A super-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation

Abstract

The present application belongs to the technical field of induced earthquakes caused by hot dry rock mining, and provides a super-large physical simulation system for induced earthquakes and safety regulation of hot dry rock development, comprising: an experimental model, the experimental model comprising a top surface, a bottom surface and a side surface, a distributed stress loading system being arranged on the top surface, the bottom surface and the side surface of the experimental model, a heating feedback system being arranged between the distributed stress loading system and the bottom surface and the side surface of the experimental model, and an injection well and a production well being opened diagonally on the upper edge of the experimental model; the present application arranges a first temperature sensor, a high-temperature resistant deformation sensor, and a high-temperature resistant fluid pressure sensor on a prefabricated fault, and arranges high-temperature resistant acoustic emission and microseismic sensors at the boundary of the experimental model, and comprehensively monitors the prefabricated fault during the experiment, thereby realizing the whole-process monitoring of the incubation process of induced earthquakes caused by hot dry rock injection and mining, the slip of the prefabricated fault and the rupture of the bedrock, and revealing the mechanism of induced earthquakes.

Description

Technical Field

[0001] The present application belongs to the technical field of hot dry rock mining-induced earthquakes, and specifically relates to a super-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation. Background Art

[0002] Field testing is one of the important means to study the earthquakes induced by hot dry rock development and safety regulation. This method truly restores the process of hot dry rock development, but its shortcomings are also obvious. It requires a lot of manpower and material resources. At the same time, once an earthquake is really induced, the consequences are also serious. In addition, it is difficult to carry out accurate and reliable monitoring of faults in the environment of the engineering site, and it is difficult to carry out the study of a single variable. Therefore, the influence of many factors on the earthquakes induced by hot dry rock injection and production is not clear. The study of the mechanism of earthquakes induced by hot dry rock development based on indoor experiments has always been a hot topic, but most of them focus on induced earthquakes during hydraulic fracturing. The problem of induced earthquakes during injection and production has been ignored. In addition, the existing simulation system still has limitations in simulating the dry hot rock environment. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0004] To solve the above problems, this application provides a large-scale physical simulation system for hot dry rock development-induced earthquakes and safety regulation, including:

[0005] An experimental model, the experimental model comprising a top surface, a bottom surface, and side surfaces, the top surface, bottom surface, and side surfaces of the experimental model being provided with a distributed stress loading system, a heating feedback system being provided between the distributed stress loading system and the bottom surface and side surfaces of the experimental model, and an injection well and a production well being provided diagonally along the upper edge of the experimental model;

[0006] a prefabricated fault, the prefabricated fault being arranged in the experimental model and located between the injection well and the production well;

[0007] a fluid injection system for hydraulically fracturing the experimental model through the injection well to form a connected fracture network between the injection well and the prefabricated fault;

[0008] a fluid production system, wherein the fluid production system hydraulically fractures the experimental model through the production well to form a connected fracture network between the production well and the prefabricated fault;

[0009] The fluid injection system injects fluid into the injection well, and the fluid is discharged to the fluid production system through the fracture network. The fluid injection system and the fluid production system collect the fluid temperature before injection and the fluid temperature after discharge;

[0010] A detection system is provided on the experimental model and the prefabricated fault, and is used to detect the stress state, deformation degree and temperature distribution of the prefabricated fault, and can also detect the rupture condition of the prefabricated fault and the surrounding area.

[0011] Optionally, the detection system includes a first sensor assembly and a second sensor assembly, wherein the first sensor assembly is arranged on the prefabricated fault, and the second sensor assembly is arranged on the bottom surface, top surface and side surface of the experimental model.

[0012] Optionally, the first sensor assembly includes: a first temperature sensor, a high temperature resistant deformation sensor, and a high temperature resistant fluid pressure sensor, wherein the first temperature sensor, the high temperature resistant deformation sensor, and the high temperature resistant fluid pressure sensor are arranged on the prefabricated fault;

[0013] The second sensor assembly includes: high-temperature resistant acoustic emission sensors and microseismic sensors, which are arranged on the top surface, bottom surface and side surfaces of the experimental model.

[0014] Optionally, the detection system further includes: an analog-to-digital converter, an amplifier, and a detection controller, and the detection controller is electrically connected to the first sensor component and the second sensor component through the analog-to-digital converter and the amplifier.

[0015] Optionally, the fluid injection system includes: a water reservoir, an injection pressure pump, an injection flow pump, a pre-accumulator, a pre-filter, a tracer, and a second temperature sensor;

[0016] An injection pipeline is provided between the water reservoir and the injection well, and the injection pressure pump, the injection flow pump, the pre-accumulator, the pre-filter, the tracer and the second temperature sensor are sequentially arranged on the injection pipeline.

[0017] Optionally, the fluid production system includes: a third temperature sensor, a post-filter, a post-accumulator, a production flow pump, a production pressure pump and a wastewater tank;

[0018] An extraction pipeline is provided between the wastewater pool and the production well, and the third temperature sensor, the post-filter, the post-accumulator, the extraction flow pump and the extraction pressure pump are sequentially provided on the extraction pipeline.

[0019] Optionally, the distributed stress loading system is used to apply true triaxial stress to the experimental model, and a thermal insulation cooling system is provided between the distributed stress loading system, the top surface of the experimental model and the heating feedback system.

[0020] Optionally, the heating feedback system includes:

[0021] A bottom heating element, the bottom heating element being arranged on the bottom surface of the experimental model;

[0022] a side heating element, wherein the side heating element is provided on a side surface of the experimental model;

[0023] A heating controller is electrically connected to the bottom heating element and the side heating element.

