Multifunctional rock test system and method under multi-field coupling conditions

Abstract

The present application provides a multifunctional rock test system under multi-field coupling conditions, which is internally provided with a reaction chamber in which a rock sample is placed, and is internally provided with an axial force loading control system, a confining pressure oil circulation system, a high-temperature heating and control system, an injection pump system, a temperature and strain measurement system, each subsystem is in communication connection with a computer display and control system and is respectively used for controlling the pressure or temperature in the reaction chamber; a test method based on the system comprises the following steps: 1) processing a rock sample; 2) assembling the rock sample; 3) loading the rock sample into the reaction chamber; 4) assembling the reaction chamber; 5) initializing the system and fixing the rock sample; 6) providing a confining pressure environment for the rock sample; 7) providing a high-temperature environment for the rock sample; 8) providing a triaxial high-pressure environment for the rock sample; 9) providing a chemical field and a permeation pressure environment for the rock sample; 10) providing a water pressure for the rock sample and monitoring the pressure, temperature and strain changes; 11) pressure relief and cooling and recovering the confining pressure oil; 12) arranging and data processing.

Description

Technical Field

[0001] This invention relates to the field of geological testing technology, specifically to a multifunctional rock testing system and method under multi-field coupling conditions. Background Technology

[0002] In a wide range of fields, including geological engineering, energy development, and infrastructure construction, the accurate assessment of the physical, mechanical, and hydrological properties of rocks, as the basic building blocks of the Earth's crust, directly impacts the safety and economic efficiency of engineering projects. In particular, with the efficient utilization of oil shale resources, the development of hot dry rock geothermal energy, and the continuous advancement of deep-buried tunnels and large-scale mining projects, the need to understand and predict the behavior of rocks under complex environmental conditions is becoming increasingly urgent. These complex environmental conditions often involve multi-field coupling (THMC) interactions involving temperature, hydrology, mechanical, and chemical factors. The interactions of these factors significantly affect the physical state, mechanical response, and fluid transport characteristics of rocks.

[0003] Traditional rock testing systems often focus on the independent study of single or a few factors, neglecting the complexity of multi-field coupling effects in actual geological environments. For example, during oil shale development, rising temperatures not only directly affect the rock's strength and deformation characteristics but also influence fluid permeability by altering the rock's internal pore structure, thus affecting hydraulic fracturing efficiency. In hot dry rock geothermal systems, the chemical reaction between high-temperature, high-pressure water and rock significantly alters the rock's mechanical properties and seepage performance. Tunnel and mining engineering often face stability problems under the coupled effects of multiple factors such as groundwater seepage, stress concentration, and rock weathering. Therefore, it is necessary to design a testing system and method capable of simulating multi-field coupling conditions and conducting triaxial tests, permeability tests, hydraulic fracturing tests, and coupled tests. Summary of the Invention

[0004] The purpose of this invention is to provide a multifunctional rock testing system and method that simulates the physical and hydrological properties of rocks under THMC conditions, simplifies test procedures, improves test efficiency, provides accurate test results, and is applicable to a variety of rock samples under multi-field coupling conditions.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A multifunctional rock testing system under multi-field coupling conditions is a test space with a built-in reaction chamber containing a rock sample. The test space is equipped with an axial force loading control system, a confining pressure oil circulation system, a high-temperature heating and control system, an injection pump system, and a temperature and strain measurement system. Each system in the test space is connected to a remote computer display and control system and is used to control the pressure or temperature conditions in the reaction chamber.

[0007] The axial force loading control system applies axial force to the rock sample by controlling the axial force column at the bottom of the test space to move up and down through a servo hydraulic press.

[0008] The confining pressure oil circulation system uses a bidirectional electric pump to control the confining pressure oil to enter and exit through the confining pressure oil inlet valve and confining pressure oil outlet valve set in the test space, so as to inject confining pressure oil into the reaction chamber to provide a high pressure environment for the rock sample.

[0009] The high-temperature heating and control system heats the confining oil in the reaction chamber through heating wires installed on the inner wall of the test space, thereby providing a high-temperature environment for the rock sample;

[0010] The injection pump system pumps fracturing fluid or chemical solution from the external fracturing fluid tank and chemical solution tank into the rock sample through the reaction chamber double-way valve. After use, the fracturing fluid or chemical solution flows into the liquid recovery tank through the outflow high-pressure valve.

[0011] The temperature and strain measurement system includes several temperature probes and axial and radial strain gauges placed on the outer wall of the rock sample.

[0012] Furthermore, the upper and lower ends of the rock sample are respectively connected to an upper pad and a lower pad. The upper pad is located between the top wall of the reaction chamber and the upper end of the rock sample, and the lower pad is located between the bottom wall of the reaction chamber and the lower end of the rock sample. The rock sample is wrapped with a high-elastic rubber tube, and the upper and lower ends of the rubber tube are tightly connected and fixed to the upper and lower pads respectively.

