Hydraulic fracturing simulation device

Abstract

The invention provides a hydraulic fracturing simulation device, which comprises a pressure pump, a function module, an execution module, a visual display module and a valve assembly, the function module comprises a sand mixing unit and an oil-water separation unit, the execution module comprises a shaft simulation unit and a multi-stage crack simulation unit, and the shaft simulation unit and the multi-stage crack simulation unit are communicated. A gradient pressure triggering structure is arranged in the multi-stage crack simulation unit so as to realize multi-stage crack progressive expansion; the valve assembly comprises a first valve, a second valve, a third valve and a fourth valve, the first valve is connected with the pressure pump and the sand mixing unit, the second valve is connected with the sand mixing unit and the shaft simulation unit, the third valve is connected with the pressure pump and the oil-water separation unit, and the fourth valve is connected with the oil-water separation unit and the shaft simulation unit; thus, through integrated design, a valve assembly double-loop switching mechanism and gradient triggering and visual collaborative layout, the requirements for integration, continuity, high simulation and high precision of the hydraulic fracturing experiment are met, and the hydraulic fracturing experiment system fully meets the requirements for industry core development.

Description

Technical Field

[0001] This application belongs to the field of oil and gas extraction technology, and in particular relates to a hydraulic fracturing simulation device. Background Technology

[0002] Hydraulic fracturing technology is a core technology in energy fields such as oil and gas field development and shale gas extraction. Its principle is to inject fracturing fluid into the well using a high-pressure pump, causing the formation to form fractures and fill them with proppant, thereby improving the oil and gas seepage channels. To ensure the effectiveness and safety of on-site fracturing operations, two types of core experiments need to be carried out in an indoor simulation device before construction: one is the sedimentation and migration experiment of proppant in fracturing fluid, which is used to optimize proppant selection and injection parameters; the other is the formation fracture dynamic propagation experiment, which is used to explore the fracture extension law and morphological characteristics.

[0003] In related technologies, proppant settling and migration experiments and crack dynamic propagation experiments are conducted using two independent sets of equipment, each with complete pressure supply, fluid processing and observation modules.

[0004] However, the simulation methods in the relevant technologies have obvious defects: on the one hand, the two independent sets of equipment require separate site planning, which increases the costs of equipment procurement, site modification and operation and maintenance manpower; on the other hand, the fracture simulation is simple and deviates greatly from the actual progressive expansion law of the strata; the two types of experiments are carried out in stages, which cannot simulate the continuous process on site, and the data lacks synergistic correlation, which misleads the optimization of construction parameters; furthermore, the visualization display module is independent and not compatible with the fracture simulation structure, which cannot capture the instantaneous expansion dynamics of the fracture, the experiment is not continuous, and only static endpoint data can be obtained. The data dimension is single and it is difficult to fully reveal the fracturing mechanism. Summary of the Invention

[0005] This application provides a hydraulic fracturing simulation device to at least solve the aforementioned problems in the related art.

[0006] To achieve the above objectives, this application provides the following technical solution: a hydraulic fracturing simulation device, comprising: A pressure pump is used to provide the pressure required for experiments. The functional modules include a sand mixing unit and an oil-water separation unit. The sand mixing unit is used to prepare proppant and fracturing fluid carrying fluid, and the oil-water separation unit is used to store and purify the fracturing fluid required for fracture propagation experiments. The execution module includes a wellbore simulation unit and a multi-level fracture simulation unit, which are connected. The multi-level fracture simulation unit has a built-in gradient pressure triggering structure to achieve progressive expansion of multi-level fractures. The visualization module is used to capture dynamic images of the progressive expansion of multi-level cracks in real time and synthesize three-dimensional visualization data. The valve assembly includes a first valve, a second valve, a third valve, and a fourth valve. The first valve connects the pressure pump to the input end of the sand mixing unit; the second valve connects the output end of the sand mixing unit to the wellbore simulation unit; the third valve connects the pressure pump to the input end of the oil-water separation unit; and the fourth valve connects the output end of the oil-water separation unit to the wellbore simulation unit. By switching the valve assembly on and off, the sand mixing unit or oil-water separation unit is selectively connected to the execution module to construct a proppant sedimentation and migration experimental loop or a crack dynamic propagation experimental loop. The visualization display module works in conjunction with the gradient pressure triggering structure of the multi-level crack simulation unit to capture the propagation dynamics of each level of crack in real time.

[0007] In some alternative implementations, the multi-stage crack simulation unit includes a housing, a connecting pipe, a first crack channel, a second crack channel, and a third crack channel. One end of the connecting pipe is connected to the wellbore simulation unit. A one-way valve is provided between the connecting pipe and the wellbore simulation unit. The one-way valve is a one-inlet, two-outlet type one-way valve. The inlet of the one-way valve is connected to the wellbore simulation unit, and the first outlet of the one-way valve is connected to the connecting pipe. The one-way valve is open along the flow direction of the fracturing fluid or sand-carrying fluid to prevent fluid backflow. The other end of the connecting pipe extends into the housing. The first crack channel is located inside the housing and communicates with the connecting pipe. The second crack channel is located inside the housing and communicates with the first crack channel. The third crack channel is located inside the housing and communicates with the second crack channel. A first pressure triggering component is provided in the first crack channel, a second pressure triggering component is provided in the second crack channel, and a third pressure triggering component is provided in the third crack channel. The triggering pressure of the first pressure triggering component is less than the triggering pressure of the second pressure triggering component, and the triggering pressure of the second pressure triggering component is less than the triggering pressure of the third pressure triggering component, so as to form a gradient pressure triggering structure.

[0008] In some alternative embodiments, the first pressure triggering component includes a first baffle and a first elastic member. The first baffle is used to seal the communication port between the first crack channel and the connecting pipe. One end of the first elastic member abuts against the first baffle, and the other end abuts against the end wall of the first crack channel away from the communication port. The second pressure triggering component includes a second baffle and a second elastic member. The second baffle is used to seal the communication port between the second crack channel and the first crack channel. One end of the second elastic member abuts against the second baffle, and the other end abuts against the end wall of the second crack channel away from the communication port. The third pressure triggering component includes a third baffle and a third elastic member. The third baffle is used to seal the communication port between the second crack channel and the third crack channel. One end of the third elastic member abuts against the third baffle, and the other end abuts against the end wall of the third crack channel away from the communication port.

[0009] In some alternative implementations, there are multiple first crack channels, each first crack channel is connected to multiple second crack channels in its own extension direction, and each second crack channel is connected to multiple third crack channels in its own extension direction. Each first crack channel, each second crack channel, and each third crack channel are provided with multiple stops at intervals along their own extension direction; The first crack channel has a stop in its own extending direction to prevent the first baffle from rebounding and resetting; the second crack channel has a stop in its own extending direction to prevent the second baffle from rebounding and resetting; and the third crack channel has a stop in its own extending direction to prevent the third baffle from rebounding and resetting.

