An experimental system and method for energy storage fracturing

Abstract

This paper provides an experimental system and an experimental method for energy storage fracturing. The experimental system includes: a rock sample device, on the upper end face of which multiple simulation wells with the same depth are vertically arranged, and an encryption well is arranged between two adjacent simulation wells. The upper end face and the lower end face of the rock sample device are respectively provided with an upper saturation hole and a lower saturation hole. The system also includes a clamping device for clamping the rock sample device, a fracturing fluid injection device for injecting fracturing fluid into the simulation wells, a simulated water injection device for injecting simulated water into the rock sample, a simulated oil injection device for injecting simulated oil into the rock sample, a pressure sensor for monitoring the pressure in the simulation wells, a monitoring device for monitoring the pressure of the encryption well, and a pressure loading device for pressurizing the rock sample. This paper can provide an experimental basis for the selection of various energy storage fracturing fluids in actual mines and the optimization of well group energy storage fracturing methods.

Description

Technical Field

[0001] The present invention relates to the oil field, and in particular, to an experimental system and an experimental method for energy storage fracturing. Background Art

[0002] In existing low-permeability oilfield reservoirs, the physical properties are poor and it is difficult to establish injection-production relationships. Moreover, as the development years of production wells increase, the formation pressure continuously decreases, and the fracturing effect is difficult to guarantee, resulting in poor liquid supply capacity and low production efficiency in most production wells. How to improve formation energy and maintain a reasonable formation pressure has become the main factor restricting the efficient development of low-permeability oilfields. In recent years, injecting different energy storage media through fracturing has gradually become the main research direction, which is of great significance for the development of production wells in low-permeability oilfields.

[0003] Currently, various injectable energy storage media have been proposed, such as fresh water, sewage, natural gas, CO2, N2, etc. And due to differences in geological conditions and engineering factors, the energy storage effects of the same energy storage medium are different. The existing technology evaluates the energy storage effect mainly through indoor imbibition experiments to study energy storage and flowback after fracturing, and numerical simulations to study the influence of energy storage fracturing parameters on development effects. However, due to the imperfect experimental devices in the existing technology, the experimental results deviate greatly from the actual situation and cannot be applied to actual oil fields.

[0004] Therefore, there is an urgent need for an experimental system for energy storage fracturing to conduct energy storage fracturing experiments under laboratory conditions, so as to provide an experimental basis for the selection of various energy storage fracturing fluids and the optimization of well group energy storage fracturing methods in actual oil fields. Summary of the Invention

[0005] The purpose of the embodiments of this article is to provide an experimental system and an experimental method for energy storage fracturing, so as to provide an experimental basis for the selection of various energy storage fracturing fluids and the optimization of well group energy storage fracturing methods in actual oil fields.

[0006] To achieve the above object, on the one hand, the embodiments of this article provide an experimental system for energy storage fracturing, including:

[0007] A rock sample device, the rock sample device includes the rock samples required for the experiment, the rock sample device is arranged vertically, a plurality of simulation wells with equal depth are opened in the upper end surface of the rock sample device along the vertical direction, an encrypted well is opened between two adjacent simulation wells, a low-compressibility fluid is arranged in the encrypted well, and the encrypted well has the same depth as the simulation well;

[0008] A bottom-open wellbore is arranged in the simulation well, and the simulation well includes a wellbore section and an open-hole section at the bottom of the well; a sealed wellbore with a sealed bottom is arranged in the encrypted well;

[0009] The upper end face and the lower end face of the rock sample device are respectively communicated with an upper saturation hole and a lower saturation hole. The upper saturation hole is used to introduce simulated water or simulated oil into the rock sample, and the lower saturation hole is used to introduce simulated water into the rock sample and discharge the fluid in the rock sample.

[0010] The experimental system further includes a clamping device for clamping the rock sample device, a fracturing fluid injection device for injecting fracturing fluid into the simulated well, a simulated water injection device for injecting simulated water into the rock sample, a simulated oil injection device for injecting simulated oil into the rock sample, a pressure sensor for monitoring the pressure in the simulated well, a monitoring device for monitoring the pressure of the infill well, a fluid injection device for injecting a specified fluid into the closed wellbore of the infill well, a pressure loading device for pressurizing the rock sample, a fluid collection device for collecting the fluid discharged from the rock sample, and a vacuum pumping device for evacuating the rock sample.

[0011] Preferably, the experimental system further includes: a control device and a processing device;

[0012] The control device is used to control the experimental system to conduct an energy storage fracturing experiment;

[0013] The processing device is used to evaluate the energy storage fracturing effect of the energy storage fracturing experiment.

[0014] Preferably, the rock sample device further includes an upper plug;

[0015] The upper plug is arranged on the upper end face of the rock sample. The upper saturation hole is located in the upper plug. A plurality of the simulated wells and the infill well all penetrate through the upper plug and extend into the rock sample;

[0016] The clamping device is arranged in the vertical direction. The clamping device includes a housing, a lower plug and a rubber sleeve;

[0017] The housing is fixedly connected with the rubber sleeve. The rubber sleeve is sleeved on the outer periphery of the rock sample and is used to apply confining pressure to the rock sample. The housing is detachably connected with the lower plug. The lower plug abuts against the lower end face of the rock sample and is used to fix the rock sample. The lower saturation hole is located in the lower plug.

[0018] Preferably, the upper saturation hole is a first upper saturation hole, and the first upper saturation hole is located at the center of the upper plug;

[0019] Or, the upper saturation hole is a plurality of second upper saturation holes, and the plurality of second upper saturation holes are evenly distributed on the upper plug;

[0020] The lower saturation hole is one or more.

[0021] Preferably, a diversion groove is formed at one end of the upper plug close to the rock sample, and the diversion groove is used to evenly distribute the simulated oil or simulated water flowing into the rock sample through the upper saturation holes on the upper end face of the rock sample.

[0022] Preferably, the diversion groove includes a plurality of concentric grooves and a plurality of connecting grooves. The plurality of concentric grooves are concentrically arranged with the first upper saturation hole as the center, and the plurality of connecting grooves are evenly distributed and connect the plurality of concentric grooves;

[0023] Alternatively, the diversion groove is a surrounding groove, and the surrounding groove is spirally surrounded with the first upper saturation hole as the center;

[0024] Alternatively, the diversion groove includes a plurality of transverse grooves and a plurality of longitudinal grooves. The plurality of transverse grooves and the plurality of longitudinal grooves are interconnected and arranged in a grid shape for connecting a plurality of the second upper saturation holes.

[0025] Preferably, an axial pressure chamber is formed between the lower plug and the outer shell, a confining pressure chamber is formed between the rubber sleeve and the outer shell, and the axial pressure chamber communicates with the confining pressure chamber;

[0026] An axial pressure hole is formed at the bottom end of the outer shell, and the axial pressure hole is used to connect the axial pressure chamber and the pressure loading device. The rock sample is pressurized by pressurizing the axial pressure chamber and the confining pressure chamber through the pressure loading device;

[0027] Alternatively, the pressure loading device includes a confining pressure loading device and an axial pressure loading device. An axial pressure chamber is formed between the lower plug and the outer shell, and a confining pressure chamber is formed between the rubber sleeve and the outer shell;

[0028] An axial pressure hole is formed at the bottom end of the outer shell, and the axial pressure hole is used to connect the axial pressure chamber and the axial pressure loading device. The rock sample is pressurized by pressurizing the axial pressure chamber through the axial pressure loading device;

[0029] The lower plug is provided with a confining pressure hole, and the confining pressure hole is used to connect the confining pressure chamber and the confining pressure loading device. The rock sample is pressurized by pressurizing the confining pressure chamber through the confining pressure loading device.