[0013] Furthermore, the upper pad is a triaxial test upper pad, which consists of a fixed upper column and a pad body, with the fixed upper column inserted into the top wall of the reaction chamber; the lower pad is a non-seepage and non-hydraulic fracturing lower pad, which consists of a fixed lower column and a pad body, with the fixed lower column inserted into the axial force column connected to the bottom wall of the reaction chamber.

[0014] Furthermore, the upper pad is a hydraulic fracturing test upper pad, which consists of a water injection pipe and a pad body. The water injection pipe passes through the central axis of the pad body, and the upper end of the water injection pipe is inserted into the top wall of the reaction chamber and connected to the two-way valve of the reaction chamber through a pipe. The lower end of the water injection pipe is inserted into the pre-drilled hole of the rock sample. The lower pad is a seepage or hydraulic fracturing lower pad, which consists of a permeable grid, a water collection funnel, a pad body, a fixed outer pipe, and a water outlet pipe. The upper end of the pad body is concave to form a water collection funnel. A permeable grid is laid on the upper side of the water collection funnel. The water outlet pipe runs through the fixed outer pipe. The fixed outer pipe and the water outlet pipe pass through the pad body, and their lower ends are connected to the high-pressure valve of the outflowing liquid through a pipe.

[0015] Furthermore, the upper pad is a seepage or seepage heat exchange test upper pad, which consists of an inner injection pipe, an outer injection pipe, a permeation grid, and a pad body. The inner injection pipe passes through the outer injection pipe, and the inner and outer injection pipes are inserted into the top wall of the reaction chamber and connected to the double-way valve of the reaction chamber through pipes. A permeation grid is provided inside the pad body. The lower pad is a seepage or hydraulic fracturing lower pad, which consists of a permeation grid, a water collection funnel, a pad body, a fixed outer pipe, and an outlet pipe. The upper end of the pad body is concave to form a water collection funnel, and a permeation grid is laid on the upper side of the water collection funnel. An outlet pipe passes through the fixed outer pipe, and the fixed outer pipe and the outlet pipe pass through the pad body and their lower ends are connected to the high-pressure valve of the outflowing liquid through pipes.

[0016] Furthermore, the upper pad is a seepage and hydraulic fracturing test pad, which consists of a fracturing fluid injection pipe, a chemical solution injection pipe, an external fixed pipe, a permeable grid, and a pad body. The fracturing fluid injection pipe and the chemical solution injection pipe are arranged side by side and connected to the reaction chamber double-way valve through pipes. The external fixed pipe penetrates the pad body, and a permeable grid is provided inside the pad body. The lower pad is a seepage or hydraulic fracturing lower pad, which consists of a permeable grid, a water collection funnel, a pad body, a fixed external pipe, and a water outlet pipe. The upper end of the pad body is concave to form a water collection funnel, and a permeable grid is laid on the upper side of the water collection funnel. The water outlet pipe is connected inside the fixed external pipe. The fixed external pipe and the water outlet pipe penetrate the pad body, and their lower ends are connected to the outflow liquid high-pressure valve through pipes.

[0017] Furthermore, the reaction chamber base is provided with several pulleys on both sides, and the bottom wall of the test space is provided with slide rails on both sides. The pulleys can slide in the slide rails to push the reaction chamber forward or backward.

[0018] Furthermore, condensation pipes are installed on both sides of the bottom of the test space. The condensation pipes are connected to the external cooling system. The confining pressure oil flows into the condensation pipes through the oil outlet valve of the reaction chamber, is cooled, and then is recovered to the confining pressure oil circulation system through the confining pressure oil outlet valve.

[0019] A multifunctional rock testing method under multi-field coupling conditions includes the following steps:

[0020] Step S1) Processing rock samples

[0021] Use a rock sample cutting machine to process the rock sample into a cylindrical shape, set pre-fabricated fractures or simulated faults as needed, and drill a certain depth in the center of the rock sample to form a water guide hole.

[0022] Step S2) Assemble the rock sample

[0023] The rock sample is clamped between the upper pad and the lower pad with seepage or hydraulic fracturing in the seepage and hydraulic fracturing test, and then put into the high-elasticity rubber sleeve. The two ends of the rubber sleeve are tightly sealed to the upper and lower pads. Several temperature probes and axial and radial strain measuring instruments are installed and adjusted.

[0024] Step S3) The rock sample is loaded into the reaction chamber.

[0025] Unlock the inner lock handle to open the test space switch door, push out the reaction chamber through pulleys and slides, and load the high-elastic rubber cylinder containing the rock sample and the upper and lower pads into the reaction chamber;

[0026] Step S4) Assemble the reaction chamber

[0027] Push the reaction chamber into the test space, connect the upper end of the fracturing fluid injection pipe to the reaction chamber double valve through a pipe, insert the lower end into the rock sample of the pre-drilled hole, connect the upper end of the chemical solution injection pipe to the reaction chamber double valve through a pipe, and insert the fixing outer pipe of the lower pad block into the fixing hole of the axial force column to fix the rock sample.

