Non-isothermal true triaxial multiphase seepage fracturing test system

Abstract

The invention relates to the technical field of true triaxial tests, and discloses a non-isothermal true triaxial multiphase seepage fracturing test system which comprises a multiphase fluid preparation subsystem, a true triaxial test subsystem and a metering subsystem. The multiphase fluid preparation subsystem comprises a liquefying device, a liquid phase output device and a mixed temperature control device, and outlets of the liquefying device and the liquid phase output device are communicated with an inlet of the mixed temperature control device; the true triaxial test subsystem comprises a cavity in which a test sample can be arranged, a loading device capable of applying loading forces to the test sample in the horizontal transverse direction, the horizontal longitudinal direction and the axial direction, and a heating device capable of controlling the temperature in the cavity; the cavity is provided with an inlet communicated with an outlet of the mixed temperature control device and an outlet communicated with an inlet of the metering subsystem. The test system provided by the invention can provide a test environment highly matched with an actual stratum for deep rock characteristic research.

Description

Technical Field

[0001] This invention relates to the field of true triaxial testing technology, and in particular to a non-isothermal true triaxial multiphase flow fracturing test system. Background Technology

[0002] Deep rock and soil space development and resource utilization is a current research hotspot in the energy and engineering fields, encompassing key technological directions such as reservoir rock fracturing and permeability enhancement, gas-water / oil multiphase flow and displacement, gas-water-rock interaction testing, and shale gas development and utilization. These engineering and resource development processes generally involve complex thermo-hydraulic-mechanical multi-field coupling effects. The coupling between multiple phases in these thermo-hydraulic-mechanical fields directly affects development efficiency and engineering stability, and is a core factor determining technological feasibility. However, existing thermo-hydraulic-mechanical multi-field multiphase coupling tests rely on the combined operation of triaxial testing equipment and seepage testing equipment. This testing mode places extremely high demands on the accuracy of stress loading, the stability of temperature control, and the ability to simultaneously acquire multiple parameters during the testing process.

[0003] Traditional triaxial flow-mechanism coupling test apparatuses suffer from three main problems in simulating complex working conditions: First, the application of confining pressure using an isobaric loading mode, where the horizontal and longitudinal confining pressures are of equal magnitude, fails to reproduce the actual three-dimensional unequal stress field experienced by the formation rock, leading to a deviation between the simulated test conditions and real working conditions, thus affecting the test results. Second, the apparatus lacks sufficient fluid phase control capability and adaptability design for supercritical fluids such as supercritical CO2, making it impossible to conduct flow characteristic tests on such fluids and limiting the research of the apparatus in the field of supercritical fluids. Third, the temperature of the test sample and the temperature of the injected fluid cannot be independently controlled, making it difficult to accurately complete key tests such as the study of rock permeability under non-isothermal conditions and the analysis of fracturing mechanisms, thus hindering the exploration of complex temperature-flow-mechanism coupling effects. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a non-isothermal true triaxial multiphase flow fracturing test system.

[0005] This invention provides a non-isothermal true triaxial multiphase flow fracturing test system, comprising a multiphase fluid preparation subsystem capable of preparing multiphase test fluid, a true triaxial test subsystem capable of conducting non-isothermal true triaxial multiphase flow fracturing tests, and a metering subsystem capable of measuring gas and liquid flow rates. The multiphase fluid preparation subsystem includes a liquefaction device capable of liquefying gas, a liquid phase output device capable of outputting liquid, and a mixing and temperature control device capable of mixing and controlling the temperature of liquefied gas and liquid. The outlets of the liquefaction device and the liquid phase output device are both connected to the inlet of the mixing and temperature control device. The true triaxial test subsystem includes a cavity capable of holding the test sample, a loading device capable of applying horizontal transverse, horizontal longitudinal, and axial loading forces to the test sample, and a heating device capable of controlling the temperature inside the cavity. The cavity has an inlet connected to the outlet of the mixing and temperature control device and an outlet connected to the inlet of the metering subsystem.

[0006] Optionally, the true triaxial testing subsystem also includes a pressure chamber, a true triaxial fixture located within the pressure chamber, and the cavity being the inner cavity of the true triaxial fixture.

