CN115165502A

CN115165502A - Preparation method of test rock sample and multi-field coupling test method

Info

Publication number: CN115165502A
Application number: CN202210869746.0A
Authority: CN
Inventors: 林涛; 赵志宏; 张晋通; 王佳铖; 陈进帆
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-07-22
Filing date: 2022-07-22
Publication date: 2022-10-11

Abstract

The invention provides a preparation method of a test rock sample and a multi-field coupling test method, wherein the preparation method of the test rock sample comprises the following steps: selecting stones for preparing the test rock sample; processing the stone block into first and second particles; preparing the first particles into a lower sample; preparing the second particles into an upper sample; stacking the upper sample on the lower sample; drilling two jacks on the upper surface of the upper sample; drilling a plurality of mounting holes on the surface of the test rock sample; based on the technical scheme of the invention, the test rock sample is set into the lower sample and the upper sample which are made of particles with different particle sizes, so that the structural composition of the test rock sample is highly fit with the actual structure of the reservoir rock core. Two receptacles are provided through the top sample in a first direction to accurately simulate the actual seepage of fluid in the reservoir. Temperature and pressure sensors are inserted into the surface of the test rock sample, so that the pressure and temperature data of the test rock sample in the test process can be completely and comprehensively acquired.

Description

Preparation method of test rock sample and multi-field coupling test method

Technical Field

The invention relates to the technical field of dry hot rock reservoir reconstruction and geothermal resource exploitation, in particular to a preparation method of a test rock sample and a multi-field coupling test method.

Background

At present, partial engineering experience is accumulated in deep ground energy exploitation, and the key for mastering the deep ground energy exploitation is to deeply analyze the influence mechanism of the multi-field coupling effect on the development of the deep ground energy.

The temperature and pressure data of the test rock sample acquired by the multi-field coupling test method in the related art are not complete and comprehensive enough. Therefore, the calculated permeability and heat production variation of the rock have larger deviation with actual data, and accurate data support cannot be provided for the research of hot rock reservoir reformation and geothermal resource exploitation.

In other words, the multi-field coupling test method in the related art has the problem that the acquired temperature data and test data of the test rock sample are not complete and comprehensive enough.

Disclosure of Invention

In order to solve the problems in the prior art, the application provides a preparation method of a test rock sample and a multi-field coupling test method, and solves the problem that temperature data and test data of the test rock sample acquired by the multi-field coupling test method are incomplete and comprehensive.

The invention relates to a preparation method of a test rock sample, wherein the test rock sample is a cube and comprises a lower sample and an upper sample arranged on the lower sample, and the preparation method comprises the following steps:

selecting stones for preparing a test rock sample;

step two, processing the stone blocks into first particles and second particles;

wherein the particle size of the first particles is smaller than the particle size of the second particles;

preparing the first particles into a lower sample;

step four, preparing the second particles into an upper sample;

step five, piling the upper sample on the lower sample;

step six, drilling two jacks on the upper surface of the upper sample;

wherein, two jacks penetrate through the upper sample along a first direction, one of the two jacks is used for injecting test fluid, and the other jack is used for extracting the test fluid seeped from the test rock sample;

drilling a plurality of mounting holes on the surface of the test rock sample;

wherein, the mounting hole is used for installing temperature sensor, pressure sensor or temperature and pressure sensor.

In one embodiment, step three specifically includes the following steps:

a first step of making a first granule into a plurality of first cubic units;

in a second step, a plurality of first cubic cells are stacked into a lower sample.

In one embodiment, step four specifically includes the steps of:

a first step of making second particles into a plurality of second cubic units;

in a second step, a plurality of second cubic units are stacked to form an upper sample.

In one embodiment, in step seven, the mounting holes are provided at four corner positions of the surface of the first cubic unit or the second cubic unit constituting the surface of the test rock sample.

In one embodiment, in step six, the central axes of the two insertion holes are located on the first longitudinal center section a of the test rock sample, and the two insertion holes are symmetrically arranged relative to the second longitudinal center section b of the test rock sample.

The invention provides a multi-field coupling test method, which adopts a multi-field coupling test system and a test rock sample prepared by the preparation method, and comprises the following steps:

step one, installing a test rock sample in a multi-field coupling test system;

secondly, preloading the test rock sample through a multi-field coupling test system;

step three, heating and pressurizing the multi-field coupling test system to test temperature and pressure values;

step four, carrying out stress loading on the test rock sample through a multi-field coupling test system;

fifthly, carrying out fracture water injection and water pumping on the test rock sample through a multi-field coupling test system;

and step six, monitoring and processing the test data obtained in the test process through a multi-field coupling test system.

In one embodiment, the multi-field coupling test system comprises a pressure loading device, a fluid injection device, a fluid acquisition device and a data acquisition device, wherein the first step specifically comprises the following steps:

firstly, mounting temperature and pressure sensors of a data acquisition device in a mounting hole of a test rock sample;

secondly, leading out the leads of the temperature and pressure sensors from a test rock sample;

thirdly, installing the test rock sample in a pressure loading device;

fourthly, leading the wires of the temperature and pressure sensors out of the pressure loading device and electrically connecting the wires with a data collector of the data collecting device;

and fifthly, respectively inserting the injection pipe of the injection device and the water pumping pipe of the fluid collection device into the two insertion holes of the test rock sample.

In one embodiment, the multi-field coupling test system further comprises a temperature control device and a gas pressurization device, and the step three specifically comprises the following steps:

firstly, injecting gas into a pressure loading device through a gas pressurizing device for pressurizing;

secondly, heating the temperature in the pressure loading device to a test temperature value through a temperature control device;

thirdly, the temperature in the pressure loading device is constantly kept at a test temperature value through a temperature control device;

and fourthly, enabling the pressure in the pressure loading device to be constantly kept at the test pressure value through the gas pressurizing device.

In one embodiment, step four specifically includes the steps of:

firstly, applying stress in the z-axis direction to a test rock sample at a constant speed through a pressure loading device until the stress value is stable;

secondly, applying stress in the x-axis direction to the test rock sample at a constant speed through a pressure loading device until the stress value is stable;

and thirdly, applying stress in the y-axis direction to the test rock sample at a constant speed through a pressure loading device until the stress value is stable.

In one embodiment, step five specifically includes the following steps:

firstly, injecting liquid into a test rock sample at a constant loading rate through a fluid injection device;

step two, synchronously observing the change of temperature and pressure data in the data acquisition device;

thirdly, when the temperature and pressure data are changed, the injection pressure is kept unchanged;

and fourthly, pumping water to the test rock sample at a constant loading rate through a fluid collecting device.