[0028] Step S5) Initialize the system and fix the rock sample

[0029] Open the remote computer display and control system, start the servo hydraulic press, control the servo hydraulic press through the computer display and control system to push the axial force column upward and monitor the pressure through the connected pressure sensor. First, apply a small axial pressure to the rock sample to fix it.

[0030] Step S6) Provide confining pressure environment for the rock sample.

[0031] Close the reaction chamber double-way valve and the reaction chamber oil outlet valve, open the confining pressure oil inlet valve, inject confining pressure oil into the reaction chamber through the confining pressure oil circulation system, and control the amount of confining pressure oil through the computer display and control system to provide a confining pressure environment for the rock sample.

[0032] Step S7) Provide a high-temperature environment for the rock sample.

[0033] The high-temperature heating and control system controls the heating wire to heat the confining oil in the reaction chamber, providing a high-temperature environment for the rock sample.

[0034] Step S8) Provide a triaxial high-pressure environment for the rock sample.

[0035] The servo hydraulic press is controlled by a computer display and control system to adjust the axial pressure, and combined with the confining pressure provided by the confining pressure oil, a triaxial high-pressure environment is provided to the rock sample.

[0036] Step S9) Provide the rock sample with a chemical field and osmotic pressure environment.

[0037] Open the injection liquid high-pressure double-way valve, the reaction chamber double-way valve, and the outflow liquid high-pressure valve. The prepared chemical solution stored in the chemical solution tank is pumped into the chemical solution injection pipe through the injection pump system. Then, it permeates downward into the sample through the permeation grid, forming a uniform osmotic pressure to provide a chemical field environment and osmotic pressure environment for the rock sample.

[0038] Step S10) Apply water pressure to the rock sample and monitor changes in pressure, temperature, and strain.

[0039] The fracturing fluid stored in the fracturing fluid tank is injected into the fracturing fluid injection pipe through the injection pump system, thereby applying water pressure to the rock sample until it is broken. The liquid flowing through the rock sample is collected through the water collection funnel in the pad block and discharged to the liquid recovery tank through the water outlet pipe. The injection pressure, temperature and strain changes during this process are recorded and transmitted to the computer display and control system for real-time display and storage.

[0040] Step S11) Depressurize, cool, and recover confining pressure oil

[0041] After the test is completed, close the double-way valve of the reaction chamber, open the oil outlet valve and the confining pressure oil outlet valve of the reaction chamber, and release the confining pressure to normal pressure through the confining pressure oil circulation system. Then, the high-temperature hydraulic oil is drawn into the condensation pipe for cooling and then returned to the oil tank of the confining pressure oil circulation system.

[0042] Step S12) Organize and process data

[0043] The computer display and control system controls the servo hydraulic press to descend the reaction chamber, open the test space switch door, push the reaction chamber out through pulleys and slides, remove the rock sample, process the data, and conduct the next test.

[0044] Furthermore, if the rock sample does not require hydrostatic testing, step S10 is omitted; if the rock sample does not require osmotic pressure testing, step S9 is omitted; if the rock sample only undergoes triaxial pressure testing, steps S9 and S10 are omitted.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] This invention relates to a multifunctional rock testing system and method under multi-field coupling conditions, which simulates the physical and hydrological properties of rocks under THMC conditions, simplifies test procedures, improves test efficiency, and provides accurate test results. It is applicable to a variety of rock samples. Attached Figure Description

[0047] Figure 1 This is a schematic cross-sectional view of the system of the present invention.

[0048] Figure 2 This is a schematic diagram of the structure of the pad block in the triaxial test of the present invention.

[0049] Figure 3 This is a schematic diagram of the structure of the pad block in the hydraulic fracturing test of the present invention.

[0050] Figure 4 This is a schematic diagram of the structure of the pad block in the seepage or seepage heat transfer test of the present invention.

[0051] Figure 5 This is a schematic diagram of the structure of the pad block in the seepage and hydraulic fracturing test of the present invention.

[0052] Figure 6 This is a schematic diagram of the structure of the pad block under the present invention in the test of no seepage and no hydraulic fracturing.

[0053] Figure 7 This is a schematic diagram of the structure of the underfill block with seepage or hydraulic fracturing according to the present invention.

[0054] Figure 8 This is a schematic diagram showing the positional relationship between the reaction chamber and the test system of the present invention.

[0055] Figure 9 This is a schematic diagram of the reaction chamber pulley structure of the present invention.

[0056] Figure 10 This is a schematic diagram of the reaction chamber slide structure of the present invention.