[0024] Optionally, the heat preservation and cooling system includes:

[0025] a thermal insulation layer, the thermal insulation layer being provided on the bottom heating element, the side heating element and the top surface of the experimental model;

[0026] a cooling layer, the cooling layer being arranged between the thermal insulation layer and the distributed stress loading system;

[0027] A cooling unit, wherein the cooling unit water outlet is connected to the cooling layer water inlet, the cooling unit water inlet is connected to the cooling layer water outlet, an inlet temperature monitoring device is provided between the cooling unit water outlet and the cooling layer water inlet, and an outlet temperature monitoring device is provided between the cooling unit water inlet and the cooling layer water outlet.

[0028] Optionally, the prefabricated fault is one of a normal fault, a reverse fault and a strike-slip fault.

[0029] The ultra-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation provided in the embodiments of the present invention has the following beneficial effects:

[0030] 1. Compared with the traditional dry hot rock development induced earthquake simulation experimental system, this application uses 3D printing one-piece molding technology to construct a five-meter-level large-scale deep three-dimensional physical model, which depicts the geometric characteristics of the prefabricated fault structure more finely. While significantly improving the scale of indoor experiments in dry hot rock development, it makes the prefabricated fault simulation closer to real geological conditions, effectively improving the reliability of the experimental results.

[0031] 2. This application adds a distributed stress loading system to make the stress environment of the experimental model closer to the real occurrence environment; through the setting of the thermal feedback system and the thermal insulation cooling system, a 400°C ultra-high dry hot rock simulation environment is achieved, and at the same time, the temperature gradient loading can be realized, highly reproducing the deep geothermal environment.

[0032] 3. By directly installing the first temperature sensor, high-temperature resistant deformation sensor, and high-temperature resistant fluid pressure sensor on the prefabricated fault, and arranging high-temperature resistant acoustic emission and microseismic sensors at the boundary of the experimental model, the prefabricated fault was comprehensively monitored during the experiment, realizing the full process monitoring of the gestation process of induced earthquakes caused by hot dry rock injection and production, prefabricated fault slip and bedrock rupture, and revealing the mechanism of induced earthquakes.

[0033] 4. This application adopts different injection and production methods through the fluid injection system and the fluid production system, and then compares and analyzes the impact of different injection and production methods on induced earthquakes through monitoring by the monitoring system, explains the mechanism of earthquakes induced by different injection and production methods, and forms a safe injection and production method for hot dry rocks. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a main structural diagram of the simulation system of the present invention;

[0035] Figure 2 This is a structural diagram of the experimental model of the present invention;

[0036] Figure 3 This is a diagram showing the internal structure of the experimental model of the present invention;

[0037] Figure 4 A three-dimensional structural diagram showing the connection between the distributed stress loading system of the present invention and the experimental model;

[0038] Figure 5 This is a main cross-sectional structural diagram of the connection between the distributed stress loading system of the present invention and the experimental model;

[0039] Figure 6 This is a three-dimensional structural diagram of the monitoring point distribution on the preset fault of the present invention;

[0040] Figure 7 This is a main structural diagram of the monitoring point distribution on the preset fault of the present invention;

[0041] Figure 8 This is a side view structural diagram of the monitoring point distribution on the preset fault of the present invention;

[0042] Figure 9 This is a top-view structural diagram of the monitoring point distribution on the preset fault of the present invention;

[0043] Figure 10 A diagram of the normal fault structure of the prefabricated fault of the present invention;

[0044] Figure 11 A reverse fault structure diagram of the prefabricated fault of the present invention;

[0045] Figure 12 This is a strike-slip fault structure diagram of the prefabricated fault of the present invention.

[0046] The reference numerals indicate:

[0047] 1. Experimental model; 11. Injection well; 12. Production well; 2. Distributed stress loading system; 3. Heating feedback system; 31. Bottom heating element; 32. Side heating element; 33. Heating controller; 4. Prefabricated fault; 41. Normal fault; 42. Reverse fault; 43. Strike-slip fault; 5. Fluid injection system; 51. Reservoir; 52. Injection pressure pump; 53. Injection flow pump; 54. Pre-accumulator; 55. Pre-filter; 56. Tracer; 57. Second temperature sensor; 6. Fluid recovery system; 61. Third temperature sensor 62. Post-filter; 63. Post-accumulator; 64. Production flow pump; 65. Production pressure pump; 66. Wastewater tank; 7. Detection system; 71. First temperature sensor; 72. High-temperature deformation sensor; 73. High-temperature fluid pressure sensor; 74. High-temperature acoustic emission and microseismic sensor; 75. Analog-to-digital converter; 76. Amplifier; 77. Detection controller; 8. Thermal insulation and cooling system; 81. Thermal insulation layer; 82. Cooling layer; 83. Cooling unit; 84. Inlet temperature monitoring device; 85. Outlet temperature monitoring device. DETAILED DESCRIPTION

[0048] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0050] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0051] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0052] See also Figures 1-12 As shown, according to an embodiment of the present application, a large-scale physical simulation system for induced earthquakes and safety regulation in hot dry rock development is provided, comprising:

[0053] Experimental model 1, which includes a top surface, a bottom surface, and side surfaces. A distributed stress loading system 2 is provided on the top surface, the bottom surface, and the side surfaces of the experimental model 1. A heating feedback system 3 is provided between the distributed stress loading system 2 and the bottom surface and the side surfaces of the experimental model 1. An injection well 11 and a production well 12 are provided diagonally along the upper edge of the experimental model 1.