[0007] Optionally, it also includes a bracket with a lifting device on it. The lifting device has a lifting end that can move up and down. The pressure chamber includes a base and a shell with an open bottom. The shell is connected to the lifting end of the lifting device. The shell can move downward under the drive of the lifting device to cover the true triaxial fixture and seal against the base. The bottom of the shell is sealed by the base.

[0008] Optionally, the true triaxial test subsystem also includes a first flow channel and a second flow channel. One end of the first flow channel is connected to the outlet of the mixing temperature control device, and the other end is connected to the cavity. One end of the second flow channel is connected to the cavity, and the other end is connected to the inlet of the metering subsystem.

[0009] Optionally, the loading device includes an axial pressure booster capable of applying an axial loading force to the test sample, a first confining pressure booster capable of applying a horizontal transverse loading force to the test sample, and a second confining pressure booster capable of applying a horizontal longitudinal loading force to the test sample.

[0010] Optionally, the metering subsystem includes a gas-liquid separation container with a separation chamber. The outlet of the true triaxial test subsystem is connected to the separation chamber of the gas-liquid separation container via an outlet pipe. The top of the gas-liquid separation container is connected to a gas extraction metering device that can extract gas from the separation chamber and measure the gas flow rate. The bottom of the gas-liquid separation container is connected to a liquid extraction metering device that can extract liquid from the separation chamber and measure the liquid flow rate.

[0011] Optionally, it also includes a control unit. The air pumping and metering device is equipped with a pressure sensor that is electrically connected to the control unit. The pressure sensor monitors the pressure in the separation chamber in real time. When the monitored value is greater than the preset value, the control unit starts the air pumping and metering device. When the monitored value is less than the preset value, the control unit shuts down the air pumping and metering device.

[0012] Optionally, a first conductive probe is provided at the outlet of the lead tube, and a second conductive probe is provided at the inlet of the liquid metering device. The first and second conductive probes are electrically connected to a power supply via wires. A liquid metering pump is connected to the wires, and the liquid metering pump is connected to the bottom of the separation chamber via an inlet pipe. When the first conductive probe contacts the liquid in the separation chamber, the power supply provides power to the liquid metering pump; when the liquid does not contact the first conductive probe, the power supply cannot provide power to the liquid metering pump.

[0013] Optionally, the liquefaction device includes a dual-cylinder plunger pump, a gas delivery component capable of outputting gas at a corresponding pressure, a condensation component capable of receiving and condensing the gas, the outlet of the gas delivery component being connected to the inlet of the condensation component, the outlet of the condensation component being connected to the inlet of the dual-cylinder plunger pump, and the outlet of the dual-cylinder plunger pump being connected to the inlet of the mixing and temperature control device.

[0014] Optionally, the mixing temperature control device includes a balancing container and a temperature control device capable of controlling the temperature inside the balancing container. The balancing container has two inlets connected to the outlets of the liquefaction device and the liquid phase output device, respectively, and a balancing container outlet connected to the cavity inlet.

[0015] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: 1. By setting up a loading device, it is possible to apply horizontal, longitudinal, and axial loading forces to the test sample. Since the horizontal and longitudinal forces can be set and adjusted according to the test requirements, it is possible to reproduce the stress differences in different horizontal directions of the strata and special geostress conditions such as earthquakes and blasting. It solves the problem that traditional devices cannot reproduce the real environment of deep rocks, and provides a test environment that is highly consistent with the actual strata for the study of deep rock characteristics.

[0016] 2. By setting up a liquefaction device, liquefied gas that meets the experimental requirements can be prepared; by setting up a liquid output device, liquid that meets the experimental requirements can be output. The two are mixed and temperature controlled in a mixing and temperature control device to produce the fluid required for the experiment, thereby improving the control of the fluid phase state, making the simulated environment of the experiment closer to the natural environment, and enabling the experimental system of the present invention to conduct relevant research on supercritical fluids.

[0017] 3. By setting up a mixing temperature control device, the temperature of the injected test fluid can be controlled; by setting up a heating device, the temperature of the test sample can be controlled; therefore, the test system of the present invention can control the temperature of the test fluid and the test sample, flexibly construct different temperature conditions, and stably carry out non-isothermal permeation tests and non-isothermal fracturing tests. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a non-isothermal true triaxial multiphase flow fracturing test system provided in Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the true triaxial test subsystem provided in Embodiment 1 of the present invention.