[0030] Preferably, the simulated oil injection device and the simulated water injection device are connected in parallel to form a combined device. One end of the combined device is connected with an injection pump, and the other end is connected with a combined valve;

[0031] One end of the combined valve away from the combined device is simultaneously communicated with the upper saturation hole and the lower saturation hole, and a simulated water valve is further arranged between the combined valve and the lower saturation hole.

[0032] Preferably, the processing device is used for:

[0033] Select a test well from the simulated wells for energy storage fracturing and shut-in well testing;

[0034] Use the other simulated wells except the test well as monitoring wells;

[0035] During the process of energy storage fracturing and shut-in well testing in the test well, use the pressure sensor to monitor and record the pressure values of the test well and the monitoring wells in the rock sample in real time, and use the monitoring device to monitor and record the pressure value of the infill well in real time, as well as the first time when the infill well first generates a pressure response;

[0036] Determine the formation pressure evaluation factor according to the pressure values of the test well, the monitoring wells and the infill well, and the volume of the energy storage fracturing fluid when performing energy storage fracturing on the test well;

[0037] Perform fracturing and shut-in well testing on the monitoring wells;

[0038] During the process of fracturing and shut-in well testing on the monitoring wells, record the second time when the infill well first generates a pressure response;

[0039] According to the first time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the energy storage fracturing fluid when performing energy storage fracturing on the test well; the second time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the fracturing fluid when performing fracturing on the monitoring well, determine the fracture state evaluation factor;

[0040] Determine the oil production evaluation factor according to the pressure values of the test well, the monitoring wells and the infill well, and the oil production after fracturing of the test well and the monitoring wells;

[0041] Obtain the effect of energy storage fracturing according to the formation pressure evaluation factor, the fracture state evaluation factor, and the oil production evaluation factor.

[0042] On the other hand, the embodiments of the present invention provide an experimental method for energy storage fracturing applied to the control device based on the above experimental system for energy storage fracturing, including:

[0043] Obtain a prepared rock sample, wherein the prepared rock sample is provided with simulated wells and infill wells;

[0044] Clamp the rock sample through the clamping device;

[0045] Vacuum the rock sample by using the vacuum device;

[0046] Pressurize the rock sample by using the pressure loading device;

[0047] Use the simulated water injection device to inject simulated water into the rock sample until the rock sample is water-saturated;

[0048] Using the simulated oil injection device, inject simulated oil into the rock sample until the rock sample is oil-saturated;

[0049] Among them, when simulating repeated energy storage fracturing, during the process of injecting simulated oil into the rock sample, the oil pressure is greater than the set oil pressure. Use the fracturing fluid injection device to inject fracturing fluid into the simulated well for fracturing, and use the fluid collection device to collect the simulated oil discharged from the rock sample to deplete the formation pressure; when simulating primary energy storage fracturing, the oil pressure during the process of injecting simulated oil into the rock sample is not greater than the set oil pressure;

[0050] Select a test well in the simulated well with the wellbore pressure lower than the set pressure for energy storage fracturing and shut-in.

[0051] As can be seen from the technical solutions provided by the embodiments of this article above, through the experimental system in this article, according to the experimental method in this article, various different energy storage fracturing fluids can be replaced for experiments, and the experimental results of various different energy storage fracturing fluids and various different energy storage fracturing methods can be obtained. Furthermore, it can provide an experimental basis for the selection of various energy storage fracturing fluids in the actual oilfield and the optimization of the well group energy storage fracturing method.

[0052] To make the above and other purposes, features, and advantages of this article more obvious and understandable, the following specific preferred embodiments are given, and in conjunction with the accompanying drawings, the detailed description is as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of this article or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of this article. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0054] Figure 1 Shows the projected view after the cross-section of the rock sample device provided by the embodiment of this article;

[0055] Figure 2 Shows the overall structural schematic diagram of an energy storage fracturing experimental system provided by the embodiment of this article;

[0056] Figure 3 Shows the top view of the rock sample clamped by the clamping device provided by the embodiment of this article;

[0057] Figure 4 Shows the projected view after the cross-section of another rock sample device provided by the embodiment of this article;

[0058] Figure 5Shows another overall structural schematic diagram of an energy storage fracturing experimental system provided by the embodiments of the present disclosure;

[0059] Figure 6 Shows a top view of another rock sample clamped by a clamping device provided by the embodiments of the present disclosure;

[0060] Figure 7 Shows an overall structural schematic diagram of a diversion groove provided by the embodiments of the present disclosure;

[0061] Figure 8 Shows an overall structural schematic diagram of another diversion groove provided by the embodiments of the present disclosure.

[0062] Description of the reference signs in the drawings:

[0063] 1. Outer shell; 2. Fracturing fluid injection device; 26. Fracturing fluid plunger pump; 27. First fracturing fluid valve; 28. Fracturing fluid container; 29. Second fracturing fluid valve; 3. Simulated water injection device; 31. First simulated water valve; 32. Simulated water container; 33. Second simulated water valve; 4. Simulated oil injection device; 41. First simulated oil valve; 42. Simulated oil container; 43. Second simulated oil valve; 5. Fluid injection device; 51. Fluid plunger pump; 52. First specified fluid valve; 53. Specified fluid container; 54. Second specified fluid valve; 7. Pressure loading device; 71. Axial pressure plunger pump; 72. Axial pressure valve; 8. Fluid collection device; 81. Fluid valve; 82. Fluid container; 9. Vacuum pumping device; 91. Vacuum pumping valve; 92. Vacuum pump; 10. Rock sample; 11. Upper plug; 111. First upper saturation hole; 1111. Concentric groove; 1112. Communication groove; 112. Second upper saturation hole; 1121. Transverse groove; 1122. Longitudinal groove; 113. Filler hole; 12. Lower plug; 121. Lower saturation hole; 13. Rubber sleeve; 14. Simulated well; 141. Wellbore section; 142. Bottom hole open hole section; 15. Infill well; 16. Injection well; 19. Confining pressure chamber; 20. Axial pressure hole; 21. Axial pressure chamber; 22. Injection pump; 23. Combination valve; 24. Simulated water valve; 25. Water injection device; 251. Water injection plunger pump; 252. First water injection valve; 253. Water injection container; 254. Second water injection valve. Detailed implementation manners

[0064] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present disclosure.

[0065] In recent years, injecting different energy storage media through fracturing has gradually become the main research direction, which is of great significance for the development of oil production wells in low-permeability oilfields.

[0066] At present, various injectable energy storage media have been proposed, such as fresh water, sewage, natural gas, CO2, N2, etc. Due to differences in geological conditions and engineering factors, the energy storage effects of the same energy storage medium are different. The existing technology evaluates the energy storage effect mainly through indoor imbibition experiments to study energy storage and backflow after fracturing, and numerical simulation to study the influence of energy storage fracturing parameters on the development effect. However, due to the imperfect experimental device in the existing technology, the experimental results are quite different from the actual situation and cannot be applied to actual mines.

[0067] To solve the above problems, the embodiments of this article provide an experimental system and method for energy storage fracturing. When the system or device product in practice is executed, it can be executed sequentially or in parallel according to the methods shown in the embodiments or the drawings.

