A method and system for reservoir modification of oil shale

Abstract

The application discloses a reservoir reconstruction method and system for oil shale, and the reservoir reconstruction method comprises the following steps: collecting a core rock sample of a to-be-reconstructed reservoir, and constructing a physical model of the to-be-reconstructed reservoir according to reservoir characteristic parameters of the current rock sample; based on the physical model, a plurality of alternative reconstruction schemes for realizing the alternative implementation of heat injection reconstruction and fracturing reconstruction are utilized to perform physical simulation on the current to-be-reconstructed reservoir, so that the crack morphology formed in the reservoir by each alternative reconstruction scheme is predicted, and through comparison of each crack morphology, the best crack morphology suitable for the implementation of heat injection mining is screened out, and then the reconstruction scheme for forming the best crack morphology is taken as the best reconstruction scheme; and the actual to-be-reconstructed reservoir is reconstructed by using the best reconstruction scheme, so that the best crack morphology is formed. The application realizes large-scale reconstruction of the oil shale reservoir, and effectively improves the heat injection efficiency of in-situ mining of the oil shale.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil shale reservoir transformation, and in particular relates to a method and system for oil shale reservoir transformation. Background Art

[0002] During in-situ heat injection mining of oil shale, the pores and cracks within the shale act as channels for heat transfer and exchange. Fractures within the oil shale reservoir facilitate rapid heat dissipation from injected high-temperature steam, allowing for the pyrolysis of a larger area of ​​the shale. Therefore, to maximize the effectiveness of in-situ oil shale mining, it is necessary to construct a substantial fracture network within the reservoir.

[0003] The heat injection process of oil shale inevitably leads to pyrolysis and thermal fracturing of the reservoir. Pyrolysis creates numerous pores within the reservoir, while thermal fracturing results in the appearance of microcracks. In other words, the pyrolysis and thermal fracturing of the reservoir caused by the heat injection process results in the simultaneous presence of pores and microcracks within the reservoir. Given that the presence of natural fractures in reservoir reconstruction facilitates the formation of a fracture network, it follows that the pores and microcracks generated by heat injection also facilitate the formation of a fracture network during hydraulic fracturing. However, most currently proposed oil shale reservoir reconstruction schemes fail to fully utilize the impact of the pyrolysis (pore formation) and thermal fracturing (microcrack formation) during the heat injection process on the heat injection efficiency, resulting in low heat injection efficiency for in-situ oil shale mining. Furthermore, existing technologies have not explored and applied the impact of the pores and microcracks generated during the oil shale heat injection process on the initiation and propagation of hydraulic fracturing fractures, nor the influence of the heat injection-hydraulic fracturing cycle on the final fracture morphology within the reservoir. Summary of the Invention

[0004] In order to solve the above problems, an embodiment of the present invention provides a reservoir transformation method for oil shale, comprising: collecting core samples of the reservoir to be transformed, and constructing a physical model of the reservoir to be transformed based on the reservoir characteristic parameters of the current sample; based on the physical model, using multiple alternative transformation schemes for realizing alternating implementation of heat injection transformation and fracturing transformation, performing a transformation physical simulation of the current reservoir to be transformed, thereby predicting the fracture morphology formed in the reservoir by each alternative transformation scheme, and by comparing each fracture morphology, screening the optimal fracture morphology suitable for implementing heat injection mining, and then using the transformation scheme that forms the optimal fracture morphology as the optimal transformation scheme; and using the optimal transformation scheme to transform the actual reservoir to be transformed to form the optimal fracture morphology.

[0005] Preferably, before performing physical simulation of the transformation of the current reservoir to be transformed, the reservoir transformation method also includes: using a plurality of preset injection and production construction schemes to perform physical simulation of heat injection transformation of the current reservoir to be transformed, so as to predict the formation time of the fracture morphology under each injection and production construction scheme based on the optimal fracture morphology, and take the injection and production construction scheme corresponding to the shortest formation time as the optimal injection and production construction scheme, wherein the injection and production construction scheme includes but is not limited to the distribution of the injection and production well network and the well spacing.

[0006] Preferably, the reservoir transformation method further comprises: using the optimal injection-production construction plan to perform drilling and completion processing on the actual reservoir to be transformed, and after the drilling and completion process is completed, insulating the injection wellbore to reduce energy loss during the transformation process.

