A particle migration simulation device and method considering graded confining pressure and seam network morphology

Abstract

The present invention relates to the field of tunnel surrounding rock crack reinforcement and oil and gas development, and proposes a particle migration simulation device and method considering graded confining pressure and crack network morphology, the device includes a mixing tank, a feeder, a screw pump and a crack module, the feeder output end is connected to the mixing tank inlet, the mixing tank outlet is connected to the screw pump input end through a control valve, the screw pump output end is connected to the crack module inlet through a first electromagnetic flowmeter, there are multiple crack module inlets, each crack module inlet is provided with a gate valve between the first electromagnetic flowmeter, and the crack module outlet is connected to the waste liquid tank through a second electromagnetic flowmeter; the crack module includes four submodules, namely a general crack module, a variable crack width crack module, a rough crack module, and a closed crack module, and each submodule is provided with a camera. The present invention can obtain more accurate migration laws of granular materials in cracks, which is helpful to better design a granular slurry pumping scheme in actual engineering production and reduce production costs.

Description

Technical Field

[0001] The invention relates to the field of tunnel surrounding rock crack reinforcement and oil and gas development, and in particular to a particle migration simulation device and method taking into account graded confining pressure and crack network morphology. Background Art

[0002] As my country's tunnel engineering gradually develops towards the central and western regions, a number of gypsum rock tunnels with high geostress, high osmotic pressure, high water sensitivity and strong disturbance have emerged. The rock mass produces many complex cracks after water dissolution and expansion. On-site construction usually adopts the method of fracture grouting to reinforce the surrounding rock. At the same time, a large part of my country's oil and gas reservoirs are dense, high-pressure and low-permeability reservoirs, which are relatively difficult to exploit and have unsatisfactory subsequent production. During on-site production, granular materials are pumped into the reservoir cracks to support the cracks, prevent the cracks from closing, improve the fracture conductivity, and thus increase production.

[0003] Complex cracks are encountered during tunnel excavation and oil and gas production. The method of pumping granular slurry into the cracks is used to improve the working capacity of the cracks. In oil and gas production, a granular slurry mixed with proppant and conveying fluid is pumped into the cracks. The cement slurry pumped into the rock mass of the tunnel fracture is also a granular slurry. The diffusion and migration process of slurry in the cracks is the result of the combined action of the rock mass fracture network and slurry seepage. Factors such as the roughness, inclination, opening of the cracks and the properties of the slurry itself can cause complex nonlinear flow behavior of granular slurry. Therefore, exploring the migration law of granular materials in cracks has important practical guiding significance for improving the diffusion effect of particles in cracks and optimizing the working capacity of cracks.

[0004] Studying the migration behavior of granular materials can help to better design granular slurry pumping schemes in engineering production and reduce production costs. Factors such as the composition of granular slurry, pumping speed, and physical properties of granular materials will affect the migration behavior of granular materials in cracks. At the same time, the surface morphology of cracks is also an important factor affecting the migration behavior of granular materials. Cracks in strata or rock formations are usually irregular and intricate fracture networks. Granular materials are affected by the rough walls of the cracks, and their migration behaviors in cracks with different roughness and tortuosity are different, and their migration behaviors in smooth flat cracks are also different. Most existing fracture simulation devices use two smooth flat plates to simulate fractures, which cannot reflect different fracture morphologies and are difficult to simulate closer to real fractures, so it is impossible to obtain more accurate migration laws of granular materials in fractures. The test results are quite different from the actual situation. Summary of the invention

[0005] In order to solve the problems in the background technology and effectively simulate different crack morphologies, such as equal-width cracks, variable-width cracks, rough cracks, etc., the present application provides a particle migration simulation device and method that considers graded confining pressure and fracture network morphology, so as to solve the problem of simulating rough and tortuous cracks in complex formations in existing research methods, restore more real crack surface morphologies, study the influence of complex crack morphologies on particle material migration and sand bank morphology, and thus facilitate the optimization of particle material design parameters for on-site fracturing operations. The technical solution is as follows:

[0006] A particle migration simulation device considering graded confining pressure and fracture network morphology, comprising a stirring tank, a feeder, a screw pump and a fracture module, wherein the output end of the feeder is connected to the inlet of the stirring tank, the outlet of the stirring tank is connected to the input end of the screw pump through a control valve, the output end of the screw pump is connected to the inlet of the fracture module through a first electromagnetic flowmeter, the inlet of the fracture module is multiple, a gate valve is provided between each inlet of the fracture module and the first electromagnetic flowmeter, and the outlet of the fracture module is connected to a waste liquid tank through a second electromagnetic flowmeter;

[0007] The crack module includes four sub-modules, namely a general crack module, a variable width crack module, a rough crack module and a closed crack module. During the test, the number and types of sub-modules constituting the crack module can be freely combined and matched, and each sub-module is provided with a camera for observing the movement of particles in the sub-module.