[0068] It should be noted that the terms "first", "second", etc. in the specification, claims and the above drawings of this article are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of this article described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0069] This article shows an experimental system for energy storage fracturing. It should be noted that this experimental system is applied in a laboratory environment and can simulate the energy storage fracturing experiment of low-permeability or tight oil and gas reservoirs. Refer to Figure 1 , the experimental system includes:

[0070] A rock sample device, the rock sample device includes the rock sample 10 required for the experiment. The rock sample device is arranged in the vertical direction. A plurality of simulation wells 14 with the same depth are opened on the upper end surface of the rock sample device in the vertical direction. An encryption well 15 is opened between two adjacent simulation wells 14. A low-compressibility fluid is arranged in the encryption well 15, and the encryption well 15 is of the same depth as the simulation well 14.

[0071] A wellbore with an open bottom is provided in the simulated well 14. The wellbore can be made of metal or other materials capable of withstanding pressure. The simulated well 14 includes a wellbore section 141 and an open-hole section at the bottom 142. The bottom of the simulated well 14 is not sealed. A sealed wellbore with a sealed bottom is provided in the infill well 15. The sealed wellbore can also be made of metal or other materials capable of withstanding pressure.

[0072] Referring to Figure 1 and Figure 2 The upper and lower end faces of the rock sample device are respectively connected with an upper saturation hole and a lower saturation hole 121. The upper saturation hole is used to introduce simulated water or simulated oil into the rock sample. The lower saturation hole 121 is used to introduce simulated water into the rock sample and discharge the fluid in the rock sample 10.

[0073] Combined with Figure 3 Specifically, the rock sample device further includes an upper plug 11;

[0074] The upper plug 11 is arranged on the upper end face of the rock sample 10. The upper saturation hole is located in the upper plug 11. A plurality of the simulated wells 14 and the infill well 15 all penetrate through the upper plug 11 and extend into the rock sample 10;

[0075] The clamping device is arranged in the vertical direction. The clamping device includes a housing 1, a lower plug 12 and a rubber sleeve 13;

[0076] The housing 1 is fixedly connected with the rubber sleeve 13. The rubber sleeve 13 is sleeved on the outer periphery of the rock sample 10 for fixing the rock sample 10. The housing 1 is detachably connected with the lower plug 12. The lower plug 12 abuts against the lower end face of the rock sample 10 for fixing the rock sample 10. The lower saturation hole is located in the lower plug 12. In addition to the function of fixing the rock sample 10, the rubber sleeve 13 can also isolate the fluid between the rock sample 10 and the confining pressure chamber 19 and play a role in protecting the rock sample 10.

[0077] Generally speaking, the rock sample 10 is cylindrical. During the preparation of the rock sample 10, a cylindrical mold needs to be prepared first, and an upper plug 11 with holes and an upper saturation hole is prepared, and the upper plug 11 and the mold are combined and sealed.

[0078] Insert a wellbore with a sealing rubber plug at the bottom into the hole of the simulation well 14 in the upper plug 11. Of course, the sealing rubber plug can also be made of other materials, which will not be elaborated herein. The purpose is to fill the open hole section 142 of the bottom of the well in advance. Insert a sealed wellbore with a sealed bottom into the hole of the infill well 15 in the upper plug 11. The lengths of the wellbore with a sealing rubber plug at the bottom and the sealed wellbore are equal, approximately 1 / 2 - 2 / 3 of the depth of the rock sample 10. The sealing rubber plug is the reserved open hole section 142 of the bottom of the well. External threads are provided at the lower ends of the wellbore and the sealed wellbore. The purpose of the external threads is to increase the friction between the rock sample 10 and the wellbore, facilitating well cementing. To facilitate injecting fluids into the simulation well 14 and the infill well 15 through pipelines in the later stage, a conversion interface can be set at the wellheads of the simulation well 14 and the infill well 15.

[0079] A stuffing hole 113 can be provided in the upper plug 11. Quartz sand, cement, and water are mixed and stirred in a certain proportion to form magma. A funnel is installed on the stuffing hole 113, and the magma is poured into the mold through the funnel, or directly connected to the stuffing hole 113 through a pipeline to pour the magma into the mold. A transparent observation window (not shown) can be set on the mold. Experimenters can observe the pouring situation of the magma through the transparent observation window. Stop pouring when the magma liquid level is about to contact the upper plug 11.

[0080] After standing for a period of time, after the magma solidifies, demolding can be carried out. After demolding, the sealing rubber plug at the bottom of the wellbore is taken out, exposing the open hole section 142 of the bottom of the well. The rock sample 10 can also be an outcrop or downhole core sample, processed into a preset size, drilled according to the well pattern layout, the wellbore is reserved, placed in the mold, and then the simulation well and the infill well are inserted into the rock sample for well cementing.

[0081] The experimental system further includes a clamping device for clamping the rock sample device. During the assembly of the experimental system, first place the clamping device horizontally, push the rock sample 10 with the upper plug 11 into the clamping device, install the lower plug 12 with a lower saturation hole 121, and then turn the clamping device to the vertical direction and connect the inlet end and the outlet end pipelines. The purpose of turning the clamping device to the vertical direction is to avoid uneven energy storage caused by the influence of gravity during the experiment, so that the energy storage fracturing fluid diffuses in the same plane.

[0082] The experimental system further includes a fracturing fluid injection device 2 for injecting fracturing fluid into the simulated well 14, a simulated water injection device 3 for injecting simulated water into the rock sample 10, a simulated oil injection device 4 for injecting simulated oil into the rock sample 10, a pressure sensor (not shown) for monitoring the pressure in the simulated well 14, a monitoring device (not shown) for monitoring the pressure inside the sealed wellbore of the infill well 15, a fluid injection device 5 for injecting a specified fluid into the sealed wellbore of the infill well, a pressure loading device 7 for pressurizing the rock sample 10, a fluid collection device 8 for collecting the fluid discharged from the rock sample 10, a vacuum pumping device 9 for evacuating the rock sample 10, a control device (not shown) for controlling the experimental system to conduct an energy storage fracturing experiment, and a processing device (not shown) for evaluating the energy storage fracturing effect of the energy storage fracturing experiment.

[0083] Referring to Figure 1 and Figure 3 , wherein the upper saturation hole is a first upper saturation hole 111, and the first upper saturation hole 111 is located at the center of the upper plug 11; or, referring to Figure 4 and Figure 6 , the upper saturation hole is a plurality of second upper saturation holes 112, and the plurality of second upper saturation holes 112 are uniformly distributed on the upper plug 11;

[0084] Referring to Figure 2 , the lower saturation hole 121 is one or more.

[0085] One end of the upper plug 11 close to the rock sample 10 is provided with a diversion groove, and the diversion groove is used to uniformly distribute the simulated oil or simulated water flowing into the rock sample 10 through the upper saturation hole on the upper end face of the rock sample 10. According to the different numbers and positions of the upper saturation holes, the setting methods of the diversion groove are also different. Specifically, referring to Figure 7 , the diversion groove includes a plurality of concentric grooves 1111 and a plurality of connecting grooves 1112. The plurality of concentric grooves 1111 are concentrically arranged with the first upper saturation hole 111 as the center, and the plurality of connecting grooves 1112 are uniformly distributed and connected to the plurality of concentric grooves 1111; or, the diversion groove is a surrounding groove (not shown), and the surrounding groove is spirally surrounded with the first upper saturation hole 111 as the center; or, referring to Figure 8 , the diversion groove includes a plurality of transverse grooves 1121 and a plurality of longitudinal grooves 1122. The plurality of transverse grooves 1121 and the plurality of longitudinal grooves 1122 are connected to each other in a grid pattern for connecting the plurality of second upper saturation holes 112. Of course, the diversion groove can also be set by other methods that can be conceived by those skilled in the art.

