An experimental device and method for studying the sand-carrying performance of carbon dioxide fracturing fluid

Abstract

The application discloses an experimental device and method for researching sand-carrying performance of carbon dioxide fracturing fluid, and belongs to the technical field.The experimental device for researching sand-carrying performance of carbon dioxide fracturing fluid comprises a sand supply assembly, a carbon dioxide pressurizing assembly, a mixing and injecting assembly, a visual reaction kettle assembly and a data acquisition assembly; the visual reaction kettle assembly comprises a reaction kettle shell, a fracture simulation assembly and a confining pressure loading cavity; the fracture simulation assembly is surrounded by high-pressure-resistant transparent plates to form a simulated fracture; the circumferential side wall of the simulated fracture is closed, and only fluid inlets and outlets are arranged; the confining pressure loading cavity is formed by an annular space between the inner wall of the reaction kettle shell and the outer wall of the fracture simulation assembly; the confining pressure loading cavity applies full-circumferential uniform confining pressure to the fracture simulation assembly through an external confining pressure supply source, accurately restores the closing effect of overburden pressure on the fracture, and overcomes the defect that a free-state flat plate model cannot simulate formation stress.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to an experimental apparatus and method for studying the proppant-carrying performance of carbon dioxide fracturing fluid. Background Technology

[0002] Carbon dioxide fracturing is a key technology for developing low-permeability, tight oil and gas reservoirs. The migration and placement morphology of proppant in the fractures directly determine the fracturing effect.

[0003] The migration, stacking, and placement patterns of proppant in fractures are the core content of research on the proppant carrying capacity of fracturing fluids, which directly affects the success rate of fracturing operations and the long-term conductivity of fractures. In actual reservoirs, fractures are subjected to pressure from overlying strata, and the closure stress on the fracture walls directly affects the proppant placement pattern, embedding characteristics, and the final conductivity of the fractures.

[0004] Currently, research on the proppant-carrying capacity of fracturing fluids mainly employs physical simulation experiments. By building visualized fracture models, the migration and placement of proppant within the fractures are observed. Existing simulation devices mostly use hydraulic fracturing proppant-carrying simulation devices. These devices are simple in structure and low in cost, and can meet the basic research needs of conventional water-based fracturing fluids. However, the fracture devices in existing simulation devices use free-state flat plate models. In these models, the fracture walls are in a free state or only subject to simple constraints, making it difficult to simulate the pressure of overlying strata and withstand the high-pressure conditions of liquid carbon dioxide. Moreover, the confining pressure medium often comes into direct contact with the fracture cavity, leading to crosstalk and resulting in large errors between experimental and actual data. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in the prior art and provide an experimental apparatus and method for studying the proppant carrying capacity of carbon dioxide fracturing fluid.

[0006] This invention provides an experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid, comprising a proppant supply assembly, a carbon dioxide pressurization assembly, a mixing and injection assembly, a visualization reactor assembly, and a data acquisition assembly. The visualization reactor assembly includes a reactor shell, a fracture simulation assembly, and a confining pressure loading chamber. The fracture simulation assembly is constructed by enclosing a simulated fracture with a high-pressure resistant transparent plate. The circumferential sidewalls of the simulated fracture are closed, with only fluid inlets and outlets, while the top and bottom are open. A gap exists between the circumferential sidewalls of the fracture simulation assembly and the sidewalls of the reactor shell, forming an annular space with the inner wall of the reactor shell to create the confining pressure loading chamber, physically isolating it from the simulated fracture. The confining pressure loading chamber is connected to an external confining pressure supply source, applying full circumferential confining pressure to the fracture simulation assembly. The reactor shell has a visualization window opposite the simulated fracture. The outlets of the proppant supply assembly and the carbon dioxide pressurization assembly are both connected to the mixing and injection assembly and connected to the inlet of the simulated fracture. The data acquisition assembly acquires data through the visualization window.

[0007] Preferably, the reactor shell includes a reactor body and a cover plate, which are fastened together by a first fixing screw; the crack simulation component specifically includes two high-pressure resistant transparent plates arranged at intervals, which are positioned inside the reactor shell by a fixing bracket and a second fixing screw; the high-pressure resistant transparent plates are sealed around their perimeter by side sealing strips, and their two ends are connected to inlets and outlets, and are sealed together by a third fixing screw and an annular sealing strip.