[0010] In some alternative implementations, the multi-level crack simulation unit is a transparent structure to accommodate visualization capture requirements; The visualization module includes at least one camera unit, which is deployed around the periphery of the multi-level crack simulation unit to capture dynamic images of the progressive expansion of multi-level cracks in real time, and synthesizes three-dimensional visualization data in conjunction with the data processing unit.

[0011] In some alternative implementations, the hydraulic fracturing simulation apparatus also includes a return pipeline; One end of the return pipeline is connected to the second outlet of the one-way valve, and the other end is connected to the pressure pump. A fifth valve is installed on the return pipeline to control the opening and closing of the return pipeline, so as to form a closed loop in the proppant sedimentation and migration experimental circuit, and to make the sand-carrying liquid continuously circulate and migrate.

[0012] In some alternative implementations, the hydraulic fracturing simulation device also includes an attitude adjustment component; the attitude adjustment component is connected to the wellbore simulation unit and is used to adjust the tilt angle of the wellbore simulation unit to simulate the migration and settling behavior of proppant in different well types.

[0013] In some alternative implementations, the hydraulic fracturing simulation device also includes a heating module connected in series at the inlet end of the wellbore simulation unit, used to preheat the fracturing fluid or proppant-carrying fluid to the target temperature and maintain a constant temperature.

[0014] In some optional implementations, a pressure gauge and a sixth valve are also provided between the heating module and the wellbore simulation unit; The pressure gauge is used to monitor the pressure of fracturing fluid or sand-carrying fluid in the pipeline, and the sixth valve is used to control the opening and closing of this section of the pipeline.

[0015] In some optional implementations, when constructing the proppant settling and transport experimental loop, the first valve and the second valve are open, while the third valve and the fourth valve are closed, and the proppant-carrying fluid enters the wellbore simulation unit sequentially through the sand mixing unit and the second valve; When constructing the dynamic fracture propagation experimental loop, the third and fourth valves are turned on, while the first and second valves are turned off. The purified fracturing fluid passes through the oil-water separation unit and the fourth valve in sequence into the wellbore simulation unit and the multi-stage fracture simulation unit. A dye is added to the fracturing fluid to improve the visualization and recognition of the multi-stage fracture propagation process.

[0016] In the aforementioned hydraulic fracturing simulation device, on the one hand, by integrating the pressure pump, functional modules, execution modules, visualization display modules, and valve assemblies into a single device, and selectively connecting the sand mixing unit or oil-water separation unit with the execution module through the on / off switching of the valve assemblies, separate devices are no longer required for proppant settling and migration experiments and fracture dynamic propagation experiments. This directly saves the separate installation space and equipment placement space required for split devices, achieving an integrated design of the hydraulic fracturing simulation device and effectively solving the core defects of existing split devices, such as large footprint and high cost. On the other hand, through the dual-loop switching mechanism controlled by the valve assemblies, the orderly switching and continuous conduct of the two types of experiments within the same device can be achieved, eliminating the need for stages on different devices. The operation ensures that the core parameters of the two types of experiments remain consistent, forming a close synergistic relationship between the experimental data. This effectively avoids the misleading optimization of construction parameters caused by the lack of data correlation in existing technologies, significantly enhancing the guiding value of experimental data for on-site construction. Furthermore, the gradient pressure triggering structure built into the multi-level fracture simulation unit works in conjunction with the visualization display module, enabling more sensitive capture of the expansion dynamics of each level of fracture. This allows for more accurate acquisition of full-cycle data on fracture expansion and the synthesis of three-dimensional visualization data. This not only solves the shortcomings of existing technologies, such as simple fracture simulation and large deviations from real formation patterns, but also compensates for the incompatibility of the independent visualization display module and the lack of dynamic data, greatly improving the simulation accuracy of fracture simulation and the comprehensiveness of experimental data. Thus, through integrated design, a dual-loop switching mechanism for valve components, and a synergistic layout of gradient triggering and visualization, the integrated, continuous, highly realistic, and high-precision requirements of hydraulic fracturing experiments are achieved, fully meeting the core development demands of the industry.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0019] Figure 1 A schematic diagram of the hydraulic fracturing simulation device in an embodiment of this application is shown; Figure 2 It shows Figure 1 Schematic diagram of the main structure of a multi-level crack simulation unit; Figure 3 It shows Figure 2 Schematic diagram of the structure of the multi-level crack simulation unit along the III-III direction; Figure 4 It shows Figure 2 Schematic diagram of the structure of the multi-level crack simulation unit along the IV-IV direction; Figure 5 It shows Figure 3 A schematic diagram of the second crack channel and the second pressure triggering component; Figure 6 It shows Figure 3 A schematic diagram of the third crack channel and the third pressure triggering component; Figure 7 This illustration shows a structural diagram of a wedge-shaped stop block in an embodiment of this application. Figure 8 A schematic diagram of a stop member with a toothed structure is shown in an embodiment of this application.

[0020] Explanation of the numbers in the diagram: 11. Pressure pump; 12. Functional module; 121. Sand mixing unit; 122. Oil-water separation unit; 13. Execution module; 131. Wellbore simulation unit; 132. Multi-stage fracture simulation unit; 1321. Housing; 1322. Connecting pipe; 1323. First fracture channel; 1324. Second fracture channel; 1325. Third fracture channel; 1326. First pressure triggering component; 13261. First baffle; 13262. First elastic element; 1327. Second pressure triggering component; 13271. Second baffle; 13272. Second elastic element; 1328. Third pressure triggering component; 13281. Third baffle. Plate; 13282, Third elastic element; 1329, Stop element; 13291, Wedge-shaped locking block structure; 132911, Stop channel; 132912, Wedge block; 132913, Return spring; 13292, Locking tooth structure; 132921, Locking tooth; 132922, Locking groove; 132923, Stop spring; 14, Visual display module; 15, Valve assembly; 151, First valve; 152, Second valve; 153, Third valve; 154, Fourth valve; 16, Return pipeline; 17, Attitude adjustment assembly; 18, Fifth valve; 19, Heating module; 20, Pressure gauge; 21, Sixth valve; 22, Check valve. Detailed Implementation

[0021] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] In related technologies, simulation devices mainly adopt a split-type design, meaning that separate equipment is configured for proppant settling and migration experiments and fracture dynamic propagation experiments, with each set of equipment possessing complete pressure supply, fluid processing, and observation modules. However, the simulation devices in these technologies have significant drawbacks: Firstly, the two independent sets of equipment require separate site planning, increasing the costs of equipment procurement, site modification, and maintenance manpower; secondly, the fracture simulation is simplistic and deviates significantly from the actual progressive propagation patterns of the formation; the two types of experiments are conducted in stages, failing to simulate the continuous process in the field, resulting in a lack of data correlation and misleading optimization of construction parameters; thirdly, the visualization module is independent and incompatible with the fracture simulation structure, failing to capture the instantaneous dynamic propagation of fractures, resulting in discontinuous experiments, obtaining only static endpoint data, and having a single data dimension, making it difficult to comprehensively reveal the fracturing mechanism.

