Device and method for testing comprehensive performance of proppant for cracks

Abstract

The invention provides a comprehensive performance testing device and method for a crack proppant, and a fluid injection mechanism is connected to a crack in a rock sample arranged in a triaxial loading mechanism in a sealing manner, and is used for injecting a matrix, the proppant and an exciting agent into the crack in the rock sample; the fluid flowback mechanism is connected to a crack in the rock sample and is used for storing fluid flowback from the crack of the rock sample; the rock sample is arranged in the triaxial loading mechanism in a sealed mode, and the triaxial loading mechanism is used for applying axial pressure and confining pressure to the rock sample so as to simulate the triaxial stress state borne by underground deep reservoirs and cracks. And the test result acquisition and analysis mechanism is used for acquiring data and images in the comprehensive performance test process of the proppant so as to analyze and evaluate the change of the diversion performance of the proppant before and after expansion. According to the device and the test method, the triaxial stress state borne by a reservoir and a crack can be simulated, and the comprehensive test of migration, expansion and flow conductivity of the self-expanding proppant in the rock crack can be realized.

Description

Technical Field

[0001] The present application relates to the field of deep underground structure reconstruction, and in particular to a comprehensive performance testing device for a crack proppant and a testing method thereof. Background Art

[0002] In the process of transformation and development of underground structures such as oil and gas, geothermal energy, and minerals, reservoir fracturing is an important means to increase reservoir permeability and increase production. Proppant is an important part of reservoir fracturing transformation technology. After the cracks are generated by fracturing, proppants need to be injected into the cracks to keep the cracks open and prevent them from closing after the pressure is released. The rational use of proppants can enhance the stability of cracks, effectively optimize the crack network, improve the efficiency of underground resource extraction, reduce the impact on the environment, and ensure the sustainability of engineering projects.

[0003] Conductivity is the most important indicator to measure the improvement of reservoir fracture permeability by proppants. Testing and evaluating the conductivity of proppants through experiments is a prerequisite for selecting the appropriate proppant type and optimizing the process parameters of proppants such as particle size and concentration in reservoir fracturing transformation. At present, the test method for proppant conductivity is mainly the petroleum and natural gas industry standard "SY∕T 6302-2019 Test Method for Conductivity of Fracturing Proppants" issued by the National Energy Administration. The device used is a fracture conductivity meter developed in accordance with the API standard. This method uses two rock plates in the diversion chamber to simulate the reservoir, evenly lays proppants between the two rock plates to simulate the effect of proppants on the fractures, applies uniform normal pressure to the rock plates to simulate the closing pressure of the fractures, measures the pressure difference between the inlet and outlet of the fracture during fluid displacement, and calculates the permeability of the fracture and the conductivity of the proppant through Darcy's law.

[0004] This method has several problems: ① The proppant is pre-filled in the fracture in a uniform manner, which makes it difficult to reflect the migration process of the proppant in the fracture during the injection process of the actual project, and it is also difficult to observe the distribution morphology of the proppant in the fracture; ② The rock plate only bears normal pressure and is in a state of uniaxial loading, which cannot reflect the triaxial stress state of the reservoir in the actual project, resulting in only the simulation of the most ideal tension fractures, and cannot simulate more complex fractures such as shear fractures; ③ It is impossible to carry out new proppant tests such as temperature changes or chemical reagents to stimulate expansion, making it difficult to observe the expansion effect and evaluate the changes in conductivity before and after expansion.

[0005] Therefore, how to achieve comprehensive testing of the migration, expansion and conductivity of self-expanding proppants in fractures is of great significance for the process design and engineering application of this new type of proppant under complex geological conditions. Summary of the invention

[0006] One of the purposes of the present application is to provide a comprehensive performance testing device and method for proppants for fractures, which can realize comprehensive testing of migration, expansion and conductivity of self-expanding proppants in fractures, and evaluate changes in proppant conductivity before and after expansion.

[0007] The technical solution of this application is: A device for testing comprehensive properties of proppants for fractures comprises a fluid injection mechanism, a fluid return mechanism, a triaxial loading mechanism and a test result acquisition and analysis mechanism; the fluid injection mechanism is connected to a fracture in a rock sample sealed in the triaxial loading mechanism and is used to respectively inject a matrix, a proppant and an activator into the fracture in the rock sample, the matrix being used to transport the proppant into the fracture in the rock sample, and the activator being used to activate the proppant to expand; the fluid return mechanism is connected to the fracture in the rock sample and is used to store fluid returned from the fracture in the rock sample; the rock sample is sealed in the triaxial loading mechanism, and the triaxial loading mechanism is used to respectively apply axial pressure and confining pressure to the rock sample to simulate the triaxial stress state borne by deep underground reservoirs and fractures; the test result acquisition and analysis mechanism is used to acquire data and images during the test of the comprehensive properties of the proppant, so as to analyze and evaluate the changes in the flow conductivity of the proppant before and after expansion.

[0008] As a technical solution of the present application, the fluid injection mechanism includes a matrix storage tank, an activator storage tank, a first high-pressure plunger pump, a second high-pressure plunger pump, a fluid heating temperature controller and a proppant addition tank; the matrix storage tank and the first high-pressure plunger pump are connected through a first pneumatic valve and a first connecting pipe; the activator storage tank and the second high-pressure plunger pump are connected through a second pneumatic valve and a second connecting pipe; the first high-pressure plunger pump is connected to the inlet of the fluid heating temperature controller through a third pneumatic valve and a third connecting pipe, for conveying a matrix injection source to the fluid heating temperature controller; the second high-pressure plunger pump is connected to the inlet of the fluid heating temperature controller through a fourth pneumatic valve and The fourth connecting pipe is connected to the inlet of the fluid heating thermostat, and is used to transport the stimulant injection source to the fluid heating thermostat; the fluid heating thermostat is connected to the top of the crack of the rock sample through the fifth pneumatic valve, the sixth pneumatic valve and the fifth connecting pipe; the top of the proppant addition tank is connected to the upper part of the fifth connecting pipe through the seventh pneumatic valve and the sixth connecting pipe, and the bottom end is connected to the lower part of the fifth connecting pipe through the eighth pneumatic valve and the seventh connecting pipe; the fifth pneumatic valve is located between the fluid heating thermostat and the sixth connecting pipe; the sixth pneumatic valve is located between the sixth connecting pipe and the seventh connecting pipe.

[0009] As a technical solution of the present application, a first fluid pressure sensor is provided at the inlet of the fluid heating temperature controller.

[0010] As a technical solution of the present application, a mass flow meter, a safety valve, a second fluid pressure sensor and a first fluid temperature sensor are sequentially arranged on the fifth connecting pipe; the second fluid pressure sensor is used to monitor the pressure of the fluid in the fifth connecting pipe in real time; the first fluid temperature sensor is used to monitor the temperature of the fluid in the fifth connecting pipe in real time.

[0011] As a technical solution of the present application, the fluid return mechanism includes a fluid recovery tank; the fluid recovery tank is connected to the bottom of the crack of the rock sample through an eighth connecting pipe; the eighth connecting pipe is provided with a ninth pneumatic valve, a volume flow meter, a second fluid temperature sensor, a third fluid pressure sensor and a pressure regulating valve in sequence from close to to away from the rock sample; the third fluid pressure sensor is used to monitor the pressure of the fluid in the eighth connecting pipe in real time; the second fluid temperature sensor is used to monitor the temperature of the fluid in the eighth connecting pipe in real time; the pressure regulating valve is used to adjust the return pressure at the crack outlet of the rock sample in real time.

[0012] As a technical solution of the present application, the three-axis loading mechanism includes a sealing cylinder, an axial hydraulic transmission assembly, an upper sealing pad, a lower sealing pad and a circumferential hydraulic transmission assembly; the rock sample seal is arranged in the pressure chamber of the sealing cylinder; the upper sealing pad is arranged on the top of the rock sample; the lower sealing pad is arranged at the bottom of the rock sample; one end of the axial hydraulic transmission assembly extends into the pressure chamber and is transmission-connected to the top of the upper sealing pad for applying axial pressure to the rock sample; the hydraulic end of the circumferential hydraulic transmission assembly is connected to the pressure chamber for injecting liquid into the pressure chamber to apply confining pressure to the rock sample.

[0013] As a technical solution of the present application, the sealing cylinder includes a cylinder body, an upper cover, a base and a clamp; the cylinder body is fastened to the base through the clamp; and the upper cover is arranged on the top of the cylinder body.

