Wheel type multi-lithology true triaxial hydraulic fracturing test device and use method thereof

Abstract

The invention discloses a wheel type multi-lithology true triaxial hydraulic fracturing test device and a using method thereof, the wheel type multi-lithology true triaxial hydraulic fracturing test device comprises a stress loading system, a pump injection system and a wheel type clamping system, and a bearing wheel disc is arranged in the wheel type clamping system; the bearing wheel disc is provided with at least two clamping areas which are uniformly arranged in the circumferential direction, and the bearing wheel disc is also provided with a test area; the clamping area can be used for clamping multi-lithologic rock samples; the test area is located at the loading center of the stress loading system and does not rotate along with the bearing wheel disc, and the pumping system is used for pumping fracturing fluid to the multi-lithology rock sample. The rock samples are preloaded on the bearing wheel disc, switching of different rock samples can be achieved, and the test efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of fracturing test devices, in particular to a wheel-type multi-lithology true triaxial hydraulic fracturing test device and a use method thereof. Background Art

[0002] True triaxial hydraulic fracturing physical simulation test is an important means to study the crack expansion law and mechanism during hydraulic fracturing. It can restore the expansion process of underground rock cracks more realistically and is an important basis for scientific research. With the advancement of science and technology, the research on hydraulic fracturing of single lithology layered rocks can no longer meet the needs of scientific research. Therefore, it is of great significance to study the crack expansion law during hydraulic fracturing of multi-lithology combined layered rocks.

[0003] During the experimental research, a single horizontal geostress loading method cannot well reflect the stress state of the rock mass in the actual rock formation, and has certain limitations in studying the expansion of cracks during hydraulic fracturing. A wheel-type multi-lithology true triaxial hydraulic fracturing test device can apply horizontal geostresses of different magnitudes on different lithology rock formations. It can not only simulate the stress conditions of rocks in the actual formation, but also flexibly change the test conditions to study the expansion laws and penetration characteristics of cracks in multi-lithology layered reservoirs.

[0004] The rock samples required for the hydraulic fracturing physical simulation test are large in size, and the heavy fixtures make the clamping process complicated and pose certain safety hazards. After a fracturing test, the tedious disassembly and clamping process must be repeated continuously, which seriously affects the test efficiency.

[0005] Therefore, it is of great significance to develop a hydraulic fracturing test device that can not only load horizontal ground stress in layers but also improve the test efficiency.

[0006] Publication (Announcement) No.: CN111366472B, discloses a true triaxial hydraulic fracturing physical simulation device for variable core size, including a hydraulic pressure stabilizing source, a true triaxial simulation test frame and a comprehensive injection control device for fracturing fluid. The true triaxial simulation test frame is connected to the hydraulic pressure stabilizing source to provide hydraulic pressure for the fracturing experiment, and the true triaxial simulation test frame is connected to the comprehensive injection control device for fracturing fluid to control the injection of fracturing fluid during the experiment. The true triaxial simulation test frame is provided with layered pressure application and height-adjustable confining pressure application devices in the X, Y, and Z directions, respectively, so as to be suitable for simulating different stress pressures on the surface of the sample in close contact. The beneficial effect of this prior art is that it can be used to carry out true triaxial hydraulic fracturing experiments on underground cores taken on site, and to study the cracking and expansion laws of cracks in real underground formations.

[0007] The prior art has the problem that the process of replacing rock samples is complicated and inefficient.

[0008] Publication (Announcement) No.: CN116735367A, discloses a true triaxial rock and soil test device and its test method, which relates to the technical field of mining engineering test devices, the test device includes a triaxial loading module, the triaxial loading module includes a triaxial servo loading system and a triaxial bearing system, the triaxial servo loading system is used to apply pressure in the X, Y and Z directions to the triaxial bearing system; a grouting module, the grouting module is connected to the grouting fracturing pipe in the triaxial bearing system through a pipeline; a hydraulic fracturing module, the hydraulic fracturing module is connected to the grouting fracturing pipe in the triaxial bearing system through a pipeline; a data acquisition and analysis module, the data analysis and acquisition module is connected to the ultrasonic transmitting sensor and receiving sensor in the triaxial bearing system through a line. The prior art adopts the test method carried out by the above test device, which can carry out triaxial grouting and triaxial hydraulic fracturing tests, and can carry out true triaxial hydraulic fracturing and grouting tests of intact rock mass, and can also carry out grouting tests of true triaxial tests of loose bodies.