[0008] Preferably, the reactor body is made of Hastelloy; the high-pressure resistant transparent plate is a sapphire plate; the visualization window is a sapphire window, and a sealing structure consisting of a metal and annular rubber is provided between it and the reactor shell.

[0009] Preferably, the confining pressure supply source includes a confining pressure pump and a confining pressure medium storage tank. The confining pressure pump is connected to the confining pressure loading chamber through a pipeline, and a pressure gauge is provided on the pipeline.

[0010] The mixing and injection assembly includes a sand mixing device and a constant pressure and constant speed displacement pump. The sand mixing device is equipped with a dynamic stirrer for mixing liquid carbon dioxide with proppant. The constant pressure and constant speed displacement pump pumps the sand-carrying liquid into the simulated fracture.

[0011] Preferably, the carbon dioxide pressurization assembly includes a carbon dioxide gas source, a plunger booster pump, and an intermediate container, the intermediate container being used for pressure stabilization; the sand supply assembly includes multiple sand storage tanks and a screw pump, the sand storage tanks storing dyed proppant, and the screw pump delivering the proppant to the mixing and injection assembly via pipeline.

[0012] Preferably, the data acquisition component includes an image acquisition component and a pressure detection component, with the image acquisition component aligned with the visualization window; the outlet of the simulated crack is connected to a waste liquid tank via a pipeline.

[0013] Preferably, the confining pressure medium is water or antifreeze.

[0014] The preferred experimental method for the experimental setup includes the following steps: The confining pressure supply source is activated to inject a medium into the confining pressure loading chamber, thereby applying confining pressure to the crack simulation component. The carbon dioxide is pressurized to a liquid state by the mixing and injection component and mixed with the proppant to form a proppant-carrying liquid. The proppant-carrying liquid is injected into the simulated fracture, and the migration and placement of the proppant are recorded in real time by the visualization reactor component, while pressure data is collected simultaneously. The experiment is repeated by changing the confining pressure or injection parameters to obtain the influence law.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The annular space between the inner wall of the reactor shell and the outer wall of the fracture simulation component creates a physical isolation between the simulated fractures. The confining pressure medium acts only on the periphery of the fracture component and will not seep into the sand-carrying fluid system, ensuring the purity of the experimental fluid. Furthermore, the confining pressure loading chamber applies uniform confining pressure to the fracture simulation component through an external confining pressure supply source, replicating the closing effect of the overlying strata pressure on the fractures. This overcomes the deficiency of free-state plate models in simulating formation stress, reduces the error between experimental and actual data, and improves the accuracy of the experiment. Attached Figure Description

[0016] Figure 1 This is a flowchart of the overall process flow of the device of the present invention.

[0017] Figure 2 This is a schematic diagram of the reactor part of the present invention.

[0018] Figure 3 This is a schematic diagram of the main structure of the reactor of the present invention.

[0019] Figure 4 This is a schematic diagram of the visualized crack plate structure of the present invention.

[0020] Figure 5 This is a schematic diagram of the explosion structure of the reactor of the present invention.

[0021] Figure 6 This is a schematic diagram of the exploded structure of the cracked plate according to the present invention.

[0022] Figure 7 This is a schematic diagram of the side sealing strip structure of the present invention.

[0023] Figure 8This is a schematic diagram of the visualization window structure of the present invention.

[0024] Figure 9 This is a schematic diagram of the high-pressure resistant transparent plate structure of the present invention.

[0025] Figure 10 This is a schematic diagram of the annular sealing strip structure of the present invention.

[0026] Figure 11 This is a schematic diagram of the fixing frame structure of the present invention.

[0027] Explanation of reference numerals in the attached drawings: 1. Constant pressure and constant speed displacement pump; 2. Intermediate container; 3. Sand mixing device; 4. Sand storage tank; 5. Screw pump; 6. Image acquisition component; 7. Waste liquid tank; 8. Reactor; 9. Gas flow meter; 10. Confining pressure pump; 11. Carbon dioxide gas source; 12. Pressure detection component; 13. First fixing screw; 14. Cover plate; 15. Reactor body; 16. Visualization window; 17. Second fixing screw; 18. Fixing frame; 19. High pressure resistant transparent plate; 20. Inlet / outlet; 21. Third fixing screw; 22. Side sealing strip; 23. Annular sealing strip; 24. Confining pressure loading chamber. Detailed Implementation

[0028] The following is in conjunction with the appendix Figures 1-11 To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0029] The terms "first," "second," and similar words used in the patent application specification and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "inner," "outer," "upper," "lower," "far," "near," "front," and "rear" are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. The drawings in this invention are not strictly drawn to scale; the specific dimensions and quantity of each structure can be determined according to actual needs. The drawings described in this invention are merely structural schematic diagrams.