In one embodiment, step six specifically includes the following steps:

firstly, acquiring stress and displacement data in a test process according to preset interval time by a data acquisition device;

step two, synchronously acquiring liquid injection amount data, water pumping amount data and test rock sample pressure and temperature data through a data acquisition device;

and thirdly, calculating the permeability and the heat extraction quantity of the test rock sample according to the data.

In one embodiment, the permeability of the test rock sample is calculated by a reservoir permeability formula, which is:

where ρ is _f Is the fluid density; s is a water storage coefficient; p is a radical of _f Is the fluid pressure; t is a time variable; kappa is reservoir permeability; μ is the hydrodynamic viscosity; g is the acceleration of gravity; z is a vertical coordinate; q _m Is a source of fluid mass.

Specifically, in one embodiment, the heat of sampling of the test rock sample is calculated by a heat equation:

Q＝C _p,f m(T-T _s )

wherein Q is the heat of collection; c _p,f The specific heat capacity of the fluid under constant pressure; m is the mass of the produced fluid; t is the temperature of the produced fluid; t is a unit of _s Is the temperature of the reservoir rock mass.

The features mentioned above can be combined in various suitable ways or replaced by equivalent features as long as the object of the invention is achieved.

Compared with the prior art, the preparation method of the test rock sample and the multi-field coupling test method provided by the invention at least have the following beneficial effects:

the test rock sample is set into a lower sample and an upper sample which are made of particles with different particle sizes, so that the structure of the test rock sample forms an actual structure which is highly attached to the core of the reservoir. Two jacks penetrate through the upper sample along a first direction, namely the test fluid radiates seepage from the middle part of the crack surface to the periphery, so that the actual seepage condition of the fluid in the reservoir can be accurately simulated. Temperature and pressure sensors are inserted into the surface of the test rock sample, so that the pressure and temperature data of the test rock sample in the test process can be completely and comprehensively acquired. The calculated permeability and the heat collection variable quantity of the rock can be ensured to be more practical in the mode, and accurate data support is further provided for the research of hot rock reservoir transformation and geothermal resource exploitation.

Drawings

The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the accompanying drawings. Wherein:

FIG. 1 shows a schematic of the structure of a multi-field coupling assay system of the present invention;

FIG. 2 is a view showing the assembly of the thermostatic environmental chamber of FIG. 1 and the components attached thereto (along the x-axis);

FIG. 3 is a view showing the assembly of the thermostatic environmental chamber of FIG. 1 and the components attached thereto (along the y-axis);

FIG. 4 shows a connection relationship diagram (axial side view) of a fracture network sample with an injection pipe and a pumping pipe in the invention;

FIG. 5 shows a connection relationship diagram (main view) of a fracture network sample, an injection pipe and a water pumping pipe in the invention;

FIG. 6 shows a method flow diagram of a method of preparing a test rock sample of the present invention;

FIG. 7 shows a method flow diagram of the multi-field coupling assay method of the present invention.

In the drawings, like parts are given like reference numerals. The drawings are not to scale.

Reference numerals:

10. a pressure loading device; 11. a loading box; 121. a loading rod; 13. a pressure plate; 20. a fluid injection device; 21. an injection pipe; 22. an injection pump; 23. a first control valve; 30. a fluid collection device; 31. a water pumping pipe; 32. a suction pump; 33. a second control valve; 40. a data acquisition device; 41. temperature and pressure sensors; 42. a data acquisition unit; 43. a computing terminal; 50. a constant temperature environment box; 51. an inner cavity; 52. a constant temperature cover; 53. a constant temperature box body; 60. a gas pressurizing device; 61. a nitrogen gas cylinder; 62. a booster pump; 63. a high-pressure buffer tank; 64. a pressure reducing valve; 65. a pressurization line; 70. a safety pressure relief device; 71. a pressure sensor; 72. a safety valve; 73. a pressure relief line; 80. a temperature control device; 81. a temperature collector; 82. a temperature controller; 83. a temperature monitor; 90. a shaft cooling device; 91. a shaft cooling chamber; 911. a water inlet; 912. a water outlet; 92. a cover plate; 93. a body; 100. a preheating device; 110. an adhesive; 120. a seal ring; 200. testing a rock sample; 201. a fracture network sample; 2011. an upper sample; 2012. lower sample.

Detailed Description

The invention will be further explained with reference to the drawings.

It should be noted that the test rock sample 200 refers to a crack-containing or complete heat storage sample, which is a cube with a side of 1000 mm. The fracture samples can be divided into single-fracture samples and fracture network samples 201, wherein the single fractures of the single-fracture samples are distributed horizontally, are positioned in the middle of the height of the test rock sample 200 and consist of upper fracture blocks and lower fracture blocks. The fracture network sample 201 (see fig. 4 and 5) may be processed into a regular block by linear cutting or other methods, for example, if a cube with a side length of 250mm is used, 64 identical cubes are required to be piled up to form a model sample, or different types of materials may be cast in place or laid layer by layer to serve as a heat storage sample.

The test rock sample 200 adopted by the multi-field coupling test method is specifically a fracture network sample 201, and the preparation method of the test rock sample 200 is mainly used for preparing the fracture network sample 201.

As shown in fig. 6, the present invention provides a method for preparing a test rock sample, the test rock sample is a cube, the test rock sample includes a lower test specimen 2012 and an upper test specimen 2011 disposed on the lower test specimen 2012, and the preparation method includes:

selecting stones for preparing a test rock sample;

wherein the particle diameter (1-5 mm) of the first particles is smaller than the particle diameter (10-20 mm) of the second particles;

step three, preparing the first particles into a lower sample;

step four, preparing the second particles into an upper sample;

step five, piling the upper sample on the lower sample;

step six, drilling two jacks on the upper surface of the upper sample;

wherein two jacks penetrate through the upper sample along a first direction (z-axis direction), one of the two jacks is used for injecting test fluid, and the other jack is used for extracting the test fluid seeping out of the test rock sample;

step seven, arranging a plurality of mounting holes on the surface of the test rock sample;

wherein the mounting holes are used for mounting temperature and pressure sensors.