[0057] Reference numerals: 1. Liquid recovery tank; 2. Axial force loading control system; 3. Confining pressure oil circulation system; 4. Computer display and control system; 5. High-temperature heating and control system; 6. Injection pump system; 7. Fracturing fluid tank; 8. Chemical solution tank; 9. Temperature and strain measurement system; 10. High-pressure two-way valve for injected liquid; 11. Two-way valve for reaction chamber; 12. Upper pad; 13. Left wall of reaction chamber; 14. Temperature probe; 15. Reaction chamber; 16. Axial and radial strain gauge; 17. Heating wire; 18. Rock sample; 19. Rubber cylinder; 20. Reaction chamber oil outlet valve; 21. Pulley; 22. Slide rail; 23. Condensation pipe; 24. Lower pad; 25. High-pressure valve for outflowing liquid; 26. Test space, 27. Servo hydraulic press, 28. Confining pressure oil outlet valve, 29. Right wall of reaction chamber, 30. Confining pressure oil inlet valve, 121. Upper pad for triaxial test, 1211. Fixed upper column, 1212. Pad body one, 122. Upper pad for hydraulic fracturing test, 1221. Water injection pipe, 1222. Pad body two, 123. Upper pad for seepage or seepage heat transfer test, 1231. Inner injection pipe, 1232. Outer wall of injection pipe, 1233. Permeability grid one, 1234. Pad body three, 124. Upper pad for seepage and hydraulic fracturing test, 1241. Fracturing fluid injection pipe, 1242. Chemical solvent Liquid injection pipe, 1243. Permeation grid II, 1244. Pad body IV, 1245. Fixed outer pipe, 241. Lower pad without seepage and hydraulic fracturing, 2411. Pad body V, 2412. Fixed lower column, 242. Lower pad with seepage or hydraulic fracturing, 2421. Permeation grid III, 2422. Water collection funnel, 2423. Pad body VI, 2424. Fixed outer pipe II, 2425. Water outlet pipe, 211. Pulley support, 212. Concave pulley, 221. Slide support, 222. Convex slide, 31. Front wall of test space, 32. Test space switch door, 33. Inner lock handle. Detailed Implementation

[0058] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0059] like Figure 1As shown, the multifunctional rock testing system under multi-field coupling conditions consists of a test space 26, with a reaction chamber 15 inside. The reaction chamber 15 includes a left wall 13 and a right wall 29. A rock sample 18 is placed inside the reaction chamber 15. The test space 26 is equipped with an axial force loading control system 2, a confining pressure oil circulation system 3, a high-temperature heating and control system 5, an injection pump system 6, and a temperature and strain measurement system 9. Each system in the test space 26 is communicatively connected to a remote computer display and control system 4 and is used to control the pressure or temperature conditions inside the reaction chamber 15. The axial force loading control system 2 applies axial force to the rock sample 18 by controlling the up-and-down movement of the axial force column at the bottom of the test space 26 through a servo hydraulic press 27. The confining pressure oil circulation system 3 controls the confining pressure oil through a bidirectional electric pump. The confining pressure oil inlet valve 30 and confining pressure oil outlet valve 28, set in the test space 26, are used to inject confining pressure oil into the reaction chamber 15 to provide a high-pressure environment for the rock sample 18. The high-temperature heating and control system 5 heats the confining pressure oil in the reaction chamber 15 through the heating wire 17 set in the inner wall of the test space 26, thereby providing a high-temperature environment for the rock sample 18. The injection pump system 6 pumps the fracturing fluid (clean water, supercritical carbon dioxide, etc.) or chemical solution from the external fracturing fluid tank 7 and chemical solution tank 8 into the rock sample through the reaction chamber double-way valve 11. After use, the fracturing fluid or chemical solution flows into the liquid recovery tank 1 through the liquid outflow high-pressure valve 25. The temperature and strain measurement system 9 includes several temperature probes 14 and axial and radial strain gauges 16 placed on the outer wall of the rock sample 18.

[0060] The upper and lower ends of the rock sample 18 are respectively connected to the upper pad 12 and the lower pad 24. The upper pad 12 is located between the top wall of the reaction chamber 15 and the upper end of the rock sample 18, and the lower pad 24 is located between the bottom wall of the reaction chamber 15 and the lower end of the rock sample 18. The rock sample 18 is wrapped with a high-elastic rubber cylinder 19, and the upper and lower ends of the rubber cylinder 19 are tightly connected and fixed to the upper pad 12 and the lower pad 24 respectively.

