Supercritical fluid quantitative triaxial stress adsorption and deformation test system and method

Abstract

The invention discloses a supercritical fluid quantitative triaxial stress adsorption and deformation testing system and method, and belongs to the technical field of supercritical fluid adsorption testing. The test system comprises an oil bath constant-temperature circulating heating system, a gas supply system, a real-time data monitoring and operating system, an experimental gas safety alarm system, a supercritical fluid storage kettle, a visual constant-volume piston constant-pressure reference kettle and a false triaxial sample kettle, the test system utilizes a 1000mL constant-volume piston constant-pressure reference kettle and a false triaxial sample kettle to realize a quantitative constant-pressure adsorption / desorption experiment of a supercritical fluid under a triaxial stress condition and determine the adsorption deformation of a triaxial direction material, and can more truly simulate the adsorption deformation of the supercritical fluid under deep triaxial ground stress and ground temperature conditions. The adsorption / desorption whole-process experiment in the supercritical fluid high-temperature and high-pressure reservoir and the deformation of the test material caused by adsorption / desorption provide technical reference for deep gas storage and the like.

Description

Technical Field

[0001] The invention relates to a supercritical fluid quantitative triaxial stress adsorption and deformation testing system and method, belonging to the technical field of supercritical fluid adsorption testing. Background Art

[0002] As global warming and the greenhouse effect intensify, the combination of carbon dioxide geological storage and deep unconventional resource development technology has become a key solution to reduce greenhouse gas emissions. However, the geological conditions of deep unconventional resource reservoirs are often high temperature, high pressure, and high ground stress. The occurrence of unconventional resources and the injected sealed gas are transformed into a supercritical state under the reservoir environment. Its adsorption and desorption characteristics can be used to predict the utilization rate of unconventional resources in the reservoir, the carbon dioxide storage capacity, and to evaluate the stability and safety of the reservoir.

[0003] Taking deep supercritical carbon dioxide enhanced coalbed methane extraction as an example, the fluid is always in a high-pressure state during the whole process of using carbon dioxide displacement to exploit deep coalbed methane resources, and when the reservoir temperature reaches the critical point, it turns into a supercritical state (ScCO2). Compared with coalbed methane (methane), deep coal seams have a stronger adsorption effect on supercritical carbon dioxide, and ScCO2 has a strong extraction effect on coal-based organic matter. Generally speaking, temperature and pressure are the main factors affecting the adsorption performance of deep reservoirs on supercritical fluids. At the same time, the adsorption process of reservoir matrix and supercritical fluid is accompanied by energy changes, which are mainly manifested in macroscopic manifestations of pressurization heat release and decompression adsorption, adsorption heat release and desorption heat absorption. Changes in reservoir temperature and pressure will significantly affect its mechanical properties, reduce the utilization rate of reservoir resources, and threaten the overall stability and safety of the reservoir. Therefore, studying the temperature changes during the constant pressure adsorption / desorption process of supercritical fluids is of great significance for evaluating the efficiency and safety of deep reservoir resource utilization.

[0004] In the prior art, the static volume method and the magnetic levitation mass method are mainly used for supercritical fluid adsorption experiments. In the static volume method experiment, it is impossible to ensure that the pressure is always the set value during the entire adsorption process. The sample weight used in the magnetic levitation mass method experiment is often less than 10g. The small sample amount cannot accurately measure the actual adsorption / desorption amount of the sample. Traditional isothermal adsorption experiments are all carried out in a closed sample kettle. Adsorption / desorption experiments under real triaxial stress conditions are rarely carried out, and there is a lack of test methods and means for measuring the sample volume change caused by adsorption / desorption during the experiment. Summary of the invention

[0005] In order to solve the above problems, the present invention aims to provide a supercritical fluid quantitative triaxial stress adsorption and deformation test system and method, which realizes the quantitative constant pressure adsorption / desorption experiment of supercritical fluid under triaxial stress conditions and the experiment of measuring the adsorption deformation of adsorbent materials in triaxial directions. The test system uses a pseudo triaxial sample kettle and a 1000mL visual constant volume piston constant pressure reference kettle to realize the quantitative constant pressure adsorption / desorption experiment of supercritical fluid and the direct measurement of volume deformation during the experiment, providing a technical reference for deep gas storage, etc.

[0006] The deep high temperature and high pressure conditions simulated by the present invention are: reservoir depth>800m, temperature>35℃, pressure>8MPa; the two main equipments used are 1000mL visual constant volume piston constant pressure reference kettle and pseudo triaxial sample kettle, the kettle materials of these two equipments are made of 316L stainless steel (temperature resistance limit 150℃, pressure resistance limit 80MPa) that is resistant to high temperature, high pressure and corrosion, and the pseudo triaxial sample kettle is equipped with radial claw extensometer and axial displacement sensor, so as to realize the quantitative constant pressure adsorption / desorption experiment of supercritical fluid under deep reservoir (high temperature and high pressure) conditions, and the real-time determination of the volume change of the sample during the experiment, which provides technical reference for deep geological gas sealing, etc. In addition, the 1000mL constant volume piston constant pressure reference kettle used in the present invention is adjusted by injecting / discharging liquid into the lower cavity of the constant volume piston constant pressure reference kettle under constant pressure by a precision double-cylinder injection pump to adjust the position of the piston piece in the cavity, so as to realize the precise pressure control adsorption / desorption experiment under high temperature and constant pressure (specific pressure) of supercritical fluid. At the same time, deformation measuring devices are set in the radial and axial directions of the pseudo-triaxial sample kettle to realize real-time measurement of the volume change of the adsorbed material during constant pressure adsorption / desorption, and the data are transmitted to the temperature and pressure data collector and computer for recording and curve drawing.

[0007] The present invention provides a supercritical fluid quantitative triaxial stress adsorption and deformation testing system, which is used to simulate the whole process experiment of supercritical fluid quantitative constant pressure adsorption / desorption under high temperature and high pressure conditions at a reservoir depth of more than 800m, and simultaneously measure the volume change of the sample generated during the whole experiment, so as to realize the quantitative constant pressure experiment of the supercritical fluid and the direct measurement of the deformation during the experiment. The testing system includes an oil bath constant temperature circulation heating system, a gas supply system, a real-time data monitoring and operating system, an experimental gas safety alarm system, a supercritical fluid storage kettle, a visual constant volume piston constant pressure reference kettle and a pseudo triaxial sample kettle;