[0008] Preferably, the first electromagnetic flowmeter and the second electromagnetic flowmeter are connected to a first flowmeter monitor and a second flowmeter monitor, respectively.

[0009] Preferably, each of the crack module inlets is connected to a branch pipe, and one end of the plurality of branch pipes close to the first electromagnetic flowmeter is connected to the first electromagnetic flowmeter through a main pipe, and a check valve is provided on the main pipe.

[0010] Preferably, the general crack module comprises a first main body, the first main body comprises two first acrylic plates and two first sealing strips, the first sealing strips have a rectangular cross-section, and the two first sealing strips are respectively fixed at the top and the bottom between the two first acrylic plates;

[0011] The variable seam width crack module includes a second body, the second body includes two second acrylic plates and two second sealing strips, the cross-sectional shape of the second sealing strip is an isosceles trapezoid, and the two second sealing strips are respectively fixed at the top and bottom between the two second acrylic plates;

[0012] The rough crack module includes a third body, which includes a third acrylic plate, a rough panel and a third sealing strip, one side of the rough panel is a rough surface, two third sealing strips are respectively fixed at the top and bottom between the third acrylic plate and the rough panel, and the rough surface of the rough panel is close to the third sealing strip;

[0013] The closed crack module includes a fourth main body, which includes a fourth acrylic plate, an acrylic plate frame, a pressurizing mechanism and two fourth sealing strips, wherein the two fourth sealing strips are respectively fixed at the top and bottom between the fourth acrylic plate and the acrylic frame, and the pressurizing mechanism includes a plurality of pressurizing cylinders, a closed pressurizing block and an oil pump for controlling the movement of the pressurizing cylinder pistons. The plurality of pressurizing cylinders are arranged in the acrylic frame and are arranged in a rectangular array, and the closed pressurizing block is fixed to one end of the pressurizing cylinder piston close to the fourth acrylic plate, and an elastic diaphragm is fixed to one end of the closed pressurizing block close to the fourth acrylic plate, and adjacent elastic diaphragms are bonded by flexible filling strips, and the elastic diaphragm and the adjacent acrylic frame part are also bonded by flexible filling strips.

[0014] Preferably, the outer sides of the first body, the second body, the third body and the fourth body are all connected with an aluminum alloy frame for supporting and fixing the submodule by bolts.

[0015] Preferably, the crack module also includes a direction-changing adapter, which includes a plurality of interconnected interfaces, each interface is connected to a sub-module through a first module adapter, one end of each sub-module away from the direction-changing adapter is connected to a fixed plate through a second module adapter, and a plurality of flow ports connected to the sub-modules are provided on the fixed plate, the flow port connected to one sub-module is an inlet of the crack module, and the flow port connected to another sub-module is an outlet of the crack module.

[0016] Preferably, the first module adapter and the second module adapter are both frame structures, one end of the first module adapter is fixedly connected to the direction-changing adapter by bolts, and the other end of the first module adapter is fixedly connected to the aluminum alloy frame of the submodule by bolts;

[0017] One end of the second module adapter is fixedly connected to the aluminum alloy frame of the submodule by bolts, and the other end of the second module adapter is fixedly connected to the fixing plate by bolts.

[0018] Preferably, waterproof rubber rings are provided at the contact points between the first module adapter and the sub-module body, the contact points between the first module adapter and the direction-changing adapter, the contact points between the second module connector and the sub-module body, and the contact points between the second module adapter and the fixing plate.

[0019] A particle transport simulation method considering graded confining pressure and fracture network morphology includes the following steps:

[0020] S1. According to the rock properties of the stratum to be studied, rocks with cracks are obtained through fracture experiments or direct collection at the engineering site, and the crack surface is scanned to extract three-dimensional point cloud data. The three-dimensional point cloud data is processed and key parameters are determined. The key parameters include the fractal dimension of the crack surface, the crack opening, the root mean square of the crack surface height, and the standard deviation of the crack surface;

[0021] S2. Conduct a preliminary experiment under the closed crack module, inject clean water into the closed crack module, start the oil pump, and drive the pressurized oil cylinder to drive the closed pressurized block to move. Monitor the pressure in the elastic diaphragm of the closed pressurized block and the pressure in the oil cylinder through the pressure sensor, monitor the displacement of the elastic diaphragm through the displacement sensor, obtain the displacement-pressure curve of the elastic diaphragm, calibrate the pressurization parameters of the closed crack module, and obtain the pressurization rate range, which is used as a reference for the pressurization rate selected in the formal experiment;

[0022] S3. According to the key parameters of the obtained three-dimensional point cloud data, a rough plate model simulating the crack morphology is generated by a computer, and a rough plate is processed by a 3D engraving machine to assemble a rough crack module;