[0020] Figure 3 This is a schematic diagram of the loading device provided in Embodiment 1 of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of the true triaxial fixture provided in Embodiment 1 of the present invention.

[0022] Figure 5 This is a schematic diagram of the metering subsystem provided in Embodiment 1 of the present invention.

[0023] Explanation of reference numerals in the attached drawings: 1. Gas cylinder; 2. Gas cylinder regulating valve; 3. First pressure transmitter; 4. Gas booster pump; 401. Booster pump control valve; 402. Booster pump inlet check valve; 403. Booster pump outlet check valve; 5. Control unit; 6. First shut-off valve; 7. Condensate storage tank; 8. First temperature transmitter; 9. Second pressure transmitter; 10. Condensation equipment; 11. Second shut-off valve; 111. Insulated pipe 1; 12. Pipe insulation layer; 13. Double-cylinder plunger pump; 14. Third shut-off valve; 141. Insulated pipe II; 15. Balance container; 16. Temperature control equipment; 17. Third pressure transmitter; 18. Second pressure transmitter; 19. Fourth shut-off valve; 20. Piston pump; 21. Fifth shut-off valve; 22. Liquid storage container; 23. Sixth shut-off valve; 231. Inlet pipe; 24. Seventh shut-off valve; 25. Axial pressure booster; 250. Booster control valve; 251. First pressure rod; 2567. Hydraulic power unit; 26. First confining pressure booster; 260. Booster pressure transmitter; 261. Second pressure rod; 27. Second confining pressure... 271. Intensifier; 28. Third pressure rod; 29. ​​Oil tank; 20. Vacuum pump; 21. Oil tank control valve; 22. Heating device; 33. Back pressure valve; 34. Eighth shut-off valve; 35. Gas-liquid separation container; 36. Pressure sensor; 37. High-precision gas metering pump; 38. Dryer; 39. Liquid metering pump; 30. Outlet pipe; 31. Inlet pipe; 322. First conductive probe; 323. Liquid level; 324. Second conductive probe; 325. Inlet pipe; 326. Wire 1; 327. Conductor Line 2; 3213, Miniature power supply; 33, Pressure chamber; 330, Base; 331, Fluid channel; 332, Sensor interface; 333, Internal temperature sensor; 334, Sealing ring; 34, Test supplies; 35, True triaxial fixture; 350, Seepage interface; 351, Upper pressure head; 352, Lower pressure head; 353, Side pressure plate; 354, Sealing sleeve; 36, Support; 361, Sliding rail; 362, Slide rod; 363, Lifting device; 364, Slider; 37, Displacement sensor; 38, Acoustic monitoring sensor. Detailed Implementation

[0024] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Example 1: like Figure 1 As shown, this embodiment provides a non-isothermal true triaxial multiphase flow fracturing test system, including a multiphase fluid preparation subsystem capable of preparing multiphase test fluid, a true triaxial test subsystem capable of conducting non-isothermal true triaxial multiphase flow fracturing tests, and a metering subsystem capable of measuring gas and liquid flow rates. The multiphase fluid preparation subsystem includes a liquefaction device capable of liquefying gas, a liquid phase output device capable of outputting liquid, and a mixing and temperature control device capable of mixing and controlling the temperature of liquefied gas and liquid. The outlets of the liquefaction device and the liquid phase output device are both connected to the inlet of the mixing and temperature control device. The true triaxial test subsystem includes a cavity capable of setting up test samples, a loading device capable of applying horizontal transverse, horizontal longitudinal, and axial loading forces to the test samples, and a heating device 29 capable of controlling the temperature inside the cavity. The cavity has an inlet connected to the outlet of the mixing and temperature control device and an outlet connected to the inlet of the metering subsystem.

[0027] Control unit 5 is electrically connected to the multiphase fluid preparation subsystem, the true triaxial test subsystem, and the metering subsystem, respectively. That is, all sensors and valves are electrically connected to control unit 5.

[0028] The true triaxial test subsystem also includes a pressure chamber 33 and a true triaxial clamp 35 located in the pressure chamber 33, with the cavity being the inner cavity of the true triaxial clamp 35.