[0054] Prefabricated fault 4, which is set in the experimental model 1 and located between the injection well 11 and the production well 12;

[0055] A fluid injection system 5 is configured to perform hydraulic fracturing on the experimental model 1 through the injection well 11, so as to form a connected fracture network between the injection well 11 and the prefabricated fault 4;

[0056] The fluid production system 6 performs hydraulic fracturing on the experimental model 1 through the production well 12, so as to form a connected fracture network between the production well 12 and the prefabricated fault 4;

[0057] The fluid injection system 5 injects fluid into the injection well 11, and the fluid is discharged to the fluid production system 6 through the fracture network. The fluid injection system 5 and the fluid production system 6 collect the fluid temperature before injection and the fluid temperature after discharge;

[0058] Detection system 7, detection system 7 is set on the experimental model 1 and the prefabricated fault 4, and is used to detect the stress state, deformation degree and temperature distribution of the prefabricated fault 4, and can also detect the rupture condition of the prefabricated fault 4 and the surrounding area.

[0059] Specifically, the experimental model 1 is printed using 3D printing equipment and has a size of 5m×5m×5m. Compared with traditional models, it can more realistically reflect the actual scale of the hot dry rock reservoir. The distributed stress loading system 2 arranged on its top, bottom and side surfaces can realize true three-dimensional stress loading on the experimental model 1, which is used to simulate the stress environment of the hot dry rock in the formation. The heating feedback system 3 arranged between the distributed stress loading system 2 and the bottom and side surfaces of the experimental model 1 is used to heat the experimental model 1 to simulate the thermal environment of the hot dry rock and improve the accuracy of the experimental results. The injection well 11 and the production well 12 are opened diagonally on the experimental model 1, providing a reliable channel for subsequent fluid injection and production.

[0060] A prefabricated fault 4 is located within experimental model 1, between injection well 11 and production well 12. The dimensions of prefabricated fault 4 are 2 m × 1.5 m × 0.3 m, and its strike and dip within experimental model 1 are determined based on the simulation requirements. After the distributed stress loading system 2 applies boundary stress to experimental model 1 to the target value, the stress loading is maintained constant. The heating feedback system 3 heats experimental model 1 to the target value and then maintains the temperature constant. A fluid injection system 5 injects fluid into experimental model 1 through injection well 11, fracturing the model and forming a connected fracture network between injection well 11 and prefabricated fault 4. Simultaneously, a fluid extraction system 6 injects fluid into experimental model 1 through production well 12, fracturing the model and forming a fracture network between production well 12 and prefabricated fault 4. During this process, a detection system 7 monitors the fracturing process and accurately locates the fracture location, enabling exploration of crack propagation patterns during hydraulic fracturing and revealing the mechanisms underlying earthquakes induced by hydraulic fracturing in hot dry rocks.

[0061] After a connected fracture network is formed between the injection well 11 and the production well 12 and the prefabricated fault 4, the fluid injection system 5 injects fluid in a flow injection manner. The fluid injection system 5 can record the temperature of the injected fluid. The fluid is extracted by the fluid production system 6 in a flow control manner through the fracture network, and the fluid production system 6 records the temperature of the produced fluid. During the fluid injection period, the detection system 7 monitors the rupture, temperature, fluid pressure and slip conditions of the prefabricated fault 4. When a sudden and rapid slip of the prefabricated fault 4 is detected, accompanied by a large number of rupture events, it is considered that an earthquake event has been induced. At this time, the injection is stopped and the experimental data is saved. Then, by changing the flow control injection and production to pressure control injection and production or circulation control injection and production, the experimental data is re-collected to monitor the slip characteristics and rupture conditions of the prefabricated fault 4 until an earthquake event is induced again. After the experiment is completed, the formula Q=CM(T out -T in ) Calculate the total heat extraction, Q-total heat extraction, C-specific heat capacity of fluid, M-mass of fluid, Tout - Temperature of produced fluid, T in -The temperature of the injected fluid can be used to calculate the heat extraction efficiency of the hot dry rock during the fluid injection and production process. The flow rate and pressure of the fluid can be monitored according to the injection pump and the production pump, and the volume of the fluid can be obtained through the flow rate and time, and then the mass of the fluid can be obtained. The data monitored by the detection system 7 is used to calculate the slip pattern of the prefabricated fault 4, the temperature evolution, the spatial distribution of the fluid pressure, and the magnitude of the earthquake. The impact of different injection and production methods on induced earthquakes is compared and analyzed, and the mechanism of earthquake induction by different injection and production methods is explained, so as to form a safe injection and production method for hot dry rocks.

[0062] Among them, the materials of experimental model 1 and prefabricated fault 4 are a mixture of various materials such as quartz sand, barite powder, high-strength gypsum, cement, paraffin and silicate cement. Their mechanical properties and thermal properties are highly similar to those of hot dry rocks and natural faults.

[0063] When 3D printing the experimental model 1, the injection well 11 and the production well 12 were arranged diagonally on the experimental model 1 using a prefabricated printing method. The distance between the injection well 11 and the production well 12 was 3.0 m, the depth was 2.5 m, the diameter was 75 mm, the open hole section was 200 mm, the casing was made of 29CrMo44 steel, and the cementing method was epoxy resin bonding.

[0064] The distributed stress loading system 2 can apply true triaxial stress to the six surfaces of the experimental model 1 , and each surface of the experimental model has 25 loading cylinders.

[0065] like Figure 1 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9 As shown, in some embodiments, optionally, the detection system 7 includes a first sensor component and a second sensor component, the first sensor component is arranged on the prefabricated fault 4, and the second sensor component is arranged on the bottom, top and side surfaces of the experimental model 1.