[0023] S4. Based on the size of the fracturing cracks, pumping plan, construction sand ratio and formation pressure during the on-site construction, and according to the similarity ratio criterion, design the required pumping displacement, sand content, proppant particle size, proppant sand ratio, pumping time and closing plan of the closed crack module in the test, and estimate the required delivery fluid volume and particle material mass;

[0024] S5. Determine the number and type of submodules according to test requirements, adjust the crack width of each submodule to the designed value, and then connect the determined submodules through a direction-changing adapter to form a crack module;

[0025] S6, opening all valves in the simulation device, and introducing the pre-fluid into the fracture module through the screw pump, so that the pre-fluid fills the entire fracture model;

[0026] After liquid flows out of each outlet of the fracture model, close the screw pump and all valves, and check the water tightness of the entire simulation device and whether it operates normally;

[0027] S7. According to the selected closing scheme, determine the closing pressure and closing displacement required for each closing pressurizing block, and set the pressure limit and pressurizing rate of the oil cylinder;

[0028] Adjust the working frequency of the feeder, the mixing tank and the screw pump;

[0029] S8, turn on the flow monitor, detect and record the electromagnetic flowmeter data, and turn on the electromagnetic flowmeter, and run until the electromagnetic flowmeter data is stable;

[0030] S9, weigh the required mass of granular materials, put a part of the granular materials directly into the mixing tank, start the mixing tank, and add the rest of the granular materials into the feeder;

[0031] Start the feeder and add the configured conveying liquid into the mixing tank at a constant rate;

[0032] Open the gate valve at the entrance of the fracture module, start the oil pump, open the control valve, and start the screw pump. Use the screw pump to introduce the conveying fluid and granular material into the fracture module. At the same time, turn on the camera to record the movement and laying behavior of the granular material in each submodule;

[0033] S10, when all the granular materials are pumped into the fracture model, the pumping is stopped, and the gate valve at the entrance of the fracture module is closed, and the camera records the final shape of the sand bank formed by the granular materials in the submodule;

[0034] S11, open all valves in the simulation device, pump clean water into the fracture module, flush the fracture module, and the flushed granular materials enter the waste liquid tank to wait for recovery;

[0035] S12, exporting the video data in the camera and the data of each electromagnetic flowmeter, post-processing the data, determining the characteristic parameters of the particle accumulation morphology in the crack model, and completing an experiment.

[0036] The beneficial effects of the present invention are:

[0037] The present invention can effectively simulate different types of cracks and form a crack network, which is closer to real cracks. In addition, each submodule for simulating cracks in the present invention has a simple structure and a high degree of assembly, and is easy to manufacture and use. At the same time, the present invention can simulate the migration of granular materials in cracks, and the migration of granular materials in cracks and the shape of sand banks can be experimentally obtained through the present invention.

[0038] The present invention processes cracks in modules according to the rough and tortuous types. In the experiment, different submodules can be selected and assembled according to the test requirements to form cracks of different lengths, angles, crack widths, roughness, and closure stresses, so as to simulate complex and tortuous cracks, reproduce the movement process of granular slurry in the cracks, and improve the accuracy of experimental results. The present invention can obtain more accurate migration laws of granular materials in cracks, which is helpful for better design of granular slurry pumping schemes in actual engineering production and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is an overall schematic diagram of the particle migration simulation device of the present invention;

[0040] Figure 2 It is a schematic diagram of the general crack module structure of the present invention;

[0041] Figure 3 It is a schematic diagram of the structure of the direction-changing adapter of the present invention;

[0042] Figure 4 This is a schematic diagram of the structure of the variable width crack module of the present invention;

[0043] Figure 5 This is a schematic diagram of the rough crack module structure of the present invention;

[0044] Figure 6 It is a schematic diagram of the rough panel structure of the rough crack module of the present invention;

[0045] Figure 7 The closed crack module structure of the present invention is intended;

[0046] Figure 8 It is a schematic diagram of the structure of the closed pressure block of the present invention;

[0047] Fig. 9 It is a cross-sectional view of a closed pressure block of the present invention;

[0048] Fig.10 This is a schematic diagram of the structure of the fixing plate at the entrance of the crack module of the present invention;

[0049] Fig.11 It is a schematic diagram of the structure of the fixed plate at the outlet of the crack module of the present invention.