[0030] This invention provides a liquid carbon dioxide fracturing fluid and an experimental apparatus for performance evaluation, such as... Figures 1-10 As shown, the system includes a sand supply assembly, a carbon dioxide pressurization assembly, a mixing injection assembly, a visualization reactor assembly 8, and a data acquisition assembly. The visualization reactor assembly 8 includes a reactor shell, a crack simulation assembly 9, and a confining pressure loading chamber 24. The crack simulation assembly 9 is formed by a high-pressure resistant transparent plate enclosing a simulated crack. The circumferential sidewalls of the simulated crack are closed, with only fluid inlets and outlets. The top and bottom are open. The circumferential sidewalls of the crack simulation assembly 9 have gaps with the sidewalls of the reactor shell, forming an annular space with the inner wall of the reactor shell to create the confining pressure loading chamber 24. This physically isolates the confining pressure loading chamber 24 from the simulated crack. The confining pressure loading chamber 24 is connected to an external confining pressure supply source to apply full circumferential confining pressure to the crack simulation assembly 9. The reactor shell has a visualization window 16 opposite to the simulated crack. The outlets of the sand supply assembly and the carbon dioxide pressurization assembly are connected to the mixing injection assembly and to the inlet of the simulated crack. The data acquisition assembly collects data through the visualization window 16.

[0031] In this embodiment, a simulated crack is formed by using a high-pressure resistant transparent plate 19 to enclose the crack, and with the high-strength support of the reaction vessel 8 shell, it can withstand the high pressure of several megapascals to tens of megapascals required for the liquid carbon dioxide experiment, avoiding the risk of easy breakage of acrylic or ordinary glass models. The confining pressure loading chamber 24 is formed by the annular space between the inner wall of the reactor 8 shell and the outer wall of the crack simulation component. It is physically isolated from the simulated crack. The confining pressure medium only acts on the periphery of the crack component and will not seep into the sand-carrying fluid system, thus ensuring the purity of the experimental fluid. The confining pressure loading chamber 24 applies uniform confining pressure to the fracture simulation component through an external confining pressure supply source, accurately reproducing the closure effect of overlying strata pressure on the fracture and overcoming the limitation of free-state plate models in simulating formation stress. Simultaneously, the reactor shell 8 is equipped with a visualization window 16 positioned relative to the simulated fracture. Combined with the real-time acquisition function of the data acquisition component, this solves the problems of unclear observation under high pressure and data / image asynchrony, providing a reliable experimental basis for studying proppant migration patterns.

[0032] Preferred, such as Figures 5-6 As shown, the reactor shell 8 includes a reactor body 15 and a cover plate 14, which are fastened together by a first fixing screw 13; the crack simulation component specifically includes two high-pressure resistant transparent plates 19 arranged at intervals, which are positioned inside the reactor shell 8 by a fixing bracket 18 and a second fixing screw 17; the high-pressure resistant transparent plates 19 are closed around the perimeter by side sealing strips 22, and the two ends are connected to the inlet and outlet 20, and are sealed by a third fixing screw 21 and an annular sealing strip 23.

[0033] In this embodiment, the reactor 8 shell adopts a modular design where the main body of the reactor 8 and the cover plate 14 are fastened together with fixing screws, facilitating disassembly and maintenance. The Hastelloy main body can withstand corrosion and pressure loads under low-temperature and high-pressure conditions of carbon dioxide. The crack simulation component is positioned by the fixing bracket 18 and fixing screws, ensuring that the two high-pressure resistant transparent plates 19 are arranged in parallel and spaced apart, forming a uniform simulated crack gap, avoiding plate cracking caused by stress concentration in traditional adhesive structures. The transparent plates are sealed around the perimeter by side sealing strips 22, and the two ends are sealed to the inlet and outlet 20 by annular sealing strips 23, forming a fully enclosed fluid channel to prevent sand-carrying liquid from leaking from the gaps into the confining pressure chamber, while also preventing the confining pressure medium from seeping back into the cracks. This multi-seal structure, combined with metal and rubber composite seals, can achieve zero leakage under high pressure, ensuring directional fluid flow during the experiment and improving the accuracy of data acquisition.