[0086] Referring to Figure 2, in one embodiment, an axial pressure chamber 21 is formed between the lower plug 12 and the outer shell 1, and a confining pressure chamber 19 is formed between the rubber sleeve 13 and the outer shell 1. The axial pressure chamber 21 communicates with the confining pressure chamber 19;

[0087] An axial pressure hole 20 is provided at the bottom end of the outer shell 1. The axial pressure hole 20 is used to connect the axial pressure chamber 21 and the pressure loading device 7. The pressure loading device 7 pressurizes the axial pressure chamber 21 and the confining pressure chamber 19 to pressurize the rock sample 10.

[0088] Or in another embodiment (not shown), the pressure loading device includes a confining pressure loading device and an axial pressure loading device. An axial pressure chamber is formed between the lower plug and the outer shell, and a confining pressure chamber is formed between the rubber sleeve and the outer shell. The difference from the previous embodiment is that the axial pressure chamber does not communicate with the confining pressure chamber, that is, referring to Figure 2 In the T-shaped lower plug 12, the two ends of the T-shaped head abut against the outer shell, so that the axial pressure chamber 21 does not communicate with the confining pressure chamber 19;

[0089] An axial pressure hole is provided at the bottom end of the outer shell. The axial pressure hole is used to connect the axial pressure chamber and the axial pressure loading device. The axial pressure loading device pressurizes the axial pressure chamber to pressurize the rock sample;

[0090] In another embodiment, the lower plug is provided with a confining pressure hole (not shown). The confining pressure hole is used to connect the confining pressure chamber and the confining pressure loading device (not shown). The confining pressure loading device pressurizes the confining pressure chamber to pressurize the rock sample.

[0091] Specifically, the pressure loading device 7 includes an axial pressure piston pump 71 and an axial pressure valve 72 connected in sequence. One end of the axial pressure valve 72 away from the axial pressure piston pump 71 communicates with the axial pressure hole 20.

[0092] Among them, the simulated oil injection device 4 and the simulated water injection device 3 are connected in parallel to form a combined device. One end of the combined device is connected to an injection pump 22, and the other end is connected to a combined valve 23.

[0093] One end of the combined valve 23 away from the combined device is simultaneously communicated with the upper saturation hole and the lower saturation hole 121. A simulated water valve 24 is further arranged between the combined valve 23 and the lower saturation hole 121. If simulated water is injected into the rock sample 10, the simulated oil injection device 4 is closed, the simulated water injection device 3 is opened, and both the combined valve 23 and the simulated water valve 24 are opened. At this time, simulated water can be injected into the rock sample 10 through the upper saturation hole and the lower saturation hole 121 simultaneously. If simulated oil is injected into the rock sample 10, the simulated water injection device 3 is closed, the simulated oil injection device 4 is opened, the simulated water valve 24 is closed, and the combined valve 23 is opened. At this time, simulated oil can be injected into the rock sample 10 through the upper saturation hole.

[0094] The simulated water injection device 3 includes a simulated water first valve 31, a simulated water container 32, and a simulated water second valve 33 that are connected in sequence. One end of the simulated water second valve 33 away from the simulated water container 32 is connected to the injection pump 22, and one end of the simulated water first valve 31 away from the simulated water container 32 is connected to the combined valve 23.

[0095] The simulated oil injection device 4 includes a simulated oil first valve 41, a simulated oil container 42, and a simulated oil second valve 43 that are connected in sequence. One end of the simulated oil second valve 43 away from the simulated oil container 42 is connected to the injection pump 22, and one end of the simulated oil first valve 41 away from the simulated oil container 42 is connected to the combined valve 23.

[0096] The purpose of designing this experimental system is to simulate the energy storage fracturing process in the study area in the laboratory and further analyze the energy storage fracturing effect in the study area. Simulated water is arranged in the simulated water container 32. The simulated water can be prepared from the produced water returned from the study area and distilled water in a ratio of 1:3 for simulating the formation water in the study area. Simulated oil is arranged in the simulated oil container 42. The simulated oil can be configured from the crude oil in the study area and kerosene in a ratio of 1:3 for simulating the oil produced in the study area.

[0097] Of course, during the process of simulating the energy storage fracturing in the study area, some study areas may be low-permeability oil reservoirs. For low-permeability oil reservoirs, water injection development is required. For the experimental system in this case, referring to Figure 4 and Figure 5 , a water injection well 16 needs to be opened on the upper end face of the rock sample 10. The water injection well 16 penetrates through the upper plug 11 and extends into the rock sample 10. The water injection well 16 is of the same depth as the simulated well 14. The water injection well 16 is communicated with a water injection device 25 for injecting water into the water injection well 16.

[0098] The water injection device 25 includes a water injection piston pump 251, a first water injection valve 252, a water injection container 253, and a second water injection valve 254 that are connected in sequence. One end of the second water injection valve 254 away from the water injection container 253 is connected to the wellhead of the injection well 16, and a simulated water source is provided in the water injection container 253.

[0099] To ensure the uniformity of water injection, an injection well 16 can be opened at the center of the upper end face of the rock sample 10. To facilitate the opening of the injection well 16, refer to Figure 4 and Figure 6 , the number and position of the upper saturation holes need to be set in such a way that a plurality of uniformly distributed second upper saturation holes 112 are provided in the upper plug 11; or, refer to Figure 1 and Figure 3 , a plurality of injection wells (not shown) are uniformly opened on the upper end face of the rock sample 10. To facilitate the opening of the injection wells, the number and position of the upper saturation holes need to be set in such a way that a first upper saturation hole 111 is provided at the center of the upper plug 11.

[0100] Refer to Figure 2 or Figure 5 , in the embodiments of this article, the fracturing fluid injection device 2 includes a fracturing fluid piston pump 26, a first fracturing fluid valve 27, a fracturing fluid container 28, and a second fracturing fluid valve 29 that are connected in sequence. One end of the second fracturing fluid valve 29 away from the fracturing fluid container 28 communicates with the wellheads of all the simulated wells 14. Of course, according to the different energy storage fracturing methods, the setting method of the fracturing injection device 2 is also different. The energy storage fracturing method can be: an energy storage fracturing method in which after small-displacement energy storage is carried out using an energy storage fluid, fracturing is carried out using a fracturing fluid at a set displacement, where the small displacement is less than the set displacement. At this time, two groups of fracturing injection devices 2 are provided (not shown), and the two groups of fracturing injection devices 2 are arranged in parallel. The two groups of fracturing injection devices 2 are the same except for the different solutions in the fracturing fluid containers 28. The solution in one group of fracturing fluid containers 28 is the energy storage fluid, and the solution in the other group of fracturing fluid containers 28 is the fracturing fluid. The energy storage fracturing method can also be: an energy storage fracturing method in which large-displacement direct fracturing is carried out using an energy storage fracturing fluid, where the large displacement is greater than the set displacement. At this time, one group of fracturing injection devices 2 is provided, and the solution in the fracturing fluid container 28 of this group of fracturing injection devices 2 is the energy storage fracturing fluid.

[0101] The fluid injection device 5 includes a fluid piston pump 51, a first specified fluid valve 52, a specified fluid container 53, and a second specified fluid valve 54 that are connected in sequence. One end of the second specified fluid valve 54 away from the specified fluid container 53 communicates with the wellhead of the infill well 15. The monitoring container 53 is used to hold the specified fluid, where the specified fluid is a low-compressibility fluid with a compressibility lower than the set compressibility.

[0102] The fluid collection device 8 includes a fluid valve 81 and a fluid container 82 connected in sequence. One end of the fluid valve 81 away from the fluid container 82 communicates with the lower saturation hole 121, and the fluid container 82 is used to hold the fluid flowing out of the lower saturation hole 121.