[0050] Numbers in the figure: 1, mixing tank; 2, feeder; 3, control valve; 4, screw pump; 5, control box; 6, first electromagnetic flowmeter; 7, first flowmeter monitor; 8, check valve; 9, gate valve; 10, second electromagnetic flowmeter; 11, second flowmeter monitor; 12, waste liquid tank; 13, camera; 14, fixing plate; 15, flow port; 16, branch pipeline; 17, pressurized oil cylinder; 18, elastic diaphragm; 19, pressurized block bracket; 20, oil pump; 21, closed Combined pressure block; 22. General crack module; 23. Variable width crack module; 24. Rough crack module; 25. Closed crack module; 26. Second module joint; 27. First module adapter; 28. First sealing strip; 29. ​​First acrylic plate; 30. Aluminum alloy frame; 31. Waterproof rubber ring; 32. Direction-changing adapter; 33. Second sealing strip; 34. Second acrylic plate; 35. Rough panel; 36. Rough surface transition zone; 37. Flexible filling strip. DETAILED DESCRIPTION

[0051] In order to make the present invention clearer and more understandable, the technical solution of the present invention is further described in detail below in combination with the accompanying drawings and embodiments. It should be understood that the given embodiment is only one of the implementation methods and does not represent all embodiments.

[0052] In this article, the terms "inside" and "outside" are established based on the positional relationship shown in the drawings. Depending on the different drawings, the corresponding positional relationship may also change accordingly. Therefore, they cannot be understood as an absolute limitation on the scope of protection.

[0053] The following is an explanation of the terms involved in the present invention:

[0054] Fracture aperture: The effective opening degree of the fracture, which refers to the width of the remaining storage space after the fracture gap is filled.

[0055] Fractal dimension: an indicator to measure the roughness of the crack surface. The test method of this application uses the box counting method to measure the fractal dimension of the crack surface morphology.

[0056] Root mean square: The arithmetic square root of the average of the squares of the crack surface heights.

[0057] Combined with Figure 1 -Attached Fig.11 , a particle migration simulation device considering graded confining pressure and fracture network morphology, comprising a mixing tank 1, a feeder 2, a screw pump 4 and a fracture module, wherein the output end of the feeder 2 is connected to the inlet of the mixing tank 1, and the outlet of the mixing tank 1 is connected to the input end of the screw pump 4 through a control valve 3, and the screw pump 4 is electrically connected to a control box 5, and the working parameters of the screw pump 4 are controlled by the control box 5, and the output end of the screw pump 4 is connected to the inlet of the fracture module through a first electromagnetic flowmeter 6, and the inlet of the fracture module is multiple, and a gate valve 9 is provided between each inlet of the fracture module and the first electromagnetic flowmeter 6, and the opening and closing of each inlet is controlled by an independent valve, and different opening configurations can be formed, and the outlet of the fracture module is connected to a waste liquid tank 12 through a second electromagnetic flowmeter 10;

[0058] The crack module includes four sub-modules, which are a general crack module 22, a variable crack width crack module 23, a rough crack module 24 and a closed crack module 25. During the test, the number and types of sub-modules constituting the crack module can be freely combined and matched, and each sub-module is provided with a camera 13 for observing the movement of particles in the sub-module.

[0059] Specifically, the first electromagnetic flowmeter 6 and the second electromagnetic flowmeter 10 are connected to the first flowmeter monitor 7 and the second flowmeter monitor 11 respectively. The flow monitor collects and records the flow data measured by the electromagnetic flowmeter. The measured flow data is the theoretical full pipe flow, which is converted into flow velocity data through post-processing.

[0060] Specifically, each of the crack module inlets is connected to a branch pipe 16, and one end of the plurality of branch pipes 16 close to the first electromagnetic flowmeter 6 is connected to the first electromagnetic flowmeter 6 through a main pipe, and the main pipe is provided with a check valve 8. More specifically, the crack module outlet and the crack module inlet can adopt the same structural form, that is, the crack module outlet can be provided with multiple outlets, each outlet is connected to a main pipe through a branch pipe 16, each branch pipe 16 is provided with a gate valve 9, the main pipe is provided with a check valve 8, and the second electromagnetic flowmeter 10 is located at the main pipe, so as to achieve different opening configurations.

[0061] The branch pipeline 16 and the main pipeline are preferably PVC pipelines, wherein the branch pipeline 16 is used to simulate a wellbore.

[0062] Specifically, the general crack module 22 includes a first body, the first body includes two first acrylic plates 29 and two first sealing strips 28, the cross-sectional shape of the first sealing strips 28 is rectangular, the two first sealing strips 28 are respectively fixed at the top and bottom between the two first acrylic plates 29, the first sealing strips 28 and the first acrylic plates 29 are preferably fixed by glue, and the size of the first acrylic plate 29 is preferably: 0.5m long, 0.3m high, and 3cm thick;

[0063] The variable seam width crack module 23 includes a second body, which includes two second acrylic plates 34 and two second sealing strips 33. The cross-sectional shape of the second sealing strip 33 is an isosceles trapezoid. The two second sealing strips 33 are respectively fixed at the top and bottom between the two second acrylic plates 34. The second sealing strip 33 and the second acrylic plate 34 are preferably fixed by glue. The size of the second acrylic plate 34 is preferably: 0.5m long, 0.3m high, and 3cm thick. The size of the second sealing strip 33 is preferably: 0.5m long, 3mm wide at one end, and 6mm wide at the other end.