[0066] The first sensor assembly includes: a first temperature sensor 71, a high temperature resistant deformation sensor 72 and a high temperature resistant fluid pressure sensor 73, the first temperature sensor 71, the high temperature resistant deformation sensor 72 and the high temperature resistant fluid pressure sensor 73 are arranged on the prefabricated fault 4;

[0067] The second sensor assembly includes: a high-temperature resistant acoustic emission and microseismic sensor 74 , which is arranged on the top surface, bottom surface and side surface of the experimental model 1 .

[0068] Specifically, the first sensor assembly includes a first temperature sensor 71, a high temperature resistant deformation sensor 72 and a high temperature resistant fluid pressure sensor 73. The first temperature sensor 71, the high temperature resistant deformation sensor 72 and the high temperature resistant fluid pressure sensor 73 are multiple and are installed at intervals on both sides of the prefabricated fault 4.

[0069] The first temperature sensor 71 is mainly used to collect the temperature distribution of the prefabricated fault 4. The model is PT100. Its resistance value is approximately linearly related to the temperature change. It has high accuracy and good stability. The temperature measurement range is -200~850℃. During the injection and production of hot dry rocks, it can accurately monitor the local temperature changes caused by fluid migration and rock fracture friction.

[0070] The high-temperature resistant deformation sensor 72 uses a KH high-temperature welded strain gauge, which is welded on the surface of the prefabricated fault 4. It has a self-compensation function and can work stably in a high-temperature environment of 550°C, and accurately measure the slip behavior of the prefabricated fault 4.

[0071] The high temperature resistant fluid pressure sensor 73 can withstand a high temperature of 400°C and a high pressure of 70 MPa, with an accuracy of ±1 kPa, and is mainly used for measuring the fluid pressure on the prefabricated fault 4 during experiments.

[0072] The second sensor assembly includes a high-temperature resistant acoustic emission and microseismic sensor 74, which adopts a high-temperature acoustic emission sensor based on LGS crystal and has a wide-band response capability of 28kHz-274kHz. It is arranged in an array on the top, bottom and side surfaces of the experimental model 1 to form a spatial cross-monitoring network, realizing the collection and precise positioning of fracture signals during the fluid fracturing process and the slip of the prefabricated fault 4 caused by injection, and the induced earthquake process, which is used to reveal the breeding mechanism of earthquakes induced by hot dry rock injection.

[0073] like Figure 1 As shown, in some embodiments, optionally, the detection system 7 further includes: an analog-to-digital converter 75, an amplifier 76 and a detection controller 77, and the detection controller 77 is electrically connected to the first sensor component and the second sensor component through the analog-to-digital converter 75 and the amplifier 76.

[0074] Specifically, the analog-to-digital converter 75 converts analog sensor signals from the first temperature sensor 71, the high-temperature deformation sensor 72, and other sensors into digital signals with extremely high resolution. Under the high temperatures and complex electromagnetic environment of the dry-hot rock simulation experiment, the anti-interference filter circuit built into the analog-to-digital converter 75 effectively filters out electromagnetic noise generated by the operation of equipment such as the heating feedback system 3 and the fluid injection system 5, ensuring accurate data conversion. The amplifier 76 is used to enhance weak sensor signals, ensuring that the signals are not distorted during transmission. The acoustic emission signals generated by rock fractures, captured by the high-temperature acoustic emission and microseismic sensor 74, are extremely weak and easily affected by transmission distance and environmental factors. The amplifier 76 has a wide frequency range of signal amplification capabilities, enabling targeted multi-stage amplification of these weak signals. It also employs advanced noise reduction technology to suppress noise growth while amplifying the signal. After processing by the amplifier 76, the acoustic emission signal strength is significantly enhanced, enabling subsequent data acquisition and analysis to more clearly identify characteristic parameters of rock fracture events, such as signal arrival time and waveform morphology, thereby enabling precise location and analysis of rock fracture behavior during induced earthquakes.

[0075] Detection controller 77 is connected to analog-to-digital converter 75 and amplifier 76 via a data bus, receiving processed data in real time. The intelligent algorithm built into detection controller 77 analyzes monitoring data in real time. Researchers can remotely monitor experimental progress, access historical data, and perform data analysis and model optimization via the network, greatly improving experimental convenience and research efficiency.

[0076] like Figure 1 As shown, in some embodiments, optionally, the fluid injection system 5 includes: a water reservoir 51, an injection pressure pump 52, an injection flow pump 53, a pre-accumulator 54, a pre-filter 55, a tracer 56 and a second temperature sensor 57;

[0077] An injection pipeline is provided between the water reservoir 51 and the injection well 11 , and an injection pressure pump 52 , an injection flow pump 53 , a pre-accumulator 54 , a pre-filter 55 , a tracer 56 and a second temperature sensor 57 are sequentially provided on the injection pipeline.

[0078] Specifically, the water reservoir 51 is a large-capacity design of 4m×3m×1.5m, which can meet the water demand of long-term, large-flow experiments and supply water for the entire injection system. The injection pressure pump 52 has a pressure output capacity of up to 70MPa and an accuracy of 1%FS. It applies high-pressure fluid to the injection well 11 to fracture the experimental model 1, forming a connected fracture network between the injection well 11 and the prefabricated fault 4, providing a basis for subsequent fluid circulation. The injection flow pump 53 is used for high-flow fluid injection control, with a flow rate of up to 200L / s. After the injection pressure pump 52 completes fracturing, its injection capacity is limited and cannot meet the high-flow requirements of induced earthquakes. The injection flow pump 53 intervenes to provide a greater flow control injection function. The pre-accumulator 54 can effectively absorb pressure fluctuations during the fluid injection process. When the injection pressure pump 52 starts, stops or adjusts the pressure, the accumulator can quickly release or store energy to prevent sudden pressure changes from impacting pipelines and equipment, and avoid problems such as pipeline vibration, loose connectors, and even equipment damage caused by pressure fluctuations, thereby ensuring a smooth transition of system pressure. The pre-filter 55 uses a high-precision filter mesh and a multi-layer filter structure, which can intercept impurities such as rock chips, mud, and rust in the fluid. When the fluid injection system 5 switches between different working modes or fluid backflow occurs, the pre-filter 55 can effectively protect the injection pressure pump 52, the injection flow pump 53 and other equipment, prevent impurities from entering the pump body and causing wear, extend the service life of the equipment, and ensure the smooth progress of the experiment.