[0007] Preferably, the energy loss includes but is not limited to: heat loss during the heat injection reformation process and the heat injection production process, and cooling loss of low-temperature fracturing fluid during the fracturing reformation process.

[0008] Preferably, the reservoir transformation method further comprises: using a plurality of preset heat injection transformation parameter combinations, performing heat injection transformation physical simulation only on the reservoir to be transformed, so as to obtain the correlation between each heat injection transformation parameter combination and the hot fluid swept volume, thereby obtaining the best heat injection transformation parameter combination, wherein the heat injection transformation parameters constituting the preset heat injection transformation parameter combination include but are not limited to: heat injection rounds, hot fluid injection time and hot fluid injection temperature; and using a plurality of preset fracturing transformation parameter combinations, performing fracturing transformation physical simulation only on the reservoir to be transformed, so as to obtain the correlation between each fracturing transformation parameter combination and the crack extension morphology. The correlation between the two is obtained, thereby obtaining the optimal fracturing transformation data combination, wherein the fracturing transformation parameters constituting the preset fracturing transformation parameter combination include but are not limited to: fracturing rounds and fracturing duration; using the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination, a cyclic transformation physical simulation of alternating heat injection transformation and fracturing transformation is performed on the reservoir to be transformed, thereby determining the optimal cyclic transformation rounds for forming the optimal fracture morphology and the optimal thermal fluid injection time for each round. Based on this, the current optimal transformation plan is corrected, and the corrected transformation plan is used to transform the actual reservoir to be transformed.

[0009] Preferably, the fracturing modification is one of slick water fracturing, supercritical carbon dioxide fracturing and liquid nitrogen fracturing.

[0010] Preferably, the reservoir characteristic parameters include but are not limited to: reservoir physical property parameters, pyrolysis temperature and thermal cracking critical temperature, wherein the reservoir physical property parameters include but are not limited to: oil shale porosity, equivalent permeability of pore-fracture rock mass and equivalent thermal conductivity of pore-fracture rock mass.

[0011] The present invention also provides a computer-readable storage medium comprising a series of instructions for the steps of a method for transforming an oil shale reservoir.

[0012] On the other hand, the present invention also provides a reservoir transformation system for oil shale, which includes the following modules: a reservoir parameter acquisition module, which is used to construct a physical model of the reservoir to be transformed based on the reservoir characteristic parameters of the core sample of the reservoir to be transformed currently collected; a fracture morphology prediction module, which is used to perform a physical simulation of the transformation of the current reservoir to be transformed based on the physical model and use a variety of alternative transformation schemes for realizing alternating implementation of heat injection transformation and fracturing transformation, so as to predict the fracture morphology formed in the reservoir by each alternative transformation scheme, and by comparing each fracture morphology, screen the best fracture morphology suitable for implementing heat injection mining, and then use the transformation scheme that forms the best fracture morphology as the best transformation scheme; a reservoir transformation module, which is used to use the best transformation scheme to transform the actual reservoir to be transformed to form the best fracture morphology.

[0013] Preferably, the reservoir transformation system also includes: a construction plan optimization module, which is used to use a plurality of preset injection and production construction plans to perform physical simulation of heat injection transformation on the current reservoir to be transformed, so as to predict the formation time of the fracture morphology under each injection and production construction plan based on the optimal fracture morphology, and take the injection and production construction plan corresponding to the shortest formation time as the optimal injection and production construction plan, wherein the injection and production construction plan includes but is not limited to the distribution of the injection and production well network and the well spacing.

[0014] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0015] The present invention discloses a reservoir transformation method and system for oil shale. The method first obtains reservoir characteristic parameters of the current reservoir to be transformed by taking core samples from the reservoir to be transformed, thereby constructing a physical model of the reservoir to be transformed. Then, based on the constructed physical model, a variety of alternative transformation schemes for alternately implementing heat injection and fracturing are used to perform physical simulation of the current reservoir to be transformed, thereby predicting the fracture morphology formed within the reservoir by each alternative transformation scheme, and screening the optimal fracture morphology suitable for heat injection mining. The transformation scheme that forms the optimal fracture morphology is then selected as the optimal transformation scheme. Finally, the optimal transformation scheme is implemented in the actual reservoir to be transformed until the reservoir has the optimal fracture morphology, thereby achieving the transformation of the current reservoir to be transformed. The present invention realizes large-scale transformation of oil shale reservoirs and effectively improves the heat injection efficiency of in-situ oil shale mining.