[0064] The rough crack module 24 includes a third body, which includes a third acrylic plate, a rough panel 35 and a third sealing strip. One side of the rough panel 35 is a rough surface. Two third sealing strips are respectively fixed at the top and bottom between the third acrylic plate and the rough panel 35. The rough surface of the rough panel 35 is close to the third sealing strip. The third sealing strip is preferably bonded and fixed to the rough panel 35 and the third acrylic plate by glue. Both ends of the rough panel 35 are smoothly transitioned to form a rough surface transition zone 36. Both ends of the third acrylic plate are arc-shaped chamfered. The size of the third acrylic plate is preferably 0.5m long, 0.3m high and 3cm thick.

[0065] The closed crack module 25 includes a fourth body, which includes a fourth acrylic plate, an acrylic plate frame, a pressurizing mechanism and two fourth sealing strips, the two fourth sealing strips are respectively fixed at the top and bottom between the fourth acrylic plate and the acrylic frame, the pressurizing mechanism includes a plurality of pressurizing cylinders 17, a closing pressurizing block 21 and an oil pump 20 for controlling the movement of the piston of the pressurizing cylinder 17, the plurality of pressurizing cylinders 17 are arranged in the acrylic frame and are arranged in a rectangular array, the closing pressurizing block 21 is fixed to one end of the piston of the pressurizing cylinder 17 close to the fourth acrylic plate, the elastic diaphragm 18 is fixed to one end of the closing pressurizing block 21 close to the fourth acrylic plate, the adjacent elastic diaphragms 18 are bonded by flexible filling strips 37, and the elastic diaphragm 18 and the adjacent acrylic frame part are also bonded by the flexible filling strips 37, and the size of the fourth acrylic plate is preferably 0.5m long, 0.3m high and 3cm thick.

[0066] Specifically, the outer sides of the first body, the second body, the third body and the fourth body are all connected by bolts with an aluminum alloy frame 30 for supporting and fixing the submodule. More specifically, a pressure block bracket 19 is fixed on the aluminum alloy frame 30 on the side of the pressure mechanism outside the fourth body, and the pressure cylinder 17 is fixed on the pressure block bracket 19.

[0067] Specifically, the crack module also includes a direction-changing adapter 32, which includes a plurality of interconnected interfaces, each of which is connected to a submodule through a first module adapter 27, and one end of each submodule away from the direction-changing adapter 32 is connected to a fixed plate 14 through a second module adapter, and the fixed plate 14 is provided with a plurality of flow ports 15 connected to the submodules, the flow port 15 connected to one submodule is the crack module entrance, and the flow port 15 connected to another submodule is the crack module exit. The angle between the cracks of the submodules can be changed by the direction-changing adapter 32, thereby changing the angle of migration of the granular material.

[0068] In the simulation device, each submodule is provided with a camera 13, which is preferably located 0.5 m in front of the longitudinal axis of the submodule, where the front is downstream in the particle migration direction. Each submodule as the outlet of the crack module is connected to a second solenoid valve and a waste liquid tank 12.

[0069] Specifically, the first module adapter 27 and the second module adapter are both frame structures, one end of the first module adapter 27 is fixedly connected to the direction-changing adapter 32 by bolts, and the other end of the first module adapter 27 is fixedly connected to the aluminum alloy frame 30 of the submodule by bolts;

[0070] One end of the second module adapter is fixedly connected to the aluminum alloy frame 30 of the submodule by bolts, and the other end of the second module adapter is fixedly connected to the fixing plate 14 by bolts. More specifically, the bolt connection between the direction-changing adapter 32 and the fixing plate 14 is set as an elongated slot, and the length direction of the elongated slot is the width direction of the submodule. The bolt connection between the first module adapter 27 and the second module adapter is set as a bolt hole. Taking the connection between the direction-changing adapter 32 and the first module connector as an example, when connecting, the bolt is passed through the bolt hole and the elongated slot in turn, and then the nut is threaded at the end of the bolt, and the nut is tightened to achieve fixation. The setting of the elongated slot can meet the connection requirements of submodules of different widths, and has high flexibility in use.

[0071] Specifically, waterproof rubber rings 31 are provided at the contact points between the first module adapter 27 and the sub-module body, the contact points between the first module adapter 27 and the direction-changing adapter 32, the contact points between the second module connector 26 and the sub-module body, and the contact points between the second module adapter and the fixing plate 14. The thickness of the waterproof rubber rings 31 is preferably 5 mm.