[0103] The vacuum pumping device 9 includes a vacuum pumping valve 91 and a vacuum pump 92 connected in sequence. One end of the vacuum pumping valve 91 away from the vacuum pump 92 communicates with the lower saturation hole 121 and is used to pump the rock sample 10 to vacuum.

[0104] The control device is used for:

[0105] Step 1.1: Obtain the prepared rock sample 10, wherein the prepared rock sample 10 is provided with a simulated well 14 and an encrypted well 15.

[0106] Step 1.2: Clamp the rock sample 10 by the clamping device.

[0107] Step 1.3: Use the vacuum pumping device 9 to pump the rock sample 10 to vacuum.

[0108] Step 1.4: Pressurize the rock sample by the pressure loading device.

[0109] Step 1.5: Use the simulated water injection device 3 to inject simulated water into the rock sample 10 until the rock sample 10 is water-saturated.

[0110] During the process of injecting simulated water into the rock sample 10 in this step, close the simulated oil injection device 4 and the fluid valve 81, open the simulated water injection device 3, and open both the combination valve 23 and the simulated water valve 24. At this time, simulated water can be injected into the rock sample 10 through the upper saturation hole and the lower saturation hole 121 simultaneously. After injecting for a period of time, close the simulated water injection device 3. After stabilizing for a period of time, then open the fluid valve 81 in the fluid collection device 8. When there is uniform fluid flowing out of the fluid valve 81, it means the rock sample 10 is water-saturated. When there is no uniform fluid flowing out, it means the rock sample 10 is not saturated. This step can be repeated until there is uniform fluid flowing out of the fluid valve 81;

[0111] Step 1.6: Use the simulated oil injection device 4 to inject simulated oil into the rock sample 10 until the rock sample 10 is oil-saturated.

[0112] During the process of injecting simulated oil into the rock sample 10 in this step, the simulated water injection device 3 and the fluid valve 81 are closed, the simulated oil injection device 4 is opened, the simulated water valve 24 is closed, and the combined valve 23 is opened. At this time, simulated oil can be injected into the rock sample 10 through the upper saturation hole to displace the simulated water from the rock sample 10. Then, the fluid valve 81 in the fluid collection device 8 is opened. At the beginning of the displacement, the fluid flowing out of the fluid valve 81 is simulated water. After a period of time, an oil-water mixture flows out. Finally, when the simulated water is completely displaced, simulated oil flows out. When uniform simulated oil flows out of the fluid valve 81, it indicates that the rock sample 10 is oil-saturated. When uniform simulated oil does not flow out, it indicates that the rock sample 10 is not saturated. This step can be repeated until uniform simulated oil flows out of the fluid valve 81.

[0113] During the process of injecting simulated oil into the rock sample 10 in this step, it is necessary to set the oil pressure of the simulated oil during the injection process. Specifically, since the experimental method and experimental system described in this article can be applied to simulate primary energy storage fracturing or repeated energy storage fracturing. According to different experimental simulation requirements, if the formation pressure in the initial state is not higher than the specified pressure, that is, to simulate primary energy storage fracturing, the oil pressure of the simulated oil during the process of injecting the simulated oil into the rock sample 10 is not greater than the set oil pressure. If the formation pressure in the initial state is higher than the specified pressure, that is, to simulate repeated energy storage fracturing, the oil pressure of the simulated oil during the process of injecting the simulated oil into the rock sample 10 is greater than the set oil pressure to deplete the formation pressure;

[0114] The primary fracturing and primary production are as follows: using the fracturing fluid injection device 2 to inject fracturing fluid into the simulated well 14 for fracturing, and using the fluid collection device 8 to collect the simulated oil discharged from the rock sample 10 for production.

[0115] Step 1.7: Select a test well with a wellbore pressure lower than the set pressure from the simulated well 14 for energy storage fracturing and shut-in.

[0116] The processing device is used for:

[0117] S101: Select a test well for energy storage fracturing and shut-in from the simulated well;

[0118] S102: Use the other simulated wells except the test well as monitoring wells;

[0119] S103: During the process of energy storage fracturing and shut-in of the test well, use the pressure sensor to monitor and record the pressure values of the test well and the monitoring wells in the rock sample in real time, and use the monitoring device to monitor and record the pressure value of the infill well in real time, as well as the first time when the infill well first generates a pressure response;

[0120] S104: Determine a formation pressure evaluation factor based on the pressure values of the test well, monitoring wells, and infill wells, and the volume of energy storage fracturing fluid during energy storage fracturing of the test well;

[0121] S105: Perform fracturing and shut-in on the monitoring wells;

[0122] S106: During the process of fracturing and shut-in of the monitoring wells, record the second time when the infill well first generates a pressure response;

[0123] S107: Based on the first time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the energy storage fracturing fluid during energy storage fracturing of the test well; the second time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the fracturing fluid during fracturing of the monitoring well, determine a fracture state evaluation factor;

[0124] S108: Determine an oil production evaluation factor based on the pressure values of the test well, monitoring wells, and infill wells, and the oil production after fracturing of the test well and monitoring wells;

[0125] S109: Obtain the effect of energy storage fracturing based on the formation pressure evaluation factor, fracture state evaluation factor, and oil production evaluation factor.

[0126] For an infill well, the monitoring device can be a pressure sensor. It is necessary to monitor the deformation of the low-compressibility fluid through the monitoring device, and then convert the pressure value inside the sealed wellbore of the infill well.

[0127] The specific conversion method is as follows:

[0128] 1. The wellbore of the infill well is completely filled with low-compressibility fluid. The wellbore is filled with low-compressibility fluid. After the low-compressibility fluid is compressed and generates a volume change, it will cause a small but recognizable pressure change. The pressure value of the infill well is:

[0129]

[0130] 2. The wellbore of the infill well is not filled with low-compressibility fluid. In the wellbore of the infill well where the liquid level of the low-compressibility fluid is below the ground, the wellbore pressure monitoring device is located below the liquid level of the low-compressibility fluid, and monitors the change in hydrostatic pressure caused by the rise of the liquid level of the low-compressibility fluid. It is 1 - 2 orders of magnitude smaller than the pressure change when the wellbore is completely sealed by the low-compressibility fluid. The pressure value of the infill well is:

[0131]

[0132] where dP out is the pressure value of the infill well, dP inis the pressure change in the wellbore measured by the wellbore pressure monitoring device (caused by the compression of the low-compressibility fluid in the wellbore or the rise of the liquid level), α out is the inner diameter of the wellbore of the infill well, β out is the outer diameter of the wellbore of the infill well, c is the compressibility of the low-compressibility fluid, D H is the depth of the wellbore, E is the Young's modulus of the wellbore material of the infill well, L c is the length of the casing for applying a given external pressure to produce a specific internal pressure change, which can be the length of the production casing. The production casing is the casing in contact with the reservoir, and ρ is the density of the low-compressibility fluid.

[0133] During the process of energy storage fracturing and shut-in in the test well, in addition to recording the pressure values of the test well, monitoring well, and infill well in the rock sample in real time, it is also necessary to record the first time when the infill well first generates a pressure response. Generally speaking, whether it is the test well, monitoring well, or infill well, the pressure value first rises, then decreases, and finally stabilizes to a stable value. Taking a certain monitoring well A as an example, during the process of the pressure value of monitoring well A rising, the fractures generated by the energy storage fracturing and shut-in in the test well are extending, and the pressure wave is transmitted to monitoring well A. After the shut-in starts, the pressure decreases, and the pressure value of monitoring well A will stabilize to a stable value. For the infill well, the first time when the first pressure response is generated refers to the time elapsed from the start of the fracture in the test well to the arrival of the fracture at the infill well.

