In-situ rock fracturing and permeability increasing and leaching mining physical simulation device and method

Abstract

This invention discloses a physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching injection and production, comprising a triaxial loading component, a mixing component, an injection component, an additive component, a flowback metering component, and a sample. The in-situ stress on the sample is provided by the pressure pillows in three directions within the pressure chamber of the triaxial loading component and the confining pressure of the liquid within the liquid-filled space inside the pressure chamber. The mixing component is used to prepare the in-situ leaching solution, and the additive component adds different additives to the sample. The flowback metering component is used to achieve multi-parameter monitoring. This invention can realize in-situ boundary simulation, disturbance load application, continuous preparation of in-situ leaching solution, continuous injection of in-situ leaching solution, leaching solution production and metering, multi-parameter monitoring of reservoir stimulation and production processes, and simulation of reservoir fracture expansion support during the uranium reservoir stimulation and production process. By quantitatively evaluating the influence of different factors in the production of in-situ leaching solution, it clarifies the main factors affecting reservoir production efficiency, providing a reference for further optimization of uranium reservoir production processes.

Description

Technical Field

[0001] This invention relates to the field of true triaxial physical simulation technology for rocks, and in particular to a device and method for physical simulation of in-situ rock fracturing and permeability enhancement and in-situ leaching and mining. Background Technology

[0002] In recent years, in-situ CO2-O2 leaching of uranium has been widely promoted and applied. Leaching fluid is a corrosive liquid that requires a long reaction time after entering the ore layer to leach uranium. Uranium leaching is a long-term injection and production process. Through continuous injection of leaching fluid, U4+ in the reservoir is oxidized to soluble U6+. U6+ combines with HCO3- ions in the leaching fluid and is then leached out with the leaching solution. The oxygen content, HCO3- ion concentration, and additive ratios in the leaching fluid have a significant impact on the leaching efficiency of uranium ore. Before leaching, the uranium reservoir needs to be uniformly fractured to make the ore and surrounding rock permeable to chemical solvents. Existing fractured mesh modification technologies struggle to produce a homogeneous fracture network in the reservoir, often resulting in the presence of main fractures, leading to low efficiency in leaching.

[0003] Physical simulation experiments were conducted indoors to simulate the entire process of reservoir stimulation and in-situ leaching-production under in-situ boundary conditions. Based on the experimental results, the extraction technology of tight sandstone reservoirs was optimized, thereby developing a complete set of technologies and equipment suitable for tight sandstone uranium ore reservoirs. Currently, blasting fracturing is the main reservoir stimulation method for generating homogeneous fracture networks, including CO2 micro-blasts, CH4 micro-blasts, and explosive blasting. However, existing blasting technologies are mostly applicable to blasting scenarios with free faces, and there are few studies on the physical simulation of blasting fracturing without free faces. Simulation equipment mostly uses rigid pad loading to simulate formation stress. Under rigid loading, the area 1 / 4 of the side length of the loading surface is generally considered to be unaffected by boundary stress. Under rigid loading, most areas of the sample are affected by the loading boundary, and the rigid loading boundary reflects blasting stress waves. The combination of these factors leads to distortion of fracture propagation during reservoir stimulation simulation. Furthermore, existing equipment cannot realize the physical simulation of the entire process of reservoir stimulation and in-situ leaching. In summary, existing physical simulation devices are insufficient to meet the physical simulation conditions for the entire leaching and injection-production process, mainly due to the following shortcomings: 1. The simulation of the original rock boundary conditions is distorted, failing to simulate the blasting and fracturing process of the reservoir. Under triaxial rigid loading, the stress distortion distribution area at the boundary is large, and stress wave reflection exists at the rigid boundary; 2. It cannot continuously prepare precisely proportioned leaching solutions, which is insufficient to support research on the influence of the proportions of oxygen content, HCO3- ion concentration, and additives in the leaching solution on the leaching efficiency of uranium ore. Furthermore, the preparation capacity is limited, insufficient to support physical similarity simulation experiments of continuous leaching solution injection, chemical reaction, and pumping backflow processes; 3. It cannot simulate the leaching solution production and metering process; 4. It is difficult to apply disturbance loads during reservoir stimulation; 5. The monitoring method for damage signals during the injection-production physical simulation process is singular, and the number of measurement points that can be deployed is small; 6. It cannot simulate the process of adding proppant, expansion agent, and surfactant after reservoir stimulation.

[0004] It is evident that how to achieve physical simulation of reservoir fracturing-in-situ leaching and extraction processes under in-situ conditions is a challenging issue in optimizing uranium reservoir mining technology. In particular, large-scale physical simulation devices and methods for in-situ leaching and extraction are urgent technical problems that need to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to propose a physical simulation device and method for in-situ fracturing and permeability enhancement and in-situ leaching injection and production. This device can realize the simulation of in-situ boundary, application of disturbance load, continuous preparation of in-situ leaching fluid, continuous and precise injection of in-situ leaching fluid, extraction and metering of leaching fluid, as well as multi-parameter monitoring of reservoir stimulation and production processes and simulation of reservoir fracture expansion support, etc. It can quantitatively evaluate the influence of different factors in the production of in-situ leaching fluid, thereby clarifying the main factors affecting reservoir production efficiency and providing a reference for further optimization of uranium reservoir production technology.

[0006] The technical solution adopted in this invention is:

[0007] A physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production includes a triaxial loading assembly, a mixing assembly, an injection assembly, an additive assembly, a flowback metering assembly, and a sample. The triaxial loading assembly includes a hydraulic servo system, a pressure chamber, and pressure pillows. The sample is installed in the pressure chamber, with pressure pillows located below and on four sides of the sample. The in-situ stress on the sample is provided by the pressure pillows in three directions and the confining pressure of the liquid within the pressure chamber's internal filling space. The internal pressure of the pressure pillows and the confining pressure of the liquid are provided by the hydraulic servo system. The mixing assembly includes a dissolved oxygen generator, a CO2 booster, and a mixing container group. The outlets of the dissolved oxygen generator and the CO2 booster are connected to the inlet of the mixing container group, respectively. In-situ leaching solution is prepared by uniformly mixing an oxygen-containing solution with CO2 through the mixing container group. The outlet of the mixing container group is connected to the inlet of the injection assembly. The injection assembly... The outlet is connected to the inlet of the additive component via a branch line, and the outlet of the injection component is also connected to the injection pipe of the triaxial loading component via another branch line. The injection pipe is connected to the pre-embedded pipe of the sample. The inlet of the additive component is connected to the outlet of the injection component, and the outlet of the additive component is connected to the injection pipe of the triaxial loading component. Different additives are added to the sample through the additive component. The backflow metering component includes a vacuum pump, a backflow liquid outlet pipe, a solid separator, a back pressure valve, a gas-liquid separator, a gas flow meter group, and a liquid flow meter group. The vacuum pump is connected to the injection pipe via a pipeline. The backflow liquid in the pressure chamber is discharged through the backflow liquid outlet pipe. The solid separator, back pressure valve, and gas-liquid separator are sequentially arranged on the backflow liquid outlet pipe. After the gas-liquid separator, the flow is divided into a gas pipeline and a liquid pipeline. The gas flow meter group is installed on the gas pipeline, and the liquid flow meter group is installed on the liquid pipeline.

[0008] In the above scheme, the hydraulic servo system includes an X-direction oil circuit, a Y-direction oil circuit, a Z-direction oil circuit, and a confining pressure oil circuit. The X-direction oil circuit is connected to the pressure pillow below the sample, the Y-direction oil circuit is connected to the pressure pillows on the left and right sides of the sample, the Z-direction oil circuit is connected to the pressure pillows on the front and rear sides of the sample, and the confining pressure oil circuit is connected to the liquid filling space inside the pressure chamber. During loading, the pressure value inside the pressure pillow is greater than the liquid confining pressure value.

[0009] In the above solution, the pressure pillow includes a pressure pillow shell, an elastic liner, and granular material. The elastic liner is disposed inside the pressure pillow shell and filled with granular material.

[0010] In the above scheme, the backflow metering component also includes a liquid sampler and a gas sampler. The liquid sampler is installed on the branch between the solid separator and the back pressure valve, and the gas sampler is installed on the pipeline after the gas flow meter group.