[0009] The prior art has the problem that the process of replacing rock samples is complicated and inefficient.

[0010] Publication (Announcement) No.: CN116519488B discloses a multifunctional rock triaxial visualization test system, which aims to solve the problems of insufficient overall rigidity of the test system, low resolution of the CT scanning system, entanglement of the high-pressure pipelines, circuits and signal lines of the test system, complex control system, and large overall volume. The present invention includes: an axial loading system, a high-energy accelerator CT scanning system, a turntable system, a triaxial pressure chamber, a fluid fracturing pump, a temperature pump, a confining pressure loading pump, a power oil source, and an integrated control console; the high-energy accelerator CT scanning system is driven to rotate by the turntable system to scan the internal imaging of the rock sample, and the rock sample is compressed and fracturing experiments are performed by the triaxial pressure chamber and the fluid fracturing pump. This prior art overcomes the problems of low radiation energy, low resolution, low loading reaction force frame rigidity, and pipeline entanglement during the test of the current existing equipment.

[0011] The prior art has the problem that the process of replacing rock samples is complicated and inefficient.

[0012] In summary, the technical solutions of the above-disclosed technologies, the technical problems to be solved, and the beneficial effects produced are all different from the present invention. Regarding more technical features, technical problems to be solved, and beneficial effects of the present invention, the above-disclosed technical documents do not provide any technical inspiration. Summary of the invention

[0013] In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide a wheel-type multi-lithology true triaxial hydraulic fracturing test device and a method of using the same, which can not only apply different horizontal ground stresses on different lithology strata, but also pre-load the rock samples required for the test, thereby improving the functionality of the device and reducing the time occupied by the loading and disassembly of rock samples during the test, thereby greatly improving work efficiency.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions:

[0015] A wheel-type multi-lithology true triaxial hydraulic fracturing test device and a method of using the same, comprising a stress loading system, a pumping system, and a wheel-type clamping system, wherein the wheel-type clamping system is provided with a load-bearing wheel disc; the load-bearing wheel disc is provided with at least two clamping areas evenly arranged in the circumferential direction, and the load-bearing wheel disc is also provided with a test area;

[0016] The clamping area can clamp multiple rock samples; the test area is located at the loading center of the stress loading system and does not rotate with the bearing wheel; the pumping system is used to pump fracturing fluid into the multiple rock samples.

[0017] The different lithology rocks in the multi-lithology rock sample are bonded with cement slurry to simulate the bedding, and a liquid injection port is arranged at the upper end of the multi-lithology rock sample.

[0018] The wheel-type clamping system includes a rotating shaft, a load-bearing wheel disc, a base, and a bearing support device;

[0019] The bearing support device is arranged on the base, a bearing is arranged on the upper end of the bearing support device, the load-bearing wheel is arranged on the bearing, the rotating shaft is installed at the center of the upper end surface of the load-bearing wheel and can rotate relative to the load-bearing wheel, a minimum horizontal stress reaction device is arranged on the side wall of the rotating shaft, and a vertical stress reaction device is arranged below the load-bearing wheel.

[0020] The stress loading system includes a vertical stress loading device, a maximum horizontal ground stress reaction device, a maximum horizontal ground stress applying device, and a minimum horizontal principal stress applying device;

[0021] The vertical stress loading device is arranged above the test area, the maximum horizontal ground stress reaction device is arranged on the left side of the test area, the maximum horizontal ground stress applying device is arranged on the right side of the test area, and the minimum horizontal principal stress applying device is arranged behind the test area.

[0022] The pumping system includes a liquid nitrogen pumping device, a supercritical CO 2 Pumping device, conventional fracturing fluid pumping device;

[0023] Use the pumping pipeline to pump liquid nitrogen into the device and supercritical CO 2The outlets of the pumping device and the conventional fracturing fluid pumping device are connected in parallel, and fluid valves are provided on the main and branch lines of the pumping pipeline;

[0024] During the test, the pump injection pipeline outlet is connected to the liquid injection port.