[0008] The oil bath constant temperature circulation heating system is used to provide a stable constant temperature environment for the test system, and the oil bath constant temperature circulation heating system includes a constant temperature oil bath tank, an oil injection one-way valve and a CNC circulation oil bath control box; a supercritical fluid storage kettle, a visual constant volume piston constant pressure reference kettle and a pseudo triaxial sample kettle are arranged in the constant temperature oil bath tank; the tops of the supercritical fluid storage kettle, the visual constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected by pipelines; the visual constant volume piston constant pressure reference kettle is a full-scale 1000mL constant volume piston kettle, and a liquid pressure gauge, a liquid storage tank and a precision double-cylinder injection pump are connected to the bottom of the visual constant volume piston constant pressure reference kettle; the pseudo triaxial sample kettle includes a radial claw extensometer, an axial displacement sensor, an adjustable high-pressure gas collection buffer valve and a pseudo triaxial high-sealed integrated copper sleeve, and the axial pressure and confining pressure of the sample kettle are set by the pseudo triaxial stress loading control box, and a pseudo triaxial high-sealed integrated copper sleeve is arranged in the middle to place The sample to be tested is placed, three groups of parallel axial claw extensometers are arranged radially on the copper sleeve, a set of axial displacement sensors and deformation data acquisition processors are arranged axially and connected through a data line, and adjustable high-pressure gas collection buffer valves are arranged at the inlet and outlet to collect the experimental fluid; the visual constant volume piston constant pressure reference kettle comprises an upper chamber of the constant volume piston constant pressure reference kettle and a lower chamber of the constant volume piston constant pressure reference kettle. According to the experimental pressure and temperature requirements, the position of the piston piece of the constant volume piston constant pressure reference kettle is adjusted by setting the constant pressure operation mode, thereby changing the volume of the upper chamber to realize the adsorption / desorption test of the set pressure, and adjusting by the precision double-cylinder injection pump and the liquid automatic high pressure connecting valve to realize the constant pressure adsorption / desorption experiment at each pressure point in the whole process; according to the experimental pressure and temperature requirements, the pseudo triaxial sample kettle is injected with liquid through the pseudo triaxial stress loading control box, thereby changing the axial pressure and confining pressure of the sample kettle to realize the adsorption / desorption experiment under triaxial stress conditions.

[0009] A gas supply system, the gas supply system is used to supply gas to the supercritical fluid quantitative triaxial stress adsorption and deformation testing system, and the gas supply system is connected to the supercritical fluid storage kettle through a pipeline; the real-time data monitoring and operation system includes a liquid data acquisition controller, a temperature and pressure data acquisition processor, a deformation data acquisition processor and a computer, the temperature and pressure sensors on the supercritical fluid storage kettle, the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected to the temperature and pressure data acquisition processor, the radial claw extensometer and the axial displacement sensor inside the pseudo triaxial sample kettle are connected to the deformation data acquisition processor through a transmission line, the top of the visual constant volume piston constant pressure reference kettle is connected to the temperature and pressure data acquisition processor, and the bottom is connected to the liquid data acquisition controller through a transmission line; the liquid data acquisition controller and the temperature and pressure data acquisition processor both send data information to the computer in real time through the data transmission line, and the computer is used to record the pressure and temperature data values ​​and draw change curves respectively;

[0010] The experimental gas safety alarm system is electrically connected to the computer, and includes two experimental gas concentration probes and an alarm module. The experimental gas concentration probes are arranged on both sides of the inner wall of the air-liquid interface of the constant temperature oil bath, and are used to measure the experimental gas concentration in the constant temperature oil bath. The experimental gas concentration probes are connected to the alarm module, and the alarm module is electrically connected to the computer. When the experimental gas concentration measured by the experimental gas concentration probe is higher than the set safety value, an alarm is issued, and the alarm signal is fed back to the computer.

[0011] Preferably, a fine-tuning valve and a filter are provided on the connecting pipeline between the supercritical fluid storage kettle and the visual constant-volume piston constant-pressure reference kettle; on the pipeline connecting the supercritical fluid storage kettle and the pseudo-triaxial sample kettle, the top of the kettle body of the supercritical fluid storage kettle is connected to a storage kettle temperature and pressure sensor, and the top of the pseudo-triaxial sample kettle is connected to a sample kettle temperature and pressure sensor; a second automatic high-pressure connecting needle valve is provided on the pipeline connecting the visual constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle; the top of the visual constant-volume piston constant-pressure reference kettle is connected to a reference kettle temperature and pressure sensor; the storage kettle temperature and pressure sensor, the sample kettle temperature and pressure sensor and the reference kettle temperature and pressure sensor are all electrically connected to the temperature and pressure data acquisition processor.

[0012] Preferably, the bottom of the constant temperature oil bath is connected to a CNC circulating oil bath control box, which sets the circulating oil temperature and flow rate through an oil injection one-way valve to ensure a constant temperature environment for the experimental system; an oil bath insulation cover is provided on the top of the constant temperature oil bath, and an oil bath drain port is provided on the bottom.

[0013] Preferably, a vacuum valve and a six-way regulating valve are connected above the constant-volume piston constant-pressure reference kettle, and the six-way regulating valve is respectively connected to the exhaust gas treatment chamber and the vacuum pumping device, and the vacuum pumping device includes a vacuum pump, a dryer and a vacuum gauge.

[0014] Preferably, a high-pressure visual window is provided on the constant-volume piston constant-pressure reference kettle, and a high-definition camera (located in the oil bath) is provided directly in front of the high-pressure visual window. The high-definition camera is placed in a high-temperature resistant plastic shell, and the opening of the plastic shell is blocked by a double-layer rubber plastic sealing ring, and a plastic partition is laid above the high-definition camera. The lens position of the shell adopts high-temperature resistant transparent glass, which is convenient for observing the phase change state produced during the injection and release of supercritical fluids, and observing the state of the experimental adsorbent. The data transmission line below is wrapped with a high-temperature resistant plastic tube, and is connected to an external computer through the adapter opening at the bottom of the oil bath box, so as to facilitate the transmission of image information to the computer for storage and imaging.

[0015] The present invention provides a supercritical fluid quantitative triaxial stress adsorption and deformation testing method, comprising the following steps:

[0016] Step 1, full-scale calibration of the visual constant-volume piston constant-pressure reference kettle; evacuate the supercritical fluid quantitative triaxial stress adsorption and deformation test system, place the piston plate of the inner cavity of the visual constant-volume piston constant-pressure reference kettle at the bottom, fill the reference kettle with high-pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo triaxial temperature sample kettle, inject helium into the pseudo triaxial sample kettle, and record the equilibrium pressure and temperature after the visual constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle are both adsorbed and balanced, and calculate the volume of the visual constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle. According to the law of conservation of matter and the real gas state equation PV=nZRT, the calculation formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; M He is the relative molecular mass of helium, g / mol; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ;P S is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; V0 is the inner cavity volume of the pseudo triaxial sample kettle (standard block volume), cm 3 ; Z S The pressure P is the balance pressure after the constant volume piston constant pressure reference kettle and the dual channel temperature measurement sample kettle are connected. S The helium compression factor under ; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; according to the law of conservation of mass, the calculation formula is as follows: The volume of the constant-volume piston constant-pressure reference kettle and the volume of the inner cavity of the pseudo-triaxial sample kettle are obtained; in order to make a quantitative comparison with the standard volume on the factory nameplate of the kettle body, the relative deviation ARD (absolute relative deviation) of the absolute value is defined as: Where V measure 、V standard is the measured calibration volume and the factory nameplate standard volume, cm 3 ; When the ARD value is less than 0.05%, the kettle volume calibration is correct and the next step can be performed;

[0017] Step 2: Before conducting the triaxial stress isothermal adsorption experiment, the sample to be tested is first subjected to balanced water treatment or drying treatment according to the experimental requirements, and the sample is placed in a vacuum blower at 105°C for 12 hours for drying, and then weighed again and placed in the inner cavity of the copper sleeve of the pseudo triaxial sample kettle;