[0016] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 This is a step diagram of a reservoir reconstruction method for oil shale according to an embodiment of the present application.

[0019] Figure 2 This is a schematic diagram of the fracture morphology formed by the first round of transformation of the oil shale reservoir transformation method according to an embodiment of the present application.

[0020] Figure 3 This is a schematic diagram of the fracture morphology formed by the second round of transformation of the oil shale reservoir transformation method according to an embodiment of the present application.

[0021] Figure 4 This is a module block diagram of a reservoir reconstruction system for oil shale according to an embodiment of the present application.

[0022] In this application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn to scale.

[0023] The reference numerals are as follows:

[0024] 1: Oil shale reservoir

[0025] 2: Wellbore with insulation material

[0026] 3: Wellbore perforation section

[0027] 4: Thermally induced microcracks

[0028] 5: Pyrolysis holes

[0029] 6: Oil shale pyrolysis holes under microscopic conditions

[0030] 7: Fracturing cracks formed by microcracks and pore network transformation caused by thermal cracking and pyrolysis DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings and examples, so that the present invention can fully understand how to apply technical means to solve technical problems and achieve technical effects, and thus implement the invention accordingly. It should be noted that, as long as no conflict exists, the various embodiments of the present invention and the various features of the embodiments can be combined with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0032] Additionally, the steps shown in the flowcharts of the accompanying drawings may be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in an order different from that shown.

[0033] During in-situ heat injection mining of oil shale, the pores and cracks within the shale act as channels for heat transfer and exchange. Fractures within the oil shale reservoir facilitate rapid heat dissipation from injected high-temperature steam, allowing for the pyrolysis of a larger area of ​​the shale. Therefore, to maximize the effectiveness of in-situ oil shale mining, it is necessary to construct a substantial fracture network within the reservoir.

[0034] The heat injection process of oil shale inevitably leads to pyrolysis and thermal fracturing of the reservoir. Pyrolysis creates numerous pores within the reservoir, while thermal fracturing results in the appearance of microcracks. In other words, the pyrolysis and thermal fracturing of the reservoir caused by the heat injection process results in the simultaneous presence of pores and microcracks within the reservoir. Given that the presence of natural fractures in reservoir reconstruction facilitates the formation of a fracture network, it follows that the pores and microcracks generated by heat injection also facilitate the formation of a fracture network during hydraulic fracturing. However, most currently proposed oil shale reservoir reconstruction schemes fail to fully utilize the impact of the pyrolysis (pore formation) and thermal fracturing (microcrack formation) during the heat injection process on the heat injection efficiency, resulting in low heat injection efficiency for in-situ oil shale mining. Furthermore, existing technologies have not explored and applied the impact of the pores and microcracks generated during the oil shale heat injection process on the initiation and propagation of hydraulic fracturing fractures, nor the influence of the heat injection-hydraulic fracturing cycle on the final fracture morphology within the reservoir.

[0035] Therefore, to address the above-mentioned issues, the present invention proposes a reservoir transformation method and system for oil shale. This reservoir transformation method first obtains reservoir characteristic parameters of the current reservoir to be transformed by taking core samples from the reservoir to be transformed, thereby constructing a physical model of the reservoir to be transformed. Then, based on the constructed physical model, a variety of alternative transformation schemes for alternately implementing heat injection and fracturing are used to perform a physical simulation of the transformation of the current reservoir to be transformed, thereby predicting the fracture morphology formed within the reservoir by each alternative transformation scheme, and screening the optimal fracture morphology suitable for heat injection mining. The transformation scheme that forms the optimal fracture morphology is then selected as the optimal transformation scheme. Finally, the optimal transformation scheme is implemented in the actual reservoir to be transformed until the reservoir has the optimal fracture morphology, thereby achieving the transformation of the current reservoir to be transformed. The present invention achieves large-scale transformation of oil shale reservoirs and effectively improves the heat injection efficiency of in-situ oil shale mining.