[0011] In the above scheme, the dissolved oxygen generating device includes an oxygen source, an oxygen solution stirring container, and a water source. The outlets of the oxygen source and the water source are respectively connected to the inlet of the oxygen solution stirring container, and the outlet of the oxygen solution stirring container is connected to the inlet of the mixing container group. The CO2 booster device includes a CO2 source, a CO2 booster pump, a CO2 storage tank, and a CO2 metering pump connected in sequence through pipelines. The outlet of the CO2 metering pump is connected to the inlet of the mixing container group.

[0012] In the above scheme, the outlet pipeline of the oxygen source is equipped with an oxygen pressure regulating valve, an oxygen pressure gauge and an oxygen shut-off valve; the oxygen solution stirring container is equipped with an oxygen content sensor and a level gauge (212), and the outlet pipeline of the oxygen solution stirring container is equipped with an oxygen solution metering pump and a shut-off valve (216).

[0013] In the above scheme, the inlet pipe of the CO2 storage tank is equipped with a CO2 pressure gauge, the outlet pipe of the CO2 storage tank is equipped with a CO2 safety valve and a shut-off valve (253), and the outer shell of the CO2 storage tank is equipped with a heat insulation heating jacket; the outlet pipe of the CO2 metering pump is equipped with a CO2 pressure regulating valve, a CO2 pressure gauge and a shut-off valve (263), and the outer shell of the CO2 metering pump is equipped with a heat insulation heating jacket.

[0014] In the above scheme, a level gauge (272) and a heat insulation heating jacket are installed on the outside of the mixing container group, and a shut-off valve (273) is installed on the outlet pipe of the mixing container group.

[0015] In the above scheme, the injection component adopts a dual-cylinder constant speed and constant pressure injection pump. The dual-cylinder constant speed and constant pressure injection pump includes two parallel single pumps 321 and 322. The inlet pipe of the first single pump 321 is equipped with a shut-off valve (312) and the outlet pipe is equipped with a shut-off valve (313). The inlet pipe of the second single pump 322 is equipped with a shut-off valve (314) and the outlet pipe is equipped with a shut-off valve (315). The two single pumps can independently perform liquid suction and liquid discharge actions.

[0016] In the above scheme, the additive component includes a high-pressure storage tank, a screw pump and a screw pump motor. The funnel outlet at the bottom of the high-pressure storage tank is connected to the outlet of the injection component. The additive in the high-pressure storage tank falls to the outlet under its own weight and mixes with the ground leaching solution. The screw pump motor rotates the screw pump to pump the mixed ground leaching solution into the cracks inside the sample.

[0017] In the above scheme, the triaxial loading assembly also includes an end pad block disposed around the sample. The end pad block has reserved space for the arrangement of various monitoring probes to meet the arrangement requirements of acoustic probes, strain gauges, optical fibers and electrodes, and supports the arrangement of array-type acoustic probes. The end pad block is also provided with a water distribution channel and a pad block guide hole to guide the ground leaching liquid flowing through the pre-embedded pipe and slit mesh in the sample out of the pressure chamber.

[0018] In the above scheme, the triaxial loading assembly further includes an end cap assembly, which includes an upper end cap, a lower end cap, a shear ring pad, and a shear ring. The upper end cap is installed at the upper end of the pressure chamber, and the upper end cap is provided with an upper end cap sealing ring along the circumferential direction. The lower end cap is installed at the lower end of the pressure chamber, and the lower end cap is provided with a lower end cap sealing ring along the circumferential direction. The shear ring is installed on the inner wall of the pressure chamber and located above the upper end cap, and the shear ring pad is installed between the upper end cap and the shear ring.

[0019] In the above scheme, the triaxial loading assembly further includes a support pad assembly, which includes an upper pad, a lower tray, an annular pad, and a lower pad. The upper pad is installed between the vertical end pad and the upper end cover. The lower tray is installed at the lower end of the pressure pillow below the sample. The lower pad is installed between the lower tray and the lower end cover. The annular pad is installed between the outer periphery of the lower pad and the inner wall of the pressure chamber.

[0020] In the above scheme, the upper end cover, the upper pad block, and the vertical end pad block are respectively opened at the center for applying engineering disturbance loads. The upper end of the pressure chamber is provided with a disturbance load device fixing hole. Planar seals are respectively provided between the upper end cover and the upper pad block and between the upper pad block and the vertical end pad block to prevent the confining pressure liquid from seeping out from the gaps in the pad blocks.

[0021] In the above scheme, the triaxial loading assembly further includes a wedge-shaped pad assembly disposed between the pressure pillow and the inner wall of the pressure chamber. The wedge-shaped pad assembly includes an arc-shaped wedge pad and a square wedge pad. The arc-shaped wedge pad is installed on the inner wall of the pressure chamber, and the square wedge pad is installed between the arc-shaped wedge pad and the pressure pillow.

[0022] In the above scheme, the original rock fracturing and permeability enhancement and in-situ leaching and production physical simulation device also includes a multi-parameter acquisition component. The multi-parameter acquisition component includes various monitoring probes and acquisition instruments, as well as signal cables connecting the monitoring probes and acquisition instruments. The various monitoring probes are installed in the end pad. The types of monitoring probes include acoustic emission probes, ultrasonic probes, strain gauges, optical fibers, and electrode accelerometers. The types of acquisition instruments include acoustic emission acquisition cards, acoustic wave acquisition cards, strain gauges, optical fiber instruments, resistivity acquisition instruments, and accelerometers.

[0023] Accordingly, this invention also proposes a physical simulation method for in-situ leaching and production, employing the aforementioned in-situ fracturing and permeability enhancement and in-situ leaching and production physical simulation device, comprising the following steps:

[0024] A vacuum pump is used to evacuate the sample through the injection hole and the pre-embedded tube;

[0025] Start the mixing assembly, prepare the ground leaching solution required for the simulation experiment in the mixing container group, fill the ground leaching solution with the dual-cylinder constant speed and constant pressure pump in the injection assembly, then close all shut-off valves and add additives to the additive assembly.

[0026] Original rock stress application: First, apply vertical stress to 2MPa-5MPa to fix the sample, then apply horizontal pressure of 2MPa-5MPa. After the pressure stabilizes, apply confining pressure, and then simultaneously increase the triaxial stress and confining pressure to the target pressure. During the loading process, keep the internal pressure of the pressure pillow greater than the confining pressure. Heat the pressure chamber as a whole by wrapping it with an insulating heating jacket. After the pressure stabilizes, observe whether there is confining pressure liquid flowing out of the injection hole on the end pad and the pre-embedded tube in the sample. If liquid flows out, terminate the experiment and install the next sample until no liquid flows out. Monitor and record the state of the sample, including the acoustic wave velocity of the sample, the initial strain at each measuring point, and the resistance value, as the baseline for subsequent monitoring.

[0027] Physical simulation of reservoir stimulation: A disturbance load simulation device is fixed on the pressure chamber, and a shock wave generator is pre-embedded at the bottom of the pre-embedded pipe. After excitation, a cylindrical shock wave is released to simulate the reservoir stimulation process, i.e., the construction process of homogenized fracture network. After the disturbance load is applied, the disturbance load simulation device is removed. The relevant shut-off valves of the injection component and additive component are opened, the in-situ leaching fluid injection flow rate is set, the additive is pumped into the fracture network, and the waste liquid discharged from the return flow pipeline is collected using a collection tank. After the above operations are completed, all shut-off valves are closed.

[0028] Physical simulation of in-situ leaching mining process: The mixing, injection, flowback metering, and control components are activated. The leaching solution concentration, injection pressure, and extraction pressure are set to target values. The leaching solution is injected into the sample, and the uranium ore present in the sample is extracted through a chemical reaction. The gas and liquid flow meters in the flowback metering component are used to record the gas and liquid flow rates in the extracted material, respectively. Gas and liquid samplers are used to collect the extracted gas and liquid for analysis. The backpressure valve is activated, and the backpressure valve pressure is set. The injection component is activated, and the injection flow rate is set, continuously injecting the leaching solution until… The pressure fluctuation of the injection inlet pressure gauge was less than 1 MPa / min, and the pressure gauge value was recorded. The equivalent permeability coefficient of the reservoir was calculated using Darcy's formula. During the experiment, the acoustic, optical, electrical, temperature, pressure, and flow data observed during the simulation were recorded using a multi-parameter acquisition component. By analyzing the acoustic, optical, electrical, temperature, pressure, and flow data during the reservoir stimulation and exploitation process, and by inverting the fracture network evolution process before and during the exploitation process based on the multi-parameter monitoring signals, the main factors affecting reservoir exploitation efficiency were further clarified, and a quantitative assessment of different factors was made.