[0018] Step 3, determination of the remaining free volume of the pseudo triaxial sample kettle: evacuate the entire system, place the piston plate of the constant volume piston constant pressure reference kettle cavity at the bottom, full scale state, fill the kettle with high pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high pressure connecting needle valve to inject helium into the pseudo triaxial sample kettle, and record the equilibrium pressure and temperature after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are both adsorbed and balanced. According to the law of conservation of matter and the real gas state equation PV = nZRT, calculate the free space volume, the formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; M He is the relative molecular mass of helium, g / mol; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ;P S V is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; F is the volume of free space in the pseudo triaxial sample reactor, cm 3 ; Z S The equilibrium pressure P after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected S The helium compression factor under ; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K;

[0019] Step 4, quantitative triaxial stress adsorption and deformation experiment of supercritical fluid: evacuate the whole system for 1 hour, close all valves, set the experimental environment temperature through the oil bath constant temperature circulation heating system; inject high-pressure gas into the storage kettle, and observe the temperature and pressure values; when the pressure fluctuation range is less than 0.1psi / h, and the temperature fluctuation range is less than 0.025℃ / h, the state value is used as the standard value for measuring the equilibrium, open the fine-tuning valve, and inject the supercritical fluid with the set pressure value into the upper chamber of the constant-volume piston constant-pressure reference kettle, observe the phase change of the fluid through the high-definition camera, and record the equilibrium pressure and temperature of the constant-volume piston constant-pressure reference kettle. When the pressure and temperature reach equilibrium, open the second automatic high-pressure connecting needle valve and the liquid automatic high-pressure connecting valve, and pass The precision double-cylinder injection pump pushes the piston plate according to the set pressure value to change the volume of the lower chamber of the constant-volume piston constant-pressure reference kettle, and the supercritical gas in the upper chamber of the constant-volume piston constant-pressure reference kettle is injected into the pseudo-triaxial sample kettle at a constant pressure. When the pseudo-triaxial stress reaches the set value, the second automatic high-pressure connecting needle valve is closed to wait for adsorption equilibrium. In this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range and the temperature fluctuation range reach the equilibrium standard, it is considered that the adsorption pressure has reached equilibrium. After being closed and static for 24 hours, the deformation data is recorded to complete the adsorption and deformation experiments at the current pressure point.

[0020] Step 5. After the previous pressure adsorption experiment is completed, open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle again to gradually increase the pressure at 1MPa to perform the constant-pressure adsorption experiment at the next pressure point until all adsorption pressure experiments are completed. According to the law of conservation of mass, the formula for calculating the adsorption amount of the adsorption process at one experimental pressure point is as follows: Where n ex The sample to be tested in the experimental false triaxial sample kettle is at the set pressure P e The Gibbs adsorption capacity under the condition of mol is mol; m is the mass of the sample to be tested in the experiment, g; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; P e is the set pressure of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment, MPa; Z e is the set pressure P of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment e Gas compressibility factor under V R is the full scale volume of the upper chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; ΔV is the volume change of the lower chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; V F is the remaining free volume in the pseudo-triaxial sample kettle, cm3 ; Gibbs adsorption capacity of the whole adsorption experiment (GSE n ) is as follows: Where n is the total number of pressure values ​​to be measured in the experiment; GSE n is the sum of n ΔGBEs; ΔGBE i is the adsorption amount at the i-th test pressure value;

[0021] Step 6. After the highest adsorption pressure in step 5 is achieved, open the vacuum valve and six-way regulating valve connected to the upper part of the constant volume piston constant pressure reference kettle, connect the exhaust gas treatment chamber, and vent the supercritical fluid in the upper chamber of the constant volume piston constant pressure reference kettle. At the same time, push the piston piece of the lower chamber of the constant volume piston constant pressure reference kettle to the top of the kettle body through the precision double-cylinder injection pump according to the set pressure value, then close the vent valve of the constant volume piston constant pressure reference kettle, open the second automatic high-pressure connecting needle valve, and inject the high-pressure gas in the false triaxial sample kettle into the constant volume piston constant pressure reference kettle until the false triaxial sample kettle is vented. After the pressure value in the inner cavity of the axial sample kettle reaches the target value, the second automatic high-pressure connecting needle valve is closed to wait for desorption equilibrium; during this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range is less than 0.1psi / h and the temperature fluctuation range is less than 0.025℃ / h, it is considered that the desorption and deformation experiments under the desorption pressure are completed;

[0022] Step 7: Open the vacuum valve, six-way regulating valve and vacuum pump, and gradually reduce the pressure to 1 MPa to conduct a constant-pressure desorption experiment at the next pressure point until all desorption pressure experiments are completed.

[0023] After all pressure value tests are completed, the sample kettle will be disassembled and the sample will be taken out to analyze the adsorption performance and volume change characteristics of the adsorption material on the supercritical fluid at two points before and after the experiment.

[0024] Preferably, before step 1, an air tightness check of the pseudo triaxial sample kettle is performed, and the specific operation steps are as follows: Pseudo triaxial sample kettle air tightness test: place the standard block V0 in the pseudo triaxial high-sealed integrated copper sleeve, and alternately load the sample kettle axial pressure and confining pressure to the set value through the pseudo triaxial stress loading control box. The volume stress calculation formula of the test sample is as follows: In the formula, σ s ,σ fare axial stress and confining pressure, MPa; P1 and P2 are gas pressures at the inlet and outlet of the sample kettle, MPa. The radial claw extensometer and axial displacement sensor are zeroed, and helium with a pressure 1.5 times higher than the maximum experimental pressure is introduced into the kettle for more than 24 hours. The temperature of the constant temperature oil bath is adjusted to the reservoir temperature, and the computer system page curve is continuously observed. If the pressure indication changes less than 0.1psi / h and the temperature indication changes less than 0.025℃ / h, it means that the air tightness is good, and then proceed to step 1.

[0025] Beneficial effects of the present invention:

[0026] (1) The present invention utilizes a pseudo triaxial sample kettle and a 1000 mL visual constant volume piston constant pressure reference kettle to realize the constant pressure adsorption / desorption experiment of supercritical fluid and the measurement of sample volume change during the adsorption material experiment. The experimental device has a simple structure, is easy to operate, has good use effect, and is easy to promote.

[0027] (2) The quantitative triaxial stress adsorption and deformation test system of the supercritical fluid of the present invention has a simple structure and safe experimental operation. Both data recording and curve drawing can be automated. Experimental data can be semi-quantitatively calculated, and the results are highly accurate and reliable. A pseudo triaxial sample kettle and a 1000mL visual constant volume piston constant pressure reference kettle are used to realize constant pressure adsorption / desorption experiments of supercritical fluids under real triaxial stress conditions and direct measurement of volume changes in the adsorption material experimental process. The present invention transforms the traditional isothermal adsorption system, designs a constant volume piston constant pressure reference kettle and a pseudo triaxial sample kettle, and uses helium, an automatic high pressure connecting needle valve and a precision double cylinder injection pump to perform constant pressure operation of the experimental system during the experiment, thereby realizing constant pressure control of the supercritical fluid adsorption / desorption process, and further eliminating the experimental errors of temperature and adsorption amount measurement caused by pressure changes. At the same time, the sample kettle adopts a triaxial stress loading structure to more accurately determine the temperature changes and material adsorption performance during the supercritical fluid adsorption process under real formation triaxial stress conditions, solving the problem of triaxial high pressure isothermal adsorption tests and direct measurement of sample volume changes during adsorption in current experimental technical equipment.