[0036] Example 1

[0037] Figure 1 This is a step diagram of the reservoir transformation method for oil shale in the embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0038] like Figure 1 As shown, in step S110, core samples of the reservoir to be transformed are collected, and a physical model of the reservoir to be transformed is constructed based on the reservoir characteristic parameters of the current sample. The present invention determines the transformation scheme applicable to the actual reservoir to be transformed through numerical simulation. Therefore, in the embodiment of the present application, it is necessary to first collect core samples in the reservoir to be transformed, and then obtain the reservoir characteristic parameters of the current sample by performing experimental analysis and other processing on the collected core samples. The reservoir characteristic parameters of the current sample are consistent with the reservoir characteristic parameters of the reservoir to be transformed, so the reservoir characteristic parameters of the current sample can be used to construct a physical model of the reservoir to be transformed, and finally a physical model with exactly the same reservoir characteristic parameters as the actual reservoir to be transformed is obtained, which can be used to simulate the fracture morphology formed by reservoir transformation, so that the physical model is used as the corresponding numerical model to realize the numerical simulation of the fracture morphology formed by reservoir transformation.

[0039] The reservoir characteristic parameters of this embodiment are parameters that affect the fracture morphology formed by reservoir transformation. In a specific embodiment of this application, the reservoir characteristic parameters include but are not limited to: reservoir physical parameters, pyrolysis temperature and thermal cracking critical temperature, among which the reservoir physical parameters include but are not limited to: oil shale porosity The equivalent permeability (keff) of porous-fractured rock mass and the equivalent thermal conductivity (ceff) of porous-fractured rock mass.

[0040] In practical application, oil shale will pyrolyze and thermally crack during the heat injection process, and the pyrolysis and thermal cracking will form micro-pores and micro-cracks in the oil shale reservoir, and the micro-pores and micro-cracks will further induce the formation of a fracture network in the oil shale reservoir. The fracture network formed in the oil shale reservoir provides a flow channel for the heat fluid, that is, the presence of the fracture network enables the heat fluid used for the in-situ mining to be efficiently transferred and heat transferred in the reservoir during the heat injection mining process. Accordingly, the heat injection efficiency of the in-situ mining of oil shale is effectively improved.

[0041] After the physical model is constructed, in step S120, based on the physical model, a plurality of alternative modification schemes for alternately implementing the heat injection modification and the fracture modification are used to perform a modification physical simulation on the current reservoir to be modified, so as to predict the fracture morphology formed in the reservoir by each alternative modification scheme, and by comparing each fracture morphology, the best fracture morphology suitable for the heat injection mining is screened, and then the modification scheme forming the best fracture morphology is taken as the best modification scheme. In view of the characteristics that the internal part of the oil shale reservoir can pyrolyze and thermally crack after the heat fluid is injected, the present application proposes a cyclic reservoir modification method based on the alternately implemented heat injection modification and fracture modification, so as to realize the large-scale modification of the oil shale reservoir. Specifically, the present embodiment presets a plurality of alternative modification schemes for alternately implementing the heat injection modification and the fracture modification, and by implementing each alternative scheme on the physical model, a modification physical simulation is performed on the current reservoir to be modified, so as to predict the fracture morphology formed in the current reservoir to be modified by each alternative modification scheme. Then, the fracture morphology formed by each alternative modification scheme is analyzed and compared, and the best fracture morphology suitable for the heat injection mining (for example, the fracture morphology with the largest coverage area) is screened. Finally, the modification scheme forming the best fracture morphology is taken as the best modification scheme.

[0042] After the best modification scheme is obtained, in step S130, the actual reservoir to be modified is modified by using the best modification scheme to form the best fracture morphology. In the present embodiment, the actual reservoir to be modified is implemented by the best modification scheme, so that the best fracture morphology can be formed in the actual reservoir to be modified. Accordingly, when the best fracture morphology is formed in the actual reservoir to be modified, the present application realizes the large-scale modification of the actual reservoir to be modified, and the heat injection efficiency is higher when the modified reservoir is subjected to the heat injection in-situ mining.