According to the steps, the test rock sample is arranged into a lower sample 2012 and an upper sample 2011 which are made of particles with different particle sizes, so that the structural composition of the test rock sample is highly consistent with the actual structure of the reservoir core. Two jacks penetrate through the upper sample 2011 along a first direction (height direction), namely, the test fluid radiates seepage from the middle of a crack surface (a contact surface of the upper sample 2011 and the lower sample 2012) to the periphery, so that the actual seepage condition of the fluid in the reservoir can be accurately simulated. Temperature and pressure sensors are inserted into the surface of the test rock sample 200, so that the pressure and temperature data of the test rock sample 200 in the test process can be completely and comprehensively acquired. By the method, the calculated permeability and the heat collection variable quantity of the rock can be ensured to be more practical, and accurate data support is provided for research of hot rock reservoir transformation and geothermal resource exploitation.

Specifically, in one embodiment, large size stones containing natural minerals at the outmost locations of a certain heat storage and separation area are selected and processed into different particle sizes. The formation with larger size and better pore permeation conditions can be laid with larger size particles (second particles), while the formation with smaller size and poorer pore permeation conditions can be laid with smaller size particles (first particles) to form a 1000X 1000mm sample.

Specifically, in one embodiment, the temperature and pressure sensors mounted on the fracture network specimen 201 are miniature temperature and pressure sensors, i.e., the miniature pressure sensors are integrated with the miniature temperature sensors, and have a smaller volume than the general temperature and pressure sensors, and are mounted in small holes (mounting holes) of the fracture network specimen 201.

Of course, the micro pressure sensor and the micro temperature sensor may be separately installed in the small hole of the fracture network sample 201 according to the actual situation.

Specifically, in one embodiment, the micro temperature and pressure sensor wires are routed out of the test rock sample 200 along the mounting holes, and the port of each mounting hole with the micro temperature and pressure sensors is sealed with a high temperature resistant epoxy.

Specifically, in one embodiment, step three specifically includes the following steps:

a first step of making a first granule into a plurality of first cubic units;

Specifically, in one embodiment, the step four specifically includes the following steps:

a first step of making second particles into a plurality of second cubic units;

Specifically, as shown in FIG. 5, in one embodiment, the first cube cell is the same size as the second cube cell.

Specifically, as shown in fig. 4 and 5, in one embodiment, the number of first cube cells is 32 and the number of second cube cells is 32.

Specifically, as shown in fig. 4 and 5, in one embodiment, in step seven, mounting holes are provided at four corner positions of the surface of the first cubic unit or the second cubic unit constituting the surface of the test rock sample 200.

Specifically, as shown in fig. 4 and 5, in one embodiment, in step six, the central axes of the two insertion holes are located on the first longitudinal center section a of the test rock sample 200, and the two insertion holes are symmetrically arranged with respect to the second longitudinal center section b.

It should be noted that the longitudinal center section is the central axis of the over-test rock sample 200, and the over-test rock sample 200 is parallel to each other at the midpoint of opposite sides, and is a vertical section that bisects the test rock sample 200 in half.

As shown in fig. 7, the present invention further provides a multi-field coupling test method, the multi-field coupling test system includes a pressure loading device 10, a fluid injection device 20, a fluid collection device 30 and a data collection device 40, and the first step specifically includes the following steps:

firstly, mounting temperature and pressure sensors of a data acquisition device in a mounting hole;

thirdly, installing the test rock sample in a pressure loading device;

and fifthly, respectively inserting the injection pipe of the injection device and the water pumping pipe of the fluid collection device into the two jack holes of the test rock sample.

It should be noted that the order of the first to third steps may be adjusted, or the three steps may be performed simultaneously.

Specifically, in one embodiment, step five specifically includes the following steps:

injecting liquid into a test rock sample at a constant loading rate through a fluid injection device;

Specifically, in one embodiment, step six specifically includes the following steps:

the method comprises the following steps that firstly, data of three-way stress and three-way displacement in a test process are collected through a data collecting device according to preset interval time;

Specifically, in one embodiment, the permeability of the test rock sample is calculated by the reservoir permeability formula:

where ρ is _f Is fluid density (kg/m) ³ ) (ii) a S is a water storage coefficient; p is a radical of _f Is the fluid pressure (Pa); t is a time variable(s); kappa is reservoir permeability (m) ² ) (ii) a μ is hydrodynamic viscosity (Pa · s); g is gravity acceleration (m/s) ³ ) (ii) a z is a vertical coordinate; q _m Is a fluid mass source (kg/(m) ³ S)). In the formula, the water storage coefficient S and the reservoir permeability kappa are to be evaluated and can be evaluated through more than two groupsSimultaneously solving an equation to obtain the test; a plurality of temperature and pressure sensors are arranged in the test rock sample, and the pressure field of the whole rock sample can be obtained through interpolation, so that the fluid pressure p _f Can be obtained by a data acquisition device, and the others are all known values.

Q＝C _p,f m(T-T _s )

wherein Q is the heat of collection (J); c _p,f The specific heat capacity of the fluid under constant pressure (J/(kg. K)); m is the mass (kg) of the produced fluid; t is the temperature (K) of the produced fluid; t is _s Is the temperature (K) of the reservoir rock mass. In the formula, the heat quantity Q is to be evaluated; the mass m of the produced fluid can be obtained through the liquid injection amount data in the data acquisition device, and the mass of the fluid can be obtained according to the volume and the density of the liquid recorded by the fluid acquisition device; others are known values.

In addition, the pressure and temperature data obtained by the data acquisition device can be interpolated by methods such as nearest interpolation, cubic spline interpolation and the like to obtain the pressure and temperature field of the whole reservoir; and establishing a model under the same condition in numerical simulation software, wherein the condition comprises the density and permeability of the particle material, the distribution of a fracture network, the boundary mechanical condition of the model, the pressure and temperature of injection port fluid and the like, and obtaining the pressure and temperature field of the reservoir through finite element calculation, so that the pressure and temperature field is compared with the numerical calculation results of the pressure sensor and the temperature sensor in the test result, and the verification and the comparison are carried out.

As shown in fig. 1 to 3, the present invention provides a multi-field coupling test system, which comprises a pressure loading device 10, a fluid injection device 20, a fluid collection device 30 and a data collection device 40. The test rock sample 200 is mounted on the pressure loading device 10, the pressure loading device 10 can apply pressure to the test rock sample 200, the fluid injection device 20 is connected with the test rock sample 200, and the fluid injection device 20 is used for injecting liquid into the test rock sample 200. The fluid collection device 30 is connected with the test rock sample 200, the fluid collection device 30 is used for collecting liquid flowing out of the test rock sample 200, the data collection device 40 is connected with the test rock sample 200, the fluid injection device 20 and the fluid collection device 30, and the data collection device 40 is used for collecting temperature and pressure data of the test rock sample 200, the fluid injection device 20 and the fluid collection device 30.