[0014] As a technical solution of the present application, the axial hydraulic transmission assembly includes a first servo hydraulic pump, a ninth connecting pipe, an axial hydraulic transmission and a pressure rod; the first servo hydraulic pump is connected to the axial hydraulic transmission through the ninth connecting pipe; the axial hydraulic transmission is transmission-connected to the top of the pressure rod; the top of the pressure rod extends out of the upper cover, and the lower seal is clamped in the cylinder and extends into the pressure chamber and is movably arranged on the top of the upper sealing gasket.

[0015] As a technical solution of the present application, the circumferential hydraulic transmission assembly includes a second servo hydraulic pump and a tenth connecting pipe; the second servo hydraulic pump is connected to the bottom of the pressure chamber through the tenth connecting pipe for injecting liquid into the pressure chamber.

[0016] As a technical solution of the present application, the rock sample is composed of two semi-cylinders, and the middle part has the crack that penetrates the top and bottom and extends axially.

[0017] As a technical solution of the present application, the test result collection and analysis mechanism includes a fiber grating strain sensor, a high-pressure sealed fiber optic connector, a transmission fiber, a fiber grating demodulator, a CT ray source, a CT detector and an electronic computer; the fiber grating strain sensor is evenly wound on the outer peripheral side of the rock sample, and the end is led out through the high-pressure sealed fiber optic connector and connected to the fiber grating demodulator through the transmission fiber; the fiber grating demodulator is used to demodulate the received optical signal and perform quasi-distributed measurement of the annular strain of the rock sample by wavelength division multiplexing; the CT ray source and the CT detector are respectively arranged at intervals outside the opposite sides of the three-axis loading mechanism, and the X-rays emitted by the CT ray source pass through the rock sample and are received by the CT detector to obtain an image of the distribution of the proppant in the cracks of the rock sample; the electronic computer is electrically connected to the fiber grating demodulator and the CT detector respectively, and is used to receive and store the collected data.

[0018] As a technical solution of the present application, the arrangement direction of the fiber Bragg grating in the fiber Bragg grating strain sensor is set at an angle to the horizontal cross section of the rock sample.

[0019] As a technical solution of the present application, the matrix includes supercritical carbon dioxide.

[0020] A method for testing the comprehensive performance of a fracture proppant is provided, using the above-mentioned device for testing the comprehensive performance of a fracture proppant, and comprises the following steps: S1, installing the rock sample in the comprehensive performance testing device for the fracture proppant, and applying confining pressure and axial pressure to the rock sample respectively, so that the rock sample reaches a set triaxial stress state; S2, injecting the proppant into the fracture of the rock sample, and allowing the proppant to migrate in the fracture; S3, performing a conductivity test on the proppant before expansion; S4, stimulating the proppant in the fracture to cause the proppant to expand; S5, performing a conductivity test on the expanded proppant; S6, evaluating the conductivity of the environmentally responsive self-expanding proppant.

[0021] As a technical solution of the present application, in step S1, the following steps are specifically included: S11, before the test, the cylindrical rock is cut into two symmetrical semi-cylinders, and the two semi-cylinders are cleaned and placed in a drying oven for drying; S12, installing a lower sealing pad on the base of the pressure chamber of the cylinder of the triaxial loading mechanism, laying a nylon filter with a mesh diameter smaller than the particle size of the proppant on the lower sealing pad; assembling the two semi-cylinders into the rock sample and installing it on the lower sealing pad, then installing an upper sealing pad on the top of the rock sample, and wrapping a heat shrink tube on the outside of the rock sample; connecting the fluid injection mechanism to the inlet of the fracture through the upper sealing pad, and connecting the fluid return mechanism to the outlet of the fracture through the lower sealing pad; S13, winding and installing a fiber Bragg grating strain sensor on the outer peripheral side of the rock sample, leading out the fiber Bragg grating strain sensor from the high-pressure sealed optical fiber connectors respectively installed on the top and bottom of the base in sequence, and connecting it to the fiber Bragg grating demodulator via the transmission optical fiber; providing an upper cover for sealing the cylinder body on the top of the cylinder body, installing a pressure rod in the upper cover that is transmission-connected to the first servo hydraulic pump in the three-axis loading mechanism, and extending into the pressure chamber and being located on the top of the upper sealing pad; S14, applying axial pressure to the rock sample through the first servo hydraulic pump so that the pressure rod contacts the upper sealing pad; injecting silicone oil into the pressure chamber through the second servo hydraulic pump in the triaxial loading mechanism to load the rock sample to the target confining pressure, and at the same time driving the axial hydraulic transmission connected to the first servo hydraulic pump to continue loading the rock sample to the target axial pressure, so that the rock sample is in a target triaxial stress state.

[0022] As a technical solution of the present application, in step S2, the following steps are specifically included: S21, configuring the environmentally responsive self-expanding proppant according to a pre-designed proppant injection scheme, and placing the proppant in the fluid injection mechanism into a proppant addition tank; S22, opening the first pneumatic valve and the third pneumatic valve in the fluid injection mechanism, starting the first high-pressure plunger pump in the fluid injection mechanism, and pumping the liquid carbon dioxide in the matrix storage tank in the fluid injection mechanism into the fluid heating temperature controller in the fluid injection mechanism to generate supercritical carbon dioxide at a specified temperature and pressure; S23, closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the sixth pneumatic valve in the fluid injection mechanism, and closing the ninth pneumatic valve in the fluid return mechanism; opening the fifth pneumatic valve after the fluid heating temperature controller, and continuously injecting supercritical carbon dioxide into the cracks of the rock sample until the reading of the second fluid pressure sensor in the fluid injection mechanism reaches the target value; S24, opening the ninth pneumatic valve, and adjusting the pressure regulating valve in the fluid return mechanism so that the reading of the third fluid pressure sensor in the fluid return mechanism reaches the target value; S25, adding the proppant into the proppant adding tank, opening the seventh pneumatic valve and the eighth pneumatic valve, so that the proppant is injected into the fracture along with the supercritical carbon dioxide; S26, continuously recording the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; S27, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ; Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; S28, when the measured flow rate, fluid pressure and fluid temperature are completely stable, closing the first high-pressure plunger pump, the first pneumatic valve and the third pneumatic valve, and closing the seventh pneumatic valve and the eighth pneumatic valve to exhaust the supercritical carbon dioxide in the fracture; S29, starting the CT ray source in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample, receiving and obtaining an image of the distribution of the proppant in the fracture through the CT detector in the test result acquisition and analysis mechanism, and analyzing to obtain the distribution of the proppant in the fracture.

[0023] As a technical solution of the present application, in step S3, the following steps are specifically included: S31, pumping liquid carbon dioxide into the fluid heating temperature controller in the fluid injection mechanism through the first high-pressure plunger pump and the matrix storage tank in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, and opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism; opening the ninth pneumatic valve in the fluid return mechanism, and opening the pressure regulating valve in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor in the fluid return mechanism is 1 atmosphere, so that the supercritical carbon dioxide flows through the fracture guided by the proppant; S32, continuously record the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; after the flow in the fracture stabilizes, if the reading of the volume flow meter is q and the reading of the second fluid pressure sensor is p i , then the average conductivity of the crack is calculated as follows; ; Where: q is the reading of the volume flow meter; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample, cm; D is the diameter of the rock sample, cm; p i is the reading of the second fluid pressure sensor; p0 is 101 kPa; S33, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ; Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; The average permeability K of the fracture measured before the proppant expansion is f1 Calculate as follows: ; Where: F f is the average conductivity of the fracture; H is the height of the rock sample; W f (z) is the distribution of the fracture opening along the height of the rock sample; z is the height coordinate of different positions of the rock sample.

[0024] As a technical solution of the present application, in step S4, the following steps are specifically included: S41, storing the pre-configured activator solution in the activator storage tank in the fluid injection mechanism; S42, opening the second pneumatic valve and the fourth pneumatic valve in the fluid injection mechanism, starting the second high-pressure plunger pump in the fluid injection mechanism, and pumping the activator solution in the activator storage tank into the fluid heating temperature controller in the fluid injection mechanism, so that the activator solution reaches the target pressure and temperature; S43, closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism, and opening the ninth pneumatic valve in the fluid flowback mechanism, and continuously injecting the stimulant solution into the fracture to stimulate the expansion of the proppant in the fracture; S44, continuously recording the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; S45, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ; Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; S46, when the measured flow rate, fluid pressure and fluid temperature are completely stable, closing the second high-pressure plunger pump, the second pneumatic valve and the fourth pneumatic valve, stopping the injection of the activator solution, and draining the activator solution in the rock sample; S47, start the CT ray source in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample, receive and obtain the image of the distribution of the proppant in the crack through the CT detector in the test result acquisition and analysis mechanism, analyze and obtain the expansion of the proppant in the crack and the resulting change in the opening of the crack, and compare and verify the analysis result with the monitoring result of the fiber grating strain sensor.