[0025] To address the aforementioned issues, this application integrates the pressure pump, functional modules, execution modules, visualization display modules, and valve assemblies into a single device. The selective connection between the sand mixing unit or oil-water separation unit and the execution module is achieved through the on / off switching of the valve assemblies. This eliminates the need for separate devices for proppant settling and migration experiments and fracture dynamic propagation experiments, directly saving the separate installation and equipment placement space required for split-type devices. This integrated design of the hydraulic fracturing simulation device effectively solves the core drawbacks of existing split-type devices, such as large footprint and high cost. Furthermore, the dual-loop switching mechanism controlled by the valve assemblies enables the orderly switching and continuous execution of the two types of experiments within the same device, eliminating the need for phased operation on different equipment and ensuring... The two types of experiments maintain consistent core parameters such as pressure and temperature, creating a close synergistic relationship between the experimental data. This effectively avoids the misleading optimization of construction parameters caused by a lack of data correlation in existing technologies, significantly enhancing the guiding value of experimental data for on-site construction. The gradient pressure triggering structure built into the multi-level fracture simulation unit works in conjunction with the visualization display module, enabling more sensitive capture of the expansion dynamics of each fracture level. This allows for more accurate acquisition of full-cycle data on fracture expansion and the synthesis of 3D visualization data. This not only solves the shortcomings of existing technologies, such as simple fracture simulation and large deviations from real formation patterns, but also compensates for the incompatibility of the independent visualization display module and the lack of dynamic data, greatly improving the simulation accuracy of fracture simulation and the comprehensiveness of experimental data. Thus, through integrated design, a dual-loop switching mechanism for valve components, and a synergistic layout of gradient triggering and visualization, the integrated, continuous, highly realistic, and high-precision requirements of hydraulic fracturing experiments are met, fully aligning with the core development demands of the industry.

[0026] The various embodiments of this application will be described below with reference to the accompanying drawings.

[0027] Combination Figure 1In some optional embodiments, this application provides a hydraulic fracturing simulation device, which includes a pressure pump 11, a functional module 12, an execution module 13, a visualization display module 14, and a valve assembly 15. The pressure pump 11 provides the pressure required for the experiment; the functional module 12 includes a sand mixing unit 121 and an oil-water separation unit 122. The sand mixing unit 121 is used to prepare a proppant-carrying fluid for fracturing fluid, and the oil-water separation unit 122 is used to store and purify the fracturing fluid required for the fracture propagation experiment; the execution module 13 includes a wellbore simulation unit 131 and a multi-stage fracture simulation unit 132, which are connected. The multi-stage fracture simulation unit 132 has a built-in gradient pressure triggering structure to achieve progressive multi-stage fracture propagation; the visualization display module 14 is used to capture dynamic images of the progressive multi-stage fracture propagation in real time and synthesize three-dimensional visualization data; the valve assembly 15 includes a first valve 151, a second valve 152, a third valve 153, and a fourth valve. The valve assembly 154 has four valves: a first valve 151 connecting the pressure pump 11 to the input of the sand mixing unit 121; a second valve 152 connecting the output of the sand mixing unit 121 to the wellbore simulation unit 131; a third valve 153 connecting the pressure pump 11 to the input of the oil-water separation unit 122; and a fourth valve 154 connecting the output of the oil-water separation unit 122 to the wellbore simulation unit 131. By switching the valve assembly 15 on and off, the sand mixing unit 121 or the oil-water separation unit 122 can be selectively connected to the execution module 13 to construct a proppant settling and migration experimental loop or a fracture dynamic propagation experimental loop. The visualization display module 14 works in conjunction with the gradient pressure triggering structure of the multi-level fracture simulation unit 132 to capture the propagation dynamics of each level of fracture in real time.

[0028] In the aforementioned hydraulic fracturing simulation device, on the one hand, by integrating the pressure pump 11, functional module 12, execution module 13, visualization display module 14, and valve assembly 15 into the same device, and selectively connecting the sand mixing unit 121 or oil-water separation unit 122 with the execution module 13 through the on / off switching of the valve assembly 15, separate devices are not required for proppant settling and migration experiments and fracture dynamic propagation experiments. This directly saves the separate installation space and equipment placement space required for split devices, realizing the integrated design of the hydraulic fracturing simulation device and effectively solving the core defects of existing split devices, such as large footprint and high cost. On the other hand, through the dual-loop switching mechanism controlled by the valve assembly 15, the orderly switching and continuous conduction of the two types of experiments within the same device can be achieved without the need for separate devices. The phased operation on different equipment ensures that the core parameters of the two types of experiments remain consistent, creating a close synergistic relationship between the experimental data. This effectively avoids the misleading optimization of construction parameters caused by the lack of data correlation in existing technologies, significantly enhancing the guiding value of experimental data for on-site construction. Furthermore, the gradient pressure triggering structure built into the multi-level fracture simulation unit 132 works in conjunction with the visualization display module 14, enabling more sensitive capture of the expansion dynamics of each level of fracture. This allows for more accurate acquisition of full-cycle data on fracture expansion and the synthesis of three-dimensional visualization data. This not only solves the shortcomings of existing technologies, such as simple fracture simulation and large deviations from real formation patterns, but also compensates for the incompatibility of the independent visualization display module and the lack of dynamic data, greatly improving the simulation accuracy of fracture simulation and the comprehensiveness of experimental data. Thus, through integrated design, the dual-loop switching mechanism of the valve assembly 15, and the coordinated layout of gradient triggering and visualization, the integrated, continuous, highly realistic, and high-precision requirements of hydraulic fracturing experiments are achieved, fully meeting the core development demands of the industry.