In the above arrangement, the data acquisition device 40 is connected to the test rock sample 200, the fluid injection device 20 and the fluid acquisition device 30, and the data acquisition device 40 can synchronously acquire temperature and pressure data of the test rock sample 200, the fluid injection device 20 and the fluid acquisition device 30 in a multi-field coupling test. Therefore, the acquired temperature and pressure data are comprehensive and complete, so that the subsequent permeability and heat collection variable quantity of the rock can be accurately calculated, the calculated permeability and heat collection variable quantity of the rock are more practical, and accurate data support is provided for the research of hot rock reservoir transformation and geothermal resource exploitation.

Specifically, as shown in FIG. 1, in one embodiment, data collection device 40 includes temperature and pressure sensors 41, a data collector 42, and a computing terminal 43. Wherein, the temperature and pressure sensors 41 are respectively arranged on the test rock sample 200, the fluid injection device 20 and the fluid acquisition device 30, and the data acquisition device 42 is electrically connected with the temperature and pressure sensors 41. The calculation terminal 43 is electrically connected with the data collector 42, the data collector 42 is used for collecting monitoring data of the temperature and pressure sensor 41, and the calculation terminal 43 is used for processing the monitoring data collected by the data collector 42.

In the multi-field coupling test, the temperature and pressure sensors 41 can simultaneously acquire temperature and pressure data of the test rock sample 200, the fluid injection device 20 and the fluid acquisition device 30. Thus, the collected temperature and pressure data are comprehensive and complete. The data collector 42 can input the collected test data into the computing terminal 43 for computation, and finally the permeability and the heat collection variation of the rock are obtained.

Specifically, as shown in fig. 1 to 3, in one embodiment, the pressure loading device 10 includes a loading box 11 and a press. Wherein, the test rock sample 200 is installed in the loading case 11, and the press setting is in the outside of loading case 11, and the press can exert pressure to loading case 11, and loading case 11 can transmit pressure to test rock sample 200.

Specifically, as shown in fig. 1-3, in one embodiment, the press is a servo controlled rock tri-axial tester. Which can simultaneously apply pressure to the loading box 11 in three directions of x-axis, y-axis and z-axis, and the loading box 11 can simultaneously transmit the pressure in the three directions to the test rock sample 200.

It should be noted that the servo-controlled rock triaxial tester can apply normal stress (z axis) and tangential stress in two directions (x and y axes) respectively at a constant displacement rate or a force loading rate, and is simultaneously equipped with data monitoring equipment (which can be integrated in the data acquisition device 40, that is, the data acquisition device 40 further comprises force and displacement sensors for monitoring force and displacement changes of the loading rod 121), wherein the force and displacement sensors can record normal/tangential force and displacement changes in the experimental process in real time.

Specifically, as shown in fig. 1 to 3, in one embodiment, the press machine includes three loading rods 121, and the pressure loading device 10 further includes three pressure plates 13, the three pressure plates 13 are respectively disposed on three outer wall surfaces of the loading box 11, and the pressure plates 13 are located between the loading rods 121 and the loading box 11.

In the above arrangement, the pressure plate 13 is arranged to prevent the loading box 11 from being damaged by the direct contact between the loading rod 121 and the loading box 11, so that the problem that the loading box 11 needs to be replaced as a whole after being damaged by the loading rod 121 is avoided, and the use and maintenance costs of the multi-field coupling test system are saved.

Specifically, as shown in fig. 1 to 3, in one embodiment, the loading box 11 is composed of a plurality of loading plates, wherein adjacent loading plates are slidably connected, so that when the servo-controlled rock triaxial tester applies pressure to the loading box 11 in three directions of x-axis, y-axis and z-axis, the corresponding three loading plates can be pressed against three outer surfaces of the test rock sample 200 and apply pressure to the test rock sample 200.

Specifically, as shown in fig. 1-3, in one embodiment, the fluid injection apparatus 20 includes an injection tube 21, an injection pump 22, and a first control valve 23. Wherein one end of the injection pipe 21 is inserted into the test rock sample 200, the injection pump 22 is communicated with the other end of the injection pipe 21, and the first control valve 23 is provided on the injection pipe 21 for controlling the pressure of the injection pipe 21.

In the above arrangement, the test fluid can be injected into the test rock sample 200 by the injection pump 22 to cause the fluid to flow radiantly within the fissures of the test rock sample 200. The injection pipe 21 can inject the test fluid into a preset injection position in the test rock sample 200, and the first control valve 23 can control the injection pressure of the injection pipe 21.

Specifically, as shown in fig. 2, in one embodiment, the connection of the injection tube 21 to the test rock sample 200 is provided with an adhesive 110 for securing and sealing the injection tube 21.

Specifically, in one embodiment, the infusion pump 22 is a high precision infusion pump.

Specifically, in one embodiment, the first control valve 23 employs a pressure reducing valve.

Specifically, as shown in FIG. 1, in one embodiment, a set of temperature and pressure sensors 41 of the data acquisition device 40 are connected to the injection tube 21 for monitoring the injection temperature and injection pressure of the test fluid within the injection tube 21.

Specifically, as shown in fig. 1, in one embodiment, the multi-field coupling test system further includes a preheating device 100, the preheating device 100 is disposed on the injection pipe 21 of the fluid injection device 20, and the preheating device 100 is used for heating the test fluid in the injection pipe 21.

Specifically, in one embodiment, the preheating device 100 is a preheater.

Specifically, as shown in FIG. 1, in one embodiment, the fluid collection device 30 includes a suction tube 31, a suction pump 32, and a second control valve 33. Wherein, one end of the pumping pipe 31 is inserted into the test rock sample 200, the suction pump 32 is communicated with the other end of the pumping pipe 31, and the second control valve 33 is arranged on the pumping pipe 31 and used for controlling the pressure of the pumping pipe 31.

In the above arrangement, the water suction pipe 31 is inserted into a predetermined water suction position in the test rock sample 200 to be able to suck the test fluid in the test rock sample 200, and the second control valve 33 has a back pressure function to be able to control the flow pressure of the test fluid in the water suction pipe 31. The suction pump 32 can not only increase the suction pressure for the suction pipe 31 but also measure the flow rate of the test fluid in the suction pipe 31.