[0025] As a technical solution of the present application, in step S5, the following steps are specifically included: S51, pumping liquid carbon dioxide into the fluid heating temperature controller in the fluid injection mechanism through the second high-pressure plunger pump and the matrix storage tank in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism, and opening the ninth pneumatic valve in the fluid return mechanism, opening the pressure regulating valve in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor in the fluid return mechanism is 1 atmosphere, so that the supercritical carbon dioxide flows through the fracture guided by the proppant; S52, continuously record the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; after the flow in the fracture stabilizes, if the reading of the volume flow meter is q and the reading of the second fluid pressure sensor is p i , then the average conductivity of the crack is calculated as follows; ; Where: q is the reading of the volume flow meter; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample, cm; D is the diameter of the rock sample, cm; p i is the reading of the second fluid pressure sensor; p0 is 101 kPa; S53, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ; Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; Then the average permeability K of the fracture measured after the proppant expands is f2 Calculate as follows: ; Where: F f is the average conductivity of the fracture; H is the height of the rock sample; W f (z) is the distribution of the fracture opening along the height of the rock sample; z is the height coordinate of different positions of the rock sample.

[0026] As a technical solution of the present application, in step S6, if the average permeability of the fracture measured before the proppant expands is K f1 The fracture permeability measured after the proppant expands is K f2 , then the change of the proppant conductivity before and after expansion is: ; The conductivity of the environmentally responsive self-expanding proppant is evaluated based on the obtained data on the change in the conductivity of the proppant before and after expansion.

[0027] Beneficial effects of this application: (1) The present application provides a comprehensive performance test device for a proppant for a fracture, which can realize a comprehensive test of the migration, expansion and flow conductivity of a self-expanding proppant in a fracture through a fluid injection mechanism, a fluid return mechanism, a triaxial loading mechanism and a test result collection and analysis mechanism; the triaxial loading mechanism is used to load axial pressure and confining pressure on a cylindrical rock sample cut into two halves, respectively, to simulate the triaxial stress state borne by deep underground reservoirs and fractures; at the same time, during the proppant migration test, the fluid injection mechanism is used to regulate the pressure and temperature of the matrix and carry the proppant to inject it into the fracture of the rock sample, and the fluid injection mechanism is used to collect and analyze the test results. The flowback mechanism is used to adjust and control the flowback pressure at the fracture outlet to simulate the migration of proppant in fractures in actual projects; during the proppant expansion test, the stimulator is injected into the rock sample fracture through the fluid injection mechanism to stimulate the expansion of the proppant and simulate the effect of proppant expansion on the fracture in actual projects; during the comprehensive performance test, the test result collection and analysis mechanism is used to collect, store and process data and images to monitor the distribution and expansion of the proppant in the fracture, and observe the distribution of the rock sample fracture opening along the height, so as to evaluate the change of the proppant conductivity before and after expansion; (2) The present application provides a method for testing the comprehensive performance of proppants for fractures. The method can respectively carry out the temperature-pressure control and injection effects of proppants, stimulants, and diversion fluids in the three different test stages of proppant migration, expansion, and diversion. It can monitor the distribution of fracture opening with height and the distribution and expansion of proppants in fractures, and evaluate the changes in the proppant diversion performance before and after expansion. The method realizes a comprehensive test of the migration, expansion and conductivity of the self-expanding proppant in the fracture. During the proppant migration test, the pressure and temperature of the matrix are regulated by a fluid injection mechanism, and the proppant is carried and injected into the fracture of the rock sample, and the flowback pressure at the fracture outlet is regulated and controlled by a fluid return mechanism to simulate the migration of the proppant in the fracture in actual engineering. During the proppant expansion test, an activator is injected into the fracture of the rock sample by the fluid injection mechanism to stimulate the expansion of the proppant and simulate the effect of the expansion of the proppant on the fracture in actual engineering. During the comprehensive performance test, the test result collection and analysis mechanism is used to collect, store and process data and images to monitor the distribution and expansion of the proppant in the fracture, and the distribution of the rock sample fracture aperture along the height is observed, so as to evaluate the change in the conductivity of the proppant before and after expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the drawings required for use in the implementation methods will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of a comprehensive performance testing device for fracture proppant provided in the first embodiment of the present application; Figure 2 A schematic diagram of rock sample processing provided in the second embodiment of the present application; Figure 3 A schematic diagram of the steps of a method for testing the comprehensive performance of proppants for fractures provided in the second embodiment of the present application.

[0030] Icons: 1- rock sample; 2- matrix storage tank; 3- activator storage tank; 4- first high-pressure plunger pump; 5- second high-pressure plunger pump; 6- fluid heating temperature controller; 7- proppant addition tank; 8- mass flow meter; 9- first pneumatic valve; 10- second pneumatic valve; 11- third pneumatic valve; 12- fourth pneumatic valve; 13- fifth pneumatic valve; 14- sixth pneumatic valve; 15- seventh pneumatic valve; 16- eighth pneumatic valve; 17- ninth pneumatic valve; 18- first fluid pressure sensor; 19- safety valve; 20- second fluid pressure sensor; 21- first fluid temperature sensor; 22- fluid recovery tank; 23- volume flow meter; 24- second fluid temperature sensor; 25- third fluid pressure sensor device; 26-pressure regulating valve; 27-upper sealing pad; 28-lower sealing pad; 29-cylinder; 30-upper cover; 31-base; 32-clamp; 33-axial hydraulic actuator; 34-pressure rod; 35-servo hydraulic source; 36-fiber Bragg grating strain sensor; 37-high-pressure sealed fiber optic connector; 38-transmission fiber; 39-fiber Bragg grating demodulator; 40-CT ray source; 41-CT detector; 42-electronic computer; 43-first connecting tube; 44-second connecting tube; 45-third connecting tube; 46-fourth connecting tube; 47-fifth connecting tube; 48-sixth connecting tube; 49-seventh connecting tube; 50-eighth connecting tube; 51-ninth connecting tube; 52-tenth connecting tube. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0033] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0034] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is usually placed when in use. These are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0035] In addition, in the present application, unless otherwise clearly specified and limited, the first feature being above or below the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, the first feature being above, above, and above the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being below, below, and below the second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0036] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] First embodiment: Please refer to Figure 1The present application provides a comprehensive performance testing device for a fracture proppant, which can realize the comprehensive test of the migration, expansion and flow conductivity of the self-expanding proppant in the fracture; it mainly includes a fluid injection mechanism, a fluid return mechanism, a triaxial loading mechanism and a test result acquisition and analysis mechanism; wherein the fluid injection mechanism is connected to the fracture in the rock sample 1 sealed in the triaxial loading mechanism, and is used to inject a matrix, a proppant and an exciter into the fracture in the rock sample 1 respectively, the matrix is ​​used to transport the proppant to the fracture in the rock sample 1, and the exciter is used to excite the proppant to expand; at the same time, the fluid return mechanism is connected to the fracture in the rock sample 1, and is used to store the fluid returned from the fracture in the rock sample 1; and the rock sample 1 is sealed in the triaxial loading mechanism, and the triaxial loading mechanism is used to apply axial pressure and confining pressure to the rock sample 1 respectively, so as to simulate the triaxial stress state borne by the deep underground reservoir and the fracture; in addition, the test result acquisition and analysis mechanism is used to collect data and images in the process of the comprehensive performance test of the proppant, so as to analyze and evaluate the changes in the flow conductivity of the proppant before and after expansion. And the matrix can be supercritical carbon dioxide.

[0039] It should be noted that the cylindrical rock sample 1 cut into two halves is loaded with axial pressure and confining pressure respectively through a triaxial loading mechanism to simulate the triaxial stress state of deep underground reservoirs and fractures; at the same time, a set of fluid injection mechanisms and fluid return mechanisms are designed to realize the temperature-pressure control and injection of proppants, stimulants, and diversion fluids in the three different test stages of proppant migration, expansion, and diversion; at the same time, during the proppant migration test, the pressure and temperature of the matrix are regulated by the fluid injection mechanism and the proppant is injected into the fracture of the rock sample 1, and the return pressure at the fracture outlet is adjusted and controlled by the fluid return mechanism to simulate the migration of proppant in the fracture in actual engineering; during the proppant expansion test, the fluid injection mechanism is used to inject proppant into the rock sample 1. An activator is injected into the crack to stimulate the expansion of the proppant and simulate the effect of the expansion of the proppant on the crack in an actual project; in the process of comprehensive performance testing, the test result acquisition and analysis mechanism is used to collect, store and process data and images to monitor the distribution and expansion of the proppant in the crack, and observe the distribution of the crack opening of rock sample 1 along the height, so as to evaluate the change in the proppant conductivity before and after expansion; and a set of test result acquisition and analysis mechanisms is established, which can monitor the distribution of the crack opening along the height through the fiber grating strain sensor 36 and the distribution and expansion of the proppant in the crack through CT scanning, and the calculation formula of the average permeability of the crack is corrected based on the change in the opening, and finally the change in the proppant conductivity before and after expansion is evaluated.