[0079] Tracer 56, a radioactive substance such as barium or iodine, is mixed into the fluid at a predetermined ratio during injection by controlling the degree of valve opening. As the fluid flows through the fracture network, tracer 56 adheres to the surface of the fault and surrounding fractures. After the experiment, cutting the experimental model 1 can visually demonstrate the fracture extension, distribution range, and fluid migration path, providing researchers with clear visualization of rock mass failure during slip of the prefabricated fault 4. A second temperature sensor 57 is installed on the injection pipeline to monitor the temperature changes of the injected fluid in real time.

[0080] like Figure 1 As shown, in some embodiments, optionally, the fluid production system 6 includes: a third temperature sensor 61, a post-filter 62, a post-accumulator 63, a production flow pump 64, a production pressure pump 65 and a wastewater tank 66;

[0081] A production pipeline is provided between the wastewater pool 66 and the production well 12 , and a third temperature sensor 61 , a post-filter 62 , a post-accumulator 63 , a production flow pump 64 and a production pressure pump 65 are sequentially provided on the production pipeline.

[0082] Specifically, the third temperature sensor 61 is used to monitor the temperature of the produced fluid, and the post-filter 62 adopts a multi-layer composite filter structure, which can effectively intercept rock chips, broken rock particles and other impurities carried in the produced fluid. During the experiment, hydraulic fracturing and fluid flow may cause rock fragments inside the experimental model 1 to enter the production pipeline. The post-filter 62 can prevent these impurities from entering the production flow pump 64 and the production pressure pump 65, avoiding damage to the equipment due to wear, greatly extending the service life of the equipment, and ensuring the long-term stable operation of the production system. The post-accumulator 63 is mainly responsible for stabilizing the pressure fluctuations during the production process. When the production pressure pump 65 starts and stops or adjusts the pressure, and the production flow pump 64 adjusts the flow, the post-accumulator 63 can quickly absorb or release pressure, maintain the pressure in the pipeline stable, and prevent problems such as pipeline vibration and interface leakage caused by sudden pressure changes.

[0083] Production pressure pump 65 can reach a maximum pressure of 70 MPa with an accuracy of 1% FS. During the initial stages of production and injection, it is primarily used to hydraulically fracture the gap between production well 12 and prefabricated fault 4, creating a continuous fluid flow channel and facilitating subsequent production and injection operations. After fracturing, production flow pump 64, with a flow rate output of up to 200 L / s, can quickly and stably extract the high-temperature fluid from experimental model 1 after heat exchange. If production pressure pump 65's extraction capacity is limited after fracturing and cannot meet the requirements of hot dry rock injection-induced seismicity, production flow pump 64 intervenes to provide greater flow control and production. Wastewater tank 66, measuring 4 m × 3 m × 1.5 m, is designed to accommodate wastewater generated during extended experiments. Its maximum discharge rate is 2000 L / h, ensuring timely discharge of wastewater.

[0084] like Figure 1 As shown, in some embodiments, optionally, the distributed stress loading system 2 is used to apply true triaxial stress to the experimental model 1, and a thermal insulation cooling system 8 is provided between the distributed stress loading system 2 and the top surface of the experimental model 1 and the heating feedback system 3.

[0085] Specifically, the distributed stress loading system 2 can apply true triaxial stress to the six surfaces of the experimental model 1 to simulate the stress environment of hot dry rock in the stratum. The heating feedback system 3 is used to heat the experimental model 1 to simulate the thermal environment of hot dry rock. Since the safe operating temperature of the distributed stress loading system 2 is not higher than 55°, the thermal insulation cooling system 8 is installed on the inner side of the distributed stress loading system 2 to ensure the safety of the distributed stress loading system 2.

[0086] like Figure 1 、 2 As shown in FIG. 3 , in some embodiments, optionally, the heating feedback system 3 includes:

[0087] A bottom heating element 31 is provided on the bottom surface of the experimental model 1;

[0088] A side heating element 32 is provided on a side of the experimental model 1;

[0089] The heating controller 33 is electrically connected to the bottom heating element 31 and the side heating element 32 .

[0090] Specifically, the heating feedback system 3 includes a bottom heating element 31, a side heating element 32, and a heating controller 33. The bottom heating element 31 is installed at the bottom of the experimental model 1, and its size matches the bottom surface of the experimental model 1. There are four groups of side heating elements 32, which are installed on the four sides of the experimental model 1. The bottom heating element 31 and the side heating element 32 are each made up of five small heating plates. Each heating plate is composed of multiple heating rods and can be independently controlled. When some heating rods fail, the adjacent heating rods can automatically increase power to compensate and maintain the overall heating effect stable. This not only improves the reliability of the heating system, but also facilitates subsequent maintenance and replacement. The coordinated operation of the bottom heating element 31 and the side heating element 32 can form a wrap-around heating environment around the experimental model 1, achieving a high-temperature simulation of up to 400°C, with a heating rate stably controlled at 5°C / h, simulating the real geothermal environment of dry hot rock.