[0025] A computer control system is also provided;

[0026] The computer control system includes a display device and a wheel-type clamping control device, a stress loading control device, a pumping control device, and a data acquisition and sorting device connected to the display device;

[0027] The wheel-type clamping control device is connected to the clamping area;

[0028] The stress loading control device is connected to the vertical stress loading device, the maximum horizontal ground stress applying device, and the minimum horizontal principal stress applying device;

[0029] The data acquisition and collating device is connected to the maximum horizontal ground stress reaction device, the vertical stress reaction device, and the minimum horizontal ground stress reaction device;

[0030] The pumping control device is connected with the pumping system.

[0031] The wheel-type clamping control device controls the clamping action of the clamping area;

[0032] The pumping control device controls the liquid nitrogen pumping device, the supercritical CO 2 Start and stop the pumping device and conventional fracturing fluid pumping device, and control the on and off of the fluid valve;

[0033] The display device displays the working status of the clamping area, the stress loading status of the three axes, the stress reaction force data of the three axes, and the working status of the pumping system.

[0034] A method for using a wheel-type multi-lithology true triaxial hydraulic fracturing test device comprises the following steps:

[0035] S1. Test preparation: prepare at least two multi-lithology rock samples, place the prepared multi-lithology rock samples in the clamping area of ​​the load-bearing wheel, and pre-clamp them;

[0036] S2: Stress loading preparation: by rotating the load wheel, a multi-lithology rock sample is placed in the test area, and the stress loading system is controlled to complete the stress loading preparation of the X, Y, and Z axes;

[0037] During stress loading preparation, the top surface of the multi-lithology rock samples in the test area faces the vertical stress loading device, and the vertical stress reaction device is moved to ensure that the force applied by the vertical stress loading device can be completely received by the vertical stress reaction device; the vertical stress loading device is controlled by controlling the stress loading system so that the stress loading surface is closely attached to and fixed to the upper surface of the multi-lithology rock samples, completing the Z-axis preparation;

[0038] The minimum horizontal geostress reaction device is rotated to make it close to the side of the rock sample; the minimum horizontal geostress loading device is controlled by the stress loading system to make the stress loading surface close to the side of the rock sample, and the multi-lithology rock samples are fixed together with the minimum horizontal geostress reaction device to complete the Y-axis preparation;

[0039] The maximum horizontal in-situ stress loading device is controlled by the stress loading system to make the stress loading surface close to the side of the rock sample. At the same time, the maximum horizontal in-situ stress reaction device is controlled to make the stress loading surface close to the side of the multi-lithology rock sample. The multi-lithology rock samples are fixed together with the maximum horizontal in-situ stress loading device to complete the X-axis preparation.

[0040] At this point, the six surfaces of the multi-lithology rock samples have been fully fixed.

[0041] S3, stress loading: continue to control the stress loading system, apply the various lithology rock samples the stress required for the test in all directions, and keep the various lithology rock samples stable under the stress state for a period of time;

[0042] S4: Fracturing test: inject conventional fracturing fluid into multi-lithology rock samples by controlling the pumping system, and increase the pressure step by step to reach the pressure required for the test;

[0043] Then, conventional fracturing fluid is continuously injected into the multi-lithology rock samples to start conventional fracturing fluid fracturing test;

[0044] After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted;

[0045] S5: Replace the test sample, rotate the wheel to switch to other rock samples of different lithologies and repeat the test.

[0046] In one embodiment of the present invention, the use steps are adjusted.

[0047] S4: Fracturing test: Injecting CO into multi-lithology rock samples through a controlled pumping system 2 , by increasing the pressure step by step, the required pressure for the test is reached;

[0048] Then continue to inject CO into the multi-lithology rock samples 2 , start CO 2 Fracturing test;

[0049] After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted;

[0050] In one embodiment of the present invention, the use steps are adjusted.

[0051] S4: Fracturing test: Liquid nitrogen is injected into the multi-lithology rock samples by controlling the pumping system, and the pressure required for the test is reached by increasing the pressure step by step;

[0052] Then, liquid nitrogen is continuously injected into the multi-lithology rock samples to start the liquid nitrogen fracturing test;

[0053] After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted;

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention preloads the rock sample on the load wheel, which can realize the switching of different rock samples and greatly improve the test efficiency;

[0056] 2. The present invention applies different magnitudes of ground stress to multiple layers of hydraulically fractured rocks, thereby realistically simulating the actual stress state of the rocks;