[0040] Furthermore, the fluid injection mechanism includes a matrix storage tank 2, an exciter storage tank 3, a first high-pressure plunger pump 4, a second high-pressure plunger pump 5, a fluid heating thermostat 6 and a proppant adding tank 7; the matrix storage tank 2 and the first high-pressure plunger pump 4 are connected through a first pneumatic valve 9 and a first connecting pipe 43; the exciter storage tank 3 and the second high-pressure plunger pump 5 are connected through a second pneumatic valve 10 and a second connecting pipe 44; the first high-pressure plunger pump 4 is connected to the inlet of the fluid heating thermostat 6 through a third pneumatic valve 11 and a third connecting pipe 45, for conveying a matrix injection source into the fluid heating thermostat 6; the second high-pressure plunger pump 5 is connected to the fluid heating thermostat 6 through a fourth pneumatic valve 12 and a fourth connecting pipe 46 The inlet is used to transport the stimulant injection source to the fluid heating thermostat 6; and a first fluid pressure sensor 18 is provided at the inlet of the fluid heating thermostat 6; the fluid heating thermostat 6 is connected to the top of the crack of the rock sample 1 through the fifth pneumatic valve 13, the sixth pneumatic valve 14 and the fifth connecting pipe 47; the top of the proppant addition tank 7 is connected to the upper part of the fifth connecting pipe 47 through the seventh pneumatic valve 15 and the sixth connecting pipe 48, and the bottom end is connected to the lower part of the fifth connecting pipe 47 through the eighth pneumatic valve 16 and the seventh connecting pipe 49; the fifth pneumatic valve 13 is located between the fluid heating thermostat 6 and the sixth connecting pipe 48; the sixth pneumatic valve 14 is located between the sixth connecting pipe 48 and the seventh connecting pipe 49. In addition, a mass flow meter 8, a safety valve 19, a second fluid pressure sensor 20 and a first fluid temperature sensor 21 are sequentially arranged on the fifth connecting pipe 47; the second fluid pressure sensor 20 is used to monitor the pressure of the fluid in the fifth connecting pipe 47 in real time; the first fluid temperature sensor 21 is used to monitor the temperature of the fluid in the fifth connecting pipe 47 in real time.

[0041] Therefore, the matrix injection source and the stimulant injection source are connected in parallel and connected to the fluid heating temperature controller 6 with the first fluid pressure sensor 18 in front, and then discharged by the fifth pneumatic valve 13; then connected to the parallel pipeline composed of the seventh pneumatic valve 15, the eighth pneumatic valve 16, the proppant addition tank 7 and the sixth pneumatic valve 14, and then connected to the cracks of the rock sample 1 in the pressure chamber of the triaxial loading mechanism through the mass flow meter 8, the second fluid pressure sensor 20 and the first fluid temperature sensor 21.

[0042] It should be noted that the first high-pressure plunger pump 4 and the second high-pressure plunger pump 5 can realize the continuous injection of water, carbon dioxide and other types of acid and alkali solutions in the range of 0-80MPa; the fluid heating thermostat 6 can heat the coil through a water bath, and the heater and the electric thermostat therein control the constant temperature heating of the water in the cabin, thereby adjusting the temperature of the fluid flowing through the coil, and the temperature adjustment range is room temperature-100°C; the first fluid pressure sensor 18 and the safety valve 19 can monitor the pressure of the pipeline fluid in real time, and the measurement range of the two is 0-100MPa, with an accuracy of ±0.5%; the second temperature sensor can monitor the temperature of the pipeline fluid in real time, and the measurement range is -50-300°C, with an accuracy of ±0.5%.

[0043] Furthermore, the fluid return mechanism includes a fluid recovery tank 22; wherein, the fluid recovery tank 22 is connected to the bottom of the crack of the rock sample 1 through an eighth connecting pipe 50; at the same time, the eighth connecting pipe 50 is sequentially provided with a ninth pneumatic valve 17, a volume flow meter 23, a second fluid temperature sensor 24, a third fluid pressure sensor 25 and a pressure regulating valve 26 from close to to away from the rock sample 1; in addition, the third fluid pressure sensor 25 is used to monitor the pressure of the fluid in the eighth connecting pipe 50 in real time; the second fluid temperature sensor 24 is used to monitor the temperature of the fluid in the eighth connecting pipe 50 in real time; and the pressure regulating valve 26 is used to adjust the return pressure at the crack outlet of the rock sample 1 in real time.

[0044] After the fluid is discharged from the rock sample 1 in the pressure chamber of the triaxial loading system, it is discharged into the fluid recovery tank 22 through the ninth pneumatic valve 17, the volume flowmeter 23, the third fluid pressure sensor 25, the second fluid temperature sensor 24, and the pressure regulating valve 26. The ninth pneumatic valve 17 controls whether the fluid in the rock sample 1 is discharged; the third fluid pressure sensor 25 can monitor the pressure of the pipeline fluid in real time, and its measurement range is 0-100MPa, and the accuracy is ±0.5%; and its second temperature sensor can monitor the temperature of the pipeline fluid in real time, and its measurement range is -50-300℃, and the accuracy is ±0.5%; the pressure regulating valve 26 can adjust the backflow pressure at the fracture outlet in real time, and its upper limit of the adjustment range is the upstream injection pressure, and the lower limit is 0; in addition, the fluid recovery tank 22 is used to store the fluid discharged from the rock sample 1.

[0045] Furthermore, the three-axis loading mechanism includes a sealing cylinder, a servo hydraulic source 35, an axial hydraulic transmission assembly, an upper sealing pad 27, a lower sealing pad 28 and a circumferential hydraulic transmission assembly; wherein the sealing cylinder includes a cylinder body 29, an upper cover 30, a base 31 and a clamp 32, wherein the cylinder body 29 is fastened to the base 31 by the clamp 32; the upper cover 30 is arranged on the top of the cylinder body 29; the rock sample 1 is composed of two semi-cylinders, and a crack is provided in the middle portion that runs through the top and bottom and extends in the axial direction, and the rock sample 1 is sealed in the pressure chamber of the sealing cylinder; at the same time, the upper sealing pad 27 is arranged on the top of the rock sample 1; the lower sealing pad 28 is arranged at the bottom of the rock sample 1; the fifth connecting pipe 47 passes through the bottom of the base 31 The top of the base 31 extends into the pressure chamber, and passes through the middle of the top of the upper sealing pad from one side of the upper sealing pad, and is connected to the top of the crack; the eighth connecting pipe 50 passes through the bottom top of the base 31 and extends into the pressure chamber, and passes through the middle of the top of the lower sealing pad from one side of the lower sealing pad, and is connected to the bottom of the crack; in addition, the servo hydraulic source 35 is hydraulically connected to the axial hydraulic transmission assembly and the circumferential hydraulic transmission assembly respectively; one end of the axial hydraulic transmission assembly extends into the pressure chamber, and is transmission-connected to the top of the upper sealing pad block 27, for applying axial pressure to the rock sample 1; and the hydraulic end of the circumferential hydraulic transmission assembly is connected into the pressure chamber, for injecting liquid into the pressure chamber to apply confining pressure to the rock sample 1.

[0046] The axial hydraulic transmission assembly includes a first servo hydraulic pump, a ninth connecting pipe 51, an axial hydraulic transmission device 33 and a pressure rod 34; the servo hydraulic source 35 is connected to the first servo hydraulic pump, and the first servo hydraulic pump is connected to the axial hydraulic transmission device 33 through the ninth connecting pipe 51; the axial hydraulic transmission device 33 is transmission-connected to the top of the pressure rod 34; the top of the pressure rod 34 extends out of the upper cover 30, and the lower seal is clamped in the cylinder 29 and extends into the pressure chamber and is movably arranged on the top of the upper sealing gasket.

[0047] The circumferential hydraulic transmission assembly includes a second servo hydraulic pump and a tenth connecting pipe 52; the servo hydraulic source 35 is connected to the second servo hydraulic pump; the second servo hydraulic pump is connected to the bottom of the pressure chamber through the tenth connecting pipe 52 for injecting liquid into the pressure chamber.