[0029] The beneficial effects of this invention are:

[0030] This invention enables the simulation of the original rock boundary, application of disturbance loads, continuous preparation of leaching fluid, continuous and precise injection of leaching fluid, extraction and metering of leaching fluid, as well as multi-parameter monitoring and simulation of reservoir fracture expansion support during the entire process of reservoir stimulation and extraction. Among these:

[0031] 1. This invention uses a pressure pillow to apply the original rock stress of the sample. Particle energy-absorbing material is filled in the elastic lining of the pressure pillow to absorb the stress shock wave generated during the blasting process and suppress the rebound of the boundary stress wave. At the same time, liquid confining pressure is applied to improve the stress distortion at the boundary under rigid loading, which can meet the loading requirements of the original rock stress of the reservoir.

[0032] 2. This invention applies disturbance load by fixing a disturbance load simulation device at the top of the pressure chamber and pre-embedding a shock wave generator at the bottom of the pre-embedded pipe. After excitation, a cylindrical shock wave is released to simulate the reservoir stimulation process, i.e., the construction process of homogenized fracture network.

[0033] 3. This invention prepares leaching solution by mixing components, controlling the temperature and pressure conditions of oxygen solution and CO2 respectively, and then using oxygen solution metering pump and CO2 metering pump to add oxygen solution and CO2 of a certain concentration to the mixing container group to mix and prepare leaching solution. Two or more mixing container groups that can be switched are set up to meet the need for continuous preparation of leaching solution in the physical simulation of leaching mining.

[0034] 4. This invention outputs leaching fluid at a set flow rate and pressure using a dual-cylinder constant-speed and constant-pressure injection pump of the injection component. During this process, an additive component can be used to quantitatively add proppant, swelling agent, and surfactant to the leaching fluid and inject it into the modified reservoir fracture network, thus meeting the research needs on the effects of different additives on reservoir modification.

[0035] 5. Different types of monitoring probes can be arranged in the end pads to meet the multi-parameter acquisition needs during the in-situ leaching and injection process.

[0036] 6. Use injection and flowback metering components to measure reservoir equivalent permeability and recovery rate; quantitatively rate reservoir stimulation and exploitation effectiveness. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall structure of the original rock fracturing and permeability enhancement and in-situ leaching and mining physical simulation device of the present invention;

[0039] Figure 2 yes Figure 1 The diagram shows the structure of the triaxial loading component of the physical simulation device for in-situ rock fracturing and permeability enhancement and in-situ leaching and production.

[0040] Figure 3 yes Figure 2 The diagram shows the structural schematic of the pressure pillow of the triaxial loading assembly.

[0041] Figure 4 yes Figure 2 A schematic diagram of the end pad of the triaxial loading assembly shown;

[0042] Figure 5 yes Figure 2 The diagram shows the structure of the lower end cap of the triaxial loading assembly.

[0043] In the diagram: 11-Hydraulic servo system, 111-X-direction oil circuit, 112-Y-direction oil circuit, 113-Z-direction oil circuit, 114-Containing pressure oil circuit, 12-Pressure chamber, 121-Disturbance load device fixing hole, 122-Lifting lug, 123-Pressure chamber base, 124-Pressure chamber internal filling space, 131-Upper end cover, 1311-Upper end cover sealing ring, 1312-Upper end cover vent valve, 1313-Upper end cover vent, 132-Lower end cover, 1321-Lower end cover sealing ring, 1322-Monitoring signal line through-chamber connector, 1323-Pressure pipe through-chamber connector, 1324-Cross-shaped lower pad placement area, 1325, 1327-Through-chamber Hole, 1326 - Circular lower pad placement area, 133 - Shear ring pad, 134 - Shear ring, 141 - Arc-shaped wedge pad, 142 - Square wedge pad, 151 - Horizontal end pad, 1511 - Blind hole for monitoring probe arrangement, 1512 - Through hole for monitoring probe arrangement, 1513 - Water distribution trough, 1514 - Cable trough, 1515 - Pad guide hole, 152 - Vertical end pad, 161 - Upper pad, 1611 - Planar seal, 162 - Lower tray, 163 - Annular pad, 164 - Lower pad, 17 - Pressure pillow, 171 - Pressure pillow outer shell, 172 - Elastic liner, 173 - Granular material, 174 - Pressure pillow high-pressure pipe

[0044] 21-Oxygen solution stirring container; 211-Oxygen content sensor; 212-Level gauge; 214-Motor; 215-Oxygen solution metering pump; 217-Oxygen circulation pump; 22-Oxygen source; 221-Oxygen pressure regulating valve; 222-Oxygen pressure gauge; 223-Oxygen shut-off valve; 23-CO2 source; 24-CO2 booster pump; 25-CO2 storage tank; 251-CO2 pressure gauge; 252-CO2 safety valve; 26-CO2 metering pump; 261-CO2 pressure regulating valve; 262-CO2 pressure gauge; 27-Mixing container assembly; 271-Variable frequency motor; 272-Level gauge; 28-Water source.

[0045] 318 - Safety valve, 319 - Injection port pressure gauge, 320 - Injection pipe, 321 - First single pump, 322 - Second single pump.

[0046] 41-High-pressure storage tank, 42-Screw pump, 43-Screw pump motor

[0047] 51-Vacuum pump, 511-High-pressure shut-off valve, 512-Dryer, 52-Solid separator, 521-Return liquid outlet pipe, 522-Outlet pressure gauge, 53-Back pressure valve, 531-Back pressure valve buffer container, 532-Back pressure gauge, 533-Back pressure tracking pump, 54-Gas-liquid separator, 541-Dryer, 542-Gas flow meter assembly, 543-Liquid flow meter assembly, 544-Return liquid storage tank, 55-Gas sampler, 56-Liquid sampler, 57-Collection tank.

[0048] 6-Multi-parameter acquisition component, 61-Monitoring probe, 62-Internal signal cable, 63-External signal cable ，

[0049] 7-Control component, 71-Control signal line,

[0050] 8-Sample, 81-Seam mesh, 82-Precast groove, 83-Embedded pipe,

[0051] 213, 216, 281, 253, 263, 273, 312, 313, 314, 315, 316, 317, 44, 45, 46, 551, 552, 561, 562, 571, 58 - Stop valve. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0053] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0054] In this invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0055] Example 1: Device Example

[0056] like Figure 1As shown, an embodiment of the present invention provides a physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production, comprising a triaxial loading component, a mixing component, an injection component, an additive component, a flowback metering component, a multi-parameter acquisition component, a control component, and a sample. The triaxial loading component includes a hydraulic servo system 11, a pressure chamber 12, and pressure pillows 17. The sample 8 is installed in the pressure chamber 12. Pressure pillows 17 are respectively located below and on the four sides of the sample 8. The in-situ stress on the sample 8 is provided by the pressure pillows 17 in three directions and the confining pressure of the liquid within the liquid-filled space 124 inside the pressure chamber. The internal pressure of the pressure pillows 17 and the confining pressure of the liquid are provided by the hydraulic servo system 11. The mixing component is used to prepare the in-situ leaching solution and includes a dissolved oxygen generator, a CO2 pressurization device, and a mixing container group 27. The outlets of the dissolved oxygen generator and the CO2 pressurization device are respectively connected to the inlet of the mixing container group 27, and the outlet of the mixing container group 27 is connected to the inlet of the injection component. The outlet of the injection component is connected to the inlet of the additive component via one branch, and the outlet of the injection component is also connected to the injection tube of the triaxial loading component via another branch. The injection tube is connected to the pre-embedded tube 83 of the sample 8. The inlet of the additive component is connected to the outlet of the injection component, and the outlet of the additive component is connected to the injection tube 320 of the triaxial loading component. Different additives are added into the sample 8 through the additive component. The backflow metering assembly includes a vacuum pump 51, a backflow liquid outlet pipe 521, a solid separator 52, a back pressure valve 53, a gas-liquid separator 54, a gas flow meter group 542, and a liquid flow meter group 543. The vacuum pump 51 is connected to the injection pipe 320 via a pipeline. The backflow liquid in the pressure chamber 12 is discharged through the backflow liquid outlet pipe 521. The solid separator 52, the back pressure valve 53, and the gas-liquid separator 54 are sequentially arranged on the backflow liquid outlet pipe 521. After the gas-liquid separator 54, the flow meter group splits into a gas pipeline and a liquid pipeline. The gas flow meter group 542 is installed on the gas pipeline, and the liquid flow meter group 543 is installed on the liquid pipeline. The sample 8 is a square sample. The sample 8 has a pre-fabricated groove 82 and a pre-embedded pipe 83. The function of the pre-fabricated groove 82 is to guide the crack initiation and propagation. During the simulation modification process, a crack network 81 is generated in the sample 8. The expansion of the crack network 81 will connect the pre-embedded pipe 83 and the surface of the sample 8.