Specifically, as shown in fig. 2, in one embodiment, the joint of the pumping tube 31 and the test rock sample 200 is provided with an adhesive 110 for fixing and sealing the pumping tube 31.

Specifically, in one embodiment, the second control valve 33 employs a backpressure valve.

Specifically, in one embodiment, the extraction pump 32 is a high precision extraction pump.

Specifically, as shown in fig. 1, in one embodiment, a set of temperature and pressure sensors 41 of the data acquisition device 40 are connected to the suction tube 31 for monitoring the infusion temperature and infusion pressure of the test fluid within the suction tube 31.

Specifically, in one embodiment, the fluid collection device 30 further includes a chiller disposed on the suction line 31 between the draw pump 32 and the second control valve 33. In the test process, the test fluid injected into the test rock sample 200 flows to the four sides of the fracture in a radiation mode and flows out of the test rock sample 200 through the water pumping pipe 31, due to the pressure limitation of the backpressure valve, the test fluid is liquid, and the flow can be measured through the high-precision extraction pump after being cooled by the cooler.

Specifically, as shown in fig. 1 to 3, in one embodiment, the multi-field coupling test system further includes a constant temperature environment box 50, the loading box 11 is disposed in the constant temperature environment box 50, and the loading rod 121 is telescopically disposed on the constant temperature environment box 50.

Specifically, as shown in fig. 1 to 3, in one embodiment, three loading rods 121 are respectively inserted into the thermostatic environmental chamber 50 in a telescopic manner from three directions, i.e., x-axis, y-axis and z-axis.

Specifically, as shown in fig. 1 to 3, in one embodiment, a sealing ring 120 is provided between the load lever 121 and the thermostatic environmental chamber 50 for sealing.

Specifically, as shown in fig. 1, in one embodiment, the multi-field coupling test system further includes a temperature control device 80, and the temperature control device 80 is in communication with the inner cavity 51 of the constant temperature environment box 50 for controlling the temperature of the inner cavity 51.

Specifically, as shown in fig. 1, in one embodiment, the temperature control device 80 includes a temperature collector 81, a temperature controller 82, and a temperature monitor 83.

Wherein, the temperature controller 82 and the temperature monitor 83 are electrically connected with the temperature collector 81. The temperature monitor 83 is used to monitor the internal temperature of the thermostatic-environment tank 50, and the temperature controller 82 is used to control the internal temperature of the thermostatic-environment tank 50.

Specifically, as shown in fig. 1, in one embodiment, the multi-field coupling test system further includes a gas pressurizing device 60, and the gas pressurizing device 60 is communicated with the inner cavity 51 of the constant temperature environment box 50 and is used for pressurizing the inner cavity 51.

Specifically, as shown in fig. 1, in one embodiment, the gas pressurizing means 60 includes a nitrogen gas cylinder 61, a pressure reducing valve 64, a pressurizing pump 62, a high-pressure buffer tank 63, and a pressurizing line 65. Among them, a nitrogen gas cylinder 61, a pressure reducing valve 64, a pressurizing pump 62, and a high-pressure buffer tank 63 are provided on a pressurizing line 65. The nitrogen gas cylinder 61 supplies an inert gas into the inner chamber 51, and thus the gas injection pressure of the inner chamber 51 can be adjusted by the pressure reducing valve 64 and the pressurizing pump 62, and the high-pressure buffer tank 63 ensures the stability of the injection gas pressure. The injected gas pressure provides a high pressure environment for the constant temperature environment box 50, so that the injected test fluid in the constant temperature environment box 50 under the action of high temperature can be ensured not to be gasified, and the permeability of the cracks of the test rock sample 200 can be stably measured.

Specifically, as shown in FIG. 1, in one embodiment, a set of temperature and pressure sensors 41 of the data acquisition device 40 are connected to the pressurization line 65 for acquiring the pressure and temperature of the gas within the pressurization line 65.

Specifically, as shown in fig. 1, in one embodiment, the multi-field coupling test system further includes a safety pressure relief device 70, where the safety pressure relief device 70 is communicated with the inner cavity 51 of the constant temperature environment box 50, and is used for controlling the pressure of the inner cavity 51 not to exceed a preset safety pressure value.

Specifically, as shown in FIG. 1, in one embodiment, the safety relief device 70 includes a relief line 73, a pressure sensor 71, and a safety valve 72.

The pressure sensor 71 is disposed on the pressure relief line 73, one end of the pressure relief line 73 extends into the thermostatic environmental chamber 50 to communicate with the inner chamber 51 thereof, and the safety valve 72 communicates with the other end of the pressure relief line 73.

When the gas pressure in the constant temperature environment box 50 exceeds the rated pressure value, the safety valve 72 is opened, so that the pressure in the constant temperature environment box 50 is unloaded, and the safety of the test process is further ensured.

Specifically, as shown in fig. 1 to 3, in one embodiment, the multi-field coupling test system further includes a shaft cooling device 90, and the shaft cooling device 90 is disposed on an outer circumference of the loading bar 121 for cooling the loading bar 121.

Specifically, as shown in fig. 1 to 3, in one embodiment, the shaft cooling device 90 has a shaft cooling cavity 91, the loading rod 121 is partially located in the shaft cooling cavity 91, and the shaft cooling cavity 91 is provided with cooling water for cooling the loading rod 121.

Specifically, as shown in fig. 1 to 3, in one embodiment, the constant temperature environment tank 50 includes a constant temperature tank body 53 and a constant temperature cover 52 that covers the constant temperature tank body 53.

A seal ring 120 is provided between the lower end of the thermostatic cover 52 and the thermostatic box 53, and the seal ring 120 is used to seal a gap between the thermostatic cover 52 and the thermostatic box 53. The upper end of the constant temperature cover 52 is provided with a shaft cooling cavity 91, a loading rod 121 arranged along the z axis is telescopically arranged in the shaft cooling cavity 91, the upper end cover of the constant temperature cover 52 is provided with a cover plate 92, and a sealing ring 120 is arranged between the cover plate 92 and the upper end of the constant temperature cover 52 for sealing. A seal ring 120 is provided between the load lever 121 and the thermostat case 53 and the thermostat cover 52 for sealing. The shaft cooling chamber 91 is provided with a water inlet 911 and a water outlet 912, so that cooling water is continuously introduced into the shaft cooling chamber 91 to continuously cool the loading rod 121, thereby improving the cooling capacity of the shaft cooling device 90.