[0028] (3) The experimental scheme of the present invention proposes a new measurement method for supercritical fluid isothermal adsorption experiments, which can be compared with actual engineering conditions more realistically, and effectively avoid experimental errors caused by experimental pressure changes and indirect temperature measurements, thereby improving the accuracy and reliability of experimental data; by automatically collecting data and drawing curves through real-time monitoring and control systems, the experimental errors of human measurement results can be effectively reduced; through the experimental gas safety alarm system and waste treatment system, the safety, efficiency, low carbon and environmental protection of the entire experimental process can be effectively guaranteed; it can explore the adsorption performance of the adsorbent material on supercritical fluids and its own volume change characteristics under quantitative constant pressure conditions during the entire adsorption / desorption process, thereby providing guidance for the economy and safety of deep unconventional resource utilization and geological sealing storage layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the pseudo triaxial sample kettle;

[0030] Figure 2 It is a structural schematic diagram of a visual constant volume piston constant pressure reference kettle;

[0031] Figure 3 It is a schematic diagram of the overall structure of a supercritical fluid quantitative triaxial stress adsorption and deformation testing device;

[0032] In the figure, 1, gas cylinder; 2, pneumatic valve; 3, one-way ball valve; 4, first automatic high-pressure connecting needle valve; 5, filter; 6, gas booster pump; 7, constant temperature oil bath; 8, oil bath drain port; 9, oil bath insulation cover; 10, oil injection one-way valve; 11, CNC circulating oil bath control box; 12, precision double-cylinder injection pump; 13, liquid pressure gauge; 14, liquid data acquisition controller; 15, supercritical fluid storage kettle; 16, oil bath temperature sensor; 17, constant volume piston constant pressure reference kettle; 18, fine-tuning valve; 19, storage kettle temperature and pressure sensor; 20, reference kettle temperature and pressure sensor; 21, second automatic high-pressure connecting needle valve; 22, sample kettle temperature and pressure sensor; 23, false Three-axis sample kettle; 24. Vacuum valve; 25. Six-way regulating valve; 26. Waste gas treatment chamber; 27. Vacuum gauge; 28. Dryer; 29. ​​Vacuum pump; 30. Temperature and pressure data acquisition processor; 31. Computer; 32. Constant volume piston constant pressure reference kettle upper chamber; 33. Constant volume piston constant pressure reference kettle lower chamber; 34. Liquid storage tank; 35. Liquid automatic high-pressure connecting valve; 36. Fake three-axis stress loading control box; 37. Radial claw extensometer; 38. Axial displacement sensor; 39. Adjustable high-pressure gas production buffer valve; 40. Fake three-axis high-seal integrated copper sleeve; 41. High-pressure visual window; 42. High-definition camera; 43. Experimental gas concentration probe; 44. Deformation data acquisition processor. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The purpose of the present invention is to provide a supercritical fluid quantitative triaxial stress adsorption and deformation test system and method to realize the thermal effect of supercritical fluid constant pressure adsorption / desorption process under deep reservoir conditions. The experimental device uses a dual-channel temperature measurement sample kettle and a 1000mL constant volume piston constant pressure reference kettle to realize the internal and external surface temperature measurement during the constant pressure adsorption / desorption experiment of supercritical fluid and the adsorption material experiment, providing guidance for the economy and safety of deep unconventional resource utilization and geological sealing storage.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figures 1 to 3 As shown, the present invention provides a supercritical fluid quantitative triaxial stress adsorption and deformation test system, which is used to simulate the supercritical fluid quantitative constant pressure adsorption / desorption whole process experiment under high temperature and high pressure conditions at a reservoir depth of more than 800m, and at the same time measure the sample volume change generated during the whole experiment, and can realize the quantitative constant pressure experiment of the supercritical fluid and the direct measurement of the deformation during the experiment. The test system includes an oil bath constant temperature circulation heating system, a gas supply system, a real-time data monitoring and operating system, an experimental gas safety alarm system, a supercritical fluid storage kettle 15, a visual constant volume piston constant pressure reference kettle 17 and a pseudo triaxial sample kettle 23;

[0037] The oil bath constant temperature circulation heating system is used to provide a stable constant temperature environment for the test system, and the oil bath constant temperature circulation heating system includes a constant temperature oil bath tank 7, an oil injection one-way valve 10 and a CNC circulation oil bath control box 11; a supercritical fluid storage kettle 15, a visual constant volume piston constant pressure reference kettle 17 and a pseudo triaxial sample kettle 23 are arranged in the constant temperature oil bath tank 7; the tops of the supercritical fluid storage kettle 15, the visual constant volume piston constant pressure reference kettle 17 and the pseudo triaxial sample kettle 23 are connected to each other through pipelines; ... The piston constant pressure reference kettle 17 is a full-scale 1000mL constant volume piston kettle. A liquid pressure gauge 13, a liquid storage tank 34 and a precision double-cylinder injection pump 12 are connected to the bottom of the visual constant volume piston constant pressure reference kettle. The pseudo triaxial sample kettle 23 sets the axial pressure and confining pressure of the sample kettle through a pseudo triaxial stress loading control box 36. A pseudo triaxial high-sealed integrated copper sleeve 40 is set in the middle to place the sample. Three sets of parallel axial claw extensometers 37 are set in the radial direction of the copper sleeve, and a set of axial displacement sensors 38 and deformation data acquisition and processing are set in the axial direction. The device 44 is connected via a data line, and adjustable high-pressure gas collection buffer valves 39 are arranged at the inlet and outlet to collect the experimental fluid, and the sample to be tested is placed inside the fake three-axis high-seal integrated copper sleeve 40; the visual constant-volume piston constant-pressure reference kettle comprises an upper chamber 32 of the constant-volume piston constant-pressure reference kettle and a lower chamber 33 of the constant-volume piston constant-pressure reference kettle. According to the experimental pressure and temperature requirements, the position of the piston piece of the constant-volume piston constant-pressure reference kettle is adjusted by setting the constant-pressure operation mode, thereby changing the volume of the upper chamber to realize the adsorption / desorption test of the set pressure, The constant pressure adsorption / desorption experiment at each pressure point in the whole process is realized by adjusting the precision double-cylinder injection pump 12 and the liquid automatic high-pressure connecting valve 35; the pseudo triaxial sample kettle, including the radial claw extensometer 37, the axial displacement sensor 38, the inlet (outlet) adjustable high-pressure gas collection buffer valve 39 and the pseudo triaxial high-sealing integrated copper sleeve 40, injects liquid through the pseudo triaxial stress loading control box 36 according to the experimental pressure and temperature requirements, thereby changing the axial pressure and confining pressure of the sample kettle to realize the adsorption / desorption experiment under triaxial stress conditions.

[0038] A gas supply system is used to supply gas to the supercritical fluid quantitative triaxial stress adsorption and deformation testing system. The gas supply system is connected to the supercritical fluid storage kettle 15 through a pipeline; the gas supply system includes a gas cylinder 1, a pneumatic valve 2, a one-way ball valve 3, a first automatic high-pressure connecting needle valve 4 and a filter 5 connected in sequence, and the outlet end of the filter 5 is connected to a gas booster pump 6 for gas pressurization to meet the supercritical fluid pressure required for the experiment.