[0061] The upper pad 12 is divided into four types: upper pad 121 for triaxial tests, upper pad 122 for hydraulic fracturing tests, upper pad 123 for seepage or seepage heat transfer tests, and upper pad 124 for seepage and hydraulic fracturing tests. For example... Figure 2 As shown, the triaxial test pad 121 consists of a fixed upper column 1211 and a pad body 1212, with the fixed upper column 1211 inserted into the top wall of the reaction chamber 15. Figure 3 As shown, the hydraulic fracturing test pad 122 consists of a water injection pipe 1221 and a pad body 1222. The water injection pipe 1221 passes through the central axis of the pad body 1222. The upper end of the water injection pipe 1221 is inserted into the top wall of the reaction chamber 15 and connected to the reaction chamber double-way valve 11 via a pipe. The lower end of the water injection pipe 1221 is inserted into the pre-drilled hole of the rock sample 18. Figure 4 As shown, the pad 123 in the seepage or seepage heat transfer test consists of an inner injection pipe 1231, an outer injection pipe 1232, a permeation grid 1233, and a pad body 1234. The inner injection pipe 1231 passes through the outer injection pipe 1232. The inner injection pipe 1231 and the outer injection pipe 1232 are inserted into the top wall of the reaction chamber 15 and connected to the double-way valve 11 of the reaction chamber through a pipe. The permeation grid 1233 is installed inside the pad body 1234. Figure 5 As shown, the pad 124 in the seepage and hydraulic fracturing test consists of a fracturing fluid injection pipe 1241, a chemical solution injection pipe 1242, a fixed outer pipe 1245, a second permeable grid 1243, and a pad body 1244. The fracturing fluid injection pipe 1241 and the chemical solution injection pipe 1242 are arranged side by side and connected to the reaction chamber double valve 11 through pipes. The fixed outer pipe 1245 passes through the pad body 1244, and the second permeable grid 1243 is provided inside the pad body 1244.

[0062] The lower pad 24 is divided into two types: a lower pad 241 with no seepage and no hydraulic fracturing, and a lower pad 242 with seepage or hydraulic fracturing. For example... Figure 6 As shown, the seepage-free and hydraulically fracturing-free lower pad 241 consists of a fixed lower column 2412 and a pad body 2411. The fixed lower column 2412 is inserted into the axial force column connected to the bottom wall of the reaction chamber 15. Figure 7 As shown, the seepage or hydraulic fracturing pad 242 consists of a permeable grid 3 2421, a water collection funnel 2422, a pad body 6 2423, a fixed outer pipe 2 2424, and a water outlet pipe 2425. The upper end of the pad body 6 2423 is concave to form a water collection funnel 2422. The permeable grid 3 2421 is laid on the upper side of the water collection funnel 2422. The water outlet pipe 2425 runs through the fixed outer pipe 2 2424. The fixed outer pipe 2 2424 and the water outlet pipe 2425 pass through the pad body 6 2423, and their lower ends are connected to the high-pressure valve 25 for the outflowing liquid through a pipe.

[0063] The test space 26 has condensation pipes 23 installed on both sides of the bottom. The condensation pipes 23 are connected to the external cooling system. The confining pressure oil flows into the condensation pipes 23 through the reaction chamber oil outlet valve 20, is cooled, and then is recovered to the confining pressure oil circulation system 3 through the confining pressure oil outlet valve 28.

[0064] like Figure 8 As shown, the front of the test space 26 is an openable test space front wall 31. The test space front wall 31 is equipped with a test space switch door 32 and an inner lock handle 33. Opening the test space switch door 32 allows for easy entry and exit of the reaction chamber 15.

[0065] like Figure 9 , 10As shown, the reaction chamber 15 has several pulleys 21 on both sides of its base, preferably two on each side for a total of four. The test space 26 has slide rails 22 on both sides of its bottom wall. The pulleys 21 can slide within the slide rails 22 to advance or depress the reaction chamber 15. Specifically, each pulley 21 includes a pulley bracket 211 and a concave pulley 212. The pulley bracket 211 is connected and fixed to both sides of the bottom of the reaction chamber 15, and the concave pulley 212 is axled to the pulley bracket 211, with a groove in the middle. The slide rails 22 include a slide rail bracket 221 and a convex slide rail 222. The slide rail bracket 221 is connected and fixed to both sides of the bottom wall of the test space 26, and the convex slide rail 222 matches the concave pulley 212.

[0066] Preferably, the rock sample 18 is processed into a cylindrical sample. Samples for hydraulic fracturing need to be pre-drilled, and samples for seepage tests or triaxial tests can be pre-formed with cracks, joint strips, etc.

[0067] Example 1: Hydraulic fracturing and osmotic pressure test of rock samples under THMC multi-field coupling conditions

[0068] A multifunctional rock testing method under multi-field coupling conditions includes the following steps:

[0069] Step S1) Processing rock samples

[0070] Use a rock sample cutting machine to process the rock sample into a cylindrical shape, set pre-fabricated fractures or simulated faults as needed, and drill a certain depth in the center of the rock sample to form a water guide hole.

[0071] Step S2) Assemble the rock sample

[0072] The rock sample 18 is clamped between the upper pad 124 and the lower pad 242 with seepage or hydraulic fracturing in the seepage and hydraulic fracturing test, and is put into the high-elastic rubber sleeve 19. The two ends of the rubber sleeve 19 are tightly sealed to the upper and lower pads. Several temperature probes 14 and axial and radial strain measuring instruments 16 are installed and adjusted.

[0073] Step S3) The rock sample is loaded into the reaction chamber.