[0029] Combination Figure 2 and Figure 3In some optional embodiments, the multi-stage fracture simulation unit 132 includes a housing 1321, a connecting pipe 1322, a first fracture channel 1323, a second fracture channel 1324, and a third fracture channel 1325. One end of the connecting pipe 1322 is connected to the wellbore simulation unit 131, and a one-way valve 22 is provided between the connecting pipe 1322 and the wellbore simulation unit 131. The one-way valve 22 is a one-inlet, two-outlet one-way valve. The inlet of the one-way valve 22 is connected to the wellbore simulation unit 131, and the first outlet of the one-way valve 22 is connected to the connecting pipe 1322. The one-way valve 22 is open along the flow direction of the fracturing fluid or sand-carrying fluid to prevent fluid backflow. The other end of the connecting pipe 1322 extends into the housing 1321, and the first fracture channel 1323 is located in the housing 1321. The first crack channel 1324 is located inside the housing 1321 and communicates with the first crack channel 1323. The third crack channel 1325 is located inside the housing 1321 and communicates with the second crack channel 1324. The first crack channel 1323 is provided with a first pressure triggering component 1326, the second crack channel 1324 is provided with a second pressure triggering component 1327, and the third crack channel 1325 is provided with a third pressure triggering component 1328. The triggering pressure of the first pressure triggering component 1326 is less than the triggering pressure of the second pressure triggering component 1327, and the triggering pressure of the second pressure triggering component 1327 is less than the triggering pressure of the third pressure triggering component 1328, so as to form a gradient pressure triggering structure.

[0030] Thus, by setting the multi-level fracture simulation unit 132 as a hierarchical interconnected structure of connecting pipe 1322, first fracture channel 1323, second fracture channel 1324, and third fracture channel 1325, and adding a one-way valve 22 between the connecting pipe 1322 and the wellbore simulation unit 131, the internal layout of the multi-level fracture network is directly simplified without the need for additional complex fracture diversion and anti-backflow structures, while clarifying the orderly path of fracture propagation. The progressively increasing pressure setting of the gradient pressure triggering component can accurately control the progressive opening of each level of fracture in a preset order, solving the problems of chaotic fracture simulation and large deviation from the actual formation law in existing devices. The design of the one-way valve 22, which is conductive along the fluid flow direction, effectively avoids the backflow of fracturing fluid or sand-carrying fluid, ensuring stable loop pressure, avoiding triggering distortion caused by backflow, and further improving the simulation accuracy of fracture simulation and the stability of experimental data.

[0031] In some preferred embodiments, one end of the connecting pipe 1322 is detachably connected to the wellbore simulation unit 131; specifically, the detachable connection can be a threaded connection, a snap-fit ​​connection, etc., and to ensure sealing, one end of the connecting pipe 1322 and the wellbore simulation unit 131 are also sealed with a sealing ring or sealant.

[0032] Combination Figure 4 , Figure 5and Figure 6 In some optional embodiments, the first pressure triggering assembly 1326 includes a first baffle 13261 and a first elastic member 13262. The first baffle 13261 is used to seal the communication port between the first crack channel 1323 and the connecting pipe 1322. One end of the first elastic member 13262 abuts against the first baffle 13261, and the other end abuts against the end wall of the first crack channel 1323 away from the communication port. The second pressure triggering assembly 1327 includes a second baffle 13271 and a second elastic member 13272. The second baffle 13271 is used to seal the second crack channel 1324 and the first... A communication port between two crack channels 1323, one end of the second elastic member 13272 abuts against the second baffle 13271, and the other end abuts against the end wall of the second crack channel 1324 away from the communication port; the third pressure triggering assembly 1328 includes a third baffle 13281 and a third elastic member 13282, the third baffle 13281 is used to seal the communication port between the second crack channel 1324 and the third crack channel 1325, one end of the third elastic member 13282 abuts against the third baffle 13281, and the other end abuts against the end wall of the third crack channel 1325 away from the communication port.

[0033] For example, the first elastic element 13262, the second elastic element 13272, and the third elastic element 13282 can all be springs; the trigger threshold for the first elastic element 13262 to press against the first baffle 13261 is 0.8-1.2 MPa, the trigger threshold for the second elastic element 13272 to press against the second baffle 13271 is 1.5-2.0 MPa, and the trigger threshold for the third elastic element 13282 to press against the third baffle 13281 is 2.5-3.0 MPa.

[0034] Thus, the first pressure triggering component 1326, the second pressure triggering component 1327, and the third pressure triggering component 1328 all adopt a structure that combines a baffle with an elastic element. This structure is simple, and the triggering threshold can be adjusted according to the elastic coefficient and deformation of the elastic element, enabling high-efficiency and high-precision adjustment of the triggering threshold for each level of crack channel. At the same time, the baffle has both sealing and triggering functions, and when matched with the corresponding elastic element, it ensures the consistency of the triggering pressure in different batches of experiments, thereby enhancing the reliability of the experimental data.

[0035] Combination Figure 3In some optional embodiments, there are multiple first crack channels 1323, each first crack channel 1323 is connected to a connecting pipe 1322, each first crack channel 1323 is connected to multiple second crack channels 1324 in its own extension direction, and each second crack channel 1324 is connected to multiple third crack channels 1325 in its own extension direction; each first crack channel 1323, each second crack channel 1324, and each third crack channel 1325 are provided with multiple stop members 1329 at intervals in their own extension directions; the stop members 1329 provided in the first crack channel 1323 in its own extension direction are used to prevent the first baffle 13261 from rebounding and resetting, the stop members 1329 provided in the second crack channel 1324 in its own extension direction are used to prevent the second baffle 13271 from rebounding and resetting, and the stop members 1329 provided in the third crack channel 1325 in its own extension direction are used to prevent the third baffle 13281 from rebounding and resetting.

[0036] Thus, by connecting multiple first fracture channels 1323 to the connecting pipe 1322, and arranging each level of channel in a multi-branched pattern where each first fracture channel 1323 connects to multiple second fracture channels 1324, and each second fracture channel 1324 connects to multiple third fracture channels 1325, there is no need to build an additional independent complex fracture simulation module. This accurately reproduces the dense distribution characteristics of main fracture clusters and multi-level branch fractures in real strata, solving the problem that existing devices can only simulate single-channel or simple branch fractures and have large deviations from the real strata morphology. At the same time, the multiple sets of stoppers 1329 spaced apart in the extension direction of each level of channel can not only prevent the rebound and reset after the baffle is triggered and opened, but also prevent the fracture from expanding. The rebound sealing channel allows for tiered blocking through intermittent layout, adapting to different fracture propagation depths under varying pressures. This ensures fractures maintain varying degrees of opening, consistent with the uneven fracture propagation depth and opening characteristics of real formations. Furthermore, it provides a realistic channel environment with multiple widths and branches for subsequent proppant settling and migration experiments, avoiding the biased nature of experimental data caused by a single channel configuration. In addition, the direct connection between the multiple first fracture channels 1323 and the connecting pipe 1322 expands the initial coverage of the fracture network, further enhancing the comprehensiveness and simulation of multi-stage fractures. This allows experimental data to better reflect the fracturing patterns under complex formation conditions, increasing its guiding value for on-site construction.