[0039] The real-time data monitoring and operating system includes a liquid data acquisition controller 14, a temperature and pressure data acquisition processor 30, a deformation data acquisition processor 44 and a computer 31. The temperature and pressure sensors on the supercritical fluid storage kettle 15, the constant volume piston constant pressure reference kettle 17 and the pseudo triaxial sample kettle 23 are connected to the temperature and pressure data acquisition processor 30. The radial claw extensometer 37 and the axial displacement sensor 38 inside the pseudo triaxial sample kettle are connected to the deformation data acquisition processor 44 through a transmission line. The top of the visible constant volume piston constant pressure reference kettle 17 is connected to the temperature and pressure data acquisition processor, and the bottom is connected to the liquid data acquisition controller 14 through a transmission line. The liquid data acquisition controller 14 and the temperature and pressure data acquisition processor 30 both send data information to the computer 31 in real time through the data transmission line. The computer is used to record the pressure and temperature data values ​​and draw change curves respectively, and send feedback instructions through the computer. The computer 31 sends the data to the device for control; the temperature and pressure data acquisition processor 30 includes an RS485 signal converter; the specific control process is: the temperature and pressure sensor is connected to the RS485 signal converter through a data line, and the signal converter transmits the data to the temperature and pressure monitoring interface of the computer, and a curve is drawn according to the temperature and pressure values; the constant volume piston constant pressure reference kettle 17, the liquid pressure gauge 13 and the precision double cylinder injection pump 12 are connected through an experimental pipeline, and the internal pressure of the constant volume piston constant pressure reference kettle 17 is fed back to the liquid data acquisition controller 14, and then the data information is sent to the computer 31 in real time through the data transmission line. The computer 31 adjusts the piston plate position in the constant volume piston constant pressure reference kettle 17 according to the experimental setting parameters and real-time data (through the feedback signal of the pressure value, the computer sends instructions to adjust the piston plate position), thereby achieving the purpose of the supercritical fluid constant pressure adsorption / desorption experiment;

[0040] The experimental gas safety alarm system is electrically connected to the computer 31, and the experimental gas safety alarm system includes two experimental gas concentration probes 43 and an alarm module. The experimental gas concentration probes are arranged on both sides of the inner wall of the air-liquid interface of the constant temperature oil bath, and are used to measure the experimental gas concentration in the constant temperature oil bath. The experimental gas concentration probes are connected to the alarm module, and the alarm module is electrically connected to the computer. When the experimental gas concentration measured by the experimental gas concentration probe is higher than the set safety value, an alarm is issued, and the alarm signal is fed back to the computer. In this way, the concentration of the experimental gas inside the equipment is measured by the experimental gas concentration probe 43, and the oil bath constant temperature circulation heating system is stopped when the concentration is higher than the set safety value.

[0041] Preferably, a fine-tuning valve 18 and a filter 5 are provided on the connecting pipeline between the supercritical fluid storage kettle 15 and the visual constant-volume piston constant-pressure reference kettle 17; on the pipeline connecting the supercritical fluid storage kettle 15 and the pseudo triaxial sample kettle 23, a storage kettle temperature and pressure sensor 19 is connected to the top of the kettle body of the supercritical fluid storage kettle, and a sample kettle temperature and pressure sensor 22 is connected to the top of the pseudo triaxial sample kettle; a second automatic high-pressure connecting needle valve 21 is provided on the pipeline connecting the visual constant-volume piston constant-pressure reference kettle 17 and the pseudo triaxial sample kettle 23; a reference kettle temperature and pressure sensor 20 is connected to the top of the visual constant-volume piston constant-pressure reference kettle 17; the storage kettle temperature and pressure sensor 19, the sample kettle temperature and pressure sensor 22 and the reference kettle temperature and pressure sensor 20 are all electrically connected to the temperature and pressure data acquisition processor 30.

[0042] Preferably, the bottom of the constant temperature oil bath 7 is connected to a numerically controlled circulating oil bath control box 11, and the numerically controlled circulating oil bath control box 11 sets the temperature and flow rate of the circulating oil through an oil injection one-way valve 10 to ensure a constant temperature environment for the experimental system; an oil bath insulation cover plate 9 is provided on the top of the constant temperature oil bath, and an oil bath drain port 8 is provided on the bottom.

[0043] Preferably, a vacuum valve 24 and a six-way regulating valve 25 are connected above the constant-volume piston constant-pressure reference kettle 17 , and the six-way regulating valve is respectively connected to the exhaust gas treatment chamber 26 and the vacuum pumping device, and the vacuum pumping device includes a vacuum pump 29 , a dryer 28 and a vacuum gauge 27 .

[0044] Preferably, a high-pressure visual window 41 is provided on the constant-volume piston constant-pressure reference kettle, and a high-definition camera 42 is provided in front of the high-pressure visual window, which is located in the oil bath; the high-definition camera is placed in a high-temperature resistant plastic shell, and the opening of the plastic shell is blocked by a double-layer rubber plastic sealing ring, and a plastic partition is laid above the high-definition camera. The lens position of the shell is made of high-temperature resistant transparent glass, which is convenient for observing the phase change state produced during the injection and release of supercritical fluids, and observing the state of the experimental adsorbent. The data transmission line below is wrapped with a high-temperature resistant plastic tube, and is connected to an external computer through the adapter opening at the bottom of the oil bath box, which is convenient for transmitting image information to the computer for storage and imaging.

[0045] The present invention provides a supercritical fluid quantitative triaxial stress adsorption and deformation testing method, comprising the following steps:

[0046] Step 1, full-scale calibration of the visual constant-volume piston constant-pressure reference kettle; evacuate the supercritical fluid quantitative triaxial stress adsorption and deformation test system, place the piston plate of the inner cavity of the visual constant-volume piston constant-pressure reference kettle at the bottom, fill the reference kettle with high-pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo triaxial temperature sample kettle, inject helium into the pseudo triaxial sample kettle, and record the equilibrium pressure and temperature after the visual constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle are both adsorbed and balanced, and calculate the volume of the visual constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle. According to the law of conservation of matter and the real gas state equation PV=nZRT, the calculation formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; M He is the relative molecular mass of helium, g / mol; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ;P S is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; V0 is the inner cavity volume of the pseudo triaxial sample kettle (standard block volume), cm 3 ; Z S The pressure P is the balance pressure after the constant volume piston constant pressure reference kettle and the dual channel temperature measurement sample kettle are connected. S The helium compression factor under ; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; according to the law of conservation of mass, the calculation formula is as follows: The volume of the constant-volume piston constant-pressure reference kettle and the volume of the inner cavity of the pseudo-triaxial sample kettle are obtained; in order to make a quantitative comparison with the standard volume on the factory nameplate of the kettle body, the relative deviation ARD (absolute relative deviation) of the absolute value is defined as: Where V measure 、V standard is the measured calibration volume and the factory nameplate standard volume, cm 3 ; When the ARD value is less than 0.05%, the kettle volume calibration is correct and the next step can be performed;

[0047] Step 2: Before conducting the triaxial stress isothermal adsorption experiment, the sample to be tested is first subjected to balanced water treatment or drying treatment according to the experimental requirements, and the sample is placed in a vacuum blower at 105°C for 12 hours for drying, and then weighed again and placed in the inner cavity of the copper sleeve of the pseudo triaxial sample kettle;