[0029] In this embodiment, the heating device 29 includes an oil tank 28 capable of storing heat transfer oil and a vacuum pump 281. The outlet of the vacuum pump 281 is connected to the inlet of the pressure chamber 33. The inlet of the vacuum pump 281 and the outlet of the oil tank 28 are connected through a pipeline, and an oil tank control pump 282 is provided on the pipeline.

[0030] like Figure 2 and Figure 3As shown, it also includes a bracket 36, on which a lifting device is provided. The lifting device has a lifting end that can move up and down. The pressure chamber 33 includes a base 330 and a shell with an open bottom. The shell is connected to the lifting end of the lifting device. The shell can move downward under the drive of the lifting device to cover the true triaxial clamp 35 and seal against the base 330. The bottom of the shell is closed by the base 330.

[0031] like Figure 4 As shown, in this embodiment, the true triaxial fixture 35 includes an upper pressure head 351, a lower pressure head 352, a side pressure plate 353, and a sealing sleeve 354. A base 330 is mounted on a bracket 36 (in a gate shape) and can move back and forth to hold the housing. The base 330 is equipped with a pressure chamber sealing ring 334, several fluid channels 331 (5 in total), and sensor interfaces 332 (12 in total). The fluid channels 331 can be connected to the inlet pipe 231, the outlet pipe 324, the oil tank 28, and each confining pressure booster. The sensor interfaces 332 can communicate with the internal temperature sensor 333, displacement sensor 37, acoustic emission monitoring sensor 38, ultrasonic wave velocity sensor, and control unit 5 within the pressure chamber. The internal temperature sensor 333 is installed on any sensor interface 332 in the pressure chamber base to measure the temperature inside the pressure chamber 33. The pressure chamber sealing ring 334 is mounted on the pressure chamber base 330. The upper pressure head 351 is used to cooperate with the pressure chamber 33 to achieve cavity sealing; the seepage interface 350 is set on the upper and lower pressure heads and is used to connect the inlet pipe 231 and the outlet pipe 324 and communicate with the upper and lower ends of the test sample; the upper pressure head 351 connects the test sample 34 and the first pressure rod 251 and is used to transmit axial rigid load to the test sample, and is provided with the seepage interface 350; the lower pressure head 352 connects the test sample 34 and the pressure chamber base 330 and is used to transmit axial rigid load to the test sample, and is provided with the seepage interface 350; the side pressure plate 353 connects the test sample 34, the second pressure rod 261 and the third pressure rod 271 and is used to uniformly transmit lateral rigid load to the test sample, and is provided with acoustic detection points, which can be equipped with acoustic monitoring sensors 38; the sealing sleeve 354 is used to wrap the test sample 34 so that the test sample meets the sealing conditions required for the test (preferably heat shrink tubing and sealing rings). like Figure 3As shown, the support structure 36 is the supporting structure of the test device, on which a sliding rail 361, a sliding rod 362, a hydraulic device 363, and a slider 364 are installed. The sliding rail 361 is installed on the support 36, and the slider 364 is installed on the sliding rail 361. The slider 364 is connected to the pressure chamber 33. The sliding rail 361 is the track for the pressure chamber 33 to move vertically. The sliding rod 362 is inserted into the top of the support 36 through a sliding hole on the support 36. The lifting device 363 is installed at the bottom of the support 36 and moves the pressure chamber 33 up and down by hydraulic power. A position sensor is arranged on it to monitor and locate the specific position of the pressure chamber 33 during the up and down movement. A displacement sensor 37 is installed on the side pressure plate 353 to monitor the deformation of the test sample 34 and the displacement of the first, second, and third pressure rods. The acoustic monitoring sensor 38 includes an acoustic emission sensor or an ultrasonic wave velocity sensor, etc.

[0032] The true triaxial test subsystem also includes a first flow channel and a second flow channel. One end of the first flow channel is connected to the outlet of the mixing temperature control device, and the other end is connected to the cavity. One end of the second flow channel is connected to the cavity, and the other end is connected to the inlet of the metering subsystem.

[0033] like Figure 2 As shown, the loading device includes an axial pressure booster 25 capable of applying an axial loading force to the test sample, a first confining pressure booster 26 capable of applying a horizontal transverse loading force to the test sample, and a second confining pressure booster 27 capable of applying a horizontal longitudinal loading force to the test sample.