[0043] Next, before performing a physical simulation of the transformation of the current reservoir to be transformed, the present invention also uses a plurality of preset injection and production construction schemes to perform a heat injection transformation physical simulation of the current reservoir to be transformed. Based on the optimal fracture morphology, the formation time of the fracture morphology under each injection and production construction scheme is predicted, and the injection and production construction scheme corresponding to the shortest formation time is selected as the optimal injection and production construction scheme. On the basis of being able to form the optimal fracture morphology within the current reservoir to be transformed, this embodiment further optimizes the formation time of the optimal fracture morphology. First, a plurality of injection and production construction schemes for performing a physical simulation of the heat injection transformation of the current reservoir to be transformed are preset, and each injection and production construction scheme is respectively implemented in a physical model to perform a physical simulation of the transformation of the current reservoir to be transformed, thereby predicting the time (i.e., formation time) required for each combination scheme to form the optimal fracture morphology within the current reservoir to be transformed. Next, the time required for each combination scheme to form the optimal fracture morphology is analyzed and compared, and the injection and production construction scheme in the combination scheme corresponding to the shortest formation time is selected as the optimal injection and production construction scheme. Among them, the injection and production construction plan includes but is not limited to the distribution of the injection and production well network and the spacing between wells.

[0044] Furthermore, in order to obtain a better transformation effect for the actual reservoir to be transformed, the present invention first uses a plurality of preset heat injection transformation parameter combinations to perform heat injection transformation physical simulation only on the reservoir to be transformed, so as to obtain the correlation between each heat injection transformation parameter combination and the hot fluid swept volume, thereby obtaining the optimal heat injection transformation parameter combination; and uses a plurality of preset fracturing transformation parameter combinations to perform fracturing transformation physical simulation only on the reservoir to be transformed, so as to obtain the correlation between each fracturing transformation parameter combination and the crack extension morphology, thereby obtaining the optimal fracturing transformation data combination; finally, using the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination, a cyclic transformation physical simulation of alternating heat injection transformation and fracturing transformation is performed on the reservoir to be transformed, thereby determining the optimal cyclic transformation rounds for forming the optimal crack morphology, and the optimal hot fluid injection time for each round. Based on this, the current optimal transformation scheme is corrected, and the corrected transformation scheme is used to transform the actual reservoir to be transformed.

[0045] This embodiment implements different preset heat injection transformation schemes and different fracturing transformation schemes on the physical model to determine the optimal heat injection transformation parameter combination and the optimal fracturing transformation parameter combination, respectively, to correct the current optimal transformation scheme, and thus use the corrected transformation scheme to further improve the transformation effect of the reservoir to be transformed.

[0046] First, in practical applications, the temperature distribution in the reservoir changes accordingly after each heat injection, and this change in temperature distribution in the reservoir will affect the effect of the next heat injection transformation. Therefore, this embodiment presets multiple heat injection transformation parameter combinations and implements each heat injection transformation parameter combination on a physical model to perform a heat injection transformation physical simulation of the reservoir to be transformed. This explores the impact of each type of heat injection transformation data that constitutes the heat injection transformation parameter combination on the temperature distribution in the reservoir, thereby determining the correlation between each type of heat injection transformation parameter and the hot fluid swept volume. Based on the current correlation, the optimal heat injection transformation data for each type is determined, thereby forming a new heat injection transformation parameter combination, which is used as the optimal heat injection transformation parameter combination. Based on this, the optimal heat injection transformation parameter combination is used to correct the current optimal transformation plan, thereby achieving the optimal transformation effect for the reservoir to be transformed. In this embodiment of the present application, the heat injection transformation parameters that constitute the preset heat injection transformation parameter combination include, but are not limited to: heat injection rounds, hot fluid injection time, and hot fluid injection temperature.

[0047] In an embodiment of the present application, the injection temperature of the hot fluid is determined based on the critical temperature of pyrolysis (Ttd) and the critical temperature of thermal fracture (Ttc) of the reservoir to be transformed, wherein the critical temperature of pyrolysis is obtained based on an indoor pyrolysis experiment on the collected core samples, and the critical temperature of thermal fracture is obtained based on an indoor thermal fracture experiment on the collected core samples.