[0057] After the sample 8 is installed in the triaxial loading assembly, the triaxial original rock boundary stress of the sample 8 is applied using a flat pressure pillow 17, and liquid confining pressure is applied in the pressure chamber 12 to improve the stress uniformity of the sample 8; a disturbance is applied using an external engineering disturbance simulation device to generate a mesh 81 in the sample 8; the mixing assembly is used to continuously prepare the simulated ground leaching solution, the dissolved oxygen content in the oxygenated solution is controlled by controlling the temperature and pressure in the dissolved oxygen generator, and oxygenated water is injected into the mixing container group 27 using an oxygen solution metering pump 215; high-pressure CO2 is prepared using a CO2 pressurization component and injected into the mixing container group 27 via a CO2 metering pump 26. CO2 is precisely added to group 27, and the oxygen-containing solution and CO2 are uniformly mixed through mixing container group 27. Then, the leaching fluid is output using the injection component at a set flow rate and pressure. During this process, the additive component can quantitatively add proppant, expansion agent, and other components to the leaching fluid. Finally, the outlet pressure is set through the back pressure valve 53 of the flowback metering component. A gas-liquid separator 54 is set after the back pressure valve 53 to separate the gas and liquid. The flow rate, concentration, and composition of the flowback fluid are measured using a gas flow meter group 542, a liquid flow meter group 543, a sampler, and a chromatograph. The permeability coefficient of the reservoir is then calculated using Darcy's law to evaluate the permeability of the fracture network 81. In the above process, the mixing rate, injection flow rate, and injection pressure of the leaching fluid are controlled by the control component. The multi-parameter acquisition component is used to monitor the reservoir stimulation-leaching production physical simulation process at different measurement points and to perform multi-parameter inversion of the fracture network 81 morphology. Ultimately, quantitative research on the leaching injection and production process is achieved.

[0058] like Figure 2 As shown, the hydraulic servo system 11 includes an X-direction oil circuit 111, a Y-direction oil circuit 112, a Z-direction oil circuit 113, and a confining pressure oil circuit 114. The X-direction oil circuit 111 is connected to the pressure pillow 17 below the sample 8, the Y-direction oil circuit 112 is connected to the pressure pillows 17 on the left and right sides of the sample 8, the Z-direction oil circuit 113 is connected to the pressure pillows 17 on the front and rear sides of the sample 8, and the confining pressure oil circuit 114 is connected to the liquid filling space inside the pressure chamber 12. The triaxial pressure on the sample 8 is provided by the pressure pillows 17 in three directions and the liquid confining pressure. The internal pressure of the pressure pillows 17 and the liquid confining pressure are provided by the corresponding oil circuits and the hydraulic servo system 11. Each hydraulic branch is equipped with a servo valve, a safety valve, and a filter. A booster is installed when necessary. The injection pressure is precisely controlled by a servo controller to prevent excessive deformation of the pressure pillow 17 in one direction, which would cause the sample 8 to deviate from its center position. In addition, to prevent the oil temperature from becoming too high during continuous operation, a water chiller with cooling performance matched to the heat generation is installed. During loading, the internal pressure value of the pressure pillow 17 is greater than the liquid confining pressure value. Applying a certain confining pressure improves the uniformity of stress on the sample 8.

[0059] Further optimization includes an end pad set around the specimen 8. By slotting, opening and prefabricating interfaces in the end pad, a monitoring probe can be arranged on the surface of the specimen 8, and the signal of the monitoring probe can be transmitted using the in-chamber signal line, the signal line through-chamber connector and the out-of-chamber signal line.

[0060] The end pads and pressure pillow 17 are made of high-density alloy, which can effectively conduct the stress shock waves transmitted from the specimen 8. For example... Figure 3 As shown, the pressure pillow 17 includes a pressure pillow shell 171, an elastic liner 172, and granular material 173. The elastic liner 172 is disposed inside the pressure pillow shell 171, and the granular material 173 is filled in the elastic liner 172. This can effectively absorb the stress shock wave transmitted by the end pad and reduce the interface rebound of the stress shock wave at the loading boundary. The energy absorption performance of the granular material 173 can be adjusted by setting the particle size distribution of the granular material 173.

[0061] Further optimization includes a horizontal end pad 151 and a vertical end pad 152. The end pads are pre-installed with space for various monitoring probes, accommodating the arrangement requirements of acoustic probes, strain gauges, optical fibers, and electrodes, and supporting array-type acoustic probe arrangements. The end pads also include a water distribution channel and flow guide holes to guide the leaching liquid flowing through the embedded pipe 83 and the mesh 81 in sample 8 out of the pressure chamber 12. The horizontal end pad 151 is described as an example. Figure 5 The horizontal end pad 151 is provided with a blind hole 1511 for arranging monitoring probes, a through hole 1512 for arranging monitoring probes, a wire groove 1514, a water distribution groove 1513, and a pad guide hole 1515. Different monitoring probes are arranged in the blind hole 1511, the through hole 1512, and the wire groove 1514. The ground leaching liquid flowing through the pre-embedded pipe 83 and the mesh 81 in the sample 88 is guided out of the pressure chamber 12 through the water distribution groove 1513 and the pad guide hole 1515.

[0062] Further optimization includes an end cap assembly comprising an upper end cap 131, a lower end cap 132, a shear ring pad 133, and a shear ring 134. The upper end cap 131 is installed at the upper end of the pressure chamber 12 and has two circumferential sealing rings 1311. The lower end cap 132 is installed at the lower end of the pressure chamber 12 and has two circumferential sealing rings 1321. The shear ring 134 is installed on the inner wall of the pressure chamber 12 and located above the upper end cap 131. The shear ring 134 is annular and can be cut into multiple segments for easy installation and operation. The shear ring pad 133 is installed between the upper end cap 131 and the shear ring 134.

[0063] Further optimization includes a support pad assembly, which comprises an upper pad 161, a lower tray 162, an annular pad 163, and a lower pad 164. The upper pad 161 is installed between the vertical end pad 152 and the upper end cover 131. The lower tray 162 is installed at the lower end of the pressure pillow 17 below the sample 8. The lower pad 164 is installed between the lower tray 162 and the lower end cover 132. The annular pad 163 is installed between the outer periphery of the lower pad 164 and the inner wall of the pressure chamber 12.

[0064] like Figure 4 As shown in the figure, this embodiment illustrates two opening schemes for the lower end cap 132 corresponding to the shapes of the lower pad block 164. Figure 4 -a corresponds to the opening scheme of the lower end cover 132 when the lower pad 164 is cross-shaped. The cross-shaped lower pad placement area 1324 is used to place the lower pad 164, and the through hole 1325 is used to arrange various through joints. Figure 4 -b corresponds to the opening scheme of the lower end cover 132 when the lower pad 164 is circular. The circular lower pad placement area 1326 is used to place the lower pad 164, and the through hole 1327 is used to arrange various through-chamber connectors. The types of through-chamber connectors include, but are not limited to, monitoring signal line through-chamber connector 1322 and pressurized pipe through-chamber connector 1323. The material and sealing of the through-chamber connectors are selected according to different pressures and temperatures.

[0065] Further optimization involves center openings in the upper end cover 131, upper pad 161, and vertical end pad 152 for applying engineering disturbance loads such as drilling, blasting, and hydraulic fracturing. The upper end of the pressure chamber 12 is provided with a disturbance load device fixing hole 121 for installing an engineering disturbance simulation device. Planar seals 1611 are provided between the upper end cover 131 and the upper pad 161, and between the upper pad 161 and the vertical end pad 152, to prevent confining fluid from seeping out from the gaps in the pads.

[0066] Further optimization includes a wedge-shaped pad assembly disposed between the pressure pillow 17 and the inner wall of the pressure chamber 12. The wedge-shaped pad assembly includes an arc-shaped wedge 141 and a square wedge 142. The arc-shaped wedge 141 is installed on the inner wall of the pressure chamber 12, and the square wedge 142 is installed between the arc-shaped wedge 141 and the pressure pillow 17.