[0048] Step 3, determination of the remaining free volume of the pseudo triaxial sample kettle: evacuate the entire system, place the piston plate of the constant volume piston constant pressure reference kettle cavity at the bottom, full scale state, fill the kettle with high pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high pressure connecting needle valve to inject helium into the pseudo triaxial sample kettle, and record the equilibrium pressure and temperature after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are both adsorbed and balanced. According to the law of conservation of matter and the real gas state equation PV = nZRT, calculate the free space volume, the formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; M He is the relative molecular mass of helium, g / mol; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ;P S V is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; F is the volume of free space in the pseudo triaxial sample reactor, cm 3 ; Z S The equilibrium pressure P after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected S The helium compression factor under ; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K;

[0049] Step 4, quantitative triaxial stress adsorption and deformation experiment of supercritical fluid: evacuate the whole system for 1 hour, close all valves, set the experimental environment temperature through the oil bath constant temperature circulation heating system; inject high-pressure gas into the storage kettle, and observe the temperature and pressure values; when the pressure fluctuation range is less than 0.1psi / h, and the temperature fluctuation range is less than 0.025℃ / h, the state value is used as the standard value for measuring the equilibrium, open the fine-tuning valve, and inject the supercritical fluid with the set pressure value into the upper chamber of the constant-volume piston constant-pressure reference kettle, observe the phase change of the fluid through the high-definition camera, and record the equilibrium pressure and temperature of the constant-volume piston constant-pressure reference kettle. When the pressure and temperature reach equilibrium, open the second automatic high-pressure connecting needle valve and the liquid automatic high-pressure connecting valve, and pass The precision double-cylinder injection pump pushes the piston plate according to the set pressure value to change the volume of the lower chamber of the constant-volume piston constant-pressure reference kettle, and the supercritical gas in the upper chamber of the constant-volume piston constant-pressure reference kettle is injected into the pseudo-triaxial sample kettle at a constant pressure. When the pseudo-triaxial stress reaches the set value, the second automatic high-pressure connecting needle valve is closed to wait for adsorption equilibrium. In this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range and the temperature fluctuation range reach the equilibrium standard, it is considered that the adsorption pressure has reached equilibrium. After being closed and static for 24 hours, the deformation data is recorded to complete the adsorption and deformation experiments at the current pressure point.

[0050] Step 5. After the previous pressure adsorption experiment is completed, open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle again to gradually increase the pressure at 1MPa to perform the constant-pressure adsorption experiment at the next pressure point until all adsorption pressure experiments are completed. According to the law of conservation of mass, the formula for calculating the adsorption amount of the adsorption process at one experimental pressure point is as follows: Where n ex The sample to be tested in the experimental false triaxial sample kettle is at the set pressure P e The Gibbs adsorption capacity under the condition of mol is mol; m is the mass of the sample to be tested in the experiment, g; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; P e is the set pressure of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment, MPa; Z e is the set pressure P of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment e Gas compressibility factor under V R is the full scale volume of the upper chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; ΔV is the volume change of the lower chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; V F is the remaining free volume in the pseudo-triaxial sample kettle, cm3 ; Gibbs adsorption capacity of the whole adsorption experiment (GSE n ) is as follows: Where n is the total number of pressure values ​​to be measured in the experiment; GSE n is the sum of n ΔGBEs; ΔGBE i is the adsorption amount at the i-th test pressure value;

[0051] Step 6. After the highest adsorption pressure in step 5 is achieved, open the vacuum valve and six-way regulating valve connected to the upper part of the constant volume piston constant pressure reference kettle, connect the exhaust gas treatment chamber, and vent the supercritical fluid in the upper chamber of the constant volume piston constant pressure reference kettle. At the same time, push the piston piece of the lower chamber of the constant volume piston constant pressure reference kettle to the top of the kettle body through the precision double-cylinder injection pump according to the set pressure value, then close the vent valve of the constant volume piston constant pressure reference kettle, open the second automatic high-pressure connecting needle valve, and inject the high-pressure gas in the false triaxial sample kettle into the constant volume piston constant pressure reference kettle until the false triaxial sample kettle is vented. After the pressure value in the inner cavity of the axial sample kettle reaches the target value, the second automatic high-pressure connecting needle valve is closed to wait for desorption equilibrium; during this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range is less than 0.1psi / h and the temperature fluctuation range is less than 0.025℃ / h, it is considered that the desorption and deformation experiments under the desorption pressure are completed;

[0052] Step 7: Open the vacuum valve, six-way regulating valve and vacuum pump, and gradually reduce the pressure to 1 MPa to conduct a constant-pressure desorption experiment at the next pressure point until all desorption pressure experiments are completed.

[0053] After all pressure value tests are completed, the sample kettle will be disassembled and the sample will be taken out to analyze the adsorption performance and volume change characteristics of the adsorption material on the supercritical fluid at two points before and after the experiment.

[0054] Preferably, before step 1, an air tightness check of the pseudo triaxial sample kettle is performed, and the specific operation steps are as follows: Pseudo triaxial sample kettle air tightness test: place the standard block V0 in the pseudo triaxial high-sealed integrated copper sleeve, and alternately load the sample kettle axial pressure and confining pressure to the set value through the pseudo triaxial stress loading control box. The volume stress calculation formula of the test sample is as follows: In the formula, σ s ,σ fare axial stress and confining pressure, MPa; P1 and P2 are gas pressures at the inlet and outlet of the sample kettle, MPa. The radial claw extensometer and axial displacement sensor are zeroed, and helium with a pressure 1.5 times higher than the maximum experimental pressure is introduced into the kettle for more than 24 hours. The temperature of the constant temperature oil bath is adjusted to the reservoir temperature, and the computer system page curve is continuously observed. If the pressure indication changes less than 0.1psi / h and the temperature indication changes less than 0.025℃ / h, it means that the air tightness is good, and then proceed to step 1.