[0048] Next, this embodiment presets a variety of fracturing transformation parameter combinations, and by implementing each fracturing transformation parameter combination on the physical model, the current reservoir to be transformed is subjected to a fracturing transformation physical simulation, in order to explore the influence of each type of fracturing transformation data constituting the fracturing transformation parameter combination on the crack expansion, thereby determining the correlation between each type of fracturing transformation parameter and the crack expansion morphology. According to the current correlation, the optimal fracturing transformation data of each type is determined, thereby forming a new fracturing transformation parameter combination, and using it as the optimal fracturing transformation parameter combination. Accordingly, the optimal fracturing transformation parameter combination formed is used to correct the current optimal transformation scheme, achieving the purpose of achieving the best transformation effect for the reservoir to be transformed in terms of fracturing transformation. In the embodiment of the present application, the fracturing transformation parameters constituting the preset fracturing transformation parameter combination include but are not limited to: fracturing rounds and fracturing duration.

[0049] Finally, after obtaining the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination, this embodiment performs a cyclic transformation physical simulation of alternating heat injection transformation and fracturing transformation on the reservoir to be transformed by alternately implementing the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination on the physical model. Afterwards, when the optimal fracture morphology is formed, the number of cyclic transformation rounds that have been carried out and the optimal hot fluid injection time of each round are recorded, and the current recorded data is used as the optimal cyclic transformation round and the optimal hot fluid injection time of each round, and the current optimal transformation plan is corrected in combination with the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination. Accordingly, the corrected transformation plan is used to transform the actual reservoir to be transformed, which effectively improves the transformation effect of the actual reservoir to be transformed. In the embodiment of the present application, the alternating implementation order is the first round of heat injection, the first round of fracturing, the second round of heat injection, the second round of fracturing... and so on until the optimal fracture morphology is formed. After the first round of cyclic transformation S1 is completed, the following is obtained. Figure 2 The crack morphology shown ( Figure 2 Schematic diagram of the fracture morphology formed by the first round of transformation of the oil shale reservoir transformation method according to the embodiment of the present application), and after the second round of cyclic transformation S2 is completed, the following is obtained: Figure 3 The crack morphology shown ( Figure 3 Schematic diagram of the fracture morphology formed by the second round of transformation of the oil shale reservoir transformation method according to an embodiment of the present application. In addition, each round of cyclic transformation includes a heat injection round and a fracturing round.

[0050] In the embodiment of the present application, the fracturing transformation is one of slick water fracturing, supercritical carbon dioxide fracturing and liquid nitrogen fracturing.

[0051] Furthermore, the present invention utilizes the optimal injection-production construction plan to drill and complete the actual reservoir to be transformed. After the drilling and completion process, the injection wellbore is insulated to reduce energy loss during the transformation process. Specifically, before the actual reservoir to be transformed is transformed, the optimal injection-production construction plan is first used to drill and complete the actual reservoir to be transformed. After the drilling and completion process, the injection wellbore currently being used for fluid injection is insulated, thereby reducing energy loss caused by the injected fluid passing through the wellbore into the reservoir during the transformation process.

[0052] In the embodiments of this application, energy losses include, but are not limited to, heat loss during the thermal injection reformation process and the thermal injection recovery process, as well as cooling loss from the low-temperature fracturing fluid during the fracturing reformation process. Thus, the present invention effectively reduces energy loss from the injected fluid into the reservoir, achieving full resource utilization.

[0053] Example 2

[0054] This embodiment further provides a computer-readable storage medium storing at least one instruction, which is loaded and executed by a processor to implement the operations for oil shale reservoir transformation performed in the method of Embodiment 1. For example, the computer-readable storage medium may be a ROM (Read Only Memory), a RAM (Random Access Memory), a CD-ROM (Compact Disc-Read Only Memory), a magnetic tape, a floppy disk, or an optical data storage device.

[0055] Example 3

[0056] Based on the reservoir reconstruction method for oil shale described in the first embodiment above, the present invention further provides a reservoir reconstruction system for oil shale (hereinafter referred to as the "reservoir reconstruction system"). Figure 4 This is a module block diagram of a reservoir reconstruction system for oil shale according to an embodiment of the present application.