[0091] The heating controller 33 is used to control the power of the bottom heating element 31 and the side heating element 32. It consists of a computer, a power control cabinet and a temperature sensor. It dynamically adjusts the heating power according to the temperature conditions in different areas to achieve precise control of the target temperature.

[0092] The bottom heating element 31 and the side heating element 32 both have a size of 4.9 m×4.9 m.

[0093] like Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 As shown, in some embodiments, optionally, the heat preservation and cooling system 8 includes:

[0094] A thermal insulation layer 81 is provided on the bottom heating element 31, the side heating element 32 and the top surface of the experimental model 1;

[0095] A cooling layer 82 is provided between the thermal insulation layer 81 and the distributed stress loading system 2;

[0096] Cooling unit 83, the water outlet of cooling unit 83 is connected to the water inlet of cooling layer 82, the water inlet of cooling unit 83 is connected to the water outlet of cooling layer 82, an inlet temperature monitoring device 84 is provided between the water outlet of cooling unit 83 and the water inlet of cooling layer 82, and an outlet temperature monitoring device 85 is provided between the water inlet of cooling unit 83 and the water outlet of cooling layer 82.

[0097] Specifically, the thermal insulation layer 81 is installed on the bottom heating element 31, the side heating element 32 and the top surface of the experimental model 1 to prevent the experimental model 1 from exchanging heat with other equipment and air, resulting in rapid heat loss and making the experimental model 1 unable to reach the target temperature required for the experiment.

[0098] The thermal insulation layer 81 is made of high-strength and high-temperature resistant mica fiberboard with a uniaxial compressive strength of not less than 30 MPa, a maximum temperature resistance of up to 1000°C, a voltage breakdown resistance index of up to 20KV / MM, and a thermal conductivity coefficient of only about 0.9W / (m·K). The excellent thermal insulation performance effectively prevents the high temperature inside the experimental model 1 from being transmitted to the outside.

[0099] The cooling layer 82 is made of stainless steel and has dimensions of 4.9m×4.9m×0.1m. One side is in close contact with the thermal insulation layer 81, and the other side is in direct contact with the distributed stress loading system 2, ensuring structural strength while effectively transferring heat. Precision holes are reserved inside the cooling layer 82 and copper tubes are inserted to construct an efficient cooling liquid circulation channel. When residual heat that is not completely isolated by the thermal insulation layer 81 is transferred to the cooling layer 82, the flowing cooling liquid quickly absorbs heat through the copper tube, maintaining the temperature within a safe range, preventing the distributed stress loading system 2 from failing due to high temperature, ensuring its stable operation at a safe operating temperature not exceeding 55°C, and guaranteeing the accuracy and reliability of stress loading.

[0100] Cooling unit 83 achieves continuous cooling and recycling of the cooling liquid through a highly efficient refrigeration cycle. The water outlet of cooling unit 83 is connected to the water inlet of cooling layer 82, and the water inlet is connected to the water outlet of cooling layer 82, forming a closed cooling loop. During the circulation process, inlet temperature monitoring device 84 and outlet temperature monitoring device 85 monitor the temperature changes of the cooling liquid in real time and provide real-time feedback to the control system of cooling unit 83. If outlet temperature monitoring device 85 detects that the cooling liquid temperature exceeds the safety threshold, cooling unit 83 automatically increases the cooling power to rapidly reduce the cooling liquid temperature.

[0101] The thermal insulation layer 81 has a size of 4.9 m×4.9 m.

[0102] like Figure 10 、 Figure 11 and Figure 12As shown, in some embodiments, optionally, the prefabricated fault 4 is one of a normal fault 41 , a reverse fault 42 and a strike-slip fault 43 .

[0103] Specifically, normal faults 41, reverse faults 42, and strike-slip faults 43 are distinguished primarily based on their stress conditions: normal fault 41 is subjected to a stress state of SV>SH>Sh; reverse fault 42 is subjected to a stress state of SH>Sh>SV; and strike-slip fault 43 is subjected to a stress state of SH>SV>Sh. Different prefabricated faults 4 are used to analyze the impact of different fault types on dry hot rock injection-induced earthquakes and safety regulation. SV represents the vertical principal stress; SH represents the maximum horizontal principal stress; and Sh represents the minimum horizontal principal stress.

[0104] The ultra-large-scale physical simulation system experiment of hot dry rock development-induced earthquakes and safety regulation includes the following steps:

[0105] Step 1: Install the thermal insulation layer 81 and cooling layer 82 sequentially from top to bottom on the bottom of the bottom heating element 31. After installation, place the bottom heating element 31 on the printing platform to print a 5m×5m×5m experimental model 1. During this process, the prefabricated fault 4 can be automatically printed within the experimental model 1. During the printing process, the calibrated first temperature sensor 71, high-temperature resistant acoustic emission and microseismic sensor 74, high-temperature resistant deformation sensor 72, and high-temperature resistant fluid pressure sensor 73 are pre-embedded in designated locations according to coordinates. Similarly, the injection well 11 and production well 12 are reserved during the printing process. After printing is completed, the model is transported to a constant temperature and humidity chamber for curing for 28 days.