[0034] Preferred, such as Figures 2-6 As shown, the reactor body 15 is made of Hastelloy; the high-pressure resistant transparent plate 19 is a sapphire plate; the visualization window 16 is a sapphire window, and a sealing structure combining metal and annular rubber is provided between it and the reactor shell 8.

[0035] In this embodiment, the reliability issues of components under low-temperature and high-pressure environments are specifically addressed through material selection and sealing structure optimization: the main body of reactor 8 is made of Hastelloy, a material that combines excellent corrosion resistance, high strength, and low-temperature toughness, capable of withstanding the alternating high-pressure and low-temperature conditions in liquid carbon dioxide experiments, avoiding the risks of corrosion and low-temperature brittle fracture associated with carbon steel; the visualization crack plate is made of sapphire, with a Mohs hardness of 9 and compressive strength far exceeding that of ordinary glass and acrylic, maintaining optical transparency under high pressure to ensure clear observation of the proppant migration trajectory; the metal sealing ring bears the main pressure load, while the rubber sealing ring fills the microscopic gaps, ensuring high-pressure sealing while preventing window breakage caused by direct contact with the hard seal. This combination of materials and sealing design enables the device to operate stably under extreme temperature and pressure conditions, extending the service life of components.

[0036] Preferred, such as Figure 1 As shown, the confining pressure supply source includes a confining pressure pump 10 and a confining pressure medium storage tank. The confining pressure pump 10 is connected to the confining pressure loading chamber 24 through a pipeline, and a pressure gauge is installed on the pipeline. The mixing injection component includes a sand mixing device 3 and a constant pressure and constant speed displacement pump 1. The sand mixing device 3 is equipped with a dynamic stirrer inside, which is used to mix liquid carbon dioxide with proppant. The constant pressure and constant speed displacement pump 1 pumps the sand-carrying liquid into the simulated fracture.

[0037] In this embodiment, the controllability of experimental parameters and the uniformity of proppant-carrying fluid are improved through the coordinated design of the confining pressure supply and mixing injection components: The confining pressure supply source is equipped with a confining pressure pump 10 and a pressure gauge, which can precisely adjust the pressure value of the confining pressure loading chamber 24 to achieve continuous and stable loading from 0 to the formation simulated pressure. Combined with the full circumferential pressure characteristics of the annular cavity, it ensures that the fracture simulation component is subjected to uniform stress, truly reflecting the influence of formation stress on the proppant placement morphology. The mixing injection component integrates a proppant mixing device 3 and a constant pressure and constant speed displacement pump 1. The forced mixing action of the dynamic agitator can break the interfacial tension between carbon dioxide and proppant, avoiding the problems of sand particle agglomeration and uneven distribution that are prone to occur in static mixing, forming a stable and uniform proppant-carrying fluid. The constant pressure and constant speed displacement pump 1 maintains a constant injection pressure and displacement through closed-loop control, preventing pressure fluctuations from causing proppant sedimentation and blockage of pipelines or changes in the phase state of carbon dioxide. The two work together to ensure that the flow state of the proppant-carrying fluid in the simulated fracture is consistent with that of actual fracturing operations.

[0038] Preferred, such as Figure 1 As shown, the carbon dioxide pressurization assembly includes a carbon dioxide gas source 11, a plunger booster pump, and an intermediate container 2, which is used for pressure stabilization; the sand supply assembly includes multiple sand storage tanks 4 and a screw pump 5, in which the sand storage tanks 4 store the dyed proppant, and the screw pump 5 transports the proppant to the mixing and injection assembly through pipelines.

[0039] In this embodiment, the carbon dioxide pressurization component uses a combination of a plunger booster pump and an intermediate container 2. The plunger pump can efficiently pressurize gaseous carbon dioxide to the pressure required for liquid state. The intermediate container 2 serves as a pressure stabilizing buffer unit to eliminate pressure pulsation during the pressurization process, ensuring that the carbon dioxide entering the mixing device always remains in a liquid or supercritical state, avoiding fluctuations in sand-carrying performance caused by phase change. The sand supply component is equipped with multiple sand storage tanks 4 and screw pumps 5 to support the classified storage of proppant with different mesh sizes and densities. The screw pumps 5 achieve precise metering of proppant through the volumetric conveying principle, and can control the injection volume and injection sequence in conjunction with the pipeline flow meter.