[0037] Furthermore, the connecting pipe 1322 is also connected to a plurality of second crack channels 1324, and each second crack channel 1324 is connected to a plurality of third crack channels 1325 in its own extending direction.

[0038] Thus, by directly connecting multiple second fracture channels 1324 to the connecting pipe 1322, and then branching from each second fracture channel 1324 to multiple third fracture channels 1325, a cross-level branching structure is formed where the connecting pipe 1322 connects to multiple second fracture channels 1324, and each second fracture channel 1324 connects to multiple third fracture channels 1325. This eliminates the need for an additional transitional layout for the first fracture channel 1323, directly enriching the hierarchical diversity of the fracture network and solving the problems of fixed fracture propagation levels and the inability to simulate special formation fracture morphologies such as direct branching of secondary fractures from the main channel in existing devices. This design enables fractures to... The network possesses both full-level hierarchical branching and cross-level branching modes, more closely resembling the randomness and complexity of fracture extension in real strata (e.g., in some areas, due to special stress distribution, secondary fractures directly develop in the main channel). Simultaneously, the cross-level branching structure further simplifies the fracture layout in some areas, reducing redundant channel design and manufacturing difficulty without compromising simulation accuracy. Furthermore, this structure complements the full-level multi-branching of the first technical solution, jointly constructing a complex fracture network with multiple sources, multiple levels, and multiple morphologies. This further expands the device's adaptability to different geological conditions, making experimental scenarios more comprehensive and data more universally applicable.

[0039] In some alternative embodiments, the stop 1329 may be one of a wedge-shaped block structure 13291 or a toothed structure 13292.

[0040] Combination Figure 7 Specifically, the wedge-shaped block structure 13291 includes a stop channel 132911, a wedge block 132912, and a return spring 132913. The wedge channel is perpendicular to and connected to the corresponding crack channel. The return spring 132913 is located inside the stop channel 132911. One end of the return spring 132913 is connected to the bottom wall of the stop channel 132911, and the other end of the return spring 132913 is connected to the wedge block. The wedge block has a vertical surface and an inclined surface. In the initial state, the inclined surface of the multi-level crack simulation unit 132 faces the corresponding baffle, and the vertical surface faces away from the baffle, so as to block the corresponding baffle from resetting and moving.

[0041] Thus, the inclined design of the wedge block 132912 allows the baffle to be easily pushed open under the high pressure of fracturing fluid (compression of the return spring 132913), enabling the fracture channel to be opened. When the baffle rebounds in the opposite direction, the wedge block 132912 is reset under the action of the return spring 132913, and its vertical surface rigidly contacts the baffle, forming an irreversible one-way locking, completely preventing the baffle rebound from blocking the fracture channel, perfectly matching the characteristic of fractures continuously opening after propagation in real formations. Moreover, this wedge-shaped locking block structure is simple and easy to install.

[0042] Combination Figure 8Specifically, the locking tooth structure 13292 is disposed in the corresponding crack channel. The locking tooth structure 13292 includes locking teeth 132921, multiple locking slots 132922, and stop springs 132923. The stop springs 132923 are telescopically embedded in the corresponding baffle and can extend and retract along the radial direction of the baffle. One end of the stop springs 132923 is fixedly connected to the corresponding baffle, and the other end is fixedly connected to the locking teeth 132921. The multiple locking slots 132922 are spaced apart along the axial direction of the corresponding crack channel. The elastic force released by the stop springs 132923 can drive the locking teeth 132921 to be locked in the corresponding locking slots 132922, thereby preventing the corresponding baffle from resetting and moving.

[0043] In this way, multiple slots 132922 are distributed at intervals along the fracture channel axis, and the locking teeth 132921 can be locked into the corresponding slots 132922 according to the degree of baffle opening, so as to achieve graded locking and adapt to the different expansion depths of fractures under different pressures (such as shallow baffle opening under low pressure, locking into the near-end slot 132922, and deep opening under high pressure, locking into the far-end slot 132922). This perfectly matches the characteristics of uneven fracture expansion depth and different opening degrees in real formations, and solves the problem that the traditional stop 1329 can only lock in a single position and cannot adapt to diverse expansion scenarios.

[0044] Combination Figure 1 In some optional embodiments, the multi-level crack simulation unit 132 is a transparent structure to adapt to visualization capture requirements; the visualization display module 14 includes at least one camera assembly, which is arranged around the periphery of the multi-level crack simulation unit 132 to capture dynamic images of the progressive expansion of multi-level cracks in real time, and synthesizes three-dimensional visualization data in conjunction with the data processing unit. Exemplarily, the camera assembly can be a high-speed camera, and the number can be one, two, three, or four.

[0045] Thus, by setting the multi-level crack simulation unit 132 as a transparent structure and placing the camera components on the outer periphery of the unit, there is no need to set up an additional penetrating observation window, directly eliminating the observation blind spot caused by the non-transparent structure and ensuring the integrity of the observation perspective. The outer periphery layout of multiple camera components can capture the dynamic expansion of cracks from multiple angles, and synthesize three-dimensional visualization data in conjunction with the data processing unit, solving the problems of independent and incompatible visualization display modules and incomplete dynamic data capture in existing systems. The adaptive design of the transparent structure and camera components further improves the accuracy of dynamic image capture, provides sufficient and clear image sources for three-dimensional data synthesis, and enhances the effect of collaborative visualization layout.

[0046] In some preferred embodiments, the walls of the first crack channel 1323, the second crack channel 1324, and the third crack channel 1325 are made of a transparent material and are placed inside a housing 1321 made of a transparent material. Then, a transparent material is injected into the housing 1321 to form a robust support structure for the first crack channel 1323, the second crack channel 1324, and the third crack channel 1325. Exemplarily, the walls of the first crack channel 1323, the second crack channel 1324, and the third crack channel 1325, the housing 1321, and the transparent material injected into the housing 1321 are the same and can be either polymethyl methacrylate or a transparent photosensitive resin.

[0047] Thus, on the one hand, the channel wall, shell 1321, and filling material are all transparent, forming an unobstructed and fully transparent observation environment. This solves the problems of existing devices where non-transparent support structures obstruct the observation view and the lack of fixation in transparent channels limits the observation angle. This allows the visualization module 14 to capture the instantaneous dynamics of crack propagation (such as the trajectory of crack extension on the inner wall of the channel) and the internal details of proppant movement (such as the sedimentation and accumulation state of proppant in branch channels) from multiple directions around the periphery without blind spots. This provides a clearer and more complete image source for the synthesis of three-dimensional visualization data, further improving the accuracy and comprehensiveness of experimental data. On the other hand, the integrated support structure formed by injecting transparent material into the transparent shell 1321 can comprehensively wrap and fix the crack channels at all levels, effectively resisting the radial pressure and impact force generated during high-pressure injection of fracturing fluid, avoiding channel deformation, displacement, or rupture. This solves the problem of traditional transparent channels being easily damaged under high pressure and causing experimental interruptions due to weak structure and insufficient support. At the same time, the integrated support structure fixes the relative position of the crack channels, ensuring the consistency of the crack network layout in different batches of experiments, significantly improving the repeatability and comparability of experimental data.