[0048] It should be noted that the servo hydraulic source 35 is powered by an independent first servo hydraulic pump and a second servo hydraulic pump for axial pressure and confining pressure respectively. The first servo hydraulic pump applies axial pressure to the rock sample 1 in the pressure chamber through the axial hydraulic transmission 33 via the pressure rod 34, and the second servo hydraulic pump injects silicone oil into the pressure chamber through the hydraulic pipeline of the base 31 to apply confining pressure to the rock sample 1; the upper cover 30, the cylinder 29, the clamp 32 and the base 31 can ensure the high-pressure sealing of the pressure chamber; the upper sealing pad 27 and the lower sealing pad 28 can ensure the uniformity of axial pressure loading, and they are respectively connected to the fluid injection mechanism and the fluid return mechanism to realize the injection and discharge of the fluid in the rock sample 1. In addition, the maximum axial loading force of the three-axis loading mechanism is 2000kN, the maximum confining pressure is 70MPa, and the control accuracy is less than ±1%. The rock sample 1 that can be installed is a cylinder with a size of Φ100mm×200mm.

[0049] Furthermore, the test result collection and analysis mechanism includes a fiber Bragg grating strain sensor 36, a high-pressure sealed fiber optic connector 37, a transmission fiber 38, a fiber Bragg grating demodulator 39, a CT ray source 40, a CT detector 41 and an electronic computer 42; the fiber Bragg grating strain sensor 36 is evenly wound on the outer peripheral side of the rock sample 1, and the end is led out through the high-pressure sealed fiber optic connector 37 on the base 31 and connected to the fiber Bragg grating demodulator 39 through the transmission fiber optic 38; the fiber Bragg grating demodulator 39 is used to demodulate the received optical signal, and perform quasi-distributed measurement of the annular strain of the rock sample 1 through wavelength division multiplexing, and the measurement range is 0-100 00με, and the measurement accuracy is ±10με; the CT ray source 40 and the CT detector 41 constitute an in-situ CT scanning device with a minimum spatial resolution of 1μm. The CT ray source 40 and the CT detector 41 are respectively arranged outside the opposite sides of the cylinder 29 at intervals, and the X-rays emitted by the CT ray source 40 pass through the rock sample 1 and are received by the CT detector 41. Based on the gray value difference of different materials, a high-precision image of the distribution of the proppant in the cracks of the rock sample 1 can be obtained; the electronic computer 42 is electrically connected to the fiber grating demodulator 39 and the CT detector 41, respectively, for receiving and storing the collected data, and can carry out subsequent processing and analysis.

[0050] It should be noted that the arrangement direction of the fiber Bragg grating in the fiber Bragg grating strain sensor 36 is set at an angle to the horizontal cross section of the rock sample 1 .

[0051] Second embodiment: Please refer to Figure 2 , with reference Figure 1 and Figure 3The present application provides a method for testing the comprehensive performance of a proppant for a fracture, which can comprehensively test the migration, expansion and conductivity of a self-expanding proppant in a fracture of a rock sample 1 under a triaxial stress state; the method mainly uses the comprehensive performance testing device for a proppant for a fracture in the first embodiment for testing, and includes the following steps: S1, installing the rock sample 1 in a comprehensive performance testing device for a fracture proppant, and applying confining pressure and axial pressure to the rock sample 1, respectively, so that the rock sample 1 reaches a set triaxial stress state; S2, injecting proppant into the fracture of rock sample 1, and allowing the proppant to migrate in the fracture; S3, testing the conductivity of the proppant before expansion; S4, stimulating the proppant in the fracture to cause the proppant to expand; S5, testing the conductivity of the expanded proppant; S6, evaluate the conductivity performance of the environmentally responsive self-expanding proppant.

[0052] In step S1, the rock sample 1 is mainly installed in the triaxial loading mechanism and loaded with confining pressure and axial pressure to make it reach the specified triaxial stress state; it specifically includes the following steps: S11, before the test, a Φ100mm×200mm cylindrical rock was cut into two symmetrical semi-cylinders along the diameter and longitudinal direction, and the cut surface was the crack; the two semi-cylinders were cleaned and placed in a drying oven at 70℃ for 12h; S12, install the lower sealing pad 28 on the base 31 of the pressure chamber of the cylinder 29 of the three-axis loading mechanism, and lay a nylon filter with a mesh diameter smaller than the proppant particle size on the lower sealing pad 28; assemble the two semi-cylinders into a rock sample 1 and install it on the lower sealing pad 28, then install the upper sealing pad 27 on the top of the rock sample 1, and wrap the heat shrink tube on the outside of the rock sample 1 to isolate the confining pressure silicone oil; connect the fifth connecting pipe 47 to the entrance of the crack through the upper sealing pad 27, and connect the eighth connecting pipe 50 to the outlet of the crack through the lower sealing pad 28; check the air tightness of the fluid pipeline section by section through the first pneumatic valve 9, the second pneumatic valve 10, the third pneumatic valve 11, the fourth pneumatic valve 12, the fifth pneumatic valve 13, the sixth pneumatic valve 14, the seventh pneumatic valve 15, the eighth pneumatic valve 16, the first fluid pressure sensor 18, the second fluid pressure sensor 20, and the third fluid pressure sensor 25 to ensure that the entire fluid pipeline is well sealed; S13, a fiber Bragg grating strain sensor 36 is wound and installed on the outer peripheral side of the rock sample 1, and its fiber Bragg grating forms an angle α with the horizontal plane; the fiber Bragg grating strain sensor 36 is sequentially led out from the high-pressure sealed fiber optic connectors 37 respectively installed on the top and bottom of the base 31, and connected to the fiber Bragg grating demodulator 39 via the transmission optical fiber 38; an upper cover 30 for sealing the cylinder 29 is provided on the top of the cylinder 29, and a pressure rod 34 connected to the first servo hydraulic pump in the three-axis loading mechanism is installed in the upper cover 30, and the pressure rod 34 extends into the pressure chamber and is located on the top of the upper sealing pad 27, and the clamp 32 is clamped to ensure good sealing of the pressure chamber; S14, a small axial pressure (0.5 MPa) is first applied to the rock sample 1 through the first servo hydraulic pump to make the pressure rod 34 contact with the upper sealing pad 27; silicone oil is injected into the pressure chamber through the second servo hydraulic pump in the triaxial loading mechanism to load the rock sample 1 to the target confining pressure, and at the same time, the axial hydraulic transmission 33 connected to the first servo hydraulic pump is driven to continue to load the rock sample 1 to the target axial pressure, so that the rock sample 1 is in the target triaxial stress state.

[0053] In step S2, it is mainly to inject proppant into the rock sample 1, monitor the migration of the proppant and the effect on the cracks of the rock sample 1, and here, the matrix carrying the proppant is supercritical carbon dioxide as an example; it specifically includes the following steps: S21, configuring the environmentally responsive self-expanding proppant according to the pre-designed proppant injection scheme, and placing it in the proppant addition tank 7 in the fluid injection mechanism; S22, opening the first pneumatic valve 9 and the third pneumatic valve 11 in the fluid injection mechanism, starting the first high-pressure plunger pump 4 in the fluid injection mechanism, pumping the liquid carbon dioxide in the matrix storage tank 2 in the fluid injection mechanism into the fluid heating temperature controller 6 in the fluid injection mechanism, and simultaneously starting heating and adjusting the temperature to generate supercritical carbon dioxide at a specified temperature and pressure; S23, close the seventh pneumatic valve 15 and the eighth pneumatic valve 16 in the fluid injection mechanism, open the sixth pneumatic valve 14 in the fluid injection mechanism, and close the ninth pneumatic valve 17 in the fluid return mechanism; open the fifth pneumatic valve 13 after the fluid heating temperature controller 6, and continue to inject supercritical carbon dioxide into the cracks of the rock sample 1 until the reading of the second fluid pressure sensor 20 in the fluid injection mechanism reaches the target value; S24, opening the ninth pneumatic valve 17, and adjusting the pressure regulating valve 26 in the fluid return mechanism so that the reading of the third fluid pressure sensor 25 in the fluid return mechanism reaches the target value; S25, adding proppant to the proppant adding tank 7, and then opening the seventh pneumatic valve 15 and the eighth pneumatic valve 16 to allow the proppant to be injected into the fracture along with the supercritical carbon dioxide; S26, continuously recording the parameters measured by the mass flow meter 8, the volume flow meter 23, the second fluid pressure sensor 20, the third fluid pressure sensor 25, the first fluid temperature sensor 21, and the second fluid temperature sensor 24; S27, the circumferential strain of the rock sample 1 is monitored in real time by the fiber Bragg grating strain sensor 36 in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample 1 according to the following formula W f (z): ; Where: D is the diameter of the rock sample 1, which is generally 10 cm for this device; ε o (z) is the distribution of the readings of the fiber Bragg grating strain sensor 36 along the height of the rock sample 1, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor 36 and the horizontal cross section of the rock sample 1; S28, when the measured flow rate, fluid pressure and fluid temperature are completely stable, indicating that the distribution of the proppant in the crack of the rock sample 1 is stable, the first high-pressure plunger pump 4, the first pneumatic valve 9 and the third pneumatic valve 11 are closed, and the seventh pneumatic valve 15 and the eighth pneumatic valve 16 are closed to drain the supercritical carbon dioxide in the crack. At this time, the proppant is embedded in the rock sample 1 on both sides of the crack due to the confining pressure, forming support for the crack; S29, start the CT ray source 40 in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample 1, receive and obtain a high-precision image of the distribution of the proppant in the fracture through the CT detector 41 in the test result acquisition and analysis mechanism, and analyze the distribution of the proppant in the fracture.

