, and water in a subcritical and / or supercritical state is used as a displacing agent, which is injected at a temperature and pressure that ensure the formation of a stable high-temperature action zone in the near-wellbore zone and / or interwell space and the initiation of intra-reservoir high-temperature processes, wherein the action is carried out in a cyclic mode or in a continuous injection mode with simultaneous production of products.

2. The method according to paragraph 1, characterized in that the action is carried out in a cyclic mode, including the stages of pumping water in a subcritical and / or supercritical state, holding and / or impregnating the formation under conditions of elevated temperature and pressure and subsequent production of products, after which the cycle is repeated.

3. The method according to paragraph 1, characterized in that the action is carried out in the mode of continuous injection of water in a subcritical and / or supercritical state with the simultaneous extraction of products through production wells.

4. The method according to paragraph 1, characterized in that the water is pumped in a subcritical state at a temperature below the critical temperature of water T < 374 °C and a pressure that ensures that the water is predominantly in the liquid phase at a given temperature.

5. The method according to paragraph 1, characterized in that the water is pumped in a supercritical state at a temperature above the critical temperature of water T> 374 °C and a pressure above the critical pressure of water P> 22.1 MPa.

6. The method according to paragraph 1, characterized in that the temperature and pressure parameters of the injected water are selected in such a way as to ensure a subcritical and / or supercritical state of water in the bottomhole zone of the injection well and / or in the high-temperature impact zone in the interwell space.

7. The method according to paragraph 1, characterized in that the system of injection and production wells is formed according to an area development scheme, including at least one injection well and at least one production well within the impact area.

8. The method according to paragraph 1, characterized in that the impact is carried out at a late stage of development with increased water cut of the extracted product, typical for developed objects.

9. The method according to paragraph 1, characterized in that the impact is carried out on formations with medium-viscosity oil, the dynamic viscosity of which under formation conditions is from 10 to 500 mPa⋅s.

10. The method according to claim 1, characterized in that reagents and / or a catalytically active component in the form of a water-soluble and / or oil-soluble precursor of transition metal compounds are additionally introduced into the injected water.

11. The method according to claim 10, characterized in that compounds of nickel, iron, cobalt and / or molybdenum are used as transition metal compounds.

12. The method according to paragraph 1, characterized in that the supply of water in a subcritical and / or supercritical state is carried out with control and regulation of the temperature and pressure at the mouth of the injection well and / or on the surface in the water preparation unit.

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