[0057] like Figure 4 As shown, the reservoir stimulation system in this embodiment includes: a reservoir parameter acquisition module 41, a fracture morphology prediction module 42, and a reservoir stimulation module 43. Specifically, the reservoir parameter acquisition module 41 is implemented according to the method described in step S110 above and is configured to collect core samples of the reservoir to be stimulated and construct a physical model of the reservoir to be stimulated based on the reservoir characteristic parameters of the current sample. The fracture morphology prediction module 42 is implemented according to the method described in step S120 above and is configured to perform a physical simulation of the current reservoir to be stimulated using multiple alternative stimulation schemes for alternately implementing heat injection stimulation and fracturing stimulation based on the physical model constructed by the reservoir parameter acquisition module 41. The fracture morphology formed within the reservoir by each alternative stimulation scheme is predicted, and by comparing each fracture morphology, the optimal fracture morphology suitable for heat injection recovery is selected. The stimulation scheme that produces the optimal fracture morphology is then selected as the optimal stimulation scheme. The reservoir stimulation module 43 is implemented according to the method described in step S130 above and is configured to use the optimal stimulation scheme determined by the fracture morphology prediction module 42 to stimulate the actual reservoir to be stimulated, thereby forming the optimal fracture morphology.

[0058] Furthermore, the reservoir reconstruction system of the present invention also includes a construction scheme optimization module. This construction scheme optimization module is used to perform a heat injection reconstruction physical simulation on the reservoir to be transformed using multiple preset injection and production construction schemes. Based on the optimal fracture morphology, the module predicts the formation time of the fracture morphology under each injection and production construction scheme and selects the injection and production construction scheme corresponding to the shortest formation time as the optimal injection and production construction scheme. The injection and production construction scheme includes, but is not limited to, the distribution of the injection and production well pattern and the spacing between the wells.

[0059] The present invention discloses a reservoir transformation method and system for oil shale. The method first obtains reservoir characteristic parameters of the current reservoir to be transformed by taking core samples from the reservoir to be transformed, thereby constructing a physical model of the reservoir to be transformed. Then, based on the constructed physical model, a variety of alternative transformation schemes for alternately implementing heat injection and fracturing are used to perform physical simulation of the current reservoir to be transformed, thereby predicting the fracture morphology formed within the reservoir by each alternative transformation scheme, and screening the optimal fracture morphology suitable for heat injection mining. The transformation scheme that forms the optimal fracture morphology is then selected as the optimal transformation scheme. Finally, the optimal transformation scheme is implemented in the actual reservoir to be transformed until the reservoir has the optimal fracture morphology, thereby achieving the transformation of the current reservoir to be transformed. The present invention realizes large-scale transformation of oil shale reservoirs and effectively improves the heat injection efficiency of in-situ oil shale mining.

[0060] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by anyone skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

[0061] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

[0062] Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using a general-purpose computing device. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. Alternatively, they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0063] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art may make any modifications and variations in the form and details of the embodiments without departing from the spirit and scope of the present invention. However, the scope of patent protection of the present invention shall remain subject to the scope defined by the appended claims.

Claims

1. A method for transforming an oil shale reservoir, characterized in that: include: Collecting core samples of the reservoir to be transformed, and constructing a physical model of the reservoir to be transformed based on reservoir characteristic parameters of the current sample, wherein the reservoir characteristic parameters include reservoir physical property parameters, pyrolysis temperature, and thermal cracking critical temperature, wherein the reservoir physical property parameters include oil shale porosity, equivalent permeability of pore-fracture rock mass, and equivalent thermal conductivity of pore-fracture rock mass; Based on the physical model, a plurality of alternative transformation schemes for realizing alternating implementation of heat injection transformation and fracturing transformation are used to perform a transformation physical simulation on the current reservoir to be transformed, thereby predicting the fracture morphology formed in the reservoir by each alternative transformation scheme, and by comparing each fracture morphology, screening the best fracture morphology suitable for implementing heat injection production, and then taking the transformation scheme that forms the best fracture morphology as the best transformation scheme, wherein, before performing the transformation physical simulation on the current reservoir to be transformed, a plurality of preset injection and production construction schemes are used to perform a heat injection transformation physical simulation on the current reservoir to be transformed, thereby predicting the formation time of the fracture morphology under each injection and production construction scheme based on the best fracture morphology, and taking the injection and production construction scheme corresponding to the shortest formation time as the best injection and production construction scheme, wherein, the injection and production construction scheme includes the distribution of the injection and production well network and the well spacing; The optimal transformation scheme is used to transform the actual reservoir to be transformed to form the optimal fracture morphology.