[0055] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0056] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A supercritical fluid quantitative triaxial stress adsorption and deformation testing system, characterized in that: It is used to simulate the whole process experiment of supercritical fluid quantitative constant pressure adsorption / desorption under triaxial geostress and high temperature conditions at a depth of more than 800m, and measure the deformation of the coal body during the whole process of the experiment. It can realize the quantitative constant pressure experiment of supercritical fluid under triaxial constraint conditions and directly measure the deformation during the experiment. The test system includes oil bath constant temperature circulation heating system, gas supply system, real-time data monitoring and operation system, experimental gas safety alarm system, supercritical fluid storage kettle, visual constant volume piston constant pressure reference kettle and pseudo triaxial sample kettle; The gas supply system is connected to the supercritical fluid storage kettle through a pipeline; the real-time data monitoring and operating system includes a liquid data acquisition controller, a temperature and pressure data acquisition processor, a deformation data acquisition processor and a computer; the experimental gas safety alarm system includes two experimental gas concentration probes and an alarm module, which are electrically connected to the computer; the oil bath constant temperature circulation heating system is used to provide a stable constant temperature environment for the test system, and the oil bath constant temperature circulation heating system includes a constant temperature oil bath tank, an oil injection check valve and a CNC circulation oil bath control box; in the constant temperature oil The bath is provided with a supercritical fluid storage kettle, a visual constant volume piston constant pressure reference kettle and a pseudo triaxial sample kettle; the tops of the supercritical fluid storage kettle, the visual constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected to each other through pipelines; the visual constant volume piston constant pressure reference kettle is a full-scale 1000mL constant volume piston kettle, and a liquid automatic high-pressure connecting valve is provided at the bottom of the visual constant volume piston constant pressure reference kettle, which is connected to a liquid pressure gauge, a liquid storage tank and a precision double-cylinder injection pump through a pipeline; the pseudo triaxial sample kettle includes a radial claw extensometer, an axial displacement sensor , an adjustable high-pressure gas production buffer valve and a fake three-axis high-seal integrated copper sleeve, the axial pressure and confining pressure of the sample kettle are set by the fake three-axis stress loading control box, a fake three-axis high-seal integrated copper sleeve is set in the middle to place the sample to be tested, three groups of parallel axial claw extensometers are set in the radial direction of the copper sleeve, and a set of axial displacement sensors and deformation data acquisition processors are set in the axial direction and connected through a data line, and adjustable high-pressure gas production buffer valves are set at the inlet and outlet to collect experimental fluids; the visual constant-volume piston constant-pressure reference kettle is provided with a piston sheet inside, which divides the visual constant-volume piston constant-pressure reference kettle into an upper The upper chamber and the lower chamber, according to the experimental pressure and temperature requirements, adjust the position of the piston piece of the constant-volume piston constant-pressure reference kettle by setting the constant pressure operation mode, and then change the volume of the upper chamber to realize the adsorption / desorption experiment under the set pressure, and adjust it through the precision double-cylinder liquid injection pump and the liquid automatic high-pressure connecting valve to realize the constant-pressure adsorption / desorption experiment at each pressure point in the whole process; the pseudo-triaxial sample kettle, according to the experimental pressure and temperature requirements, injects liquid through the pseudo-triaxial stress loading control box, and then changes the axial pressure and confining pressure of the sample kettle to realize the adsorption / desorption experiment under triaxial stress conditions.

2. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: The gas supply system includes a gas cylinder, a pneumatic valve, a one-way ball valve, a first automatic high-pressure connecting needle valve and a filter connected in sequence. The outlet end of the filter is connected to a gas booster pump for gas pressurization to meet the supercritical fluid pressure required for the experiment.

3. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: The connecting pipeline between the supercritical fluid storage kettle and the visual constant volume piston constant pressure reference kettle is provided with a fine adjustment valve and a filter; on the connecting pipeline between the supercritical fluid storage kettle and the pseudo triaxial sample kettle, the top of the kettle body of the supercritical fluid storage kettle is connected with a storage kettle temperature and pressure sensor, and the top of the pseudo triaxial sample kettle is connected with a sample kettle temperature and pressure sensor; the connecting pipeline between the visual constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle is provided with a second automatic high-pressure connecting needle valve; the top of the visual constant volume piston constant pressure reference kettle is connected with a reference kettle temperature and pressure sensor; the storage kettle temperature and pressure sensor , the sample kettle temperature and pressure sensor and the reference kettle temperature and pressure sensor are all electrically connected to the temperature and pressure data acquisition processor; the radial claw extensometer and axial displacement sensor inside the pseudo triaxial sample kettle are connected to the deformation data acquisition processor through a transmission line, and the bottom of the visual constant volume piston constant pressure reference kettle is connected to the liquid data acquisition controller through a transmission line; the deformation data acquisition processor, liquid data acquisition controller and temperature and pressure data acquisition processor all send data information to the computer in real time through the data transmission line, and the computer records the pressure and temperature data values ​​and draws the change curves respectively.

4. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: The bottom of the constant temperature oil bath is connected to a numerically controlled circulating oil bath control box, which sets the circulating oil temperature and flow rate through an oil injection one-way valve to ensure a constant temperature environment for the experimental system; an oil bath insulation cover is provided on the top of the constant temperature oil bath, and an oil bath drain port is provided on the bottom.

5. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: The experimental gas concentration probe is arranged on both sides of the inner wall of the air-liquid interface of the constant temperature oil bath, and is used to measure the experimental gas concentration in the constant temperature oil bath. The experimental gas concentration probe is connected to the alarm module, and the alarm module is electrically connected to the computer. When the experimental gas concentration measured by the experimental gas concentration probe is higher than the set safety value, an alarm is issued and the alarm signal is fed back to the computer.

6. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: A vacuum valve and a six-way regulating valve are connected above the constant-volume piston constant-pressure reference kettle. The six-way regulating valve is respectively connected to the exhaust gas treatment chamber and the vacuum pumping device. The vacuum pumping device includes a vacuum pump, a dryer and a vacuum gauge.

7. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: A high-pressure visual window is provided on the visual constant-volume piston constant-pressure reference kettle, and a high-definition camera is provided in front of the high-pressure visual window; The high-definition camera is located in an oil bath and placed in a high-temperature resistant plastic shell. The opening of the plastic shell is blocked by a double-layer rubber plastic sealing ring, and a plastic partition is laid above the high-definition camera. The lens position of the high-definition camera uses high-temperature resistant transparent glass to facilitate observation of the phase change state produced during the supercritical fluid injection and release process; The data transmission line below is wrapped with a high-temperature resistant plastic tube and connected to an external computer.

8. The supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to claim 1, characterized in that: A high-pressure visual window is provided on the constant-volume piston constant-pressure reference autoclave, and a high-definition camera is provided directly in front of the high-pressure visual window. The high-definition camera is located in an oil bath and placed in a high-temperature resistant plastic shell. The opening of the plastic shell is blocked by a double-layer rubber plastic sealing ring, and a plastic partition is laid above the high-definition camera. High-temperature resistant transparent glass is used at the lens position of the high-definition camera shell, which is convenient for observing the phase change state produced during the injection and release processes of the supercritical fluid, and observing the state of the experimental adsorbent.