[0040] Preferred, such as Figure 1 As shown, the data acquisition component includes an image acquisition component 6 and a pressure detection component 12. The image acquisition component 6 is aligned with the visualization window 16. The outlet of the simulated crack is connected to the waste liquid tank 7 through a pipeline.

[0041] In this embodiment, the data acquisition component integrates image acquisition and pressure detection modules. The image acquisition component 6 is aligned with the visualization window 16 and can capture millisecond-level proppant migration, sedimentation, and collision processes with a resolution of micrometer level, clearly presenting the stacking morphology of sand particles in the crack. The pressure detection component 12 simultaneously acquires pressure data from the simulated crack inlet, outlet, and confining pressure chamber. The temporal resolution matches the image acquisition frame rate, providing multi-source data support for establishing a correlation model between sand carrying performance and process parameters. The simulated crack outlet is connected to the waste liquid tank 7, which can centrally collect the carbon dioxide and proppant mixture after the experiment, avoiding the greenhouse effect and environmental pollution caused by direct discharge. The waste liquid tank 7 is equipped with a pressure relief valve and a safety valve to ensure the safety of the pressure relief process.

[0042] Preferably, the confining medium is water or antifreeze.

[0043] In this embodiment, the reliability of the confining pressure assembly under low-temperature conditions is addressed through flexible selection of the confining pressure medium: water or antifreeze is chosen as the confining pressure medium. Water is selected for room-temperature experiments due to its low cost, small compressibility, and precise pressure transmission. For low-temperature experiments, antifreeze is used, with a freezing point below -30°C, preventing sealing failure or cavity damage caused by water freezing and expanding at low temperatures. This medium switching mechanism ensures that the confining pressure loading chamber 24 maintains good fluidity and pressure transmission efficiency across the entire temperature range, avoiding confining pressure fluctuations caused by medium phase changes and ensuring consistent experimental conditions.

[0044] The method of using the liquid carbon dioxide fracturing fluid and the experimental apparatus for performance evaluation of the present invention is as follows: Based on the pressure and temperature conditions of the overlying strata of the target reservoir, the experimental confining pressure value and the type of confining pressure medium are determined. The visualization reactor 8 components are assembled: two sapphire plates are installed inside the reactor body 15 using the fixing bracket 18 and sealing strip, ensuring uniform simulated fracture gaps and a leak-free seal; the cover plate 14 is then placed on top and secured with fixing screws, and the alignment accuracy of the visualization window 16 with the fracture area is checked. The confining pressure pump 10 is started, drawing medium from the confining pressure medium storage tank and injecting it into the confining pressure loading chamber 24. Real-time monitoring is performed using a pressure gauge until the set confining pressure value is reached and stabilized for 5 minutes. After verifying no pressure drop, the process proceeds to the next stage.

[0045] Turn on the carbon dioxide gas source 11, pressurize the gaseous carbon dioxide to a liquid state using a plunger booster pump, and then deliver it to the sand mixing device 3 after pressure stabilization in the intermediate container 2. Simultaneously start the sand supply assembly: select the sand storage tank 4 according to the experimental plan, and deliver the proppant to the sand mixing device 3 via the screw pump 5 at a set flow rate. The dynamic stirrer runs at a speed of 500-1000 rpm to ensure thorough mixing of the carbon dioxide and proppant to form a uniform sand-carrying liquid. Start the constant pressure and constant speed displacement pump 1 to pump the sand-carrying liquid into the simulated fracture inlet at a set displacement. Observe the pressure sensor data to ensure the injection pressure remains stable at the target value.