[0134] According to the pressure values of the test well, monitoring well, and infill well in the rock sample, determine the formation pressure evaluation factor. Then, it is also necessary to perform fracturing and shut-in on the monitoring well. The monitoring well may be one or more. When performing fracturing and shut-in on the monitoring well, it can be carried out one by one after sorting the pressure values in the monitoring well from small to large. For the monitoring well with a pressure response to the test well, according to the amplitude of the pressure response, the monitoring well with an amplitude greater than the amplitude threshold does not need to perform energy storage and can be directly fractured and then shut in. The monitoring well with an amplitude less than or equal to the amplitude threshold or the monitoring well without a pressure response can be used as an alternative test well, and the alternative test well can perform energy storage fracturing. In addition, the energy storage fracturing can be carried out separately. For some test wells or monitoring wells, if the initial transformation volume meets the requirements and the formation pressure drops due to long-term production, energy storage can be carried out only according to the actual situation without repeated fracturing.

[0135] During the process of fracturing and shut-in of the monitoring well, record the second time when the infill well first generates a pressure response. The second time when the first pressure response is generated refers to the time elapsed from the start of the fracture in the monitoring well to the arrival of the fracture at the infill well, and then determine the fracture state evaluation factor.

[0136] Based on the pressure values of the test wells, monitoring wells, and infill wells, as well as the oil production after fracturing of the test wells and monitoring wells, the oil production evaluation factor can be determined. Based on the formation pressure evaluation factor, fracture state evaluation factor, and oil production evaluation factor, the energy storage fracturing effect can be further obtained.

[0137] In the embodiments of the present invention, there is one or more test wells, and the basis for selecting the test wells is that the pressure in the test wells is lower than the pressure in the monitoring wells.

[0138] If there are multiple test wells, the energy storage fracturing and shut-in of the test wells according to the selected energy storage fracturing method further include:

[0139] S201: Sort the multiple test wells in ascending order of the pressure in the wells;

[0140] S202: Perform energy storage fracturing and shut-in on the test wells in the sorted order according to the selected energy storage fracturing method.

[0141] Assume that there are two or more test wells with approximately the same pressure in the multiple test wells. The test wells with approximately the same pressure can be simultaneously subjected to energy storage fracturing and shut-in. Although simultaneous energy storage fracturing and shut-in can improve work efficiency, it is necessary to further determine which test well the first pressure response of the infill well is specifically for. Therefore, preferably, the test wells are successively subjected to energy storage fracturing and shut-in in the sorted order.

[0142] In the embodiments of the present invention, the selected energy storage fracturing method includes:

[0143] An energy storage fracturing method of performing small-displacement energy storage with a fracturing fluid injection device and then performing fracturing with a set displacement, and an energy storage fracturing method of directly performing large-displacement fracturing with a fracturing fluid injection device; wherein, the small displacement is less than the set displacement, and the large displacement is greater than the set displacement.

[0144] Specifically, the energy storage fracturing method of performing fracturing with a set displacement after small-displacement energy storage is: first inject energy storage fluid into the test well at a small displacement, and then inject fracturing fluid into the test well at a set displacement after the pressure or energy storage amount in the test well reaches the expected value. No fractures will be generated in the test well during the small-displacement energy storage period, and fractures will be generated in the test well when injecting the selected fracturing fluid at a set displacement.

[0145] Specifically, the energy storage fracturing method of directly performing large-displacement fracturing is: directly inject energy storage fracturing fluid into the test well at a large displacement, and the large-displacement injection of energy storage fracturing fluid will cause fractures in the rock sample.

[0146] In the embodiments of the present invention, determining the formation pressure evaluation factor according to the pressure values of the test well, the monitoring well and the infill well, and the volume of the energy storage fracturing fluid during the energy storage fracturing of the test well further includes:

[0147] S301: Obtain the stable pressure value of the test well, the stable pressure value of the monitoring well and the stable pressure value of the infill well according to the pressure values of the test well, the monitoring well and the infill well;

[0148] S302: Obtain the average pressure value according to the stable pressure value of the test well, the stable pressure value of the monitoring well and the stable pressure value of the infill well;

[0149] S303: Obtain the formation pressure increase amplitude according to the difference between the average pressure value and the initial formation pressure value;

[0150] S304: Obtain the energy storage coefficient according to the formation pressure increase amplitude and the volume of the energy storage fracturing fluid during the energy storage fracturing of the test well;

[0151] S305: Determine the formation pressure increase amplitude and the energy storage coefficient as the formation pressure evaluation factor.

[0152] During the processes of energy storage fracturing and shut-in of the test well, the pressure values of the test well, the monitoring well and the infill well all first increase, then decrease, and finally stabilize to a stable value. Take the stable pressure values of all test wells, the stable pressure values of monitoring wells and the stable pressure values of infill wells for mean calculation to obtain the average pressure value. The initial formation pressure value is the formation pressure before the energy storage fracturing of the test well, and the formation pressure increase amplitude can be obtained from the difference between the average pressure value and the initial formation pressure value.

[0153] Furthermore, the energy storage coefficient can be calculated by the following formula:

[0154]

[0155] where, E V is the energy storage coefficient, V R is the volume of the fracturing fluid. If the energy storage fracturing method of setting the displacement after small-displacement energy storage is adopted, V R is the sum of the volume of the energy storage fluid during the energy storage process and the volume of the fracturing fluid during the fracturing process. If the energy storage fracturing method of direct large-displacement fracturing is adopted, V R is the volume of the energy storage fracturing fluid during the large-displacement fracturing process, and P n is the formation pressure increase amplitude.

[0156] The formation pressure increase amplitude and the energy storage coefficient are determined as formation pressure evaluation factors. The closer the energy storage coefficient is to the standard energy storage coefficient, the better the energy storage fracturing effect represents. Among them, the standard energy storage coefficient is determined according to the actual working conditions. The greater the formation pressure increase amplitude, the better the energy storage fracturing effect represents. Thus, the energy storage fracturing effect is evaluated through the formation pressure evaluation factors.

[0157] In the embodiments of this article, based on the first time when the infill well first generates a pressure response, the position of this infill well, and the pumping rate of the energy storage fracturing fluid when performing energy storage fracturing on the test well; the second time when the infill well first generates a pressure response, the position of this infill well, and the pumping rate of the fracturing fluid when performing fracturing on the monitoring well, determining the fracture state evaluation factor further includes:

[0158] S401: According to the first time when the infill well first generates a pressure response and the pumping rate of the energy storage fracturing fluid when performing energy storage fracturing on the test well, calculate the first response amount when the infill well first generates a pressure response;

[0159] S402: According to the first time when the infill well first generates a pressure response and the position of this infill well, obtain the fracture diffusion coefficient of the corresponding test well;

[0160] S403: According to the second time when the infill well first generates a pressure response and the pumping rate of the fracturing fluid when performing fracturing on the monitoring well, calculate the second response amount when the infill well first generates a pressure response;

[0161] S404: According to the second time when the infill well first generates a pressure response and the position of this infill well, obtain the fracture diffusion coefficient of the corresponding monitoring well;

[0162] S405: Determine the first response amount when the infill well first generates a pressure response, the fracture diffusion coefficient of the corresponding test well, the second response amount when the infill well first generates a pressure response, and the fracture diffusion coefficient of the corresponding monitoring well as the fracture state evaluation factor.