[0072] A particle transport simulation test method considering graded confining pressure and fracture network morphology comprises the following steps:

[0073] S1. According to the rock properties of the stratum to be studied, rocks with cracks are obtained through fracture experiments or direct collection at the engineering site, and the crack surface is scanned to extract three-dimensional point cloud data. The three-dimensional point cloud data is processed and key parameters are determined. The key parameters include the fractal dimension of the crack surface, the crack opening, the root mean square of the crack surface height, and the standard deviation of the crack surface;

[0074] S2. Conduct a preliminary experiment under the closed crack module 25, inject clean water into the closed crack module 25, start the oil pump 20, and drive the pressurized oil cylinder 17 to drive the closed pressurizing block 21 to move. The pressure in the elastic diaphragm 18 of the closed pressurizing block 21 and the pressure in the oil cylinder are monitored by the pressure sensor, and the displacement of the elastic diaphragm 18 is monitored by the displacement sensor to obtain the displacement-pressure curve of the elastic diaphragm 18. The pressurization parameters of the closed crack module 25 are calibrated to obtain the pressurization rate range, which is used as a reference for the pressurization rate selected in the formal experiment;

[0075] S3, according to the key parameters of the obtained three-dimensional point cloud data, a rough plate model simulating the crack morphology is generated by a computer, and a rough plate is processed by a 3D engraving machine to assemble a rough crack module 24;

[0076] S4. According to the information such as the size of the fracturing cracks, pumping plan, construction sand ratio and formation pressure during the on-site construction, and according to the similarity ratio criterion, the required pumping displacement, sand content, proppant particle size, proppant sand ratio, pumping time and closing plan of the closing crack module 25 are designed in the test, and the required delivery fluid volume and particle material mass are estimated;

[0077] S5. Determine the number and type of submodules according to the test requirements, adjust the crack width of each submodule to the designed value, and then connect the determined submodules through the direction-changing adapter 32 to form a crack module;

[0078] S6, open all valves in the simulation device, and introduce pre-fluid into the fracture module through the screw pump 4, so that the pre-fluid fills the entire fracture model;

[0079] After liquid flows out of each outlet of the fracture model, close the screw pump 4 and all valves, and check the water tightness of the entire simulation device and whether it operates normally;

[0080] S7, according to the selected closing scheme, determine the closing pressure and closing displacement required for each closing pressurizing block 21, and set the pressure limit and pressurizing rate of the oil cylinder;

[0081] Adjust the working frequency of the feeder 2, adjust the working frequency of the mixing tank 1, and adjust the working frequency of the screw pump 4;

[0082] S8, turn on the flow monitor, detect and record the electromagnetic flowmeter data, and turn on the electromagnetic flowmeter, and run until the electromagnetic flowmeter data is stable;

[0083] S9, weigh the required mass of granular materials, put a part of the granular materials directly into the mixing tank 1, start the mixing tank 1, and add the rest of the granular materials into the feeder 2;

[0084] Start the feeder 2 and add the configured conveying liquid into the mixing tank 1 at a constant rate;

[0085] Open the gate valve 9 at the entrance of the fracture module, start the oil pump 20, open the control valve 3, and start the screw pump 4, and pass the conveying liquid and granular materials into the fracture module through the screw pump 4, and at the same time turn on the camera 13 to record the movement and laying behavior of the granular materials in each submodule;

[0086] S10, when all the granular materials are pumped into the fracture model, the pumping is stopped, and the gate valve 9 at the entrance of the fracture module is closed, and the camera 13 records the final shape of the sand bank formed by the granular materials in the submodule;

[0087] S11, open all valves in the simulation device, pump clean water into the fracture module, flush the fracture module, and the flushed granular materials enter the waste liquid tank 12 to wait for recovery;

[0088] S12, exporting the video data in the camera 13 and the data of each electromagnetic flowmeter, post-processing the data, determining the characteristic parameters of the particle accumulation form in the fracture model, and completing an experiment. The particle accumulation form is the sand bank.

[0089] The above test method can also be used for rock mass fissure grouting test. The method and steps of the fissure grouting test are basically the same as a particle migration simulation test method considering graded confining pressure and fracture network morphology. The difference is that step S4 in the fissure grouting test is: according to the size of the fracturing cracks in the field construction, the pumping plan, the construction sand ratio and the formation pressure, and according to the similarity ratio criterion, the required pumping displacement, grouting liquid ratio, grouting liquid volume, pumping time and the closing plan of the closed crack module 25 are designed in the test;

[0090] Step S9 is: preparing cement slurries of different concentrations and components as required, adding the cement slurries into the stirring tank 1, adjusting the working frequency of the stirring tank 1, and keeping the stirring tank 1 turned on to continuously stir the cement slurry;

[0091] Open the gate valves 9 at the outlet and inlet of the fracture module, start the oil pump 20, open the control valve 3, and start the screw pump 4, and pass the stirred slurry into the fracture module through the screw pump 4, and at the same time turn on the camera 13 to record the slurry migration behavior in each submodule;

[0092] Step S10 is: when all the slurry is pumped into the fracture model, pumping is stopped and the gate valve 9 at the entrance of the fracture module is closed. The camera 13 records the diffusion morphology of the slurry in the submodule and weighs the weight of the slurry in each waste liquid tank 12.