[0046] After the proppant-carrying liquid enters the simulated fracture, the image acquisition component 6 is immediately activated to record the migration, sedimentation, and placement of the proppant within the fracture. Simultaneously, inlet pressure, outlet pressure, and confining pressure data are acquired to form a spatiotemporally synchronized multi-source dataset. The experiment continues until the proppant-carrying liquid is completely discharged from the fracture or the set time is reached. Then, the displacement pump and proppant supply component are shut off, the confining pressure chamber pressure is slowly released, the cover plate 14 is removed, the fracture assembly is taken out, and residual proppant and carbon dioxide are cleaned. The mixture in the waste liquid tank 7 is depressurized and recycled according to environmental protection requirements. The pipelines and reactor 8 are cleaned in preparation for the next set of experiments.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid, characterized in that, It includes a sand supply assembly, a carbon dioxide pressurization assembly, a mixing and injection assembly, a visualization reactor assembly, and an image acquisition assembly; the visualization reactor assembly includes a reactor shell, a crack simulation assembly, and a confining pressure loading chamber; the crack simulation assembly is composed of several high-pressure resistant transparent plates stacked together to form a simulated crack, the outer wall of the simulated crack is completely closed, and the crack simulation assembly has a liquid inlet and a liquid outlet on a pair of sides along the axial direction of the reactor shell; The crack simulation component is fixedly connected to the reactor shell at both ends along the axis of the reactor shell, and there is a gap between the outer wall of the crack simulation component and the inner wall of the reactor shell to form the confining pressure loading cavity. The confining pressure loading cavity is connected to an external confining pressure supply source to apply full circumferential confining pressure to the crack simulation component. The reactor shell is provided with a visualization window opposite to the simulated crack. The outlets of the sand supply assembly and the carbon dioxide pressurization assembly are both connected to the mixing injection assembly and connected to the inlet. The outlet is connected to the waste liquid tank through a pipeline. The image acquisition assembly acquires the proppant's migration trajectory, sedimentation process, and layup morphology through the visualization window.

2. The experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid as described in claim 1, characterized in that, The crack simulation component includes multiple high-pressure resistant transparent plates arranged at relative intervals. The multiple transparent plates are positioned inside the reactor shell by a fixing frame and a second fixing screw. The high-pressure resistant transparent plates are sealed around their perimeter by side sealing strips, and their two ends are connected to the inlet and outlet, and are sealed by a third fixing screw and an annular sealing strip.

3. The experimental apparatus as described in claim 2, characterized in that, The reactor shell includes a reactor body and a cover plate, which are fastened together by a first fixing screw; the reactor body is made of Hastelloy; the high-pressure resistant transparent plate is a sapphire plate; the visualization window is a sapphire window, and a sealing structure combining metal and annular rubber is provided between it and the reactor shell.

4. The experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid as described in claim 1, characterized in that, The confining pressure supply source includes a confining pressure pump and a confining pressure medium storage tank. The confining pressure pump is connected to the confining pressure loading chamber through a pipeline, and a pressure gauge is installed on the pipeline. The mixing injection assembly includes a sand mixing device and a constant pressure and constant speed displacement pump. The sand mixing device is equipped with a dynamic stirrer inside, which is used to mix liquid carbon dioxide with proppant. The constant pressure and constant speed displacement pump pumps the sand-carrying liquid into the simulated fracture.

5. The experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid as described in claim 1, characterized in that, The carbon dioxide pressurization assembly includes a carbon dioxide gas source, a plunger booster pump, and an intermediate container, the intermediate container being used for pressure stabilization; the sand supply assembly includes multiple sand storage tanks and a screw pump, the sand storage tanks storing dyed proppant, and the screw pump delivering the proppant to the mixing and injection assembly via pipeline.

6. The experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid as described in claim 1, characterized in that, It also includes a pressure detection component for detecting the injection pressure of the crack simulation component of the sand mixing device and the loading pressure of the confining pressure loading chamber.

7. The experimental apparatus for studying the proppant-carrying performance of carbon dioxide fracturing fluid as described in claim 1, characterized in that, The confining pressure medium is water or antifreeze.

8. The experimental method of the experimental apparatus as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The confining pressure supply source is activated to inject a medium into the confining pressure loading chamber, thereby applying confining pressure to the crack simulation component. The aforementioned mixing and injection assembly pressurizes carbon dioxide to a liquid state and mixes it with proppant to form a sand-carrying fluid. The proppant-carrying fluid is injected into the simulated crack, and the migration and placement of the proppant are recorded in real time through the visualization reactor assembly, while pressure data is collected simultaneously. Repeat the experiment by changing the confining pressure or injection parameters to obtain the influence pattern.

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