[0163] In S401 and S403, specifically, the first response amount or the second response amount when the infill well first generates a pressure response is calculated by the following formula:

[0164] Q = qt(13)

[0165] Among them, Q is the first response amount or the second response amount when the infill well first generates a pressure response, q is the pumping rate of the energy storage fracturing fluid when performing energy storage fracturing on the test well or the pumping rate of the fracturing fluid when performing fracturing on the monitoring well, and t is the first time or the second time when the infill well first generates a pressure response.

[0166] In S402 and S404, specifically, the fracture diffusion coefficient is calculated by the following formula:

[0167]

[0168] where D k is the fracture diffusion coefficient of the test well or monitoring well, L is the distance between the position of the infill well and the position of the corresponding test well or monitoring well, and t is the first time or the second time when the infill well first generates a pressure response.

[0169] In S405, for the test well, the smaller the fracture diffusion coefficient, the larger the first response amount, indicating that new fractures may have been generated and the fractures are relatively complex, and the energy storage fracturing effect is better. On the contrary, the larger the fracture diffusion coefficient, the smaller the first response amount, indicating that new fractures may not have been generated and the fractures are relatively simple, and the energy storage fracturing effect is worse. The same is true for the monitoring well. Therefore, the energy storage fracturing effect can be evaluated by the fracture state evaluation factor.

[0170] In the embodiments of the present invention, determining the oil production evaluation factor according to the pressure values of the test well, the monitoring well and the infill well, and the post-fracture oil production of the test well and the monitoring well further includes:

[0171] S501: Obtain the stable pressure value of the test well, the stable pressure value of the monitoring well and the stable pressure value of the infill well according to the pressure values of the test well, the monitoring well and the infill well;

[0172] S502: Obtain the average pressure value according to the stable pressure value of the test well, the stable pressure value of the monitoring well and the stable pressure value of the infill well;

[0173] S503: Obtain the formation pressure increase amplitude according to the difference between the average pressure value and the initial formation pressure value;

[0174] S504: Obtain the production increase coefficient according to the formation pressure increase amplitude and the post-fracture oil production of the test well and the monitoring well;

[0175] S505: Determine the production increase coefficient as the oil production evaluation factor.

[0176] The formation pressure increase amplitude can be obtained when determining the formation pressure evaluation factor of the well group according to the above text, which will not be elaborated here. Further, the production increase coefficient can be calculated by the following formula:

[0177]

[0178] where Ez is the production increase coefficient, M is the post-fracture oil production of the test well and the monitoring well, and P n is the formation pressure increase amplitude.

[0179] Open the production wells of the test well and the monitoring well to obtain the daily oil production of the test well and the monitoring well. By summing up the daily oil production for 365 days, the annual oil production of the test well and the monitoring well can be obtained. Of course, the quarterly oil production and monthly oil production of the test well and the monitoring well can also be calculated, which will not be elaborated in this article. The daily oil production, annual oil production, or quarterly oil production of the test well and the monitoring well can be used as the post-fracturing oil production of the test well and the monitoring well, and then the stimulation coefficient can be calculated. The larger the stimulation coefficient, the better the energy storage fracturing effect. Furthermore, the energy storage fracturing effect is evaluated through the oil production evaluation factor.

[0180] In summary, the energy storage fracturing effect can be comprehensively evaluated through the formation pressure evaluation factor, fracture state evaluation factor, and oil production evaluation factor to obtain the energy storage fracturing effect generated after the energy storage fracturing of the test well.

[0181] Based on the above-mentioned experimental system for energy storage fracturing, this article also proposes an experimental method for energy storage fracturing, which is applied to the control device and includes:

[0182] Obtain the prepared rock sample, in which the prepared rock sample is provided with a simulated well and an infill well;

[0183] Clamp the rock sample through the clamping device;

[0184] Vacuum the rock sample using the vacuum device;

[0185] Pressurize the rock sample using the pressure loading device;

[0186] Inject simulated water into the rock sample using the simulated water injection device until the rock sample is water-saturated;

[0187] Inject simulated oil into the rock sample using the simulated oil injection device until the rock sample is oil-saturated;

[0188] Among them, when simulating repeated energy storage fracturing, during the process of injecting simulated oil into the rock sample, the oil pressure is greater than the set oil pressure. Inject fracturing fluid into the simulated well for fracturing using the fracturing fluid injection device, and collect the simulated oil discharged from the rock sample using the fluid collection device to deplete the formation pressure; when simulating primary energy storage fracturing, during the process of injecting simulated oil into the rock sample, the oil pressure is not greater than the set oil pressure;

[0189] Select a test well with a wellbore pressure lower than the set pressure from the simulated well for energy storage fracturing and shut-in.

[0190] Based on the above-mentioned experimental system for energy storage fracturing, this article also proposes an energy storage fracturing effect evaluation method, which is applied to the processing device and includes:

[0191] Select a test well from the simulated wells for energy storage fracturing and shut-in well testing;

[0192] Use the other simulated wells except the test well as monitoring wells;

[0193] During the process of energy storage fracturing and shut-in well testing in the test well, use the pressure sensors to monitor and record the pressure values of the test well and the monitoring wells in the rock sample in real time, and use the monitoring device to monitor and record the pressure value of the infill well in real time, as well as the first time when the infill well first generates a pressure response;

[0194] Determine the formation pressure evaluation factor according to the pressure values of the test well, the monitoring wells and the infill well, and the volume of the energy storage fracturing fluid when performing energy storage fracturing on the test well;

[0195] Perform fracturing and shut-in well testing on the monitoring wells;

[0196] During the process of fracturing and shut-in well testing on the monitoring wells, record the second time when the infill well first generates a pressure response;

[0197] Determine the fracture state evaluation factor according to the first time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the energy storage fracturing fluid when performing energy storage fracturing on the test well; the second time when the infill well first generates a pressure response, the location of the infill well, and the pumping rate of the fracturing fluid when performing fracturing on the monitoring well;

[0198] Determine the oil production evaluation factor according to the pressure values of the test well, the monitoring wells and the infill well, and the oil production after fracturing of the test well and the monitoring wells;

[0199] Obtain the effect of energy storage fracturing according to the formation pressure evaluation factor, the fracture state evaluation factor, and the oil production evaluation factor.

[0200] Specific embodiments are used in this article to elaborate on the principles and implementation methods of this article. The description of the above embodiments is only used to help understand the method and its core idea of this article; at the same time, for those of ordinary skill in the art, according to the idea of this article, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be construed as a limitation to this article.

Claims

1. An experimental system for energy storage fracturing, characterized in that, Comprising: A rock sample device, which includes the rock samples required for the experiment. The rock sample device is arranged vertically. A plurality of simulation wells with equal depths are opened on the upper end surface of the rock sample device along the vertical direction. An encryption well is opened between adjacent two of the simulation wells. A low compressibility fluid is arranged in the encryption well, and the encryption well has the same depth as the simulation wells; A bottom-open wellbore is arranged in the simulation well. The simulation well includes a wellbore section and an open-hole section at the bottom of the well; A sealed wellbore with a sealed bottom is arranged in the encryption well; A test well selected from the simulation wells for energy storage fracturing and shut-in well testing; Regarding the other simulation wells except the test well as monitoring wells; The upper end surface and the lower end surface of the rock sample device are respectively communicated with an upper saturation hole and a lower saturation hole. The upper saturation hole is used to introduce simulated water or simulated oil into the rock sample, and the lower saturation hole is used to introduce simulated water into the rock sample and discharge the fluid in the rock sample; The rock sample device further includes an upper plug; The upper plug is arranged on the upper end surface of the rock sample. The upper saturation hole is located on the upper plug. A plurality of the simulation wells and the encryption well all penetrate through the upper plug and extend into the rock sample; The experimental system further includes a clamping device for clamping the rock sample device, a fracturing fluid injection device for injecting fracturing fluid into the simulation well, a simulated water injection device for injecting simulated water into the rock sample, a simulated oil injection device for injecting simulated oil into the rock sample, a pressure sensor for monitoring the pressure in the simulation well, a monitoring device for monitoring the pressure of the encryption well, a fluid injection device for injecting a specified fluid into the sealed wellbore of the encryption well, a pressure loading device for pressurizing the rock sample, a fluid collection device for collecting the fluid discharged from the rock sample, and a vacuum pumping device for evacuating the rock sample.