[0106] Step 2: After the maintenance is completed, casing is installed in the injection well 11 and the production well 12, and 29CrMo44 steel casing is lowered into the injection well 11 and the production well 12, and a 200mm bare hole section is reserved for fluid injection. After the casing is lowered, epoxy resin is poured between the casing and the well wall for cementing. After the cementing is completed, the detection system 7 tests the first temperature sensor 71, the high-temperature resistant acoustic emission and microseismic sensor 74, the high-temperature resistant deformation sensor 72 and the high-temperature resistant fluid pressure sensor 73, and the heating feedback system 3 tests the bottom heating element 31; after the test is normal, the side heating element 32, the thermal insulation layer 81 and the cooling layer 82 are installed, and the assembled experimental model 1 is transported to the distributed stress loading system 2, the fluid injection system 5 is connected to the injection well 11, and the fluid production system 6 is connected to the production well 12, and the sealing of the connection is checked and sorted;

[0107] Step 3: Start the distributed stress loading system 2 and apply boundary stress to the experimental model 1. After the boundary stress reaches the target value, keep the stress loading constant. At the same time, start the heating feedback system 3, the thermal insulation and cooling system 8, and the detection system 7. The heating feedback system 3 heats the experimental model 1 at a heating rate of 5°C / h, and the temperature control accuracy is accurate to ±1°C. The activation of the thermal insulation and cooling system 8 mainly plays a protective role. When the return water temperature of the cooling layer 82 is higher than 55°C, the cooling unit 83 will automatically start and actively cool down to ensure that the distributed stress loading system 2 is not damaged by temperature. The operation of the cooling unit 83 will run through the entire experimental process. The activation of the detection system 7 is used to monitor the thermal cracking behavior of the experimental model 1 and the prefabricated fault 4 under the action of thermal stress during the heating process.

[0108] When the detection system 7 monitors that the temperature on the prefabricated fault 4 reaches the target, the heating feedback system 3 is adjusted from the heating state to the insulation state, which can better maintain the temperature of the experimental model 1 while reducing energy consumption. The fluid is injected into the experimental model 1 from the injection well 11 through the fluid injection system 5 to perform hydraulic fracturing, so that a connected fracture network is formed between the injection well 11 and the prefabricated fault 4. At the same time, the production well 12 is connected through the fluid production system 6, and fluid is injected into the experimental model 1 from the production well 12 through the fluid production system 6, so that a connected fracture is also formed between the production well 12 and the prefabricated fault 4. In this process, the high-temperature resistant acoustic emission and microseismic sensor 74 accurately locates the rupture events during the fracturing process, which is used to explore the crack propagation law during the hydraulic fracturing process and reveal the breeding mechanism of earthquakes induced during the hydraulic fracturing of hot dry rocks.

[0109] After the injection well 11 and the production well 12 form a connected fracture with the prefabricated fault 4, an injection-production experiment is carried out. A large amount of fluid is injected into the experimental model 1 through the injection well 11 using an injection flow pump 53 in a flow-controlled injection manner, and the temperature of the injected water is recorded by the second temperature sensor 57. At the same time, the production flow pump 64 also extracts fluid in a flow-controlled manner, and uses the third temperature sensor 61 to record the temperature of the produced fluid. Finally, the fluid is discharged into the wastewater pool 66. During the injection period, the detection system 7 is used to monitor the rupture, temperature, fluid pressure and slip of the prefabricated fault 4. When a sudden and rapid slip of the fault is detected, accompanied by a large number of rupture events, it is considered that an earthquake event has been induced. At this time, the injection is stopped and the experimental data is saved.

[0110] By changing the flow-controlled injection-production method to a pressure-controlled injection-production method or a circulation-controlled injection-production method, where the pressure-controlled injection-production method maintains a constant pressure in the injection flow pump 53 and the production flow pump 64 during injection-production; the circulation-controlled injection-production method involves injecting the injection flow pump 53 and the production flow pump 64 for a period of time, then stopping, and then restarting the same injection method after a period of time. For example, a constant injection pressure of 10 MPa is maintained, and the injection flow pump and the production flow pump are injected for 10 days, then stopped, and then injection-production is resumed after 10 days. Experimental data is recollected to observe the slip characteristics and rupture of the fault until another earthquake event is induced. After the injection-production test is completed, tracer 56 is added, and a small amount of water is injected again using the injection flow pump 53, so that the tracer 56 remains in the fractures of the experimental model 1 and the prefabricated fault 4. After the experiment is completed, the dry hot rock similar experimental model 1 is cut to observe the expansion of the fracture.

[0111] The temperature difference of the fluid is detected by the second temperature sensor 57 and the third temperature sensor 61, and the total amount of heat extracted from the hot dry rock is calculated. The slip law of the fault, the temperature evolution, the spatial distribution of the fluid pressure and the magnitude of the earthquake are calculated based on the data of the detection system 7. The effects of different injection and production methods on induced earthquakes are compared and analyzed, and the mechanism of earthquake induction by different injection and production methods is explained to form a safe injection and production method for hot dry rocks.

[0112] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. The above are merely preferred embodiments of the present application. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present application, and such improvements and variations shall also be considered within the scope of protection of the present application.