[0067] Further optimization is achieved by designing and verifying the wall thickness of pressure chamber 12 according to current standards and specifications, and determining the material of pressure chamber 12 in conjunction with usage conditions and standards. Symmetrical lifting lugs 122 are provided on the outer wall of pressure chamber 12 for hoisting it, and a pressure chamber base 123 is provided at the lower end of pressure chamber 12. When installing sample 8, sample 8 and end pads are placed on the lower tray 162, and then hoisted into pressure chamber 12. Wedge-shaped pads are used to adjust the horizontal position of sample 8 before loading, and the vertical height of sample 8 is adjusted using the vertical pressure pillow 17.

[0068] See also Figure 1 The mixing assembly includes a dissolved oxygen generator comprising an oxygen source 22, an oxygen solution stirring container 21, and a water source 28. The oxygen source 22 and water source 28 are connected to the inlet of the oxygen solution stirring container 21, and the outlet of the oxygen solution stirring container 21 is connected to the inlet of the mixing container group 27. The outlet pipe of the oxygen source 22 is equipped with an oxygen pressure regulating valve 221, an oxygen pressure gauge 222, and an oxygen shut-off valve 223. The oxygen solution stirring container 21 is equipped with an oxygen content sensor 211 and a level gauge 212. The outlet pipe of the oxygen solution stirring container 21 is equipped with an oxygen solution metering pump 215 and a shut-off valve 216. An insulation heating jacket is installed on the outer wall of the oxygen solution stirring container 21 to control its temperature. A motor 214 is located above the oxygen solution stirring container 21. The oxygen solution stirring container 211 also has an oxygen circulation pump 217, which circulates oxygen inside the oxygen solution stirring container 21 to accelerate the mixing process. When the oxygen content reaches the target value, stirring and oxygenation are stopped. A shut-off valve 281 is installed on the outlet pipe of water source 28.

[0069] The CO2 booster unit includes a CO2 gas source 23, a CO2 booster pump 24, a CO2 storage tank 25, and a CO2 metering pump 26, which are connected in sequence via pipelines. The outlet of the CO2 metering pump 26 is connected to the inlet of the mixing container assembly 27. The inlet pipeline of the CO2 storage tank 25 is equipped with a CO2 pressure gauge 251, and the outlet pipeline of the CO2 storage tank 25 is equipped with a CO2 safety valve 252 and a shut-off valve 253. The outer shell of the CO2 storage tank 25 is fitted with an insulation and heating jacket. The outlet pipeline of the CO2 metering pump 26 is equipped with a CO2 pressure regulating valve 261, a CO2 pressure gauge 262, and a shut-off valve 263. The outer shell of the CO2 metering pump 26 is fitted with an insulation and heating jacket. The function of the CO2 pressure regulating valve 261 is to provide a stable outlet pressure for accurately metering the injected CO2 volume.

[0070] The mixing container group 27 is equipped with a variable frequency motor 271, a liquid level gauge 272 and a heat insulation heating jacket are installed on the outside of the mixing container group 27, and a shut-off valve 273 is installed on the outlet pipe of the mixing container group 27.

[0071] Further optimization involves configuring at least two sets of oxygen solution stirring vessels 21, with the volume of each vessel set according to the required flow rate. These vessels can be used in rotation to meet the needs of continuous preparation of ground leachate. The mixing vessel group 27 is configured with at least two sets of mixing vessels. These mixing vessels are pressure-resistant components that can be connected to high-pressure gas to drive the solution within them to the injection assembly.

[0072] When preparing the oxygen solution, water source 28 and shut-off valve 281 are opened to inject water into the oxygen solution stirring container 21 to the predetermined liquid level. Then, water source 28 and shut-off valve 281 are closed. Next, oxygen source 22 is opened, shut-off valve 223 is opened, shut-off valve 213 is closed, and the low pressure of oxygen pressure reducing valve 221 is adjusted to the set value. Oxygen is injected into the oxygen solution stirring container 21 using oxygen source 22 and oxygen pressure reducing valve 221. The oxygen content in the solution is monitored by oxygen content sensor 211. The oxygen content in the oxygen solution is further precisely controlled by controlling the temperature and pressure environment of the oxygen solution stirring container 21. When the oxygen content reaches the target value C, oxygen pressure reducing valve 221 is closed, shut-off valve 223 is closed, and shut-off valves 213 and 216 are opened. The oxygen solution is pumped to the mixing container group 2727 using oxygen solution metering pump 215. The volume V of the oxygen solution is recorded by level gauge 272 on the mixing container group 27.

[0073] When preparing supercritical CO2, close the shut-off valve 253, open the CO2 gas source 23, and start the CO2 booster pump 24 to pressurize the CO2 in the CO2 storage tank 25 to the target pressure P. The CO2 is then heated to above the supercritical temperature at pressure P by the external insulation heating jacket of the CO2 storage tank 25. After the CO2 storage tank 25 is filled with supercritical CO2, close the CO2 booster pump 24. When adding CO2 to the mixing container group 27, close the shut-off valves 216 and 273, open the shut-off valves 253 and 263, open the CO2 pressure reducing valve 261, set the outlet pressure to P, start the CO2 metering pump 26 to inject the preset amount of CO2 into the mixing container group 27, close the shut-off valve 263, turn on the variable frequency motor 271 to start stirring the mixture, and close the inlet shut-off valve 263 after uniform mixing. If necessary, switch to another mixing container group 27 and repeat the operation of adding oxygen solution and CO2 until the predetermined amount of ground leaching solution is prepared.

[0074] See also Figure 1The injection assembly adopts a dual-cylinder constant speed and constant pressure injection pump, which includes two parallel single pumps 321 and 322. The inlet pipe of the first single pump 321 is equipped with a shut-off valve 312 and the outlet pipe is equipped with a shut-off valve 313. The inlet pipe of the second single pump 322 is equipped with a shut-off valve 314 and the outlet pipe is equipped with a shut-off valve 315. The two single pumps can independently perform liquid suction and liquid discharge operations. During continuous injection of the leachate, shut-off valves 312, 315, 273, and 316 are open, while shut-off valves 313 and 314 are closed. The second pump 322 discharges the leachate, and the first pump 321 draws in the leachate at a rate 1.5 times the discharge rate. Once the pump is full, shut-off valve 312 closes. When the leachate is completely discharged from the second pump 322, shut-off valves 313 and 314 open, and shut-off valves 312 and 315 close. The system then switches back to the first pump 321 discharging and the second pump 322 drawing in the leachate, and this cycle repeats to achieve continuous injection of the leachate. Therefore, this invention can use two constant-speed, constant-pressure injection pumps to circulate the leachate in the mixing container group 27 and output the leachate according to a predetermined flow rate and pressure.

[0075] See also Figure 1 The additive assembly includes a high-pressure storage tank 41, a screw pump 42, and a screw pump motor 43. The lower part of the high-pressure storage tank 41 has a funnel structure, and the outlet of the injection assembly is connected to the funnel outlet at the bottom of the high-pressure storage tank 41. The additives in the high-pressure storage tank 41 fall to the outlet under their own weight and mix with the ground leachate. The screw pump motor 43 rotates the screw pump 42 to pump the mixed ground leachate into the cracks inside the sample 8. The types of additives include proppant, swelling agent, and activator.

[0076] See also Figure 1 The backflow metering assembly also includes a liquid sampler 56 and a gas sampler 55. The liquid sampler 56 is located on the branch between the solid separator 52 and the back pressure valve 53, and the gas sampler 55 is located on the pipeline after the gas flow meter group 542. After the backflow liquid flows out from the backflow liquid outlet pipe 521, it first passes through the solid separator 52 to separate solid particles. The liquid is then collected using the liquid sampler 56 and sent for testing to measure the content of oxygen and HCO3-. The back pressure valve 53 controls the backflow liquid outlet pressure, reducing it to atmospheric pressure after passing through the back pressure valve 53. After passing through the gas-liquid separator 54, the flow rates of gas and liquid in the backflow liquid are measured using the gas flow meter group 542 and the liquid flow meter group 543, respectively. The gas sampler 55 collects the gas in the backflow liquid, and the proportion of each component in the mixed gas is measured using chromatograph analysis.