2. The reservoir transformation method according to claim 1, characterized in that: The reservoir transformation method further comprises: The optimal injection-production construction plan is used to perform drilling and completion processing on the actual reservoir to be transformed, and after the drilling and completion process is completed, the injection wellbore is kept warm to reduce energy loss during the transformation process.

3. The reservoir transformation method according to claim 2, characterized in that: The energy loss includes: heat loss during the heat injection reformation process and the heat injection production process, and cold loss of low-temperature fracturing fluid during the fracturing reformation process.

4. The reservoir reconstruction method according to any one of claims 1 to 3, characterized in that: The reservoir transformation method further comprises: Using a plurality of preset heat injection modification parameter combinations, a heat injection modification physical simulation is performed only on the reservoir to be modified to obtain a correlation between each heat injection modification parameter combination and the swept volume of the hot fluid, thereby obtaining an optimal heat injection modification parameter combination, wherein the heat injection modification parameters constituting the preset heat injection modification parameter combination include: heat injection rounds, hot fluid injection time, and hot fluid injection temperature; and Using multiple preset fracturing parameter combinations, only the reservoir to be transformed is subjected to a fracturing physical simulation to obtain a correlation between each fracturing parameter combination and the fracture propagation morphology, thereby obtaining an optimal fracturing data combination, wherein the fracturing parameters constituting the preset fracturing parameter combination include: fracturing cycles and fracturing duration; Using the optimal heat injection transformation parameter combination and the optimal fracturing transformation data combination, a cyclic transformation physical simulation of alternating heat injection transformation and fracturing transformation is performed on the reservoir to be transformed, so as to determine the optimal cyclic transformation rounds for forming the optimal fracture morphology and the optimal hot fluid injection time for each round. Based on this, the current optimal transformation plan is corrected, and the corrected transformation plan is used to transform the actual reservoir to be transformed.

5. The reservoir transformation method according to claim 4, characterized in that: The fracturing reformation is one of slick water fracturing, supercritical carbon dioxide fracturing and liquid nitrogen fracturing.

6. A computer-readable storage medium, characterized in that It contains a series of instructions for executing the steps of the method for reservoir transformation of oil shale as described in any one of claims 1 to 5.

7. A reservoir transformation system for oil shale, characterized in that: The reservoir transformation system includes the following modules: A reservoir parameter acquisition module is used to construct a physical model of the reservoir to be transformed based on the reservoir characteristic parameters of the core sample currently collected from the reservoir to be transformed, wherein the reservoir characteristic parameters include reservoir physical property parameters, pyrolysis temperature, and thermal cracking critical temperature, wherein the reservoir physical property parameters include oil shale porosity, equivalent permeability of pore-fracture rock mass, and equivalent thermal conductivity of pore-fracture rock mass; a fracture morphology prediction module for performing a physical simulation of the current reservoir to be transformed based on the physical model and utilizing a plurality of alternative transformation schemes for alternately implementing heat injection and hydraulic fracturing, thereby predicting the fracture morphology formed within the reservoir by each alternative transformation scheme, and screening the optimal fracture morphology suitable for implementing heat injection recovery by comparing each fracture morphology, and then selecting the transformation scheme that forms the optimal fracture morphology as the optimal transformation scheme; A construction plan optimization module is used to perform a physical simulation of heat injection transformation of the current reservoir to be transformed using multiple preset injection and production construction plans, so as to predict the formation time of the fracture morphology under each injection and production construction plan based on the optimal fracture morphology, and select the injection and production construction plan corresponding to the shortest formation time as the optimal injection and production construction plan, wherein the injection and production construction plan includes the distribution of the injection and production well network and the well spacing; The reservoir transformation module is used to transform the actual reservoir to be transformed using the optimal transformation plan to form the optimal fracture morphology.

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