[0034] like Figure 2As shown, in this example, the loading device 29 also includes a hydraulic power unit 2567 connected to the axial pressure booster 25, the first confining pressure booster 26, the second confining pressure booster 27, and the oil tank 28, which can provide hydraulic power to the test system. The axial pressure booster 25 is used to control the rigid load of the principal stress in the Z direction in a true triaxial stress state. It can accurately control the principal stress and strain in the Z direction of the test sample by precisely controlling the loading pressure and displacement of the first pressure rod 251. It can provide a maximum static load of 1500kN and a maximum stress of 600MPa. The first confining pressure intensifier 26 is used to control the rigid load of the principal stress in the X direction under true triaxial stress. It can precisely control the principal stress and strain in the X direction of the test sample by accurately controlling the loading pressure and displacement of the second pressure bar 261, providing a maximum stress of 140 MPa with a resolution of 0.01 MPa. The second confining pressure intensifier 27 is used to control the rigid load of the principal stress in the Y direction under true triaxial stress. It can precisely control the principal stress and strain in the Y direction of the test sample by accurately controlling the loading pressure and displacement of the third pressure bar 271, providing a maximum stress of 140 MPa with a resolution of 0.01 MPa. It provides a stress of 140 MPa and a resolution of 0.005 MPa. The oil tank 28 is used to store heat transfer oil. The oil tank 28 is equipped with an oil tank control valve 282. The heat transfer oil can be silicone oil, synthetic ester oil, polytetrafluoropropylene ether oil, etc., with silicone oil being preferred. The heat transfer oil in the oil tank 28 is transported to the pressure chamber 33 via a vacuum pump 281. When filling the pressure chamber 33 with heat transfer oil, the vacuum pump 281 is activated to create a negative pressure inside the pressure chamber 33. When discharging the heat transfer oil from the pressure chamber 33, the vacuum pump is activated to create a negative pressure inside the oil tank 28. The heating of the heat transfer oil is achieved through… The heating device 29 is implemented by installing an electric heating plate on the pressure chamber to regulate the temperature of the heat transfer oil in the pressure chamber. In this embodiment, the temperature control resolution is 0.5℃, and the maximum temperature can reach 200℃. The inlet pipes of the axial pressure booster 25, the first confining pressure booster 26, the second confining pressure booster 27, and the oil tank 28 are all equipped with booster pressure transmitters 260. The outlet pipes of the axial pressure booster 25, the first confining pressure booster 26, and the second confining pressure booster 27 are all equipped with booster control valves 250. The outlet pipe of the oil tank 28 is equipped with an oil tank control valve 282.

[0035] like Figure 5 As shown, the metering subsystem includes a gas-liquid separation container 32 with a separation chamber. The outlet of the true triaxial test subsystem is connected to the separation chamber of the gas-liquid separation container 32 through an outlet pipe 324. The top of the gas-liquid separation container 32 is connected to a gas extraction metering device that can extract gas from the separation chamber and measure the gas flow rate. The bottom of the gas-liquid separation container 32 is connected to a liquid extraction metering device that can extract liquid from the separation chamber and measure the liquid flow rate.

[0036] In this embodiment, the outlet pipe 324 is provided with an eighth shut-off valve 31 and a back pressure valve 30 for controlling the pressure at the outlet end of the test sample.

[0037] like Figure 5 As shown, it also includes a control unit. The air pumping and metering device is equipped with a pressure sensor 320 that is electrically connected to the control unit. The pressure sensor 320 monitors the pressure in the separation chamber in real time. When the monitored value is greater than the preset value, the control unit starts the air pumping and metering device. When the monitored value is less than the preset value, the control unit shuts down the air pumping and metering device.

[0038] like Figure 5 As shown, in this embodiment, the gas metering device includes a high-precision gas metering pump 321, a dryer 322, and an inlet pipe 325. One end of the inlet pipe 325 is connected to the top of the gas-liquid separation container 32, and the other end is connected to the high-precision gas metering pump 321. A pressure sensor 320 and a dryer 322 are installed on the inlet pipe 325. The gas-liquid separation container 32 includes a glass sleeve and plugs installed at the upper and lower ends of the glass sleeve. The inlet pipe 325, the outlet pipe 324, and the liquid inlet pipe 329 all extend into the glass sleeve through their respective plugs. Initially, the glass sleeve contains a certain level of liquid.