[0048] Combination Figure 1 In some optional embodiments, the hydraulic fracturing simulation device further includes a return pipeline 16; one end of the return pipeline 16 is connected to the second outlet of the one-way valve 22, and the other end is connected to the pressure pump 11. Specifically, the working pressure range of the pressure pump 11 is 0.5-3.0 MPa, and a fifth valve 18 is provided on the return pipeline 16. The fifth valve 18 is used to control the opening and closing of the return pipeline 16 to form a closed loop in the proppant sedimentation and migration experimental circuit, so that the proppant-carrying fluid can continuously circulate and migrate.

[0049] Thus, by adding a return pipeline 16 to connect the wellbore simulation unit 131 and the pressure pump 11, and installing a fifth valve 18 on the pipeline, a closed loop for the proppant settling and migration experiment is directly constructed without the need for additional circulation drive equipment. This solves the problem that existing devices cannot achieve continuous circulation in proppant experiments and are difficult to observe long-term migration states. The on / off control of the fifth valve 18 can flexibly adapt to the requirements of dual experimental loops. It can be opened to form a loop during proppant experiments and closed to avoid interference during fracture experiments. In coordination with the switching mechanism of valve assembly 15, it further improves the flexibility of device operation. The closed loop design enables continuous migration of proppant-carrying fluid, more accurately reflecting the migration and settling patterns of proppant in real wellbores, and improving the accuracy of experimental data.

[0050] It should be noted that the one-way valve 22 is a single-inlet / outlet one-way valve. The one-way valve 22 only allows fluid to flow unidirectionally from the inlet to either the first or second outlet, possessing dual core functions: first, it blocks reverse flow of fluid, preventing triggering distortion or circulation disorder caused by circuit pressure fluctuations; second, it works with valve assembly 15 to achieve precise switching between the two pathways. By controlling the on / off state of valve assembly 15, it controls whether the one-way valve 22 opens the first outlet and blocks the second outlet, or opens the second outlet and blocks the first outlet, ensuring that the proppant circulation pathway and the fracturing hydraulic fracturing pathway operate independently and without cross-flow. For example, the single-inlet / outlet one-way valve can be a Y-type three-way one-way valve. The Y-type three-way one-way valve is an existing component and will not be described further here.

[0051] Combination Figure 1 In some optional embodiments, the hydraulic fracturing simulation device further includes an attitude adjustment component 17; the attitude adjustment component 17 is connected to the wellbore simulation unit 131 and is used to adjust the tilt angle of the wellbore simulation unit 131 to simulate the movement and settling behavior of proppant in different well types.

[0052] Thus, by directly connecting the attitude adjustment component 17 to the wellbore simulation unit 131, there is no need to set up an additional intermediate transfer structure, which directly simplifies the transmission link of angle adjustment and saves space. The attitude adjustment component 17 can realize flexible adjustment of the wellbore tilt angle, which solves the problem that the existing device can only simulate a single well type and has poor adaptability. It can accurately simulate the working conditions of different well types such as vertical wells, inclined wells, and horizontal wells, further expanding the applicability of the device and improving the simulation accuracy of the experiment.

[0053] Combination Figure 1 In some preferred embodiments, the attitude adjustment assembly 17 includes a first lifting drive and a second lifting drive. The driving end of the first lifting drive is rotatably connected to one end of the wellbore simulation unit 131, and the driving end of the second lifting drive is rotatably connected to the other end of the wellbore simulation unit 131. Exemplarily, both the first and second lifting drives can be hydraulic telescopic rods.

[0054] In some specific embodiments, the tilt angle can be adjusted from 0° to 90°, and the wellbore simulation unit 131 can be fixed at a preset angle by means of an angle positioning pin; the preset angle can be arbitrarily selected within the range of 0° to 90°, and for example, the preset angle can be any one of 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, etc.

[0055] Combination Figure 1 In some optional embodiments, the hydraulic fracturing simulation device further includes a heating module 19, which is connected in series at the inlet end of the wellbore simulation unit 131 to preheat the fracturing fluid or proppant-carrying fluid to a target temperature and maintain it at a constant temperature. Exemplarily, the heating module 19 may employ existing components such as electric heating wire assemblies or ceramic heating assemblies.

[0056] Thus, by connecting the heating module 19 in series with the inlet end of the wellbore simulation unit 131, there is no need to set up an additional bypass heating circuit, which directly simplifies the pipeline layout and reduces the installation complexity. The series design at the inlet end allows the fracturing fluid or sand-carrying fluid to be preheated at a constant temperature before entering the core experimental area, which solves the problem of large deviation between the experimental temperature and the actual formation temperature in existing devices, resulting in distortion of fluid characteristics. The constant temperature function of the heating module 19 can maintain the stability of the fluid temperature during the experiment and eliminate the influence of ambient temperature fluctuations on the experimental results.

[0057] Combination Figure 1 In some optional embodiments, a pressure gauge 20 and a sixth valve 21 are also provided between the heating module 19 and the wellbore simulation unit 131; the pressure gauge 20 is used to monitor the pressure of the fracturing fluid or sand-carrying fluid in the pipeline, and the sixth valve 21 is used to control the opening and closing of this section of the pipeline.

[0058] Thus, by adding a pressure gauge 20 and a sixth valve 21 between the heating module 19 and the wellbore simulation unit 131, the two functions are directly integrated without the need for an additional independent pressure monitoring and pipeline control module, simplifying the device architecture. The pressure gauge 20 monitors the fluid pressure in the pipeline in real time and can promptly report pressure anomalies, avoiding equipment damage or experimental failures caused by excessive pressure and ensuring experimental safety. The synergy between pressure monitoring and temperature control further optimizes the accuracy of experimental parameter adjustment, making the fluid environment closer to the real formation.