[0057] 3. The present invention can switch the type of liquid to be injected according to the test requirements, including liquid nitrogen, conventional fracturing fluid and supercritical CO 2 , to achieve diversified operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a structural schematic diagram of a wheel-type multi-lithology true triaxial hydraulic fracturing test device of the present invention;

[0059] Figure 2 It is a structural schematic diagram of a wheel-type clamping system of a wheel-type multi-lithology true triaxial hydraulic fracturing test device of the present invention;

[0060] Figure 3 It is a structural schematic diagram of a stress loading system of a wheel-type multi-lithology true triaxial hydraulic fracturing test device of the present invention;

[0061] Figure 4 It is a structural schematic diagram of a pumping system of a wheel-type multi-lithology true triaxial hydraulic fracturing test device of the present invention;

[0062] Figure 5 It is a structural schematic diagram of a computer control system of a wheel-type multi-lithology true triaxial hydraulic fracturing test device of the present invention;

[0063] In the figure: 1, wheel clamping system; 101, rotating shaft; 102, minimum horizontal ground stress reaction device; 103, injection port; 104, multi-lithology rock sample; 105, bearing wheel; 106, base; 107, bearing; 108, bearing support device; 109, vertical stress reaction device;

[0064] 2. Stress loading system; 201. Vertical stress loading device; 202. Maximum horizontal ground stress reaction device; 203. Maximum horizontal ground stress applying device; 204. Minimum horizontal principal stress applying device;

[0065] 3. Pumping system; 301. Liquid nitrogen pumping device; 302. Supercritical CO 2 Pumping device; 303, conventional fracturing fluid pumping device; 304, fluid valve;

[0066] 4. Computer control system; 401. Display device; 402. Wheel clamping control device; 403. Stress loading control device; 404. Pump injection control device; 405. Data acquisition and collation device. DETAILED DESCRIPTION

[0067] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] Embodiment 1:

[0069] See also Figures 1 to 5 The present invention provides a wheel-type multi-lithology true triaxial hydraulic fracturing test device and a method of using the same, comprising a wheel-type clamping system 1, a stress loading system 2, a pumping system 3, and a computer control system 4;

[0070] The wheeled clamping system 1 is used to clamp multi-lithology rock samples 104 and switch the rock samples during the test.

[0071] The different lithology rocks in the multi-lithology rock sample 104 are bonded together with cement paste to simulate the stratification. The upper end of the multi-lithology rock sample 104 is provided with a liquid injection port 103 .

[0072] The wheel clamping system includes a rotating shaft 101, a load-bearing wheel disc 105, a base 106, and a bearing support device 108; the bearing support device 108 is arranged on the base 106, and a bearing 107 is arranged on the upper end of the bearing support device 108. The load-bearing wheel disc 105 is arranged on the bearing 107. The rotating shaft 101 is installed at the center of the upper end surface of the load-bearing wheel disc 105 and can rotate relative to the load-bearing wheel disc 105. The side wall of the rotating shaft 101 is provided with a minimum horizontal stress reaction device 102, and a vertical stress reaction device 109 is provided below the load-bearing wheel disc 105.

[0073] The load-bearing wheel 105 is provided with at least two clamping areas which are evenly arranged in the circumferential direction. The load-bearing wheel 105 is also provided with a test area, in which multi-lithology rock samples 104 can be clamped. The test area is located at the loading center of the stress loading system 2 and does not rotate with the load-bearing wheel 105.

[0074] The stress loading system 2 is configured to apply different stresses on the multi-layer rock sample 104 to simulate the stress state of the rock mass in actual engineering; the stress loading system 2 includes a vertical stress loading device 201, a maximum horizontal ground stress reaction device 202, a maximum horizontal ground stress applying device 203, and a minimum horizontal principal stress applying device 204;

[0075] The vertical stress loading device 201 is arranged above the test area, the maximum horizontal ground stress reaction device 202 is arranged on the left side of the test area, the maximum horizontal ground stress applying device 203 is arranged on the right side of the test area, and the minimum horizontal principal stress applying device 204 is arranged behind the test area.

[0076] The vertical stress loading device 201 and the vertical stress reaction device 109 detect the Z axis of the rock sample;

[0077] The maximum horizontal ground stress reaction device 202 and the maximum horizontal ground stress applying device 203 detect the X-axis of the rock sample;

[0078] The minimum horizontal principal stress applying device 204 and the minimum horizontal ground stress reaction device 102 detect the Y-axis of the rock sample.