Specifically, as shown in fig. 1 to 3, in one embodiment, a body 93 is disposed on one side of the thermostat box 53 along the x-axis direction, one side of the body 93 is fixedly connected to the thermostat box 53, a shaft cooling chamber 91 is disposed on the other side of the body 93, and a loading rod 121 disposed along the x-axis is telescopically disposed in the shaft cooling chamber 91. A cover plate 92 is provided on one side of the body 93, and a seal ring 120 is provided between the cover plate 92 and the body 93 for sealing. A sealing ring 120 is provided between a load bar 121 disposed along the x-axis and the cover plate 92 and the body 93 for sealing. The shaft cooling chamber 91 is provided with a water inlet 911 and a water outlet 912, so that cooling water is continuously introduced into the shaft cooling chamber 91 to continuously cool the loading rod 121, thereby improving the cooling capacity of the shaft cooling device 90.

Specifically, in one embodiment, a body 93 is disposed on one side of the thermostat housing 53 along the y-axis direction, one side of the body 93 is fixedly connected to the thermostat housing 53, a shaft cooling chamber 91 is disposed on the other side of the body 93, and a loading rod 121 disposed along the y-axis is telescopically disposed in the shaft cooling chamber 91. A cover plate 92 is provided on one side of the body 93, and a seal ring 120 is provided between the cover plate 92 and the body 93 for sealing. A sealing ring 120 is provided between a loading rod 121 provided along the y-axis and the cover plate 92 and the body 93 for sealing. The shaft cooling chamber 91 is provided with a water inlet 911 and a water outlet 912, so that cooling water is continuously introduced into the shaft cooling chamber 91 to continuously cool the loading rod 121, thereby improving the cooling capacity of the shaft cooling device 90.

A complete embodiment of the present application is described below in conjunction with fig. 1-7:

the invention provides a multi-field coupling test system for deep ground energy engineering, which comprises a servo control rock triaxial tester, a gas pressurizing device 60, a fluid injection device 20, a fluid acquisition device 30, a temperature control device 80, a data acquisition device 40 and a safety pressure relief device 70.

Specifically, the constant temperature environment box 50 has an inner cavity (inner cavity 51) for accommodating a test rock sample, an axial loading lever (a loading rod 121 penetrating along the z-axis direction) is installed on the upper portion, an overhanging frame (a body 93) is installed on the front surface and one side of the lower portion, and a tangential loading rod (a loading rod 121 arranged along the x-axis direction or the y-axis direction) is installed in the overhanging frame. One side of the axial load bar and the two tangential load bars extend into the inner cavity, while the other side is exposed to the thermostatic environmental chamber 50. The servo-controlled rock triaxial testing machine can control the axial loading rod and the tangential loading rod to apply true triaxial stress loading to the test rock sample 200.

Specifically, the temperature control device 80 includes a temperature controller 82 and a temperature monitor 83. Both of them are extended into the cavity from the outside of the constant temperature environment box 50, wherein the temperature controller 82 can heat the air in the constant temperature environment box 50, so that the test rock sample 200 in the cavity is in a high temperature environment, and the temperature monitor 83 can dynamically monitor the temperature change of the rock sample in the constant temperature environment box 50.

Specifically, water pressure is applied to the middle position of the test rock sample 200 through the injection pipe 21 in the constant temperature environment tank 50, and the water pumping pipe 31 pumps water from the test rock sample 200. The preheater can heat the injected fluid, and the temperature adjustment range is 25-400 ℃.

Specifically, the fluid collecting device 30 can collect and measure the water output of the pumping hole of the test rock sample 200 during the test process. The fluid collection device 30 is composed of a cooler, a back pressure valve, and a high-precision pump, respectively. During the test, the test fluid injected from the injection holes of the test rock sample 200 flows radially to the four sides of the fracture.

Specifically, the gas pressurizing means includes a nitrogen gas cylinder 61, a pressure reducing valve 64, a pressurizing pump 62, and a high-pressure buffer tank 63. The nitrogen gas cylinder 61 can provide inert gas into the cavity body, so that the gas injection pressure of the cavity body can be adjusted through the pressure reducing valve 64 and the booster pump 62, and the high-pressure buffer tank 63 can ensure that the injection gas pressure is stable. The injected gas pressure provides a high pressure environment for the constant temperature environment box 50, so that the injected water flow in the cavity under the action of high temperature can be ensured not to be gasified, and the fracture permeability of the test rock sample can be stably measured.

The temperature and pressure sensors installed on the fracture network sample 201 in the application are micro temperature and pressure sensors, namely the micro pressure sensors and the micro temperature sensors are integrated together, the size of the temperature and pressure sensors is smaller than that of the general temperature and pressure sensors, and the temperature and pressure sensors are installed in a small hole of the upper sample 2011.

Of course, the micro pressure sensor and the micro temperature sensor may be separately installed in the small hole of the upper sample 2011 according to actual conditions. When the micro pressure sensor and the micro temperature sensor are separately arranged, the micro temperature sensor can be installed in the pores distributed in a cross shape inside the upper sample 2011 of the fracture network sample 201. The wires of the micro temperature sensor are led out from the wire groove drilled in the upper sample 2011 and led out through the hole dug in the top surface of the constant temperature environment box 50, and are connected to the data acquisition unit 42. The small holes, wire guides and openings in the top surface of the thermostatic environment chamber 50 inside the upper sample 2011 are all sealed with high temperature resistant epoxy. Similarly, the micro pressure sensors are installed in the small holes distributed in a cross shape inside the upper sample 2011 of the fracture network sample 201. The wires of the micro pressure sensor are led out from the wire groove drilled in the upper sample 2011 and led out from the holes dug in the top surface of the constant temperature environment box 50, and are connected to the data acquisition unit 42. The small holes, wire guides and openings in the top surface of the thermostatic environment chamber 50 inside the upper sample 2011 are all sealed with high temperature resistant epoxy.

Specifically, the safety relief device 70 includes a safety valve 72 and a pressure sensor 71. The relief valve 72 is installed at a side of the thermostatic chamber 50 to communicate with the inside of the thermostatic chamber 50. When the gas pressure in the thermostatic environmental chamber 50 exceeds the rated pressure value, the safety valve 72 is opened to unload the pressure in the thermostatic environmental chamber 50, thereby ensuring the safety of the test process.

Specifically, an axial cooling chamber (shaft cooling chamber 91) is bolted to the upper end of the axial loading rod, and a horizontal cooling chamber (shaft cooling chamber 91) is bolted to the outside of the tangential loading rod and the outside of the elongated frame.