[0059] In some optional embodiments, when constructing the proppant settling and transport experimental loop, the first valve 151 and the second valve 152 are open, while the third valve 153 and the fourth valve 154 are closed. The proppant-carrying fluid enters the wellbore simulation unit 131 sequentially through the proppant mixing unit 121 and the second valve 152. When constructing the fracture dynamic propagation experimental loop, the third valve 153 and the fourth valve 154 are open, while the first valve 151 and the second valve 152 are closed. The purified fracturing fluid enters the wellbore simulation unit 131 and the multi-stage fracture simulation unit 132 sequentially through the oil-water separation unit 122 and the fourth valve 154. A dye is added to the fracturing fluid to improve the visualization and identification of the multi-stage fracture propagation process.

[0060] Thus, by clearly defining the valve on / off logic of the dual experimental loops and adding a dye to the fracturing fluid in the fracture experiment, there is no need to set up additional complex loop switching guidance and observation enhancement devices, which directly reduces the difficulty of experimental operation and avoids experimental failures caused by valve operation errors. The addition of dye makes the fracturing fluid flow trajectory and fracture filling range clearer, solving the problem of low identification of transparent fluid in existing visualization observations. In conjunction with the visualization display module 14 and the transparent multi-level fracture simulation unit 132, it further improves the observation accuracy of fracture expansion dynamics. The clear flow path logic and observation enhancement design ensure the reproducibility of the experimental process, make the experimental data more traceable, and enhance the practicality of the device.

[0061] The proppant settling and migration experimental steps of the above-mentioned hydraulic fracturing experimental setup are roughly as follows: First, the wellbore simulation unit 131 is adjusted to the target tilt angle and locked using the attitude adjustment component 17; a pre-mixed ratio of fracturing fluid and proppant is added to the sand mixing unit 121, and stirring is started to form a uniform sand-carrying fluid; the heating module 19 is started simultaneously to preheat to the target temperature, and the visualization display module 14 is adjusted to cover all fracture channels and recording is started.

[0062] Then, the first valve 151 is opened to connect the pressure pump 11 and the sand mixing unit 121, the second valve 152 is opened to connect the sand mixing unit 121 and the wellbore simulation unit 131, the one-way valve 22 is switched to the second outlet to connect the wellbore simulation unit 131 and the return pipeline 16 in one direction, the fifth valve 18 is opened to open the return pipeline 16, the sixth valve 21 is opened to connect the sand mixing unit 121, the heating module 19 and the wellbore simulation unit 131, and the third valve 153 and the fourth valve 154 are closed to construct a closed loop of pressure pump 11, sand mixing unit 121, heating module 19, wellbore simulation unit 131, return pipeline 16 and pressure pump 11.

[0063] Next, the pressure pump 11 is started to pressurize at a preset rate. The working pressure range of the pressure pump 11 is 0.5-3.0 MPa, so that the proppant-carrying fluid is continuously circulated and injected into the wellbore simulation unit 131 and the fracture channel. The pipeline pressure is monitored in real time by the pressure gauge 20, and the migration, sedimentation and accumulation state of the proppant in the multi-branch channel is observed and recorded by the visualization display module 14. The parameters of the pressure pump 11 can be adjusted to simulate different working conditions.

[0064] Finally, after the experiment lasts 5-15 minutes, the pressure pump 11 and all connecting valves are turned off. After the pipeline is cooled to normal pressure, the sand-carrying liquid is discharged, and the experimental data is saved.

[0065] The experimental steps for the dynamic propagation of fractures in the hydraulic fracturing experimental setup described above are roughly as follows: First, fix the angle of the wellbore simulation unit 131 by adjusting the attitude component 17; inject purified fracturing fluid into the oil-water separation unit 122 and add dye to stir evenly; start the heating module 19 to preheat, debug the visualization display module 14, and check that the pressure triggering components (baffle, elastic element) in the multi-level fracture simulation unit 132 are installed in place and sealed well.

[0066] Then, open the third valve 153 to connect the pressure pump 11 with the oil-water separation unit 122, open the fourth valve 154 to connect the oil-water separation unit 122 with the wellbore simulation unit 131, open the sixth valve 21 to connect the oil-water separation unit 122, the heating module 19 and the wellbore simulation unit 131, switch the one-way valve 22 to the first outlet one-way conduction to connect the wellbore simulation unit 131 with the multi-stage fracture simulation unit 132, and close the first valve 151, the second valve 152 and the fifth valve 18 to construct the experimental circuit.

[0067] Next, the pressure pump 11 is started and the pressure is slowly increased. The parameters of the pressure pump 11 are set to 2-4 MPa high-pressure pulse with a pulse duration of 30-60 seconds. The fracturing fluid with added dye in the oil-water separation unit 122 is driven into the wellbore simulation unit 131 through the pipeline, and then injected into the multi-stage fracture simulation unit 132 through the connecting pipe 1322. The reading change of the pressure gauge 20 is monitored in real time, and the pressure rise curve at the beginning of the fracturing fluid injection is recorded to confirm that there is no abnormal pressure drop in the pipeline. As the first fracture channel 1323 expands, the pressure inside the multi-stage fracture simulation unit 132 gradually increases with the continuous injection of fracturing fluid. When the pressure reaches the initial threshold of the first fracture channel 1323 (the threshold is 0.8-1.2 MPa), the fracturing fluid first pushes open the first baffle 13261 and drives the first fracture channel 1323 to expand outward along the initial channel. At this time, the high-speed camera begins to synchronously capture the expansion pattern of the first fracture channel 1323 and records the initial expansion rate through the computer. The second fracture channel 1324 is triggered to expand, and the high pressure output of the pressure pump 11 is maintained. When the pressure in the multi-stage fracture simulation unit 132 reaches the initial threshold of the second fracture channel 1324 (the threshold is 1.5-2.0 MPa), the fracturing fluid pushes open the second baffle 13271 and enters the second fracture channel 1324, triggering the expansion of the second fracture channel 1324. The start time and expansion angle of the second fracture channel 1324 are marked in real time by a high-speed camera and a computer. When the pressure pump 11 continuously increases the pressure to the initial threshold of the third fracture channel 1325 (the threshold is 2.5-3.0 MPa), the fracturing fluid pushes open the third baffle 13281 and enters the third fracture channel 1325, realizing the progressive dynamic expansion of multi-stage fractures. At this stage, the opening pressure of the three-stage fractures and the number of expansion branches are recorded. While conducting experiments on the dynamic propagation of complex cracks, real-time dynamic images captured by a high-speed camera connected to a computer's data processing unit are synthesized in the computer into a three-dimensional observable dynamic image of the complex crack propagation, and the image is observed and recorded.

[0068] Finally, gradually reduce the pressure to zero and close pressure pump 11 and all valves. After the pipeline is reduced to atmospheric pressure, drain the fracturing fluid containing the dye and save the experimental data.

[0069] It should be noted that both the fracturing fluid and the dyeing agent are based on existing technologies in the field, and this application has not made any improvements to them. The specific formulas, preparation processes and other details are not described here.