[0054] In step S3, it is mainly used to test the conductivity of the proppant before expansion, which specifically includes the following steps: S31, pumping liquid carbon dioxide into the fluid heating temperature controller 6 in the fluid injection mechanism through the first high-pressure plunger pump 4 and the matrix storage tank 2 in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve 15 and the eighth pneumatic valve 16 in the fluid injection mechanism, and opening the fifth pneumatic valve 13 and the sixth pneumatic valve 14 in the fluid injection mechanism; opening the ninth pneumatic valve 17 in the fluid return mechanism, and opening the pressure regulating valve 26 in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor 25 in the fluid return mechanism is 1 atmosphere, so that the supercritical carbon dioxide flows through the fracture guided by the proppant; S32, continuously record the parameters measured by the mass flow meter 8, the volume flow meter 23, the second fluid pressure sensor 20, the third fluid pressure sensor 25, the first fluid temperature sensor 21, and the second fluid temperature sensor 24; after the flow in the fracture stabilizes, if the reading of the volume flow meter 23 is q (in cm 3 / s), the reading of the second fluid pressure sensor 20 is p i (in kPa), then the average conductivity of the crack (in μm 2 cm) is calculated as follows; ; Wherein: q is the reading of the volume flow meter 23; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample 1, which is generally 20 cm for this device; D is the diameter of the rock sample 1, which is generally 10 cm for this device; p i is the reading of the second fluid pressure sensor 20; p0 is 101 kPa; S33, the circumferential strain of the rock sample 1 is monitored in real time by the fiber Bragg grating strain sensor 36 in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample 1 according to the following formula: f (z): ; Where: D is the diameter of rock sample 1; ε o (z) is the distribution of the readings of the fiber Bragg grating strain sensor 36 along the height of the rock sample 1, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor 36 and the horizontal cross section of the rock sample 1; The average permeability K of the fracture measured before proppant expansion is f1 (Unit: μm 2 ) is calculated as follows: ; Where: F f is the average conductivity of the fracture; H is the height of rock sample 1; W f (z) is the distribution of fracture opening along the height of rock sample 1; z is the height coordinate of different positions of rock sample 1.

[0055] In step S4, the main step is to inject an activator solution into the rock sample 1 to activate the environmental response self-expanding proppant to expand, monitor the expansion of the proppant and the crack evolution process of the rock sample 1 caused by the expansion; specifically, the following steps are included: S41, storing the pre-configured activator solution in the activator storage tank 3 in the fluid injection mechanism; S42, opening the second pneumatic valve 10 and the fourth pneumatic valve 12 in the fluid injection mechanism, starting the second high-pressure plunger pump 5 in the fluid injection mechanism, pumping the activator solution in the activator storage tank 3 into the fluid heating temperature controller 6 in the fluid injection mechanism, and simultaneously starting heating and adjusting the temperature so that the activator solution reaches the target pressure and temperature; S43, closing the seventh pneumatic valve 15 and the eighth pneumatic valve 16 in the fluid injection mechanism, opening the fifth pneumatic valve 13 and the sixth pneumatic valve 14 in the fluid injection mechanism, and opening the ninth pneumatic valve 17 in the fluid flowback mechanism, and continuously injecting the stimulant solution into the fracture to stimulate the proppant expansion in the fracture; S44, continuously recording the parameters measured by the mass flow meter 8, the volume flow meter 23, the second fluid pressure sensor 20, the third fluid pressure sensor 25, the first fluid temperature sensor 21, and the second fluid temperature sensor 24; S45, the circumferential strain of the rock sample 1 is monitored in real time by the fiber Bragg grating strain sensor 36 in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample 1 according to the following formula: f (z): ; Where: D is the diameter of the rock sample 1, which is generally 10 cm for this device; ε o (z) is the distribution of the readings of the fiber Bragg grating strain sensor 36 along the height of the rock sample 1, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor 36 and the horizontal cross section of the rock sample 1; S46, when the measured flow rate, fluid pressure and fluid temperature are completely stable, indicating that the proppant no longer expands, the cracks in the rock sample 1 no longer change, and the whole is stable, the second high-pressure plunger pump 5, the second pneumatic valve 10 and the fourth pneumatic valve 12 are closed, the injection of the activator solution is stopped, and the activator solution in the rock sample 1 is drained; S47, start the CT ray source 40 in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample 1, receive and obtain a high-precision image of the distribution of the proppant in the crack through the CT detector 41 in the test result acquisition and analysis mechanism, analyze and obtain the expansion of the proppant in the crack and the resulting change in the opening of the crack, and compare and verify the analysis result with the monitoring result of the fiber grating strain sensor 36.

[0056] In step S5, the flow conductivity of the expanded proppant is mainly tested. Supercritical carbon dioxide is still selected as the flow conductivity fluid. The specific steps include: S51, pumping liquid carbon dioxide into the fluid heating temperature controller 6 in the fluid injection mechanism through the second high-pressure plunger pump 5 and the matrix storage tank 2 in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve 15 and the eighth pneumatic valve 16 in the fluid injection mechanism, opening the fifth pneumatic valve 13 and the sixth pneumatic valve 14 in the fluid injection mechanism, and opening the ninth pneumatic valve 17 in the fluid return mechanism, opening the pressure regulating valve 26 in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor 25 in the fluid return mechanism is 1 atmosphere, that is, p o = 101 kPa, so that supercritical carbon dioxide flows through the proppant-guided fractures; S52, continuously record the parameters measured by the mass flow meter 8, the volume flow meter 23, the second fluid pressure sensor 20, the third fluid pressure sensor 25, the first fluid temperature sensor 21, and the second fluid temperature sensor 24; after the flow in the fracture stabilizes, if the reading of the volume flow meter 23 is q and the reading of the second fluid pressure sensor 20 is p i , then the average conductivity of the crack is calculated as follows; ; Where: q is the reading of the volume flow meter 23; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample 1, cm; D is the diameter of the rock sample 1, cm; p i is the reading of the second fluid pressure sensor 20; p0 is 101 kPa; S53, the circumferential strain of the rock sample 1 is monitored in real time by the fiber Bragg grating strain sensor 36 in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample 1 according to the following formula: f (z): ; Where: D is the diameter of rock sample 1; ε o (z) is the distribution of the readings of the fiber Bragg grating strain sensor 36 along the height of the rock sample 1, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor 36 and the horizontal cross section of the rock sample 1; The average permeability K of the fracture measured after proppant expansion is f2 Calculate as follows: ; Where: F f is the average conductivity of the fracture; H is the height of rock sample 1; W f (z) is the distribution of fracture opening along the height of rock sample 1; z is the height coordinate of different positions of rock sample 1.

[0057] In step S6, if the average permeability of the fracture measured before the proppant expansion is K f1 , the fracture permeability measured after proppant expansion is K f2 , the change of proppant conductivity before and after expansion is: ; The conductivity of the environmentally responsive self-expanding proppant is evaluated based on the obtained data on the change in the conductivity of the proppant before and after expansion.