[0093] While embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the 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. A particle transport simulation device considering graded confining pressure and seam network morphology, characterized in that: The invention comprises a stirring tank (1), a feeder (2), a screw pump (4) and a crack module, wherein the output end of the feeder (2) is connected to the inlet of the stirring tank (1), the outlet of the stirring tank (1) is connected to the input end of the screw pump (4) via a control valve (3), the output end of the screw pump (4) is connected to the inlet of the crack module via a first electromagnetic flowmeter (6), the crack module has multiple inlets, a gate valve (9) is provided between each inlet of the crack module and the first electromagnetic flowmeter (6), and the outlet of the crack module is connected to a waste liquid tank (12) via a second electromagnetic flowmeter (10); The crack module comprises four submodules, which are respectively a general crack module (22), a variable crack width crack module (23), a rough crack module (24) and a closed crack module (25). During the test, the number and types of the submodules constituting the crack module can be freely combined and matched, and each submodule is provided with a camera (13) for observing the movement of particles in the submodule; The general crack module (22) comprises a first main body, the first main body comprises two first acrylic plates (29) and two first sealing strips (28), the first sealing strips (28) have a rectangular cross-section, and the two first sealing strips (28) are respectively fixed at the top and bottom between the two first acrylic plates (29); The variable-width crack module (23) comprises a second main body, the second main body comprises two second acrylic plates (34) and two second sealing strips (33), the cross-sectional shape of the second sealing strips (33) is an isosceles trapezoid, and the two second sealing strips (33) are respectively fixed at the top and the bottom between the two second acrylic plates (34); The rough crack module (24) comprises a third body, the third body comprising a third acrylic plate, a rough panel (35) and a third sealing strip, one side of the rough panel (35) is a rough surface, two third sealing strips are respectively fixed at the top and bottom between the third acrylic plate and the rough panel (35), and the rough surface of the rough panel (35) is close to the third sealing strip; The closed crack module (25) comprises a fourth body, the fourth body comprising a fourth acrylic plate, an acrylic plate frame, a pressurizing mechanism and two fourth sealing strips, the two fourth sealing strips being respectively fixed at the top and bottom between the fourth acrylic plate and the acrylic frame, the pressurizing mechanism comprising a plurality of pressurizing cylinders (17), a closing pressurizing block (21) and an oil pump (20) for controlling the movement of the pistons of the pressurizing cylinders (17), the plurality of pressurizing cylinders (17) being arranged in a rectangular array, the closing pressurizing block (21) being fixed to one end of the piston of the pressurizing cylinder (17) close to the fourth acrylic plate, the elastic diaphragm (18) being fixed to one end of the closing pressurizing block (21) close to the fourth acrylic plate, the adjacent elastic diaphragms (18) being bonded to each other by means of flexible filling strips (37), and the elastic diaphragm (18) and its adjacent acrylic frame part being bonded to each other by means of flexible filling strips (37).

2. A particle migration simulation device considering graded confining pressure and seam network morphology according to claim 1, characterized in that: The first electromagnetic flowmeter (6) and the second electromagnetic flowmeter (10) are respectively connected to a first flowmeter monitor (7) and a second flowmeter monitor (11).

3. A particle migration simulation device considering graded confining pressure and seam network morphology according to claim 1, characterized in that: Each of the crack module inlets is connected to a branch pipeline (16), and one end of the plurality of branch pipelines (16) close to the first electromagnetic flowmeter (6) is connected to the first electromagnetic flowmeter (6) via a main pipeline, and a check valve (8) is provided on the main pipeline.

4. The particle migration simulation device considering graded confining pressure and seam network morphology according to claim 1, characterized in that: The outer sides of the first body, the second body, the third body and the fourth body are all connected by bolts to an aluminum alloy frame (30) for supporting and fixing the submodule.

5. A particle migration simulation device considering graded confining pressure and seam network morphology according to claim 4, characterized in that: The crack module further comprises a direction-changing adapter (32), the direction-changing adapter (32) comprising a plurality of interconnected interfaces, each interface being connected to a submodule via a first module adapter (27), one end of each submodule away from the direction-changing adapter (32) being connected to a fixing plate (14) via a second module adapter, the fixing plate (14) being provided with a plurality of flow ports (15) connected to the submodules, the flow port (15) connected to one submodule being an inlet of the crack module, and the flow port (15) connected to another submodule being an outlet of the crack module.