[0079] The pumping system 3 is used to provide pumping pressure for the injection of fracturing fluid for hydraulic fracturing; the pumping system 3 includes a liquid nitrogen pumping device 301, a supercritical CO 2 Pumping device 302, conventional fracturing fluid pumping device 303; using pumping pipeline to pump liquid nitrogen pumping device 301, supercritical CO 2 The outlets of the pumping device 302 and the conventional fracturing fluid pumping device 303 are connected in parallel. Fluid valves 304 are provided on the main and branch lines of the pumping pipeline. During the test, the outlet of the pumping pipeline is connected to the injection port 103.

[0080] The computer control system 4 is used to control the wheel clamping system 1, the stress loading system 2, and the pumping system 3, so that the three can work according to the test sequence, and integrate the physical and mechanical information obtained by each system to obtain the required test results;

[0081] The computer control system includes a display device 401 and a wheel clamping control device 402 connected to the display device 401, a stress loading control device 403, a pumping control device 404, and a data acquisition and sorting device 405;

[0082] The wheeled clamping control device 402 is connected to the clamping area to control the clamping action of the clamping area;

[0083] The stress loading control device 403 is connected to the vertical stress loading device 201, the maximum horizontal ground stress applying device 203, and the minimum horizontal principal stress applying device 204;

[0084] The data collection and sorting device 405 is connected to the maximum horizontal geostress reaction device 202, the vertical stress reaction device 109, and the minimum horizontal geostress reaction device 102;

[0085] The pumping control device 404 is connected to the pumping system 3 to control the liquid nitrogen pumping device 301, the supercritical CO 2 Start and stop the pumping device 302 and the conventional fracturing fluid pumping device 303, and control the on and off of the fluid valve 304;

[0086] The display device 401 displays the working status of the clamping area, the stress loading status of the three axes, the stress reaction force data of the three axes, and the working status of the pumping system 3.

[0087] Specific use of the present invention:

[0088] S1. Test preparation: prepare at least two multi-lithology rock samples 104, the overall size of the multi-lithology rock sample 104 is 300mm×300mm×300mm, and cement paste is used to bond rocks of different lithologies to simulate bedding; place the prepared multi-lithology rock samples 104 in the clamping area of ​​the bearing wheel 105 and pre-clamp them;

[0089] S2: Stress loading preparation: by rotating the bearing wheel 105, a multi-lithology rock sample 104 is located in the test area, with the top surface facing the vertical stress loading device 201, and the vertical stress reaction device 109 is moved to ensure that the force applied by the vertical stress loading device 201 can be completely received by the vertical stress reaction device 109; by controlling the stress loading system 2, the vertical stress loading device 201 is controlled to make the stress loading surface close to and fixed to the upper surface of the multi-lithology rock sample 104, and the Z-axis preparation is completed;

[0090] The minimum horizontal geostress reaction device 102 is rotated to make it close to the side of the rock sample; the minimum horizontal geostress loading device 204 is controlled by the stress loading system 2 to make the stress loading surface close to the side of the rock sample 104, and the multi-lithology rock sample 104 is fixed together with the minimum horizontal geostress reaction device 102 to complete the Y-axis preparation;

[0091] The maximum horizontal in-situ stress loading device 203 is controlled by the stress loading system 2, so that the stress loading surface is closely attached to the side of the rock sample 104. At the same time, the maximum horizontal in-situ stress reaction device 202 is controlled so that the stress loading surface is closely attached to the side of the multi-lithology rock sample 104. The multi-lithology rock sample 104 is fixed together with the maximum horizontal in-situ stress loading device 203 to complete the X-axis preparation.

[0092] At this point, the six faces of the multi-lithology rock sample 104 were fully fixed;

[0093] S3, stress loading: continue to control the stress loading system 2, apply the various directional stresses required for the test to the multi-lithology rock sample 104, and stabilize the multi-lithology rock sample 104 under stress for a period of time;

[0094] S4: Fracturing test: conventional fracturing fluid is injected into the multi-lithology rock sample 104 by controlling the pumping system 3, and pumping is stopped after reaching the step pressure. After maintaining the pressure for a period of time, conventional fracturing fluid is continued to be injected to form a stable pressure environment inside the multi-lithology rock sample 104;

[0095] By increasing the pressure step by step to reach the pressure required for the test, conventional fracturing fluid is then continuously injected into the multi-lithology rock sample 104 to start the conventional fracturing fluid fracturing test;

[0096] After the multi-lithology rock sample 104 is destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted;

[0097] S5: Replace the test sample, rotate the wheel 105 to switch to other multi-lithology rock samples 104 to repeat the test.