[0077] Further optimization involves the gas flow meter consisting of 3-5 flow meters with different ranges connected in parallel, automatically switching between different ranges of gas flow meters during use; and the liquid flow meter consisting of 2-3 flow meters with different ranges connected in parallel, automatically switching between different ranges of liquid flow meters during use.

[0078] Further optimization involves adding a branch line connecting to the atmosphere on the pipeline after the gas flow meter group 542, with a shut-off valve 58 installed on the branch line.

[0079] Further optimization involves having at least three gas samplers 55, which are connected to the pipeline after the shut-off valve 552 via quick connectors. When in use, shut-off valve 58 is closed, and shut-off valves 551 and 552 are opened. After sampling is completed, shut-off valve 551 is closed, and shut-off valve 58 is opened (to connect to the atmosphere).

[0080] Further optimization involves installing a dryer 512 before the vacuum pump 5151 to prevent oil and water contamination in the vacuum pump 51. A high-pressure shut-off valve 511 is installed before the dryer 512.

[0081] Further optimization includes a back pressure valve 53 comprising a back pressure valve buffer container 531, a pressure sensor 532, and a back pressure tracking pump 533. The back pressure is set by adjusting the pressure of the back pressure tracking pump 533. The function of the back pressure buffer container 531 is to prevent the back pressure valve 53 from being overloaded by the outlet impact pressure.

[0082] The multi-parameter acquisition component includes various monitoring probes and acquisition instruments, as well as signal cables connecting the probes and acquisition instruments. The signal cables consist of an internal signal line 62, a monitoring signal line through-cabin connector 1322, and an external signal line 63, transmitting monitoring signals to the multi-parameter acquisition component. The monitoring signal line through-cabin connector 1322 exits from the lower end cover 132 of the triaxial loading component. The various monitoring probes include acoustic emission probes, ultrasonic probes, strain gauges, optical fibers, electrodes, and accelerometers. The corresponding acquisition instruments include acoustic emission acquisition cards, acoustic wave acquisition cards, strain gauges, fiber optic meters, resistivity acquisition instruments, and accelerometers. The multiple signal acquisition instruments synchronize their times using a time synchronization protocol. They use the same data transmission communication protocol to store the acquired data in a file with the same dynamic data format. Simultaneously, data stored in the database can be read, enabling multi-parameter data analysis of the experimental process.

[0083] The control components include controllers, various sensors, controllers, and actuators, forming a closed-loop control system. The actuators include: a triaxial loading component, a mixing component, an injection component, an additive component, and a backflow metering component, which can control triaxial pressure, ground leachate mixing speed, ground leachate injection speed, additive dosage, and the opening and closing of the backflow component.

[0084] Example 2: Method Example

[0085] Accordingly, this invention also proposes a physical simulation method for in-situ fracturing and permeability enhancement and in-situ leaching and production, comprising the following steps:

[0086] S1. Experimental Preparation:

[0087] S1.1, according to Figure 1 The physical simulation device for in-situ rock fracturing and permeability enhancement and in-situ leaching and extraction required for construction is shown.

[0088] S1.2 Prepare a sample 8 with known uranium content. According to the experimental requirements, set up a pre-embedded tube 83 and a pre-fabricated groove 82 in the sample 8. Use the same batch of samples 8 to measure the basic physical parameters of the sample 8, including uniaxial compressive strength, uniaxial tensile strength and permeability.

[0089] S1.3 Place the pressure pillow 17, the vertical end pad 152 and the sample 8 on the lower tray 162 in sequence. Then arrange the monitoring probe 61 and install the friction reducing plate according to the predetermined plan. Next, install the end pads 15 on the four sides. Finally, apply a sealing coating to the exposed area of ​​the sample 8 to isolate the sample 8 from the confining pressure medium during the experiment. The sealing coating must cover the boundary of the contact surface between the end pad 15 and the sample 8.

[0090] S1.4 After the adhesive has cured, use vacuum pump 51 to evacuate the sample 8 through the injection hole and the pre-embedded tube 83. Only after the sealing performance of the sample 8 after the adhesive is applied is qualified can the next step of the experiment be carried out.

[0091] S1.5 Connect the signal cable of the monitoring probe, check the monitoring probe, and record the problematic measurement points;

[0092] S1.6 Start the mixing component, mix the ground leaching solution required for the simulation experiment in the mixing container group 27, fill the ground leaching solution with the dual-cylinder constant speed and constant pressure injection pump, then close all the shut-off valves in the system, and add additives to the high pressure storage tank 41; start the multi-parameter acquisition component 6 and the control component 7.

[0093] To further optimize the process, for experiments with higher temperatures, a heating chamber is used to preheat the sample 8 to be used, thereby shortening the heating time of the sample 8 in the pressure chamber 12.

[0094] Further optimization was carried out, and the test methods for permeability and rock strength conformed to GB / T 28912 2012 and GBT50266-2013 standards. The number of rock samples tested was no less than 5, and the average value of the 5 test results was taken as the permeability and strength value of sample 8.

[0095] S2. Equipment self-test:

[0096] Check that each component is functioning properly, and check that each sensor in key areas is working properly.

[0097] Further optimization involves checking and calibrating all sensors every six months, calibrating the injection pump flow rate every six months, and checking and calibrating the monitoring probe and data acquisition instrument before each experiment.

[0098] S3, Sample 8 Installation:

[0099] S3.1 Install the lower end cover sealing ring 1321, monitoring signal line through-chamber connector 1322 and pressurization pipe through-chamber connector 1323, etc., and then install the lower end cover 132 into the lower part of the pressure chamber 12.

[0100] S3.2 After installing the annular pad 163 and the lower pad 164, install the two pairs of horizontal arc wedge-shaped pads 141, connect the cabin signal line 62 on the lower end cover 132 to the hub socket, and connect the pressure pillow high pressure pipe 174.

[0101] S3.3. Hoist the lower tray 162, the vertical pressure pillow 17, the end pad 161 and the sample 8 together to the center position of the lower pad 164 in the pressure chamber 12. Then install the horizontal pressure pillow 17 and the square wedge pad 142. Next, connect each pressure pillow 17 to the pressure pillow high pressure pipe 174. Adjust the height of the sample 8 to the predetermined position through the pressure pillow 17 under the sample 8. Then adjust the horizontal position of the sample 8 through the wedge pad 142. Control the overall installation error to be within 1mm.

[0102] S3.4 Install the flat seal 1611 and the upper end cover seal ring 1311 on the pad 161, and then install the pad 161, the upper end cover 131, the shear ring pad 133, and the shear ring 134 on the sample 8 in sequence. After the pressure chamber 12 is assembled, check each monitoring probe and record the abnormal probes.

[0103] S3.5 Connect the hydraulic servo system 11 to the three-axis pressure chamber 12, open the upper end cover vent valve 1312, connect the upper end cover vent 1313 to the atmosphere, add hydraulic oil to the pressure pillow 17, and then add hydraulic oil to the filling space 124 inside the pressure chamber 12 through the confining pressure oil circuit 114. After the hydraulic oil is full, close the vent valve 1312; connect the return metering component 5 to the return liquid outlet pipe 521.

[0104] S4. Application of original rock stress:

[0105] S4.1 First, apply vertical stress to 2MPa-5MPa at a pressurization rate of 20MPa / min, fix the specimen 8, and apply pressure to the sealing structure between the upper pads. Then apply a smaller horizontal pressure. After the pressure stabilizes, apply confining pressure, and then simultaneously increase the triaxial stress and confining pressure to the target pressure at a pressurization rate of 10MPa / min. At this time, the triaxial stress of specimen 8 is: σ i =α i ·P i , i = x, y, z, where: σ i The stress in the 8i direction of the specimen is expressed in MPa, α. i P is the force transmission coefficient of the pressure pillow 17 in the i-direction. i The pressure inside the pressure pillow 17 in the i direction is expressed in MPa. During the loading process, the internal pressure of the pressure pillow 17 is kept greater than the confining pressure. The pressure chamber 12 is heated as a whole by wrapping an insulating heating jacket around the outside of the pressure chamber 12. After the pressure is stabilized, observe whether there is any confining pressure liquid flowing out of the injection hole on the end pad and the pre-embedded tube 83 in the sample 8. If liquid flows out, the experiment is terminated and the next sample 8 is installed.

[0106] S4.2 Monitor and record the state of sample 8, including wave velocity, initial strain at each measuring point, resistance value, etc., as the baseline for subsequent monitoring.