[0070] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A hydraulic fracturing simulation device, characterized in that, The hydraulic fracturing simulation device includes: A pressure pump is used to provide the pressure required for experiments. The functional module includes a sand mixing unit and an oil-water separation unit. The sand mixing unit is used to prepare proppant and fracturing fluid carrying fluid, and the oil-water separation unit is used to store and purify the fracturing fluid required for fracture propagation experiments. The execution module includes a wellbore simulation unit and a multi-level fracture simulation unit, which are connected. The multi-level fracture simulation unit has a built-in gradient pressure triggering structure to realize the progressive expansion of multi-level fractures. The visualization module is used to capture dynamic images of the progressive expansion of multi-level cracks in real time and synthesize three-dimensional visualization data. The valve assembly includes a first valve, a second valve, a third valve, and a fourth valve. The first valve connects the pressure pump to the input terminal of the sand mixing unit; the second valve connects the output terminal of the sand mixing unit to the wellbore simulation unit; the third valve connects the pressure pump to the input terminal of the oil-water separation unit; and the fourth valve connects the output terminal of the oil-water separation unit to the wellbore simulation unit. By switching the valve assembly on and off, the sand mixing unit or oil-water separation unit and the execution module are selectively connected to construct a proppant sedimentation and migration experimental circuit or a crack dynamic propagation experimental circuit. The visualization display module works in conjunction with the gradient pressure triggering structure of the multi-level crack simulation unit to capture the propagation dynamics of each level of crack in real time.

2. The hydraulic fracturing simulation device according to claim 1, characterized in that, The multi-level crack simulation unit includes a shell, a connecting pipe, a first crack channel, a second crack channel, and a third crack channel; One end of the connecting pipe is connected to the wellbore simulation unit. A one-way valve is provided between the connecting pipe and the wellbore simulation unit. The one-way valve is a one-inlet, two-outlet one-way valve. The inlet of the one-way valve is connected to the wellbore simulation unit, and the first outlet of the one-way valve is connected to the connecting pipe. The one-way valve is open along the flow direction of the fracturing fluid or sand-carrying fluid to prevent fluid backflow. The other end of the connecting pipe extends into the interior of the housing. The first crack channel is located inside the housing and communicates with the connecting pipe. The second crack channel is located inside the housing and communicates with the first crack channel. The third crack channel is located inside the housing and communicates with the second crack channel. A first pressure triggering component is provided in the first crack channel, a second pressure triggering component is provided in the second crack channel, and a third pressure triggering component is provided in the third crack channel. The triggering pressure of the first pressure triggering component is less than the triggering pressure of the second pressure triggering component, and the triggering pressure of the second pressure triggering component is less than the triggering pressure of the third pressure triggering component, so as to form the gradient pressure triggering structure.

3. The hydraulic fracturing simulation device according to claim 2, characterized in that, The first pressure triggering component includes a first baffle and a first elastic member. The first baffle is used to seal the communication port between the first crack channel and the connecting pipe. One end of the first elastic member abuts against the first baffle, and the other end abuts against the end wall of the first crack channel away from the communication port. The second pressure triggering component includes a second baffle and a second elastic member. The second baffle is used to seal the communication port between the second crack channel and the first crack channel. One end of the second elastic member abuts against the second baffle, and the other end abuts against the end wall of the second crack channel away from the communication port. The third pressure triggering component includes a third baffle and a third elastic element. The third baffle is used to seal the communication port between the second crack channel and the third crack channel. One end of the third elastic element abuts against the third baffle, and the other end abuts against the end wall of the third crack channel away from the communication port.

4. The hydraulic fracturing simulation device according to claim 3, characterized in that, The number of the first crack channels is multiple, each of the first crack channels is connected to multiple second crack channels in its own extension direction, and each of the second crack channels is connected to multiple third crack channels in its own extension direction. Each of the first crack channels, each of the second crack channels, and each of the third crack channels are provided with a plurality of stops at intervals along their own extension direction; The first crack channel has a stop member provided in its own extension direction to prevent the first baffle from rebounding and resetting; the second crack channel has a stop member provided in its own extension direction to prevent the second baffle from rebounding and resetting; and the third crack channel has a stop member provided in its own extension direction to prevent the third baffle from rebounding and resetting.

5. The hydraulic fracturing simulation device according to claim 1, characterized in that, The multi-level crack simulation unit is a transparent structure to adapt to the needs of visualization capture; The visualization display module includes at least one camera component, which is deployed around the periphery of the multi-level crack simulation unit to capture dynamic images of the progressive expansion of multi-level cracks in real time, and synthesize three-dimensional visualization data in conjunction with the data processing unit.

6. The hydraulic fracturing simulation device according to claim 2, characterized in that, The hydraulic fracturing simulation device also includes a return pipeline; One end of the return pipeline is connected to the second outlet of the one-way valve, and the other end is connected to the pressure pump. A fifth valve is provided on the return pipeline to control the opening and closing of the return pipeline, so as to form a closed loop in the proppant sedimentation and migration experimental circuit, and to make the sand-carrying liquid continuously circulate and migrate.

7. The hydraulic fracturing simulation device according to claim 1, characterized in that, The hydraulic fracturing simulation device also includes an attitude adjustment component; the attitude adjustment component is connected to the wellbore simulation unit and is used to adjust the tilt angle of the wellbore simulation unit to simulate the migration and settling behavior of proppant in different well types.

8. The hydraulic fracturing simulation device according to claim 1, characterized in that, The hydraulic fracturing simulation device also includes a heating module, which is connected in series at the inlet end of the wellbore simulation unit to preheat the fracturing fluid or proppant-carrying fluid to the target temperature and maintain a constant temperature.

9. The hydraulic fracturing simulation device according to claim 8, characterized in that, A pressure gauge and a sixth valve are also provided between the heating module and the wellbore simulation unit; The pressure gauge is used to monitor the pressure of fracturing fluid or sand-carrying fluid in the pipeline, and the sixth valve is used to control the opening and closing of this section of the pipeline.

10. The hydraulic fracturing simulation device according to claim 1, characterized in that, When constructing the proppant settling and transport experimental loop, the first valve and the second valve are open, while the third valve and the fourth valve are closed. The proppant-carrying fluid enters the wellbore simulation unit sequentially through the sand mixing unit and the second valve. When constructing the dynamic fracture propagation experimental loop, the third valve and the fourth valve are turned on, while the first valve and the second valve are turned off. The purified fracturing fluid sequentially enters the wellbore simulation unit and the multi-stage fracture simulation unit through the oil-water separation unit and the fourth valve. The fracturing fluid contains a dye to improve the visualization and identification of the multi-stage fracture propagation process.

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