A simulation device and operation method for proppant transportation with dynamically changing crack widths

Abstract

The present invention belongs to the technical field of oil and gas engineering, and particularly relates to a simulation device and operation method for proppant transportation with dynamically changing fracture width, including a sand-carrying fluid transportation system, a fracture system, a pressure loading system, and an image capture system. The fracture system has fracture walls, a gas chamber, and a fracture chamber. During the experimental simulation, the sand-carrying fluid transportation system is used to form a sand-carrying fluid by mixing fracturing fluid and proppant, and continuously inject the sand-carrying fluid into the fracture chamber. The pressure loading system outside the fracture walls is used to pressurize the gas chamber to apply a closing pressure to the fracture walls, and the combined action with the pressure of the sand-carrying fluid in the fractures causes the fracture wall surface to move. The image capture system is used to collect the dynamic changes in the distribution of proppant during the flow of the sand-carrying fluid in the fracture chamber, so as to realize the quantitative analysis of the influence of the dynamic fracture width on proppant placement, which is of great significance for the optimization design of the construction parameters of the sand-carrying fluid in the hydraulic fracturing of unconventional reservoirs.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas engineering, and particularly relates to a simulation device and operation method for proppant transportation with dynamically changing fracture width. Background Art

[0002] At present, most of the major oilfields in China have generally entered the middle and late stages of development, and it is becoming increasingly difficult to maintain stable oil and gas production. China has rich reserves of unconventional oil and gas, and giving full play to its resource advantages plays a crucial role in ensuring China's energy security. However, the pore and permeability conditions of unconventional reservoirs are extremely poor, and traditional development technologies are difficult to economically and effectively utilize them. With the progress of oil and gas exploration and development technologies, the volume fracturing technology has become one of the most core technologies for developing such oil and gas resources, making unconventional oil and gas gradually become the main force for increasing oil and gas production.

[0003] The purpose of hydraulic fracturing is to create a high-speed seepage channel for oil and gas in unconventional reservoirs, increase the control range of oil and gas wells, and change the seepage state of reservoir fluids, thereby improving the productivity of unconventional oil and gas wells. During the fracturing process, the fracturing fluid opens fractures in the reservoir, and then the proppant-carrying fluid is used to fill the fractures with proppant to prevent the fractures from closing under the action of the closing pressure. During this process, the fractures are simultaneously affected by the closing pressure and the pressure of the proppant-carrying fluid in the fractures, and the relative magnitudes of the two pressures directly determine the opening degree of the fractures, that is, the fracture width. Correspondingly, the fracture width directly determines the flow velocity and pressure distribution of the proppant-carrying fluid in the fractures. Therefore, experimental equipment that can achieve dynamic changes in fracture width during the flow of the proppant-carrying fluid is of great significance for accurately simulating the placement of proppant.

[0004] However, in the current research on the placement of proppant in fractures after fracturing of unconventional reservoirs, there is a lack of simulation equipment and simulation methods that can achieve dynamic changes in fracture width during the transportation of the proppant-carrying fluid, and it is impossible to accurately simulate the placement characteristics of proppant in fractures, which restricts the design of unconventional oil and gas fracturing and the formulation of post-fracture development systems. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a simulation device and operation method for proppant transportation with dynamically changing fracture width. By experimentally simulating the distribution of proppant in the fracture chamber and the change in the width of the fracture chamber, it can fully reflect the dynamic change in fracture width under the combined action of the pressure of the proppant-carrying fluid and the fracture closing pressure, and has important reference significance for the optimization design of the construction parameters of the proppant-carrying fluid in the hydraulic fracturing of unconventional reservoirs.

[0006] The technical solution of the present invention is as follows:

[0007] A simulation device for proppant transportation with dynamically changing fracture width includes a proppant-carrying fluid transportation system, a fracture system, a pressure loading system, and an image capture system;

[0008] The sand-carrying fluid delivery system includes a fracturing fluid supply unit, a proppant supply unit, and a mixing and output unit. The fracturing fluid supply unit is used to quantitatively deliver fracturing fluid to the mixing and output unit. The proppant supply unit is used to quantitatively deliver proppant to the mixing and output unit. The mixing and output unit is used to mix the fracturing fluid and the proppant in proportion to form a sand-carrying fluid. The fracture system includes a protection cavity and two fracture walls. The two fracture walls are oppositely arranged in the protection cavity, and both ends of the fracture walls are connected to the side walls of the protection cavity through elastic members. A fracture chamber is formed between the two fracture walls and the side walls of the protection cavity. Air chambers are formed between the sides of the two fracture walls facing away from the fracture chamber and the side walls of the protection cavity. The fracture chamber has an inlet and an outlet. The inlet is communicated with the mixing and output unit for injecting the sand-carrying fluid into the fracture chamber. The pressure loading system has its output ends respectively connected to the two air chambers and is used to supply gas and pressurize the two air chambers simultaneously to realize the adjustment of the width of the fracture chamber. The image capture system is arranged on one side of the fracture chamber and is used to collect the dynamic change situation of the distribution of the proppant in the fracture chamber during the injection process of the sand-carrying fluid. Through the above design, it can accurately reflect the distribution condition of the proppant when the fracture chamber is in the process of dynamic width change, which has important reference significance for the optimization design of the construction parameters of the sand-carrying fluid in the hydraulic fracturing of unconventional reservoirs, fully reflects the dynamic change of the fracture width under the combined action of the pressure of the sand-carrying fluid in the fracture and the fracture closure pressure, and is more in line with the actual situation of the post-fracture development of unconventional oil reservoirs.