[0098] Embodiment 2:

[0099] Based on Example 1, the steps of use are changed.

[0100] S4: Fracturing test: CO is injected into the multi-lithology rock sample 104 by controlling the pump injection system 3. 2 After reaching the step pressure, pumping is stopped, and after maintaining the pressure for a period of time, conventional fracturing fluid is continued to be injected to form a stable pressure environment inside the multi-lithology rock sample 104;

[0101] The pressure required for the test is reached by increasing the pressure step by step, and then CO is continuously injected into the multi-lithology rock sample 104. 2 , start CO2 Fracturing test;

[0102] After the multi-lithology rock sample 104 is destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted.

[0103] Embodiment 3:

[0104] Based on Example 1, the steps of use are changed.

[0105] S4: Fracturing test: Liquid nitrogen is injected into the multi-lithology rock sample 104 by controlling the pumping system 3, and the pumping is stopped after reaching the step pressure. After maintaining the pressure for a period of time, conventional fracturing fluid is continuously injected to form a stable pressure environment inside the multi-lithology rock sample 104;

[0106] By increasing the pressure step by step to reach the pressure required for the test, liquid nitrogen is continuously injected into the multi-lithology rock sample 104 to start the liquid nitrogen fracturing test;

[0107] After the multi-lithology rock sample 104 is destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted.

[0108] It should be noted that the fixture for multi-lithology rock samples is a common rock block fixture, the computer control system is a common experimental system, the control device is a drive board, and the data acquisition and processing device is a programmable PLC or a single-chip microcomputer. Those skilled in the art are clear about this.

[0109] All components and connection methods of components not discussed in this application belong to the known technologies in this technical field and can be directly applied without further explanation.

[0110] In the present invention, the term "plurality" refers to two or more than two, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0111] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0112] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wheel-type multi-lithology true triaxial hydraulic fracturing test device, including a stress loading system and a pump injection system. It is characterized in that It also includes a wheel clamping system, wherein the wheel clamping system is provided with a load-bearing wheel disc; The load-bearing wheel disc is provided with at least two clamping areas which are evenly arranged in the circumferential direction, and the load-bearing wheel disc is also provided with a test area; The clamping area can clamp multiple rock samples; the test area is located at the loading center of the stress loading system and does not rotate with the bearing wheel; the pumping system is used to pump fracturing fluid into the multiple rock samples.

2. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 1, It is characterized in that The different lithology rocks in the multi-lithology rock sample are bonded with cement slurry to simulate the bedding, and a liquid injection port is arranged at the upper end of the multi-lithology rock sample.

3. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 2, It is characterized in that The wheel-type clamping system includes a rotating shaft, a load-bearing wheel disc, a base, and a bearing support device; The bearing support device is arranged on the base, a bearing is arranged on the upper end of the bearing support device, the load-bearing wheel is arranged on the bearing, the rotating shaft is installed at the center of the upper end surface of the load-bearing wheel and can rotate relative to the load-bearing wheel, a minimum horizontal stress reaction device is arranged on the side wall of the rotating shaft, and a vertical stress reaction device is arranged below the load-bearing wheel.

4. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 3, It is characterized in that The stress loading system includes a vertical stress loading device, a maximum horizontal ground stress reaction device, a maximum horizontal ground stress applying device, and a minimum horizontal principal stress applying device; The vertical stress loading device is arranged above the test area, the maximum horizontal ground stress reaction device is arranged on the left side of the test area, the maximum horizontal ground stress applying device is arranged on the right side of the test area, and the minimum horizontal principal stress applying device is arranged behind the test area.

5. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 4, It is characterized in that The pumping system includes a liquid nitrogen pumping device, a supercritical CO 2 Pumping device, conventional fracturing fluid pumping device; Use the pumping pipeline to pump liquid nitrogen into the device and supercritical CO 2 The outlets of the pumping device and the conventional fracturing fluid pumping device are connected in parallel, and fluid valves are arranged on the main route and the branch route of the pumping pipeline.

6. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 5, It is characterized in that During the test, the pump injection pipeline outlet is connected to the liquid injection port.

7. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 6, It is characterized in that A computer control system is also provided; The computer control system includes a display device and a wheel-type clamping control device, a stress loading control device, a pumping control device, and a data acquisition and sorting device connected to the display device; The wheel-type clamping control device is connected to the clamping area; The stress loading control device is connected to the vertical stress loading device, the maximum horizontal ground stress applying device, and the minimum horizontal principal stress applying device; The data acquisition and collating device is connected to the maximum horizontal ground stress reaction device, the vertical stress reaction device, and the minimum horizontal ground stress reaction device; The pumping control device is connected with the pumping system.

8. A wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 7, It is characterized in that The wheel-type clamping control device controls the clamping action of the clamping area; The pump injection control device controls the liquid nitrogen pump injection device, the supercritical CO 2 Start and stop the pumping device and conventional fracturing fluid pumping device, and control the on and off of the fluid valve; The display device displays the working status of the clamping area, the stress loading status of the three axes, the stress reaction force data of the three axes, and the working status of the pumping system.

9. A method for using a wheel-type multi-lithology true triaxial hydraulic fracturing test device, It is characterized in that The following steps are included: S1. Test preparation: prepare at least two multi-lithology rock samples, place the prepared multi-lithology rock samples in the clamping area of ​​the load-bearing wheel, and pre-clamp them; S2: Stress loading preparation: by rotating the load wheel, a multi-lithology rock sample is placed in the test area, and the stress loading system is controlled to complete the stress loading preparation of the X, Y, and Z axes; S3, stress loading: continue to control the stress loading system, apply the various lithology rock samples the stress required for the test in all directions, and keep the various lithology rock samples stable under the stress state for a period of time; S4: Fracturing test: inject conventional fracturing fluid into multi-lithology rock samples by controlling the pumping system, and increase the pressure step by step to reach the pressure required for the test; Then, conventional fracturing fluid is continuously injected into the multi-lithology rock samples to start conventional fracturing fluid fracturing test; After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted; S5: Replace the test sample, rotate the wheel to switch to other rock samples of different lithologies and repeat the test.

10. A method for using a wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 9, It is characterized in that During stress loading preparation, the top surface of the multi-lithology rock samples in the test area faces the vertical stress loading device, and the vertical stress reaction device is moved to ensure that the force applied by the vertical stress loading device can be completely received by the vertical stress reaction device; the vertical stress loading device is controlled by controlling the stress loading system so that the stress loading surface is closely attached to and fixed to the upper surface of the multi-lithology rock samples, completing the Z-axis preparation; The minimum horizontal geostress reaction device is rotated to make it close to the side of the rock sample; the minimum horizontal geostress loading device is controlled by the stress loading system to make the stress loading surface close to the side of the rock sample, and the multi-lithology rock samples are fixed together with the minimum horizontal geostress reaction device to complete the Y-axis preparation; The maximum horizontal in-situ stress loading device is controlled by the stress loading system to make the stress loading surface close to the side of the rock sample. At the same time, the maximum horizontal in-situ stress reaction device is controlled to make the stress loading surface close to the side of the multi-lithology rock sample. The multi-lithology rock samples are fixed together with the maximum horizontal in-situ stress loading device to complete the X-axis preparation. At this point, the six surfaces of the multi-lithology rock samples have been fully fixed.

11. A method for using a wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 9, It is characterized in that Make adjustments to step S4, S4: Fracturing test: Injecting CO into multi-lithology rock samples through a controlled pumping system 2 , by increasing the pressure step by step, the required pressure for the test is reached; Then continue to inject CO into the multi-lithology rock samples 2 , start CO 2 Fracturing test; After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted.

12. A method for using a wheel-type multi-lithology true triaxial hydraulic fracturing test device according to claim 9, It is characterized in that Make adjustments to step S4, S4: Fracturing test: Liquid nitrogen is injected into the multi-lithology rock samples by controlling the pumping system, and the pressure required for the test is reached by increasing the pressure step by step; Then, liquid nitrogen is continuously injected into the multi-lithology rock samples to start the liquid nitrogen fracturing test; After the multi-lithology rock samples are destroyed, the test is stopped, the stress loading is released, and the test data are collected and sorted.

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