6. The particle migration simulation device considering graded confining pressure and seam network morphology according to claim 5, characterized in that: The first module adapter (27) and the second module adapter are both frame structures; one end of the first module adapter (27) is fixedly connected to the direction-changing adapter (32) by bolts, and the other end of the first module adapter (27) is fixedly connected to the aluminum alloy frame (30) of the submodule by bolts; One end of the second module adapter is fixedly connected to the aluminum alloy frame (30) of the submodule via bolts, and the other end of the second module adapter is fixedly connected to the fixing plate (14) via bolts.

7. The particle migration simulation device considering graded confining pressure and seam network morphology according to claim 6, characterized in that: A waterproof rubber ring (31) is provided at the contact point between the first module adapter (27) and the submodule body, the contact point between the first module adapter (27) and the direction-changing adapter (32), the contact point between the second module connector (26) and the submodule body, and the contact point between the second module adapter and the fixing plate (14).

8. A particle migration simulation method considering graded confining pressure and fracture network morphology, implemented based on the particle migration simulation device considering graded confining pressure and fracture network morphology according to claim 1, characterized in that: The following steps are involved: S1. According to the rock properties of the stratum to be studied, rocks with cracks are obtained through fracture experiments or direct collection at the engineering site, and the crack surface is scanned to extract three-dimensional point cloud data. The three-dimensional point cloud data is processed and key parameters are determined. The key parameters include the fractal dimension of the crack surface, the crack opening, the root mean square of the crack surface height, and the standard deviation of the crack surface; S2, conducting a preliminary experiment under the closed crack module (25), injecting clean water into the closed crack module (25), starting the oil pump (20), and driving the pressurizing cylinder (17) to drive the closed pressurizing block (21) to move. The pressure in the elastic diaphragm (18) of the closed pressurizing block (21) and the pressure in the cylinder are monitored by a pressure sensor, and the displacement of the elastic diaphragm (18) is monitored by a displacement sensor to obtain a displacement-pressure curve of the elastic diaphragm (18), calibrating the pressurizing parameters of the closed crack module (25), and obtaining a pressurizing rate range, which is used as a reference for the pressurizing rate selected in the formal experiment; S3, according to the key parameters of the obtained three-dimensional point cloud data, a rough plate model simulating the crack morphology is generated by a computer, and a rough plate is processed by a 3D engraving machine to assemble a rough crack module (24); S4. Based on the on-site construction information and the similarity ratio criterion, design the required pumping displacement, sand content, proppant particle size, proppant-sand ratio, pumping time and closure plan of the fracture closure module (25) in the test, and estimate the required delivery fluid volume and particle material mass; S5, determining the number and type of submodules according to test requirements, adjusting the crack width of each submodule to a designed value, and then connecting the determined submodules through a direction-changing adapter (32) to form a crack module; S6, opening all valves in the simulation device, and introducing a pre-fluid into the fracture module through the screw pump (4), so that the pre-fluid fills the entire fracture model; After liquid flows out of each outlet of the fracture model, close the screw pump (4) and all valves, and check the water tightness of the entire simulation device and whether it is operating normally; S7, according to the selected closing scheme, determining the closing pressure and closing displacement required for each closing pressurizing block (21), and setting the pressure limit and pressurizing rate of the oil cylinder; Adjusting the operating frequency of the feeder (2), adjusting the operating frequency of the mixing tank (1), and adjusting the operating frequency of the screw pump (4); S8, turn on the flow monitor, detect and record the electromagnetic flowmeter data, and turn on the electromagnetic flowmeter, and run until the electromagnetic flowmeter data is stable; S9, weighing a required mass of granular material, placing a portion of the granular material directly into the mixing tank (1), starting the mixing tank (1), and adding the remaining granular material into the feeder (2); The feeder (2) is started, and the prepared conveying liquid is added into the mixing tank (1) at a constant rate; Open the gate valve (9) at the entrance of the fracture module, start the oil pump (20), open the control valve (3), and start the screw pump (4), and introduce the conveying liquid and granular material into the fracture module through the screw pump (4), and at the same time turn on the camera (13) to record the movement and laying behavior of the granular material in each submodule; S10, when all the granular materials are pumped into the fracture model, the pumping is stopped, and the gate valve (9) at the entrance of the fracture module is closed, and the camera (13) records the final shape of the sand bank formed by the granular materials in the submodule; S11, open all valves in the simulation device, pump clean water into the fracture module, flush the fracture module, and the flushed granular materials enter the waste liquid tank (12) to wait for recovery; S12, exporting the video data in the camera (13) and the data of each electromagnetic flow meter, post-processing the data, determining the characteristic parameters of the particle accumulation morphology in the crack model, and completing an experiment.

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