2. The experimental system for energy storage fracturing according to claim 1, characterized in that The experimental system further includes: a control device and a processing device; The control device is used to control the experimental system to conduct an energy storage fracturing experiment; The processing device is used to evaluate the energy storage fracturing effect of the energy storage fracturing experiment.

3. The experimental system for energy storage fracturing according to claim 1, wherein The clamping device is arranged vertically. The clamping device includes a housing, a lower plug and a rubber sleeve; The housing is fixedly connected with the rubber sleeve. The rubber sleeve is sleeved on the outer periphery of the rock sample and is used to apply confining pressure to the rock sample. The housing is detachably connected with the lower plug. The lower plug abuts against the lower end surface of the rock sample and is used to fix the rock sample. The lower saturation hole is located on the lower plug.

4. The experimental system for energy storage fracturing according to claim 3, characterized in that The upper saturation hole is a first upper saturation hole, and the first upper saturation hole is located at the center of the upper plug; Or, the upper saturation hole is a plurality of second upper saturation holes, and a plurality of the second upper saturation holes are evenly distributed on the upper plug; The lower saturation hole is one or more.

5. The experimental system for energy storage fracturing according to claim 4, wherein A diversion groove is opened at one end of the upper plug close to the rock sample. The diversion groove is used to evenly distribute the simulated oil or simulated water flowing into the rock sample through the upper saturation hole on the upper end surface of the rock sample.

6. The experimental system for energy storage fracturing according to claim 5, wherein, The diversion groove includes a plurality of concentric grooves and a plurality of connecting grooves. The plurality of concentric grooves are concentrically arranged with the first upper saturation hole as the center, and the plurality of connecting grooves are evenly distributed and connect the plurality of concentric grooves; Alternatively, the diversion groove is a surrounding groove, and the surrounding groove is spirally surrounded with the first upper saturation hole as the center; Alternatively, the diversion groove includes a plurality of transverse grooves and a plurality of longitudinal grooves. The plurality of transverse grooves and the plurality of longitudinal grooves are interconnected in a grid pattern for connecting a plurality of the second upper saturation holes.

7. The experimental system for energy storage fracturing according to claim 3, characterized in that, An axial pressure chamber is formed between the lower plug and the outer shell, and a confining pressure chamber is formed between the rubber sleeve and the outer shell. The axial pressure chamber communicates with the confining pressure chamber; An axial pressure hole is opened at the bottom end of the outer shell. The axial pressure hole is used to connect the axial pressure chamber and the pressure loading device, and the pressure loading device is used to pressurize the axial pressure chamber and the confining pressure chamber to further pressurize the rock sample; Alternatively, the pressure loading device includes a confining pressure loading device and an axial pressure loading device. An axial pressure chamber is formed between the lower plug and the outer shell, and a confining pressure chamber is formed between the rubber sleeve and the outer shell; An axial pressure hole is opened at the bottom end of the outer shell. The axial pressure hole is used to connect the axial pressure chamber and the axial pressure loading device, and the axial pressure loading device is used to pressurize the axial pressure chamber to further pressurize the rock sample; The lower plug is provided with a confining pressure hole. The confining pressure hole is used to connect the confining pressure chamber and the confining pressure loading device, and the confining pressure loading device is used to pressurize the confining pressure chamber to further pressurize the rock sample.

8. The experimental system for energy storage fracturing according to claim 1, wherein The simulated oil injection device and the simulated water injection device are connected in parallel to form a combined device. One end of the combined device is connected to an injection pump, and the other end is connected to a combined valve; One end of the combined valve away from the combined device is simultaneously connected to the upper saturation hole and the lower saturation hole. A simulated water valve is further provided between the combined valve and the lower saturation hole.

9. The experimental system for energy storage fracturing according to claim 2, wherein The processing device is used for: During the energy storage fracturing and shut-in process of the test well, the pressure sensor is used to monitor and record the pressure values of the test well and the monitoring well in the rock sample in real time, and the monitoring device is used to monitor and record the pressure value of the infill well in real time, and the first time when the infill well first generates a pressure response; According to the pressure values of the test well, the monitoring well and the infill well, and the initial formation pressure value of the well group formation, the formation pressure increase amplitude is obtained. Combining the volume of the energy storage fracturing fluid during the energy storage fracturing of the test well, the energy storage coefficient is obtained; Determine the formation pressure increase amplitude and the energy storage coefficient as the formation pressure evaluation factors; perform fracturing and shut-in on the monitoring well; During the fracturing and shut-in process of the monitoring well, record the second time when the infill well first generates a pressure response; According to the first time when the infill well first generates a pressure response and the pumping speed of the energy storage fracturing fluid during the energy storage fracturing of the test well, the first response amount of the pressure response first generated by the infill well is calculated; According to the first time and the position of the infill well, the fracture propagation coefficient of the corresponding test well is obtained; At the second time when the pressure response is first generated in the encryption well, and based on the pumping rate of the fracturing fluid when fracturing the monitoring well, calculate the pressure response first generated in the encryption well as the second response quantity; Based on the second time and the location of the encryption well, obtain the fracture propagation coefficient of the corresponding monitoring well; Determine the first response quantity and the fracture propagation coefficient of the corresponding test well, the second response quantity and the fracture propagation coefficient of the corresponding monitoring well as the fracture state evaluation factors of the well group; Based on the pressure values of the test well, monitoring well and encryption well, and combined with the oil production after fracturing of the test well and monitoring well, obtain the production increase coefficient and determine it as the oil production evaluation factor; Based on the formation pressure evaluation factor, fracture state evaluation factor, and the oil production evaluation factor, obtain the energy storage fracturing effect; Among them, the closer the energy storage coefficient is to the standard energy storage coefficient, the smaller the fracture propagation coefficient of the test well, the smaller the fracture propagation coefficient of the monitoring well, the greater the production increase coefficient, and the better the energy storage fracturing effect of the well group.

10. An experimental method for energy storage fracturing based on the experimental system for energy storage fracturing described in claim 2 above, characterized in that, Applied to the control device, it includes: Obtain the prepared rock sample, where the prepared rock sample is provided with a simulated well and an encryption well; Clamp the rock sample through the clamping device; Vacuum the rock sample using the vacuum device; Pressurize the rock sample using the pressure loading device; Use the simulated water injection device to inject simulated water into the rock sample until the rock sample is water-saturated; Use the simulated oil injection device to inject simulated oil into the rock sample until the rock sample is oil-saturated; Among them, when simulating repeated energy storage fracturing, during the process of injecting simulated oil into the rock sample, the oil pressure is greater than the set oil pressure. Use the fracturing fluid injection device to inject fracturing fluid into the simulated well for fracturing, and use the fluid collection device to collect the simulated oil discharged from the rock sample to deplete the formation pressure; When simulating primary energy storage fracturing, during the process of injecting simulated oil into the rock sample, the oil pressure is not greater than the set oil pressure; Select a test well with a well pressure lower than the set pressure from the simulated wells for energy storage fracturing and shut-in.

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