Compared with the prior art, the multi-field coupling test device for the deep ground energy engineering can realize true triaxial stress loading, a real-time high-temperature control system and water injection and pumping well forms, and is more suitable for the process of mining the deep ground energy in real engineering.

The following illustrates the preparation and test methods used in the present application:

1. and (5) preparing a test rock sample.

Selecting large-size stones containing natural outcrop parts of a certain thermal storage and selection area, processing the stones into large-particle and small-particle sizes, firstly laying small-particle materials on the lower half part of a sample box, and then laying large-particle materials on the upper part of the sample box. The samples were stacked to form test rock samples of 1000X 1000 mm. In the experimental rock specimen installation constant temperature environment case to place cushion (pressure plate) in three orientations at corresponding position, conveniently adopt axial loading pole, tangential loading pole (along the x axle) and tangential loading pole (along the y axle) to exert three-dimensional stress to it. Two small holes with the diameter of 3mm and the length of 500mm are drilled in the upper surface block of the test rock sample and are respectively used for installing an injection pipe and a water pumping pipe, and then installation small holes (located at four corner positions of a first cubic unit or a second cubic unit on the surface of the test rock sample 200) used for installing miniature temperature and pressure sensors are arranged at the corner positions of each small square of the test rock sample 200. Then, the miniature temperature and pressure sensors are placed in each mounting hole, the miniature temperature and pressure sensor leads are led out to the outside of the test rock sample along the mounting holes, and the port of each mounting hole in the test rock sample is sealed by high-temperature-resistant epoxy resin.

2. And (5) installing the test rock sample.

The test rock sample and the cushion block at the lower part are arranged in the positioning groove of the loading box, the lead of the miniature temperature and pressure sensor is led out along the outlet of the miniature temperature and pressure sensor arranged on the upper wall surface of the constant temperature environment box, the outlet is sealed by adopting high temperature resistant epoxy resin, and the lead is connected to the data acquisition unit. And respectively inserting an injection pipe and a water pumping pipe into the test rock sample, wherein the injection pipe is connected with a temperature sensor, a pressure sensor and a preheater and finally connected with a high-precision injection pump, and the water pumping pipe is connected with a high-precision extraction pump. Spacers were then placed on the top and sides of the test rock sample. The interface of the constant temperature environment box is formed by flange connection, and the joint can be sealed by combining a high temperature resistant O-shaped sealing ring (a sealing ring 120) and a copper ring.

3. The instrument is prepared.

The well-installed loading box is placed in a servo control rock triaxial tester, and the servo control rock tester applies a pre-normal stress to an axial loading rod installed in the loading box, so that the axial loading rod moves and is connected with an upper cushion block of the loading box. And applying pre-cutting stress to a tangential loading rod (x-axis direction) and a tangential loading rod (y-axis direction) of the loading box through a servo control rock triaxial testing machine, and sealing the axial loading rod, the tangential loading rod (x-axis direction) and the tangential loading rod (y-axis direction) with a constant temperature environment box by adopting high temperature resistant O-shaped rings (sealing rings 120). An axial cooling chamber is arranged on the constant temperature environment box through bolts, a horizontal cooling chamber is arranged on the outer side of the tangential loading rod through bolts, cold water enters from a water inlet of the horizontal cooling chamber and flows out from a water outlet, and cooling of the tangential loading rod and the sealing ring can be realized through dynamic water cooling circulation. Similarly, the outside of the constant temperature environment box is also provided with an axial cooling chamber through a bolt, cold water flows in from a water inlet of the axial cooling chamber and flows out from a water outlet of the axial cooling chamber, and the dynamic water cooling circulation can realize the cooling of the axial loading rod and the sealing ring.

4. And heating and pressurizing the constant temperature environment box.

Open the nitrogen cylinder and fill into nitrogen gas to the cavity of constant temperature environment case, open temperature control system after that, heat the nitrogen gas in the cavity through temperature controller, keep the constancy of temperature when the temperature adds to the settlement temperature 90 degrees, and then can realize the holistic high temperature environment of loading box, the temperature can be monitored by temperature monitor in real time in the cavity of intensification in-process. And the pressure reducing valve and the booster pump are regulated to inflate and pressurize the constant-temperature environment box, so that the pressure in the constant-temperature environment box is kept unchanged at 9 MPa. The safety pressure value of the safety valve is set to 10MPa.

5. And (4) stress loading.

And starting the servo control rock triaxial testing machine, applying normal stress to 20MPa at a constant speed of 0.02MPa/s, and then stably keeping. Applying shear stress: applying shear stress at a constant shear stress loading rate of 0.02MPa/s, and keeping the shear stress for 4 hours after the shear stress reaches 20MPa, so that the test piece is fully heated in a high-temperature environment.

6. Injecting water into the crack and pumping water.

Starting a preheater and setting the injection temperature of fluid to be 60 ℃, then starting a high-precision injection pump to increase water pressure from an injection pipe to the bottom of the test rock sample at a constant loading rate of 0.01MPa/s, synchronously observing the numerical conditions of each temperature and pressure sensor, and maintaining the water pressure unchanged when the pressure of each temperature and pressure sensor is obviously changed. And starting the high-precision extraction pump to pump water to the test rock sample at a constant loading rate of 0.01MPa/s through the water pumping pipe, and continuously increasing the water pressure of the high-precision injection pump at a constant loading rate of 0.01MPa/s so as to repeatedly perform the test.

Because the temperature and the pressure in the loading box are respectively 90 ℃ and 20MPa, the water under the pressure of 90 ℃ and 9MPa can not be gasified according to the saturated vapor pressure of the water under different temperatures, so the water flow is radiated and seeped from the middle part of the crack surface to the periphery, and then is collected in the water grooves on each edge of the test rock sample, and then flows out from the water pumping pipe. The flow 7 of the outlet water can be directly calculated according to the data of the high-precision extraction pump, and the data monitoring treatment is carried out.

The changes of normal stress and shear stress and changes of normal direction and shear displacement in the test process are collected according to 3s time intervals, the flow of a high-precision injection pump and a water suction pump, the temperature and pressure changes of a miniature temperature sensor and a miniature pressure sensor and the like in the test process are synchronously collected, and the permeability and the heat collection amount in the test process are calculated according to data. The test is now complete.