[0074] Unlock the inner lock handle 33 to open the test space switch door 32, push out the reaction chamber 15 through the pulley 21 and slide 22, and put the high-elastic rubber cylinder 19 containing the rock sample 18 and the upper and lower pads into the reaction chamber 15.

[0075] Step S4) Assemble the reaction chamber

[0076] Push the reaction chamber 15 into the test space 26, connect the upper end of the fracturing fluid injection pipe 1241 to the reaction chamber double valve 11 through a pipe, insert the lower end of the pipe into the pre-drilled rock sample 18, connect the upper end of the chemical solution injection pipe 1242 to the reaction chamber double valve 11 through a pipe, and insert the fixing outer pipe of the lower pad block 24 into the fixing hole of the axial force column to fix the rock sample 18.

[0077] Step S5) Initialize the system and fix the rock sample

[0078] Open the remote computer display and control system 4, start the servo hydraulic press 27, control the servo hydraulic press 27 through the computer display and control system 4 to push the axial force column upward and monitor the pressure through the connected pressure sensor, first apply a small axial pressure to the rock sample 18 to fix it;

[0079] Step S6) Provide confining pressure environment for the rock sample.

[0080] Close the reaction chamber double-way valve 11 and the reaction chamber oil outlet valve 20, open the confining pressure oil inlet valve 30, inject confining pressure oil into the reaction chamber 15 through the confining pressure oil circulation system 3, and control the amount of confining pressure oil through the computer display and control system 4 to provide a confining pressure environment for the rock sample 18.

[0081] Step S7) Provide a high-temperature environment for the rock sample.

[0082] The high-temperature heating and control system 5 controls the heating wire 17 to heat the confining oil in the reaction chamber 15, thus providing a high-temperature environment for the rock sample 18.

[0083] Step S8) Provide a triaxial high-pressure environment for the rock sample.

[0084] The computer display and control system 4 controls the servo hydraulic press 27 to adjust the axial pressure, and combined with the confining pressure provided by the confining pressure oil, provides a triaxial high-pressure environment for the rock sample 18.

[0085] Step S9) Provide the rock sample with a chemical field and osmotic pressure environment.

[0086] Open the injection liquid high-pressure double-way valve 10, the reaction chamber double-way valve 11 and the outflow liquid 25 high-pressure valve, and pump the prepared chemical solution stored in the chemical solution tank 8 into the chemical solution injection pipe 1242 through the injection pump system 6. Then, it permeates downward into the sample through the permeation grid 1243, forming a uniform osmotic pressure to provide a chemical field environment and osmotic pressure environment for the rock sample 18.

[0087] Step S10) Apply water pressure to the rock sample and monitor changes in pressure, temperature, and strain.

[0088] The fracturing fluid stored in the fracturing fluid tank 7 is injected into the fracturing fluid injection pipe 1241 through the injection pump system 6, thereby applying water pressure to the rock sample 18 until it is broken. The liquid flowing through the rock sample 18 will be collected through the water collection funnel 2422 in the pad block 4 1244 and discharged to the liquid recovery tank 1 through the water outlet pipe 2425. The injection pressure, temperature and strain changes during this process are recorded and transmitted to the computer display and control system 4 for real-time display and storage.

[0089] Step S11) Depressurize, cool, and recover confining pressure oil

[0090] After the test is completed, close the double-way valve 11 of the reaction chamber, open the oil outlet valve 20 of the reaction chamber and the confining pressure oil outlet valve 28, and release the confining pressure to normal pressure through the confining pressure oil circulation system 3. Then, the high-temperature hydraulic oil is drawn into the condensation pipe 23 for cooling and then returned to the oil tank of the confining pressure oil circulation system 3.

[0091] Step S12) Organize and process data

[0092] The computer display and control system 4 controls the servo hydraulic press 27 to descend the reaction chamber 15, open the test space 26 to open and close the door, push the reaction chamber 15 out through the pulley 21 and slide 22, take out the rock sample 18, process the data, and conduct the next test.

[0093] Example 2: Rock seepage or seepage heat transfer test under THMC multi-field coupling conditions

[0094] Based on Example 1, step S10 is omitted.

[0095] Example 3: Hydraulic fracturing test of rock samples under high temperature and high pressure conditions

[0096] Based on Example 1, step S9 is omitted.