[0058] Therefore, the method realizes the comprehensive test of the migration, expansion and conductivity of the self-expanding proppant in the fracture; during the proppant migration test, the pressure and temperature of the matrix are regulated by the fluid injection mechanism and the proppant is injected into the fracture of the rock sample 1, and the return pressure at the fracture outlet is adjusted and controlled by the fluid return mechanism to simulate the migration of the proppant in the fracture in the actual project; during the proppant expansion test, the stimulator is injected into the fracture of the rock sample 1 by the fluid injection mechanism to stimulate the expansion of the proppant and simulate the effect of the expansion of the proppant on the fracture in the actual project; during the comprehensive performance test, the test result collection and analysis mechanism is used to collect, store and process data and images to monitor the distribution and expansion of the proppant in the fracture, and the distribution of the fracture aperture of the rock sample 1 along the height is observed, so as to evaluate the change of the conductivity of the proppant before and after expansion.

[0059] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A comprehensive performance testing device for fracture proppant, characterized in that: It comprises a fluid injection mechanism, a fluid return mechanism, a triaxial loading mechanism and a test result collection and analysis mechanism; the fluid injection mechanism is connected to the cracks in the rock sample sealed in the triaxial loading mechanism, and is used to inject matrix, proppant and stimulant into the cracks in the rock sample respectively, the matrix is ​​used to transport the proppant to the cracks in the rock sample, and the stimulant is used to stimulate the expansion of the proppant; the fluid return mechanism is connected to the cracks in the rock sample, and is used to store the fluid returned from the cracks in the rock sample; the rock sample is sealed in the triaxial loading mechanism, and the triaxial loading mechanism is used to apply axial pressure and confining pressure to the rock sample respectively, so as to simulate the triaxial stress state borne by deep underground reservoirs and cracks; The test result collection and analysis mechanism is used to collect data and images during the proppant comprehensive performance test process, so as to analyze and evaluate the changes in the conductivity of the proppant before and after expansion.

2. The comprehensive performance testing device for crack proppant according to claim 1, characterized in that: The fluid injection mechanism comprises a matrix storage tank, an exciter storage tank, a first high-pressure plunger pump, a second high-pressure plunger pump, a fluid heating temperature controller and a proppant adding tank; the matrix storage tank and the first high-pressure plunger pump are connected through a first pneumatic valve and a first connecting pipe; the exciter storage tank and the second high-pressure plunger pump are connected through a second pneumatic valve and a second connecting pipe; the first high-pressure plunger pump is connected to the inlet of the fluid heating temperature controller through a third pneumatic valve and a third connecting pipe, for conveying a matrix injection source to the fluid heating temperature controller; the second high-pressure plunger pump is connected to the inlet of the fluid heating temperature controller through a fourth pneumatic valve and a fourth connecting pipe. connected to the inlet of the fluid heating thermostat, used for conveying an activator injection source to the fluid heating thermostat; the fluid heating thermostat is connected to the top of the crack of the rock sample through the fifth pneumatic valve, the sixth pneumatic valve and the fifth connecting pipe; the top of the proppant adding tank is connected to the upper part of the fifth connecting pipe through the seventh pneumatic valve and the sixth connecting pipe, and the bottom end is connected to the lower part of the fifth connecting pipe through the eighth pneumatic valve and the seventh connecting pipe; the fifth pneumatic valve is between the fluid heating thermostat and the sixth connecting pipe; the sixth pneumatic valve is between the sixth connecting pipe and the seventh connecting pipe.

3. The comprehensive performance testing device for crack proppant according to claim 2, characterized in that: A first fluid pressure sensor is arranged at the inlet of the fluid heating temperature controller.

4. The comprehensive performance testing device for fracture proppant according to claim 2, characterized in that: The fifth connecting pipe is provided with a mass flow meter, a safety valve, a second fluid pressure sensor and a first fluid temperature sensor in sequence; the second fluid pressure sensor is used to monitor the pressure of the fluid in the fifth connecting pipe in real time; the first fluid temperature sensor is used to monitor the temperature of the fluid in the fifth connecting pipe in real time.

5. The comprehensive performance testing device for fracture proppant according to claim 1, characterized in that: The fluid return mechanism includes a fluid recovery tank; the fluid recovery tank is connected to the bottom of the crack of the rock sample through an eighth connecting pipe; the eighth connecting pipe is provided with a ninth pneumatic valve, a volume flow meter, a second fluid temperature sensor, a third fluid pressure sensor and a pressure regulating valve in sequence from close to to away from the rock sample; the third fluid pressure sensor is used to monitor the pressure of the fluid in the eighth connecting pipe in real time; the second fluid temperature sensor is used to monitor the temperature of the fluid in the eighth connecting pipe in real time; the pressure regulating valve is used to adjust the return pressure at the crack outlet of the rock sample in real time.

6. The comprehensive performance testing device for fracture proppant according to claim 1, characterized in that: The three-axis loading mechanism includes a sealing cylinder, an axial hydraulic transmission assembly, an upper sealing pad, a lower sealing pad and a circumferential hydraulic transmission assembly; the rock sample is sealed in a pressure chamber of the sealing cylinder; the upper sealing pad is arranged on the top of the rock sample; the lower sealing pad is arranged at the bottom of the rock sample; one end of the axial hydraulic transmission assembly extends into the pressure chamber and is transmission-connected to the top of the upper sealing pad for applying axial pressure to the rock sample; the hydraulic end of the circumferential hydraulic transmission assembly is connected to the pressure chamber for injecting liquid into the pressure chamber to apply confining pressure to the rock sample.

7. The comprehensive performance testing device for fracture proppant according to claim 6, characterized in that: The sealing cylinder comprises a cylinder body, an upper cover, a base and a clamp; the cylinder body is fastened to the base through the clamp; and the upper cover is arranged on the top of the cylinder body.

8. The comprehensive performance testing device for fracture proppant according to claim 7, characterized in that: The axial hydraulic transmission assembly includes a first servo hydraulic pump, a ninth connecting pipe, an axial hydraulic transmission and a pressure rod; the first servo hydraulic pump is connected to the axial hydraulic transmission through the ninth connecting pipe; the axial hydraulic transmission is transmission-connected to the top of the pressure rod; the top of the pressure rod extends out of the upper cover, and the lower seal is clamped in the cylinder and extends into the pressure chamber and is movably arranged on the top of the upper sealing gasket.

9. The comprehensive performance testing device for fracture proppant according to claim 7, characterized in that: The circumferential hydraulic transmission assembly includes a second servo hydraulic pump and a tenth connecting pipe; the second servo hydraulic pump is connected to the bottom of the pressure chamber through the tenth connecting pipe, and is used to inject liquid into the pressure chamber.

10. The comprehensive performance testing device for fracture proppant according to claim 1, characterized in that: The rock sample is composed of two semi-cylinders, and has a crack in the middle which penetrates through the top and bottom and extends in the axial direction.

11. The comprehensive performance testing device for fracture proppant according to claim 1, characterized in that: The test result collection and analysis mechanism includes a fiber grating strain sensor, a high-pressure sealed fiber optic connector, a transmission fiber, a fiber grating demodulator, a CT ray source, a CT detector and an electronic computer; the fiber grating strain sensor is evenly wound on the outer peripheral side of the rock sample, and the end is led out through the high-pressure sealed fiber optic connector and connected to the fiber grating demodulator through the transmission fiber; the fiber grating demodulator is used to demodulate the received optical signal and perform quasi-distributed measurement of the annular strain of the rock sample by wavelength division multiplexing; the CT ray source and the CT detector are respectively arranged at intervals outside the opposite sides of the three-axis loading mechanism, and the X-rays emitted by the CT ray source pass through the rock sample and are received by the CT detector to obtain an image of the distribution of the proppant in the cracks of the rock sample; the electronic computer is electrically connected to the fiber grating demodulator and the CT detector respectively, and is used to receive and store the collected data.

12. The comprehensive performance testing device for fracture proppant according to claim 11, characterized in that: The arrangement direction of the fiber Bragg grating in the fiber Bragg grating strain sensor is set at an angle to the horizontal cross section of the rock sample.

13. The comprehensive performance testing device for fracture proppant according to claim 1, characterized in that: The matrix includes supercritical carbon dioxide.

14. A method for testing the comprehensive performance of a fracture proppant, using the device for testing the comprehensive performance of a fracture proppant as claimed in any one of claims 1 to 13, characterized in that: The following steps are involved: S1, installing the rock sample in the comprehensive performance testing device for the fracture proppant, and applying confining pressure and axial pressure to the rock sample respectively, so that the rock sample reaches a set triaxial stress state; S2, injecting the proppant into the fracture of the rock sample, and allowing the proppant to migrate in the fracture; S3, performing a conductivity test on the proppant before expansion; S4, stimulating the proppant in the fracture to cause the proppant to expand; S5, performing a conductivity test on the expanded proppant; S6, evaluating the conductivity of the environmentally responsive self-expanding proppant.

15. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S1, the following steps are specifically included: S11, before the test, the cylindrical rock is cut into two symmetrical semi-cylinders, and the two semi-cylinders are cleaned and placed in a drying oven for drying; S12, installing a lower sealing pad on the base of the pressure chamber of the cylinder of the triaxial loading mechanism, laying a nylon filter with a mesh diameter smaller than the particle size of the proppant on the lower sealing pad; assembling the two semi-cylinders into the rock sample and installing it on the lower sealing pad, then installing an upper sealing pad on the top of the rock sample, and wrapping a heat shrink tube on the outside of the rock sample; connecting the fluid injection mechanism to the inlet of the fracture through the upper sealing pad, and connecting the fluid return mechanism to the outlet of the fracture through the lower sealing pad; S13, winding and installing a fiber Bragg grating strain sensor on the outer peripheral side of the rock sample, leading out the fiber Bragg grating strain sensor from the high-pressure sealed fiber connectors respectively installed on the top and bottom of the base in sequence, and connecting it to a fiber Bragg grating demodulator via a transmission optical fiber; providing an upper cover for sealing the cylinder body on the top of the cylinder body, installing a pressure rod in transmission connection with the first servo hydraulic pump in the three-axis loading mechanism in the upper cover, and the pressure rod extending into the pressure chamber and being located on the top of the upper sealing pad; S14, applying axial pressure to the rock sample through the first servo hydraulic pump so that the pressure rod contacts the upper sealing pad; injecting silicone oil into the pressure chamber through the second servo hydraulic pump in the triaxial loading mechanism to load the rock sample to the target confining pressure, and at the same time driving the axial hydraulic transmission connected to the first servo hydraulic pump to continue loading the rock sample to the target axial pressure, so that the rock sample is in a target triaxial stress state.

16. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S2, the following steps are specifically included: S21, configuring the environmentally responsive self-expanding proppant according to a pre-designed proppant injection scheme, and placing the proppant in the fluid injection mechanism into a proppant addition tank; S22, opening the first pneumatic valve and the third pneumatic valve in the fluid injection mechanism, starting the first high-pressure plunger pump in the fluid injection mechanism, and pumping the liquid carbon dioxide in the matrix storage tank in the fluid injection mechanism into the fluid heating temperature controller in the fluid injection mechanism to generate supercritical carbon dioxide at a specified temperature and pressure; S23, closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the sixth pneumatic valve in the fluid injection mechanism, and closing the ninth pneumatic valve in the fluid return mechanism; opening the fifth pneumatic valve after the fluid heating temperature controller, and continuously injecting supercritical carbon dioxide into the cracks of the rock sample until the reading of the second fluid pressure sensor in the fluid injection mechanism reaches the target value; S24, opening the ninth pneumatic valve, and adjusting the pressure regulating valve in the fluid return mechanism so that the reading of the third fluid pressure sensor in the fluid return mechanism reaches the target value; S25, adding the proppant into the proppant adding tank, opening the seventh pneumatic valve and the eighth pneumatic valve, so that the proppant is injected into the fracture along with the supercritical carbon dioxide; S26, continuously recording the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; S27, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ； Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; S28, when the measured flow rate, fluid pressure and fluid temperature are completely stable, closing the first high-pressure plunger pump, the first pneumatic valve and the third pneumatic valve, and closing the seventh pneumatic valve and the eighth pneumatic valve to exhaust the supercritical carbon dioxide in the fracture; S29, starting the CT ray source in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample, receiving and obtaining an image of the distribution of the proppant in the fracture through the CT detector in the test result acquisition and analysis mechanism, and analyzing to obtain the distribution of the proppant in the fracture.

17. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S3, the following steps are specifically included: S31, pumping liquid carbon dioxide into the fluid heating temperature controller in the fluid injection mechanism through the first high-pressure plunger pump and the matrix storage tank in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, and opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism; opening the ninth pneumatic valve in the fluid return mechanism, and opening the pressure regulating valve in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor in the fluid return mechanism is 1 atmosphere, so that the supercritical carbon dioxide flows through the fracture guided by the proppant; S32, continuously record the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; after the flow in the fracture stabilizes, if the reading of the volume flow meter is q, the reading of the second fluid pressure sensor is p i , then the average conductivity of the crack is calculated as follows; ； Where: q is the reading of the volume flow meter; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample, cm; D is the diameter of the rock sample, cm; p i is the reading of the second fluid pressure sensor; p0 is 101 kPa; S33, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ； Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; The average permeability K of the fracture measured before the proppant expansion is f1 Calculate as follows: ； Where: F f is the average conductivity of the fracture; H is the height of the rock sample; W f (z) is the distribution of the fracture opening along the height of the rock sample; z is the height coordinate of different positions of the rock sample.

18. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S4, the following steps are specifically included: S41, storing the pre-configured activator solution in the activator storage tank in the fluid injection mechanism; S42, opening the second pneumatic valve and the fourth pneumatic valve in the fluid injection mechanism, starting the second high-pressure plunger pump in the fluid injection mechanism, and pumping the activator solution in the activator storage tank into the fluid heating temperature controller in the fluid injection mechanism, so that the activator solution reaches the target pressure and temperature; S43, closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism, and opening the ninth pneumatic valve in the fluid flowback mechanism, and continuously injecting the stimulant solution into the fracture to stimulate the expansion of the proppant in the fracture; S44, continuously recording the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; S45, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ； Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; S46, when the measured flow rate, fluid pressure and fluid temperature are completely stable, closing the second high-pressure plunger pump, the second pneumatic valve and the fourth pneumatic valve, stopping the injection of the activator solution, and draining the activator solution in the rock sample; S47, start the CT ray source in the test result acquisition and analysis mechanism to emit X-rays to scan the rock sample, receive and obtain the image of the distribution of the proppant in the crack through the CT detector in the test result acquisition and analysis mechanism, analyze and obtain the expansion of the proppant in the crack and the resulting change in the opening of the crack, and compare and verify the analysis result with the monitoring result of the fiber grating strain sensor.

19. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S5, the following steps are specifically included: S51, pumping liquid carbon dioxide into the fluid heating temperature controller in the fluid injection mechanism through the second high-pressure plunger pump and the matrix storage tank in the fluid injection mechanism to generate supercritical carbon dioxide; closing the seventh pneumatic valve and the eighth pneumatic valve in the fluid injection mechanism, opening the fifth pneumatic valve and the sixth pneumatic valve in the fluid injection mechanism, and opening the ninth pneumatic valve in the fluid return mechanism, opening the pressure regulating valve in the fluid return mechanism to the maximum so that the reading of the third fluid pressure sensor in the fluid return mechanism is 1 atmosphere, so that the supercritical carbon dioxide flows through the fracture guided by the proppant; S52, continuously record the parameters measured by the mass flow meter, the volume flow meter, the second fluid pressure sensor, the third fluid pressure sensor, the first fluid temperature sensor, and the second fluid temperature sensor; after the flow in the fracture stabilizes, if the reading of the volume flow meter is q, the reading of the second fluid pressure sensor is p i , then the average conductivity of the crack is calculated as follows; ； Where: q is the reading of the volume flow meter; μ is the kinematic viscosity of supercritical carbon dioxide, mPa·s; H is the height of the rock sample, cm; D is the diameter of the rock sample, cm; p i is the reading of the second fluid pressure sensor; p0 is 101 kPa; S53, the circumferential strain of the rock sample is monitored in real time by the fiber Bragg grating strain sensor in the test result collection and analysis mechanism, and the monitored data is converted into the distribution of the crack opening along the height of the rock sample according to the following formula: f (z): ； Where: D is the diameter of the rock sample; ε o (z) is the distribution of the fiber Bragg grating strain sensor readings along the height of the rock sample, with the unit of 1; α is the angle between the distribution direction of the fiber Bragg grating in the fiber Bragg grating strain sensor and the horizontal cross section of the rock sample; Then the average permeability K of the fracture measured after the proppant expands is f2 Calculate as follows: ； Where: F f is the average conductivity of the fracture; H is the height of the rock sample; W f (z) is the distribution of the fracture opening along the height of the rock sample; z is the height coordinate of different positions of the rock sample.

20. The method for testing comprehensive properties of fracture proppants according to claim 14, characterized in that: In step S6, if the average permeability of the fracture measured before the proppant expansion is K f1 The fracture permeability measured after the proppant expands is K f2 , then the change of the proppant conductivity before and after expansion is: ； The conductivity of the environmentally responsive self-expanding proppant is evaluated based on the obtained data on the change in the conductivity of the proppant before and after expansion.

Images