For the seepage process in the reservoir and the thermal convection-conduction process in the reservoir; the process of seepage in the reservoir is described using the following expression:

wherein ρ _f Is fluid density (kg/m) ³ ) (ii) a S is a water storage coefficient; p is a radical of _f Is the fluid pressure (Pa); t is a time variable(s); kappa is reservoir permeability (m) ² ) (ii) a μ is hydrodynamic viscosity (Pa · s); g is gravity acceleration (m/s) ³ ) (ii) a z is a vertical coordinate; q _m Is a fluid mass source (kg/(m) ³ S)). In the formula, the water storage coefficient S and the reservoir permeability kappa are to be evaluated, and the fluid pressure p _f Can be obtained by a data acquisition device, and the others are all known values.

Q＝C _p,f m(T-T _s )

wherein Q is the heat of collection (J); c _p,f The specific heat capacity of the fluid under constant pressure (J/(kg. K)); m is the mass (kg) of the produced fluid; t is the temperature (K) of the produced fluid; t is _s Is the temperature (K) of the reservoir rock mass. In the formula, the heat quantity Q is to be evaluated, the mass m of the produced fluid can be obtained through a data acquisition device, and the others are known values.

In addition, the pressure and temperature data obtained by the data acquisition device can be interpolated to obtain the pressure and temperature field of the whole reservoir, so that the pressure and temperature field can be verified and compared with the result obtained by numerical simulation under the same condition.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims

1. A method of preparing a test rock sample, the test rock sample being a cube, the test rock sample including a lower sample and an upper sample disposed on the lower sample, the method comprising:

selecting stones for preparing the test rock sample;

wherein the first particles have a particle size smaller than that of the second particles;

preparing the first particles into the lower sample;

preparing the second particles into the upper sample;

step five, stacking the upper sample on the lower sample;

sixthly, drilling two jacks on the upper surface of the upper sample;

wherein the two receptacles extend through the upper test specimen in a first direction, one of the two receptacles being for injecting a test fluid and the other of the two receptacles being for withdrawing the test fluid seeping from the test rock specimen;

drilling a plurality of mounting holes on the surface of the test rock sample;

wherein, the mounting hole is used for mounting a temperature sensor, a pressure sensor or a temperature and pressure sensor.

2. The method for preparing a test rock sample according to claim 1, wherein the third step specifically comprises the steps of:

a first step of making the first granules into a plurality of first cubic units;

and secondly, stacking a plurality of the first cubic units to form the lower sample.

3. The method for preparing a test rock sample according to claim 2, wherein the fourth step specifically comprises the steps of:

a first step of making the second granules into a plurality of second cubic units;

and secondly, stacking a plurality of second cubic units to form the upper sample.

4. The method of preparing a test rock sample according to claim 3, wherein in the seventh step, the mounting holes are provided at four corner positions of the surface of the first cubic unit or the second cubic unit constituting the surface of the test rock sample.

5. The method for preparing a test rock sample according to any one of claims 1 to 4, wherein, in step six, central axes of two of the insertion holes are located on a first longitudinal central section a of the test rock sample, and the two insertion holes are symmetrically arranged with respect to a second longitudinal central section b of the test rock sample.

6. A multi-field coupling test method using a multi-field coupling test system and a test rock sample prepared by the preparation method of any one of claims 1 to 5, the multi-field coupling test method comprising:

step one, installing the test rock sample in the multi-field coupling test system;

step two, preloading is carried out on the test rock sample through the multi-field coupling test system;

step four, carrying out stress loading on the test rock sample through the multi-field coupling test system;

step five, performing fracture water injection and water pumping on the test rock sample through the multi-field coupling test system;

and step six, monitoring and processing the test data obtained in the test process through the multi-field coupling test system.

7. The multi-field coupling test method according to claim 6, wherein the multi-field coupling test system comprises a pressure loading device, a fluid injection device, a fluid collection device and a data collection device, and the first step specifically comprises the following steps:

firstly, mounting temperature and pressure sensors of the data acquisition device in mounting holes of the test rock sample;

secondly, leading out the leads of the temperature and pressure sensors from the test rock sample;

thirdly, mounting the test rock sample in the pressure loading device;

8. The multi-field coupling test method according to claim 7, wherein the multi-field coupling test system further comprises a temperature control device and a gas pressurization device, and the third step specifically comprises the following steps:

a first step of injecting gas and pressurizing to the pressure loading device through the gas pressurizing device;

secondly, heating the temperature in the pressure loading device to a test temperature value through the temperature control device;

a third step of keeping the temperature in the pressure loading device at the test temperature value constantly through the temperature control device;

9. The multi-field coupling test method according to claim 7, wherein the fourth step specifically comprises the steps of:

the method comprises the following steps that firstly, z-axis direction stress is applied to a test rock sample at a constant speed through a pressure loading device, and the test rock sample is kept stable after the stress is applied to the test rock sample to a test stress value;

secondly, applying stress in the x-axis direction to the test rock sample at a constant speed through the pressure loading device until the stress value is stable;

and thirdly, applying stress in the y-axis direction to the test rock sample at a constant speed through the pressure loading device until the stress value is stable.

10. The multi-field coupling test method according to claim 7, wherein the step five specifically comprises the steps of:

a first step of injecting the test rock sample with a constant loading rate by the fluid injection device;

and fourthly, pumping water to the test rock sample at a constant loading rate through the fluid collecting device.

11. The multi-field coupling test method according to claim 7, wherein the sixth step specifically comprises the steps of:

firstly, acquiring stress and displacement data in a test process according to preset interval time through the data acquisition device;

step two, synchronously acquiring liquid injection amount data, water pumping amount data and the pressure and temperature data of the test rock sample through the data acquisition device;

12. The multi-field coupling test method according to claim 11, wherein the permeability of the test rock sample is calculated by a reservoir seepage formula, the reservoir seepage formula being:

where ρ is _f Is the fluid density; s is a water storage coefficient; t is a time variable; p is a radical of _f Is the fluid pressure; kappa is reservoir permeability; μ is the hydrodynamic viscosity; g is the acceleration of gravity; z is a vertical coordinate; q _m Is a source of fluid mass.

13. The multi-field coupling test method according to claim 11, wherein the heat quantity of the test rock sample is calculated by a heat quantity formula, wherein the heat quantity formula is as follows:

Q＝C _p,f m(T-T _s )

wherein Q is the heat of collection; c _p,f The specific heat capacity of the fluid under constant pressure; m is the mass of the produced fluid; t is the temperature of the produced fluid; t is _s Is the temperature of the reservoir rock mass.