[0097] Example 4: Triaxial Test of Rock Samples under THMC Multifield Coupling Conditions

[0098] Based on Example 1, steps S9 and S10 are omitted.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multifunctional rock testing system under multi-field coupling conditions, characterized in that: The test space is a test chamber with a built-in reaction chamber where rock samples are placed. The test space is equipped with an axial force loading control system, a confining pressure oil circulation system, a high temperature heating and control system, an injection pump system, and a temperature and strain measurement system. Each system in the test space is connected to a remote computer display and control system and is used to control the pressure or temperature conditions in the reaction chamber. The axial force loading control system applies axial force to the rock sample by controlling the axial force column at the bottom of the test space to move up and down through a servo hydraulic press. The confining pressure oil circulation system uses a bidirectional electric pump to control the confining pressure oil to enter and exit through the confining pressure oil inlet valve and confining pressure oil outlet valve set in the test space, so as to inject confining pressure oil into the reaction chamber to provide a high pressure environment for the rock sample. The high-temperature heating and control system heats the confining oil in the reaction chamber through heating wires installed on the inner wall of the test space, thereby providing a high-temperature environment for the rock sample; The injection pump system pumps fracturing fluid or chemical solution from the external fracturing fluid tank and chemical solution tank into the rock sample through the reaction chamber double-way valve. After use, the fracturing fluid or chemical solution flows into the liquid recovery tank through the outflow high-pressure valve. The temperature and strain measurement system includes several temperature probes and axial and radial strain measuring instruments placed on the outer wall of the rock sample; The rock sample is connected to an upper pad and a lower pad at its upper and lower ends, respectively. The upper pad is located between the top wall of the reaction chamber and the upper end of the rock sample. There are four types of upper pads: triaxial test upper pad, hydraulic fracturing test upper pad, seepage or seepage heat transfer test upper pad, and seepage and hydraulic fracturing test upper pad. The seepage and hydraulic fracturing test upper pad consists of a fracturing fluid injection pipe, a chemical solution injection pipe, an external fixing pipe, a permeable grid, and a pad body. The fracturing fluid injection pipe and the chemical solution injection pipe are arranged side by side and connected to the reaction chamber double-way valve through pipes. The external fixing pipe passes through the pad body, and a permeable grid is provided inside the pad body.

2. The multifunctional rock testing system under multi-field coupling conditions according to claim 1, characterized in that: The lower pad is located between the bottom wall of the reaction chamber and the lower end of the rock sample. The rock sample is wrapped with a high-elastic rubber tube, and the upper and lower ends of the rubber tube are tightly connected and fixed to the upper and lower pads, respectively.

3. The multifunctional rock testing system under multi-field coupling conditions according to claim 2, characterized in that: The upper pad of the triaxial test consists of a fixed upper column and a pad body, with the fixed upper column inserted into the top wall of the reaction chamber; the lower pad is a seepage-free and hydraulically fracturing-free lower pad, which consists of a fixed lower column and a pad body, with the fixed lower column inserted into the axial force column connected to the bottom wall of the reaction chamber.

4. The multifunctional rock testing system under multi-field coupling conditions according to claim 2, characterized in that: The hydraulic fracturing test pad consists of a water injection pipe and a pad body. The water injection pipe passes through the central axis of the pad body, and the upper end of the water injection pipe is inserted into the top wall of the reaction chamber and connected to the two-way valve of the reaction chamber through a pipe. The lower end of the water injection pipe is inserted into the pre-drilled hole of the rock sample. The lower pad is a seepage or hydraulic fracturing lower pad, which consists of a permeable grid, a water collection funnel, a pad body, a fixed outer pipe, and a water outlet pipe. The upper end of the pad body is concave to form a water collection funnel. A permeable grid is laid on the upper side of the water collection funnel. The water outlet pipe runs through the fixed outer pipe. The fixed outer pipe and the water outlet pipe pass through the pad body, and their lower ends are connected to the high-pressure valve of the outflowing liquid through a pipe.

5. The multifunctional rock testing system under multi-field coupling conditions according to claim 2, characterized in that: The upper pad for the seepage or seepage heat transfer test consists of an inner injection pipe, an outer injection pipe, a permeable grid, and a pad body. The inner injection pipe runs through the outer injection pipe. The inner and outer injection pipes are inserted into the top wall of the reaction chamber and connected to the double-way valve of the reaction chamber through a pipe. A permeable grid is installed inside the pad body. The lower pad is a seepage or hydraulic fracturing lower pad. The seepage or hydraulic fracturing lower pad consists of a permeable grid, a water collection funnel, a pad body, a fixed outer pipe, and an outlet pipe. The upper end of the pad body is concave to form a water collection funnel. A permeable grid is laid on the upper side of the water collection funnel. The outlet pipe runs through the fixed outer pipe. The fixed outer pipe and the outlet pipe run through the pad body, and their lower ends are connected to the high-pressure valve for the outflowing liquid through a pipe.

6. The multifunctional rock testing system under multi-field coupling conditions according to claim 2, characterized in that: The lower pad is a seepage or hydraulic fracturing lower pad, which consists of a seepage grid, a water collection funnel, a pad body, a fixed outer pipe, and a water outlet pipe. The upper end of the pad body is concave to form a water collection funnel, and a seepage grid is laid on the upper side of the water collection funnel. The water outlet pipe runs through the fixed outer pipe. The fixed outer pipe and the water outlet pipe run through the pad body, and their lower ends are connected to the high-pressure valve of the outflowing liquid through a pipe.