[0107] Further optimization revealed a certain difference between the internal pressure of the pressure pillow 17 and its actual output stress on the surface of the sample 8. Before the experiment, the output stress of each pressure pillow 17 within the operating pressure range was calibrated.

[0108] Further optimization involves applying a stress of 31.5 MPa or higher to the internal pressure and confining pressure of the pressure pillow 17. This requires the use of a hydraulic booster to increase the pressure. The hydraulic oil is driven between the plunger and piston by a pump, and the pressure difference is used to increase the oil pressure, thereby achieving the purpose of boosting the pressure.

[0109] S5. Reservoir Stimulation Physical Simulation:

[0110] S5.1. Fix the disturbance load simulation device using the disturbance load device fixing hole 121. Pre-embed a shock wave generator at the bottom of the hole of the pre-embedded pipe 83. Release the cylindrical shock wave after excitation to simulate the reservoir stimulation, i.e. the construction process of the homogenized fracture network 81. After the disturbance load is applied, remove the disturbance load simulation device and connect the injection component 3, the additive component 4 and the injection pipe 320.

[0111] S5.2 Open shut-off valves 273, 316, 45, 46, and 571, turn on screw pump motor 43, turn on the dual-cylinder constant speed and constant pressure injection pump, set the ground immersion liquid injection flow rate to Q, pump the additive into the mesh 81, and use the collection tank to collect the waste liquid discharged from the return drain line 521. After the above operations are completed, turn off screw pump motor 43 and dual-cylinder constant speed and constant pressure injection pump, and close all shut-off valves.

[0112] S6. Physical simulation of the in-situ leaching extraction process:

[0113] S6.1. Start the mixing component, injection component 3, flowback component 5, and control component 7. Set the leaching solution concentration, injection pressure, and extraction pressure according to the target values. Inject the leaching solution into sample 8. Extract the uranium ore present in sample 8 through a chemical reaction. Use the gas flow meter group 542 and liquid flow meter group 543 in the flowback metering component to record the gas and liquid flow rates in the extracted material. Use the gas sampler 55 and liquid sampler 56 to collect the extracted gas and liquid and send them for analysis. The theoretical extraction rate of the leaching solution is: Where ρ1 is the sample density, in kg / m³. 3 L - Sample side length, unit: m; C1 - Sample uranium mass fraction; V - Return liquid volume, unit: m³ 3 C2 is the uranium mass fraction calculated based on the test results, and ρ2 is the density of the return fluid, in kg / m³. 3 ;

[0114] S6.2. Open shut-off valves 316 and 317, start back pressure valve 53, open shut-off valve 58, set the pressure of back pressure valve 53, start injection assembly 3, set injection flow rate, and continuously inject leaching fluid until the pressure fluctuation of injection port pressure gauge 319 is less than 1 MPa / min. Record the injection port pressure gauge value. Calculate the equivalent permeability coefficient of the reservoir at this time using Darcy's formula: Where: P1 - injection pressure, unit: MPa; P2 - back pressure; μ - leaching fluid viscosity, unit: mPa·s; Q - leaching fluid flow rate, unit: cm³ 3 / s, L - sample side length, A - cross-sectional area of ​​the immersion liquid passing through the sample, unit: cm 2 ;

[0115] S6.3 During the experiment, the monitoring components record data such as sound, light, electricity, temperature, pressure, and flow observed during the simulation. By analyzing the data such as sound, light, electricity, temperature, pressure, and flow during reservoir stimulation and exploitation, and by inverting the multi-parameter monitoring signals to study the evolution process of the fracture network 81 before reservoir stimulation and during exploitation, the main factors affecting reservoir exploitation efficiency can be further clarified, and quantitative assessments can be made for different factors.

[0116] S7. Unloading and Post-treatment of Sample 8:

[0117] S7.1 After closing all shut-off valves, close the mixing component, injection component 3, backflow component 5, and multi-parameter acquisition component 6. Then open shut-off valve 571 to discharge the backflow liquid during the depressurization process to collection tank 57.

[0118] S7.2. Use the servo hydraulic system 11 to synchronously reduce the internal pressure and confining pressure of the pressure pillow 17. Set the pressure reduction rate to 30 MPa / min. The target value of the internal pressure of the pressure pillow 17 is 2 MPa, and the target value of the confining pressure is 0 MPa. After the target is reached, open the shut-off valve 1312 and extract the confining pressure fluid from the confining pressure oil circuit 114 to relieve the internal pressure of the pressure pillow 17. The pressure reduction rate is 30 MPa / min. During the unloading process, keep the confining pressure value less than the internal pressure value of the pressure pillow 17.

[0119] S7.3. Remove the high-pressure pipe connected to the injection pipe 320. After removing the shear ring 134, lift the shear ring pad 133, the upper end cover 131, and the upper pad 161 out of the pressure chamber 12. Disconnect the monitoring signal line and the high-pressure pipe of the pressure pillow 17. Then remove the horizontal square wedge pad 142 and the horizontal flat pressure pillow 17. Finally, lift the sample 8 together with the end pad, the lower pressure pillow 17, and the lower pad 164 out of the pressure chamber 12 and remove the end pad on the surface of the sample 8.

[0120] S7.4 Clean the injection component, mixing component, additive component and backflow component, and shut down the control component; send sample 8 to the analysis center for analysis and perform the following operations: taking pictures, scanning the surface morphology of sample 8, CT scanning to reconstruct the fracture network 81, NMR scanning to reconstruct the fracture network 81, acoustic scanning to reconstruct the fracture network 81, crack fracture analysis, post-cutting analysis, component analysis and other methods.

[0121] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0122] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0123] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A physical simulation device for in-situ rock fracturing and permeability enhancement and in-situ leaching and production, comprising a triaxial loading assembly, characterized in that, It also includes mixing components, injection components, additive components, backfeed metering components, and samples; The triaxial loading assembly includes a hydraulic servo system, a pressure chamber, and a pressure pillow. The sample is installed in the pressure chamber, and the pressure pillow is provided below the sample and on the four sides. The pressure pillow includes a pressure pillow shell, an elastic liner, and granular material. The elastic liner is provided inside the pressure pillow shell, and the elastic liner is filled with granular material. The original rock stress on the sample is provided by the pressure pillow in three directions and the liquid confining pressure in the liquid-filled space inside the pressure chamber. The internal pressure of the pressure pillow and the liquid confining pressure are provided by the hydraulic servo system. The mixing assembly includes a dissolved oxygen generator, a CO2 pressurizing device, and a mixing container group. The outlets of the dissolved oxygen generator and the CO2 pressurizing device are respectively connected to the inlet of the mixing container group. The oxygen-containing solution and CO2 are uniformly mixed through the mixing container group to prepare the ground leachate. The outlet of the mixing container group is connected to the inlet of the injection assembly. The outlet of the injection component is connected to the inlet of the additive component via one branch, and the outlet of the injection component is also connected to the injection tube of the triaxial loading component via another branch. The injection tube is connected to the pre-embedded tube of the sample. The inlet of the additive assembly is connected to the outlet of the injection assembly, and the outlet of the additive assembly is connected to the injection tube of the triaxial loading assembly. Different additives are added into the sample through the additive assembly. The backflow metering assembly includes a vacuum pump, a backflow liquid outlet pipe, a solid separator, a back pressure valve, a gas-liquid separator, a gas flow meter group, and a liquid flow meter group. The vacuum pump is connected to the injection pipe via a pipeline. The backflow liquid in the pressure chamber is discharged through the backflow liquid outlet pipe. The solid separator, back pressure valve, and gas-liquid separator are sequentially installed on the backflow liquid outlet pipe. After the gas-liquid separator, the flow meter group is divided into a gas pipeline and a liquid pipeline. The gas flow meter group is installed on the gas pipeline, and the liquid flow meter group is installed on the liquid pipeline.

2. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The hydraulic servo system includes an X-direction oil circuit, a Y-direction oil circuit, a Z-direction oil circuit, and a confining pressure oil circuit. The X-direction oil circuit is connected to the pressure pillow below the sample, the Y-direction oil circuit is connected to the pressure pillows on the left and right sides of the sample, the Z-direction oil circuit is connected to the pressure pillows on the front and rear sides of the sample, and the confining pressure oil circuit is connected to the liquid filling space inside the pressure chamber. During loading, the pressure value inside the pressure pillow is greater than the liquid confining pressure value.

3. The physical simulation device for in-situ rock fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The backflow metering assembly also includes a liquid sampler and a gas sampler. The liquid sampler is located on the branch between the solid separator and the back pressure valve, and the gas sampler is located on the pipeline after the gas flow meter assembly.

4. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The dissolved oxygen generating device includes an oxygen source, an oxygen solution stirring container, and a water source. The outlets of the oxygen source and the water source are respectively connected to the inlet of the oxygen solution stirring container, and the outlet of the oxygen solution stirring container is connected to the inlet of the mixing container group. The CO2 booster device includes a CO2 source, a CO2 booster pump, a CO2 storage tank, and a CO2 metering pump connected in sequence through pipelines. The outlet of the CO2 metering pump is connected to the inlet of the mixing container group.

5. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and mining according to claim 4, characterized in that, The oxygen source outlet pipeline is equipped with an oxygen pressure regulating valve, an oxygen pressure gauge, and an oxygen shut-off valve; the oxygen solution stirring container is equipped with an oxygen content sensor and a level gauge, and the oxygen solution stirring container outlet pipeline is equipped with an oxygen solution metering pump and a shut-off valve.

6. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 4, characterized in that, The CO2 storage tank is equipped with a CO2 pressure gauge on its inlet pipe and a CO2 safety valve and a shut-off valve on its outlet pipe. The outer shell of the CO2 storage tank is fitted with a heat-insulating heating jacket. The CO2 metering pump is equipped with a CO2 pressure regulating valve, a CO2 pressure gauge and a shut-off valve on its outlet pipe. The outer shell of the CO2 metering pump is fitted with a heat-insulating heating jacket.

7. The physical simulation device for in-situ rock fracturing and permeability enhancement and in-situ leaching and production according to claim 4, characterized in that, The mixing container group is equipped with a level gauge and a heat insulation heating jacket on its exterior, and a shut-off valve is installed on the outlet pipeline of the mixing container group.

8. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The injection assembly uses a dual-cylinder constant speed and constant pressure injection pump, which includes two parallel single pumps: a first single pump and a second single pump. The inlet pipe of the first single pump is equipped with a shut-off valve, and the outlet pipe of the second single pump is equipped with a shut-off valve. The two single pumps can independently perform liquid suction and liquid discharge operations.

9. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The additive assembly includes a high-pressure storage tank, a screw pump, and a screw pump motor. The funnel outlet at the bottom of the high-pressure storage tank is connected to the outlet of the injection assembly. The additive in the high-pressure storage tank falls to the outlet under its own weight and mixes with the ground leaching solution. The screw pump motor rotates the screw pump to pump the mixed ground leaching solution into the cracks inside the sample.

10. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The triaxial loading assembly also includes end blocks disposed around the sample. The end blocks have reserved space for the arrangement of various monitoring probes to meet the arrangement requirements of acoustic probes, strain gauges, optical fibers and electrodes, and support the arrangement of array-type acoustic probes. The end blocks are also provided with water distribution channels and block guide holes to guide the leaching liquid flowing through the pre-embedded pipes and mesh in the sample out of the pressure chamber.

11. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 10, characterized in that, The triaxial loading assembly further includes an end cap assembly, which includes an upper end cap, a lower end cap, a shear ring pad, and a shear ring. The upper end cap is installed at the upper end of the pressure chamber and has an upper end cap sealing ring along the circumferential direction. The lower end cap is installed at the lower end of the pressure chamber and has a lower end cap sealing ring along the circumferential direction. The shear ring is installed on the inner wall of the pressure chamber and located above the upper end cap, and the shear ring pad is installed between the upper end cap and the shear ring.

12. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 11, characterized in that, The triaxial loading assembly also includes a support pad assembly, which includes an upper pad, a lower tray, an annular pad, and a lower pad. The upper pad is installed between the vertical end pad and the upper end cover. The lower tray is installed at the lower end of the pressure pillow below the sample. The lower pad is installed between the lower tray and the lower end cover. The annular pad is installed between the outer periphery of the lower pad and the inner wall of the pressure chamber.

13. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 12, characterized in that, The upper end cover, the upper pad block, and the vertical end pad block each have a central hole for applying engineering disturbance loads. The upper end of the pressure chamber is provided with a disturbance load device fixing hole. Planar seals are respectively provided between the upper end cover and the upper pad block, and between the upper pad block and the vertical end pad block to prevent confining fluid from seeping out from the gaps in the pad blocks.

14. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 1, characterized in that, The triaxial loading assembly also includes a wedge-shaped pad assembly disposed between the pressure pillow and the inner wall of the pressure chamber. The wedge-shaped pad assembly includes an arc-shaped wedge pad and a square wedge pad. The arc-shaped wedge pad is installed on the inner wall of the pressure chamber, and the square wedge pad is installed between the arc-shaped wedge pad and the pressure pillow.

15. The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to claim 10, characterized in that, The original rock fracturing and permeability enhancement and in-situ leaching and production physical simulation device also includes a multi-parameter acquisition component, which includes various monitoring probes and acquisition instruments, as well as signal cables connecting the monitoring probes and acquisition instruments; The various monitoring probes are installed inside the end pad. The types of monitoring probes include acoustic emission probes, ultrasonic probes, strain gauges, optical fibers, and electrode accelerometers. The types of data acquisition instruments include acoustic emission acquisition cards, acoustic wave acquisition cards, strain gauges, optical fiber instruments, resistivity acquisition instruments, and accelerometers.

16. A physical simulation method for in-situ leaching and mining, characterized in that, The physical simulation device for in-situ fracturing and permeability enhancement and in-situ leaching and production according to any one of claims 1-15 includes the following steps: A vacuum pump is used to evacuate the sample through the injection hole and the pre-embedded tube; Start the mixing assembly, prepare the ground leaching solution required for the simulation experiment in the mixing container group, fill the ground leaching solution with the dual-cylinder constant speed and constant pressure pump in the injection assembly, then close all shut-off valves and add additives to the additive assembly. Original rock stress application: First, apply vertical stress to 2MPa-5MPa to fix the sample, then apply horizontal pressure of 2MPa-5MPa. After the pressure stabilizes, apply confining pressure, and then simultaneously increase the triaxial stress and confining pressure to the target pressure. During the loading process, keep the internal pressure of the pressure chamber greater than the confining pressure. Heat the pressure chamber as a whole by wrapping it with an insulating heating jacket. After the pressure stabilizes, observe whether there is confining pressure liquid flowing out of the injection hole on the end pad and the pre-embedded tube in the sample. If liquid flows out, terminate the experiment and install the next sample until no liquid flows out. Monitor and record the state of the sample, including the acoustic wave velocity of the sample, the initial strain and resistance value of each measuring point, as the baseline for subsequent monitoring. Physical simulation of reservoir stimulation: A disturbance load simulation device is fixed on the pressure chamber, and a shock wave generator is pre-embedded at the bottom of the pre-embedded pipe. After excitation, a cylindrical shock wave is released to simulate the reservoir stimulation process, i.e., the construction process of homogenized fracture network. After the disturbance load is applied, the disturbance load simulation device is removed. The relevant shut-off valves of the injection component and additive component are opened, the in-situ leaching fluid injection flow rate is set, the additive is pumped into the fracture network, and the waste liquid discharged from the return flow pipeline is collected using a collection tank. After the above operations are completed, all shut-off valves are closed. Physical simulation of in-situ leaching mining process: The mixing, injection, flowback metering, and control components are activated. The leaching solution concentration, injection pressure, and extraction pressure are set to target values. The leaching solution is injected into the sample, and the uranium ore present in the sample is extracted through a chemical reaction. The gas and liquid flow meters in the flowback metering component are used to record the gas and liquid flow rates in the extracted material, respectively. Gas and liquid samplers are used to collect the extracted gas and liquid for analysis. The backpressure valve is activated, and the backpressure valve pressure is set. The injection component is activated, and the injection flow rate is set, continuously injecting the leaching solution until… The pressure fluctuation of the inlet pressure gauge was less than 1 MPa / min, and the pressure gauge value was recorded. The equivalent permeability coefficient of the reservoir was calculated using Darcy's formula. During the experiment, the acoustic, optical, electrical, temperature, pressure, and flow data observed during the simulation were recorded using a multi-parameter acquisition component. By analyzing the acoustic, optical, electrical, temperature, pressure, and flow data during reservoir stimulation and exploitation, and by inverting the fracture network evolution process before and during reservoir stimulation based on the multi-parameter monitoring signals, the main factors affecting reservoir exploitation efficiency were further clarified, and quantitative assessments of different factors were made.

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