[0039] like Figure 5 As shown, a first conductive probe 326 is provided at the outlet of the lead-out pipe 324, and a second conductive probe 328 is provided at the inlet of the liquid metering device. The first conductive probe 326 and the second conductive probe 328 are electrically connected to a power supply via a wire. A liquid metering pump 323 is connected to the wire. The liquid metering pump 323 is connected to the bottom of the separation chamber via an inlet pipe 329. When the first conductive probe 326 is in contact with the liquid in the separation chamber, the power supply provides power to the liquid metering pump 323; when the liquid is not in contact with the first conductive probe 326, the power supply cannot provide power to the liquid metering pump 323.

[0040] like Figure 5 As shown, in this embodiment, the first conductive probe 326 and the second conductive probe 328 are both located in the glass sleeve. When the liquid surface 327 contacts the first conductive probe 326, the power supply circuit of the power source (micro power source 3213) is turned on, and otherwise it is not turned on. A wire 1 3210 is connected to the first conductive probe 326, and a wire 2 3211 is connected to the second conductive probe 328. The power source and the liquid metering pump 323 are set on the wire 1 3210, and the wire 1 and the wire 2 are connected.

[0041] like Figure 1 As shown, the liquefaction device includes a dual-cylinder plunger pump 13, a gas delivery component capable of outputting gas at a corresponding pressure, a condensation component capable of receiving and condensing the gas, the outlet of the gas delivery component being connected to the inlet of the condensation component, the outlet of the condensation component being connected to the inlet of the dual-cylinder plunger pump 13, and the outlet of the dual-cylinder plunger pump 13 being connected to the inlet of the mixing temperature control device.

[0042] like Figure 1 As shown, in this embodiment, the gas delivery assembly includes a gas booster pump 4 and a gas cylinder 1 (such as CO2) capable of providing a gas source. The outlet of the gas cylinder 1 is connected to the inlet of the gas booster pump 4, and the outlet of the gas booster pump 4 is connected to the inlet of the condensation assembly. A gas pressure regulating valve 2, a first pressure transmitter 3, and a booster pump inlet check valve 402 are sequentially installed on the pipeline between the outlet of the gas cylinder 1 and the inlet of the gas booster pump 4. The gas booster pump 4 is equipped with a booster pump control valve 401 electrically connected to the control unit 5. A booster pump outlet check valve 403 and a first shut-off valve 6 are sequentially installed on the pipeline between the outlet of the gas booster pump 4 and the inlet of the condensation assembly.

[0043] like Figure 1 As shown, the condensation assembly includes a condensation tank 7 for receiving, storing, and liquefying carbon dioxide and a condensation device 10. The inlet of the condensation tank 7 and the outlet of the gas booster pump 4 are connected by a pipeline. The condensation tank 7 is equipped with a first temperature transmitter 8 and a second pressure transmitter 9. The condensation tank 7 uses the refrigerant output from the condensation device 10 to lower the temperature of the carbon dioxide inside the condensation tank 7, thereby liquefying the carbon dioxide. The refrigerant output from the condensation device 10 can cool the dual-cylinder plunger pump 13. The inlet of the dual-cylinder plunger pump 13 and the outlet of the condensation tank 7 are connected by an insulated pipe 111. The insulated pipe 111 is equipped with a pipe insulation layer 12 and a second shut-off valve 11. The outlet of the dual-cylinder plunger pump 13 and the inlet of the mixing temperature control device are connected by an insulated pipe 141. The insulated pipe 141 is equipped with a pipe insulation layer 12 and a third shut-off valve 14.

[0044] like Figure 1 As shown, the mixing temperature control device includes a balance container 15 and a temperature control device 16 capable of controlling the temperature inside the balance container 15. The balance container 15 has two inlets that are respectively connected to the outlets of the liquefaction device and the liquid phase output device, and an outlet of the balance container 15 that is connected to the cavity inlet.