7. The multifunctional rock testing system under multi-field coupling conditions according to claim 3, 4, 5, or 6, characterized in that: The reaction chamber base is equipped with several pulleys on both sides, and the test space bottom wall is equipped with slide tracks on both sides. The pulleys can slide in the slide tracks to push the reaction chamber forward or backward.

8. The multifunctional rock testing system under multi-field coupling conditions according to claim 7, characterized in that: The test space is equipped with condensation pipes on both sides of the bottom. The condensation pipes are connected to the external cooling system. The confining pressure oil flows into the condensation pipes through the oil outlet valve of the reaction chamber, is cooled, and then is recovered to the confining pressure oil circulation system through the confining pressure oil outlet valve.

9. The test method for the multifunctional rock test system under multi-field coupling conditions as described in claim 1, characterized in that... Includes the following steps: Step S1) Processing rock samples Use a rock sample cutting machine to process the rock sample into a cylindrical shape, set pre-fabricated fractures or simulated faults as needed, and drill a certain depth in the center of the rock sample to form a water guide hole. Step S2) Assemble the rock sample The rock sample is clamped between the upper pad and the lower pad with seepage or hydraulic fracturing in the seepage and hydraulic fracturing test, and then put into the high-elasticity rubber sleeve. The two ends of the rubber sleeve are tightly sealed to the upper and lower pads. Several temperature probes and axial and radial strain measuring instruments are installed and adjusted. Step S3) The rock sample is loaded into the reaction chamber. Unlock the inner lock handle to open the test space switch door, push out the reaction chamber through pulleys and slides, and load the high-elastic rubber cylinder containing the rock sample and the upper and lower pads into the reaction chamber; Step S4) Assemble the reaction chamber Push the reaction chamber into the test space, connect the upper end of the fracturing fluid injection pipe to the reaction chamber double valve through a pipe, insert the lower end into the rock sample of the pre-drilled hole, connect the upper end of the chemical solution injection pipe to the reaction chamber double valve through a pipe, and insert the fixing outer pipe of the lower pad block into the fixing hole of the axial force column to fix the rock sample. Step S5) Initialize the system and fix the rock sample Open the remote computer display and control system, start the servo hydraulic press, control the servo hydraulic press through the computer display and control system to push the axial force column upward and monitor the pressure through the connected pressure sensor. First, apply a small axial pressure to the rock sample to fix it. Step S6) Provide confining pressure environment for the rock sample. Close the reaction chamber double-way valve and the reaction chamber oil outlet valve, open the confining pressure oil inlet valve, inject confining pressure oil into the reaction chamber through the confining pressure oil circulation system, and control the amount of confining pressure oil through the computer display and control system to provide a confining pressure environment for the rock sample. Step S7) Provide a high-temperature environment for the rock sample. The high-temperature heating and control system controls the heating wire to heat the confining oil in the reaction chamber, providing a high-temperature environment for the rock sample. Step S8) Provide a triaxial high-pressure environment for the rock sample. The servo hydraulic press is controlled by a computer display and control system to adjust the axial pressure, and combined with the confining pressure provided by the confining pressure oil, a triaxial high-pressure environment is provided to the rock sample. Step S9) Provide the rock sample with a chemical field and osmotic pressure environment. Open the injection liquid high-pressure double-way valve, the reaction chamber double-way valve, and the outflow liquid high-pressure valve. The prepared chemical solution stored in the chemical solution tank is pumped into the chemical solution injection pipe through the injection pump system. Then, it permeates downward into the sample through the permeation grid, forming a uniform osmotic pressure to provide a chemical field environment and osmotic pressure environment for the rock sample. Step S10) Apply water pressure to the rock sample and monitor changes in pressure, temperature, and strain. The fracturing fluid stored in the fracturing fluid tank is injected into the fracturing fluid injection pipe through the injection pump system, thereby applying water pressure to the rock sample until it is broken. The liquid flowing through the rock sample is collected through the water collection funnel in the pad block and discharged to the liquid recovery tank through the water outlet pipe. The injection pressure, temperature and strain changes during this process are recorded and transmitted to the computer display and control system for real-time display and storage. Step S11) Depressurize, cool, and recover confining pressure oil After the test is completed, close the double-way valve of the reaction chamber, open the oil outlet valve and the confining pressure oil outlet valve of the reaction chamber, and release the confining pressure to normal pressure through the confining pressure oil circulation system. Then, the high-temperature hydraulic oil is drawn into the condensation pipe for cooling and then returned to the oil tank of the confining pressure oil circulation system. Step S12) Organize and process data The computer display and control system controls the servo hydraulic press to descend the reaction chamber, open the test space switch door, push the reaction chamber out through pulleys and slides, remove the rock sample, process the data, and conduct the next test.

10. The multifunctional rock testing method under multi-field coupling conditions according to claim 9, characterized in that: If the rock sample does not require hydrostatic testing, step S10 is omitted; if the rock sample does not require osmotic pressure testing, step S9 is omitted; if the rock sample only undergoes triaxial pressure testing, steps S9 and S10 are omitted.

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