9. A supercritical fluid quantitative triaxial stress adsorption and deformation testing method, using the supercritical fluid quantitative triaxial stress adsorption and deformation testing system according to any one of claims 1 to 8, characterized in that The following steps are involved: Step 1: Full-scale calibration of the visual constant-volume piston constant-pressure reference kettle: evacuate the test system, place the piston plate of the inner cavity of the visual constant-volume piston constant-pressure reference kettle at the bottom, fill the reference kettle with high-pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial temperature sample kettle, inject helium into the pseudo-triaxial sample kettle, and record the equilibrium pressure and temperature after the visual constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle are both adsorbed and balanced, and calculate the volume of the visual constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle. According to the law of conservation of matter and the real gas state equation PV=nZRT, the calculation formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ; P S is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; V0 is the volume of the standard block, that is, the volume of the inner cavity of the pseudo triaxial sample kettle, cm 3 ; Z S The equilibrium pressure P after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected S The helium compression factor under the condition of ; R is the universal gas constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; liquid is injected into the lower chamber of the constant volume piston constant pressure reference kettle through a precision double-cylinder injection pump to push the piston to the half-scale position. According to the law of conservation of mass, the calculation formula is as follows: The volume of the constant-volume piston constant-pressure reference kettle and the inner cavity volume of the pseudo-triaxial sample kettle are obtained; in order to make a quantitative comparison with the standard volume on the factory nameplate of the kettle body, the relative deviation ARD of the absolute value is defined as: Where V measure 、V standard is the measured calibration volume and the factory nameplate standard volume, cm 3 ; When the ARD value is less than 0.05%, the kettle volume calibration is correct and proceed to the next step; Step 2: Sample pretreatment: Before conducting the triaxial stress isothermal adsorption experiment, the sample to be tested is first subjected to balanced water treatment or drying treatment according to the experimental requirements, and the sample is placed in a vacuum blower at 105°C for 12 hours for drying, and then weighed again and placed in the copper sleeve cavity of the pseudo triaxial sample kettle; Step 3, determination of the remaining free volume of the pseudo triaxial sample kettle: evacuate the test system, place the piston plate of the constant volume piston constant pressure reference kettle cavity at the bottom, full scale state, fill the kettle with high pressure helium, and record the equilibrium pressure and temperature in the kettle after reaching equilibrium; open the second automatic high pressure connecting needle valve to inject helium into the pseudo triaxial sample kettle, and record the equilibrium pressure and temperature after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are both adsorbed and balanced. According to the law of conservation of matter and the real gas state equation PV = nZRT, calculate the free space volume, the formula is as follows: Where P R is the initial equilibrium pressure in the constant-volume piston constant-pressure reference kettle, MPa; Z R is the initial equilibrium pressure P in the constant-volume piston constant-pressure reference kettle R Helium compression factor under R is the volume of the constant-volume piston constant-pressure reference kettle, cm 3 ;P S V is the equilibrium pressure after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected, MPa; F is the volume of free space in the pseudo triaxial sample reactor, cm 3 ; Z S The equilibrium pressure P after the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle are connected S The helium compression factor under ; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; Step 4, quantitative triaxial stress adsorption and deformation experiment of supercritical fluid: evacuate the test system for 1 hour, close all valves, and set the experimental environment temperature through the oil bath constant temperature circulation heating system; inject high-pressure gas into the supercritical fluid storage kettle and observe the temperature and pressure values; when the pressure fluctuation range is less than 0.1psi / h and the temperature fluctuation range is less than 0.025℃ / h, the state value is used as the standard value to measure the equilibrium, open the fine-tuning valve, inject the supercritical fluid with the set pressure value into the upper chamber of the constant volume piston constant pressure reference kettle, observe the fluid phase change through the high-definition camera, and record the equilibrium pressure and temperature of the constant volume piston constant pressure reference kettle. When the pressure and temperature reach equilibrium, open the second automatic high-pressure connecting needle valve and the liquid automatic high-pressure connecting valve, push the piston plate according to the set pressure value through the precision double-cylinder injection pump to change the volume of the lower chamber of the constant volume piston constant pressure reference kettle, and inject the supercritical gas in the upper chamber of the constant volume piston constant pressure reference kettle into the pseudo triaxial sample kettle at constant pressure. When the pseudo triaxial stress reaches the set value, close the second automatic high-pressure connecting needle valve and wait for adsorption equilibrium; During this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range and temperature fluctuation range reach the equilibrium standard, it is considered that the adsorption pressure has reached equilibrium. After being closed and static for 24 hours, the deformation data is recorded to complete the adsorption and deformation experiments at the current pressure point. Step 5. After the previous pressure adsorption experiment is completed, open the second automatic high-pressure connecting needle valve between the constant-volume piston constant-pressure reference kettle and the pseudo triaxial sample kettle again to gradually increase the pressure by 1 MPa to perform the constant-pressure adsorption experiment of the next pressure value until all adsorption pressure experiments are completed. According to the law of conservation of mass, the formula for calculating the adsorption amount of the adsorption process of one experimental pressure value is as follows: Where n ex The sample to be tested in the experimental false triaxial sample kettle is at the set pressure P e The Gibbs adsorption capacity under the condition of mol is mol; m is the mass of the sample to be tested in the experiment, g; R is the gas universal constant, 8.314 J / (mol·K); T is the experimental environment temperature, K; P e is the set pressure of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment, MPa; Z e is the set pressure P of the constant-volume piston constant-pressure reference kettle and the pseudo-triaxial sample kettle in the constant-pressure experiment e Gas compressibility factor under V R is the full scale volume of the upper chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; ΔV is the volume change of the lower chamber of the constant pressure reference kettle with constant volume piston, cm 3 ; V F is the remaining free volume in the pseudo-triaxial sample kettle, cm 3 ; Gibbs adsorption amount GSE of the whole adsorption experiment n The formula is as follows: Where n is the total number of pressure values ​​to be measured in the experiment; GSE n is the sum of n ΔGBEs; ΔGBE i is the adsorption amount at the i-th test pressure value; After the highest adsorption pressure in step 6 and step 5 is achieved, open the vacuum valve and the six-way regulating valve connected to the upper part of the constant volume piston constant pressure reference kettle, connect the exhaust gas treatment chamber, and vent the supercritical fluid in the upper chamber of the constant volume piston constant pressure reference kettle. At the same time, push the piston piece of the lower chamber of the constant volume piston constant pressure reference kettle to the top of the kettle body through the precision double-cylinder injection pump according to the set pressure value, then close the vent valve of the constant volume piston constant pressure reference kettle, open the second automatic high-pressure connecting needle valve, and inject the high-pressure gas in the fake triaxial sample kettle into the constant volume piston constant pressure reference kettle until the fake After the pressure value in the inner cavity of the triaxial sample kettle reaches the target value, the second automatic high-pressure connecting needle valve is closed to wait for desorption equilibrium; during this process, the temperature and pressure data acquisition processor collects the supercritical fluid pressure and temperature values ​​of the constant volume piston constant pressure reference kettle and the pseudo triaxial sample kettle, and the deformation data acquisition processor collects the data of the radial claw extensometer and the axial displacement sensor. When the system pressure fluctuation range is less than 0.1psi / h and the temperature fluctuation range is less than 0.025℃ / h, the desorption and deformation experiments under the desorption pressure are considered to be completed; Step 7: Open the vacuum valve, six-way regulating valve and vacuum pump, and gradually reduce the pressure by 1 MPa to conduct a constant-pressure desorption experiment at the next pressure value until all desorption pressure experiments are completed.

10. The method for quantitative triaxial stress adsorption and deformation testing of supercritical fluid according to claim 9, characterized in that: Before step 1, perform an air tightness check on the pseudo triaxial sample kettle. The specific steps are as follows: Air tightness test on the pseudo triaxial sample kettle: Place the standard block V0 in the pseudo triaxial high-seal integrated copper sleeve, and alternately load the sample kettle axial pressure and confining pressure to the set value through the pseudo triaxial stress loading control box. The volume stress calculation formula for the test sample is as follows: In the formula, σ s ,σ f are axial stress and confining pressure, MPa respectively; P1 and P2 are gas pressures at the inlet and outlet of the sample kettle, MPa; the radial claw extensometer and axial displacement sensor are adjusted to zero, helium with a pressure 1.5 times higher than the maximum experimental pressure is introduced into the pseudo triaxial sample kettle for more than 24 hours, the temperature of the constant temperature oil bath is adjusted to the reservoir temperature, and the computer system page curve is continuously observed. If the pressure indication changes less than 0.1psi / h and the temperature indication changes less than 0.025℃ / h, it means that the airtightness is good, then proceed to step one.

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