[0045] In this embodiment, the inlet of the balance container 15 and the outlet of the dual-cylinder plunger pump 13 are connected through the second insulated pipe 141. The balance container 15 is equipped with a third pressure transmitter 17 and a second pressure transmitter 18. The outlet of the balance container 15 and the inlet of the cavity are connected through the inlet pipe 231. The inlet pipe 231 is equipped with a pipe insulation layer 12. The inlet pipe 231 is equipped with a sixth shut-off valve 23 and a seventh shut-off valve 27 in sequence along the fluid flow direction.

[0046] In this embodiment, the liquid output device includes a plunger pump 20 and a liquid storage container 22 (water storage). The outlet of the liquid storage container 22 is connected to the inlet of the plunger pump 20, and the outlet of the plunger pump 20 is connected to the inlet of the balance container 15. A fifth shut-off valve 21 is provided on the pipeline between the outlet of the liquid storage container 22 and the inlet of the plunger pump 20, and a fourth shut-off valve 19 is provided on the pipeline between the outlet of the plunger pump 20 and the inlet of the balance container 15.

[0047] Example 2: This embodiment provides a method according to Example 1, which is used for supercritical phase or liquid phase CO2 fracturing test research under true triaxial stress.

[0048] A test method for a non-isothermal true triaxial multiphase flow fracturing test system includes: Step 1: Place the test sample 34 into the cavity of the true triaxial test subsystem; In this embodiment, the test sample 34 is loaded into the true triaxial fixture 35, and the inlet pipe 231 and outlet pipe 324 are connected through the seepage interface 350 respectively. The acoustic monitoring sensor 38, internal temperature sensor 333 and displacement sensor 37 are installed and electrically connected to the control unit 5 so that they can communicate normally. The control unit operates the pressure chamber 33 to move down and fix it on the base 330. The pressure chamber 33 is sealed under the action of the sealing ring 334.

[0049] Step 2: Start the heating device 29 to heat the test sample to the required test temperature; In this embodiment, the oil tank 28 and vacuum pump 281 are started to fill the pressure chamber 33 with heat transfer oil. After filling is completed, the heating device 29 is started to control the temperature of the pressure chamber cavity (0-200℃ controllable; if it is necessary to ensure that CO2 is in the supercritical phase, the temperature needs to be set to be higher than the critical temperature of 31.04℃). The temperature of the pressure chamber cavity is monitored in real time by the internal temperature sensor 333 to determine whether the temperature of the test sample has reached the set temperature value.

[0050] Step 3: Prepare liquefied gas using a liquefaction device, output liquid using a liquid phase output device, and mix and control the temperature of the liquefied gas and liquid using a mixing and temperature control device to produce the test fluid required for the experiment; CO2 is supplied through gas cylinder 1, and the CO2 in condensation tank 7 is liquefied through condensation equipment 10 (preferably an industrial chiller). The condensed gas is then transported to balance container 15 by a double-cylinder plunger pump 13. At the same time, a liquid phase output device transports liquid to balance container 15. The liquefied gas and liquid are mixed and temperature controlled in balance container 15 to produce the test fluid (supercritical phase or liquid phase) required for the test.

[0051] Step 4: Apply horizontal transverse, horizontal longitudinal, and axial loading forces to the test sample using a loading device; Step 5: The test fluid prepared by the multiphase fluid preparation subsystem is delivered to the cavity of the true triaxial test subsystem for fracturing test; Step 6: Measure the amount of gas and liquid produced by the true triaxial test subsystem using the metering subsystem; In this embodiment, various parameters are monitored by various sensors, and the monitored parameters are collected, stored and processed by the control unit, and corresponding charts are drawn synchronously.

[0052] Example 3: This embodiment provides a method according to Example 1, which is used for experimental research on multiphase seepage of water and supercritical CO2 under true triaxial stress.

[0053] The difference from Example 2 is that, in preparing the test fluid required for the experiment, water and supercritical phase CO2 are mixed to wet the supercritical phase CO2 with water, thereby saturating the water with CO2 and making a mixed-phase fluid. When the pressure and temperature in the equilibrium container 15 are stable, the test fluid is prepared. The remaining steps are the same as in Example 2.