Claims

1. A super-large physical simulation system for hot dry rock development-induced earthquakes and safety control, characterized by: include: An experimental model (1), the experimental model (1) comprising a top surface, a bottom surface and side surfaces, a distributed stress loading system (2) being provided on the top surface, the bottom surface and the side surfaces of the experimental model (1), a heating feedback system (3) being provided between the distributed stress loading system (2) and the bottom surface and the side surfaces of the experimental model (1), and an injection well (11) and a production well (12) being provided diagonally on the upper side of the experimental model (1); A prefabricated fault (4), the prefabricated fault (4) being arranged in the experimental model (1) and located between the injection well (11) and the production well (12); A fluid injection system (5), wherein the fluid injection system (5) performs hydraulic fracturing on the experimental model (1) through the injection well (11), so as to form a connected fracture network between the injection well (11) and the prefabricated fault (4); A fluid production system (6), wherein the fluid production system (6) performs hydraulic fracturing on the experimental model (1) through the production well (12) so as to form a connected fracture network between the production well (12) and the prefabricated fault (4); The fluid injection system (5) injects fluid into the injection well (11), and the fluid is discharged to the fluid production system (6) through the fracture network. The fluid injection system (5) and the fluid production system (6) collect the fluid temperature before injection and the fluid temperature after discharge; A detection system (7), the detection system (7) being arranged on the experimental model (1) and the prefabricated fault (4), and being used to detect the stress state, deformation degree and temperature distribution of the prefabricated fault (4), and at the same time detecting the rupture condition of the prefabricated fault (4) and the surrounding area; The detection system (7) includes a first sensor assembly and a second sensor assembly, wherein the first sensor assembly is arranged on the prefabricated fault (4), and the second sensor assembly is arranged on the bottom surface, top surface and side surface of the experimental model (1); The first sensor assembly comprises: a first temperature sensor (71), a high temperature resistant deformation sensor (72), and a high temperature resistant fluid pressure sensor (73); the first temperature sensor (71), the high temperature resistant deformation sensor (72), and the high temperature resistant fluid pressure sensor (73) are arranged on the prefabricated fault (4); The second sensor assembly comprises: a high-temperature resistant acoustic emission and microseismic sensor (74), wherein the high-temperature resistant acoustic emission and microseismic sensor (74) is arranged on the top surface, the bottom surface and the side surface of the experimental model (1); The prefabricated fault (4) is one of a normal fault (41), a reverse fault (42) and a strike-slip fault (43); The fluid injection system (5) comprises: a water reservoir (51), an injection pressure pump (52), an injection flow pump (53), a pre-accumulator (54), a pre-filter (55), a tracer (56), and a second temperature sensor (57); An injection pipeline is provided between the water reservoir (51) and the injection well (11), and the injection pressure pump (52), the injection flow pump (53), the pre-accumulator (54), the pre-filter (55), the tracer (56) and the second temperature sensor (57) are sequentially provided on the injection pipeline; The fluid production system (6) includes: a third temperature sensor (61), a post-filter (62), a post-accumulator (63), a production flow pump (64), a production pressure pump (65) and a wastewater tank (66); A production pipeline is provided between the wastewater pool (66) and the production well (12), and the production pipeline is provided with the third temperature sensor (61), the post-filter (62), the post-accumulator (63), the production flow pump (64), and the production pressure pump (65) in sequence; After the injection well (11) and the production well (12) form a connected fissure with the prefabricated fault (4), an injection and production experiment is carried out. A large amount of fluid is injected into the experimental model (1) through the injection well (11) using the injection flow pump (53) in a flow-controlled injection manner, and the temperature of the injected water is recorded by the second temperature sensor (57). At the same time, the production flow pump (64) also takes fluid in a flow-controlled manner, and uses the third temperature sensor (61) to record the temperature of the produced fluid. Finally, the fluid is discharged into the wastewater pool (66). During the injection period, the detection system (7) is used to monitor the rupture, temperature, fluid pressure and slip of the prefabricated fault (4). When it is detected that the prefabricated fault (4) slips suddenly and rapidly, accompanied by a large number of rupture events, it is considered that an earthquake event has been induced. At this time, the injection is stopped and the experimental data is saved. The flow control injection and production mode is changed to a pressure control injection and production mode or a circulation control injection and production mode, wherein the pressure control injection and production mode is to maintain the pressure of the injection flow pump (53) and the production flow pump (64) unchanged for injection and production; the circulation control injection and production mode is to stop the injection flow pump (53) and the production flow pump (64) after injection for a period of time, and then start the same injection mode again after a period of time, re-collect experimental data, and observe the slip characteristics and rupture conditions of the prefabricated fault (4) until an earthquake event is induced again.

2. The ultra-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation according to claim 1 is characterized in that: The detection system (7) further includes: an analog-to-digital converter (75), an amplifier (76) and a detection controller (77), wherein the detection controller (77) is electrically connected to the first sensor component and the second sensor component via the analog-to-digital converter (75) and the amplifier (76).

3. The ultra-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation according to claim 1 is characterized in that: The distributed stress loading system (2) is used to apply true triaxial stress to the experimental model (1), and a heat preservation and cooling system (8) is provided between the distributed stress loading system (2), the top surface of the experimental model (1), and the heating feedback system (3).

4. The ultra-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation according to claim 3 is characterized in that: The heating feedback system (3) comprises: A bottom surface heating element (31), the bottom surface heating element (31) being arranged on the bottom surface of the experimental model (1); A side heating element (32), the side heating element (32) being arranged on a side of the experimental model (1); A heating controller (33), wherein the heating controller (33) is electrically connected to the bottom heating element (31) and the side heating element (32).

5. The ultra-large physical simulation system for hot dry rock development-induced earthquakes and safety regulation according to claim 4 is characterized in that: The heat preservation and cooling system (8) comprises: a heat-insulating layer (81), the heat-insulating layer (81) being arranged on the bottom heating element (31), the side heating element (32) and the top surface of the experimental model (1); a cooling layer (82), the cooling layer (82) being arranged between the thermal insulation layer (81) and the distributed stress loading system (2); A cooling unit (83), wherein the water outlet of the cooling unit (83) is connected to the water inlet of the cooling layer (82), the water inlet of the cooling unit (83) is connected to the water outlet of the cooling layer (82), an inlet temperature monitoring device (84) is provided between the water outlet of the cooling unit (83) and the water inlet of the cooling layer (82), and an outlet temperature monitoring device (85) is provided between the water inlet of the cooling unit (83) and the water outlet of the cooling layer (82).

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