[0054] The above inventions are merely a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A non-isothermal true triaxial multiphase flow fracturing test system, characterized in that, It includes a multiphase fluid preparation subsystem capable of preparing multiphase test fluids, a true triaxial testing subsystem capable of conducting non-isothermal true triaxial multiphase seepage fracturing tests, and a metering subsystem capable of measuring gas and liquid flow rates; The multiphase fluid preparation subsystem includes a liquefaction device capable of liquefying gas, a liquid phase output device capable of outputting liquid, and a mixing and temperature control device capable of mixing and controlling the temperature of liquefied gas and liquid. The outlets of the liquefaction device and the liquid phase output device are both connected to the inlet of the mixing and temperature control device. The true triaxial testing subsystem includes a cavity for setting up the test sample, a loading device for applying horizontal transverse, horizontal longitudinal and axial loading forces to the test sample, and a heating device for controlling the temperature inside the cavity; the cavity has an inlet connected to the outlet of the mixing temperature control device, and an outlet connected to the inlet of the metering subsystem.

2. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 1, characterized in that, The true triaxial test subsystem also includes a pressure chamber and a true triaxial fixture located inside the pressure chamber, with the cavity being the inner cavity of the true triaxial fixture.

3. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 2, characterized in that, It also includes a support frame, on which a lifting device is provided. The lifting device has a lifting end that can move up and down. The pressure chamber includes a base and a shell with an open bottom. The shell is connected to the lifting end of the lifting device. The shell can move downward under the drive of the lifting device to cover the true triaxial fixture and seal against the base. The bottom of the shell is sealed by the base.

4. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 3, characterized in that, The true triaxial test subsystem also includes a first flow channel and a second flow channel. One end of the first flow channel is connected to the outlet of the mixing temperature control device, and the other end is connected to the cavity. One end of the second flow channel is connected to the cavity, and the other end is connected to the inlet of the metering subsystem.

5. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 1, characterized in that, The loading device includes an axial pressure booster capable of applying an axial loading force to the test sample, a first confining pressure booster capable of applying a horizontal transverse loading force to the test sample, and a second confining pressure booster capable of applying a horizontal longitudinal loading force to the test sample.

6. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 1, characterized in that, The metering subsystem includes a gas-liquid separation container with a separation chamber. The outlet of the true triaxial test subsystem is connected to the separation chamber of the gas-liquid separation container through an outlet pipe. The top of the gas-liquid separation container is connected to a gas extraction metering device that can extract gas from the separation chamber and measure the gas flow rate. The bottom of the gas-liquid separation container is connected to a liquid extraction metering device that can extract liquid from the separation chamber and measure the liquid flow rate.

7. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 6, characterized in that, It also includes a control unit. The air pumping and metering device is equipped with a pressure sensor that is electrically connected to the control unit. The pressure sensor monitors the pressure in the separation chamber in real time. When the monitored value is greater than the preset value, the control unit starts the air pumping and metering device. When the monitored value is less than the preset value, the control unit shuts down the air pumping and metering device.

8. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 6, characterized in that, A first conductive probe is provided at the outlet of the lead-out tube, and a second conductive probe is provided at the inlet of the liquid metering device. The first and second conductive probes are electrically connected to a power supply through corresponding wires. A liquid metering pump is connected to the wires. The liquid metering pump is connected to the bottom of the separation chamber through an inlet pipe. When the first conductive probe is in contact with the liquid in the separation chamber, the power supply provides power to the liquid metering pump; when the liquid in the separation chamber is not in contact with the first conductive probe, the power supply cannot provide power to the liquid metering pump.

9. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 1, characterized in that, The liquefaction device includes a dual-cylinder plunger pump, a gas delivery component capable of outputting gas at a corresponding pressure, a condensation component capable of receiving and condensing the gas, the outlet of the gas delivery component being connected to the inlet of the condensation component, the outlet of the condensation component being connected to the inlet of the dual-cylinder plunger pump, and the outlet of the dual-cylinder plunger pump being connected to the inlet of the mixing and temperature control device.

10. The non-isothermal true triaxial multiphase flow fracturing test system as described in claim 1, characterized in that, The mixing temperature control device includes a balance container and a temperature control device capable of controlling the temperature inside the balance container. The balance container has two inlets that are respectively connected to the outlets of the liquefaction device and the liquid phase output device, and a balance container outlet that is connected to the cavity inlet.

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