[0009] Preferably, the fracturing fluid supply unit includes a fracturing fluid storage tank, a liquid pump, a liquid flowmeter, and a liquid supply valve. The liquid outlet of the fracturing fluid storage tank is connected to the mixing and output unit through a first delivery pipe. The liquid pump is arranged on the first delivery pipe. The liquid flowmeter is arranged on the first delivery pipe and is located on the side of the liquid pump away from the fracturing fluid storage tank. The liquid supply valve is located between the fracturing fluid storage tank and the liquid pump and is installed on the first delivery pipe. The liquid pump facilitates the delivery of the fracturing fluid in the fracturing fluid storage tank to the mixing and delivery unit. The liquid flowmeter can provide real-time feedback on the fracturing fluid entering the mixing and output unit, which is convenient for quantitative delivery in proportion. At the same time, the feedback of the liquid flowmeter can facilitate the opening and closing of the liquid pump and the liquid supply valve.

[0010] Preferably, the proppant supply unit includes a proppant storage tank, a sand supply pump, and a sand outlet valve. The output port of the proppant storage tank is connected to the mixing and output unit through a second delivery pipe. The sand supply pump is arranged on the second delivery pipe. The sand outlet valve is arranged on the second delivery pipe and is located between the sand supply pump and the proppant storage tank. The sand supply pump and the sand outlet valve can be used to control the output amount of the proppant to achieve quantitative output.

[0011] Preferably, the mixed output unit includes a sand mixing tank, a sand carrying liquid valve, a screw pump, a sand carrying liquid pressure gauge, and a sand carrying liquid flow meter; the inlet of the sand mixing tank is connected to the first delivery pipe and the second delivery pipe respectively, and the outlet is connected to the crack bin through the third delivery pipe; the sand carrying liquid valve is arranged at one end of the third delivery pipe close to the sand mixing tank; the screw pump is arranged on the third delivery pipe and is located between the sand carrying liquid valve and the crack bin; the sand carrying liquid pressure gauge and the sand carrying liquid flow meter are arranged on the third delivery pipe between the crack bin and the screw pump in sequence. The sand carrying liquid pressure gauge and the sand carrying liquid flow meter can be used to monitor the flow pressure and flow rate of the sand carrying liquid in real time, which is convenient for controlling the screw pump to change the flow pressure and flow rate according to actual experimental needs, and is also convenient for recording the flow pressure and flow data of the sand carrying liquid during the experiment, providing reliable data for subsequent research and analysis.

[0012] Preferably, the protective cavity includes two protective layers, two crack inlet and outlet end plates and two crack top and bottom end plates; the two protective layers are rectangular structures and are arranged oppositely, the two crack walls are inserted in the two protective layers, the crack bin is parallel to the protective layer, and the protective layer is a light-transmissive high-strength material; the two crack inlet and outlet end plates are arranged oppositely on the left and right sides of the crack bin and are detachably connected to the two protective layers, the crack inlet and outlet end plates are perpendicular to the crack bin, and crack inlets and outlets are provided on the two crack inlet and outlet end plates, one of the crack inlet and outlet end plates is connected to the third conveying pipe, and the other crack inlet and outlet end plate is connected to a sand-carrying liquid recovery tank; the two crack top and bottom end plates are arranged oppositely on the upper and lower sides of the crack bin and are detachably connected to the protective layer. This can better ensure the accuracy of the simulation test data.

[0013] Preferably, the crack inlet and outlet end plate is uniformly provided with a plurality of the crack inlets and outlets along the length direction, an injection bin is fixedly connected to the side of one crack inlet and outlet end plate away from the crack bin, and a discharge bin is fixedly connected to the side of another crack inlet and outlet end plate away from the crack bin, the injection bin and the discharge bin are respectively connected to the crack inlets and outlets on the corresponding crack inlet and outlet end plates, and the injection bin is connected to the third delivery pipe, and the discharge bin is connected to the sand-carrying liquid recovery tank. Thereby, the effect of fully injecting the sand-carrying liquid into the crack bin can be improved, and the flow direction of the sand-carrying liquid can be simulated more realistically.

[0014] Preferably, the pressure loading system includes a gas cylinder, an air pump and a barometer; the gas cylinder is connected to the two gas chambers through a gas pipeline; the air pump is arranged on the gas pipeline; and the barometer is arranged on the gas pipeline between the air pump and the gas chamber. Thus, the distance between the two crack walls can be adjusted by changing the gas pressure in the gas chamber, so as to simulate the actual crack width.

[0015] Preferably, the image capture system includes a high-speed camera, a matrix light source, and a computer; the high-speed camera is disposed on one side of the protective layer away from the crack wall; the matrix light source is disposed on the other side of the protective layer away from the crack wall, and the matrix light source is directly opposite to the high-speed camera; the computer is electrically connected to the high-speed camera and the matrix light source respectively, and is used for controlling the opening and closing of the matrix light source and receiving the image information captured by the high-speed camera.

[0016] Preferably, the elastic member includes a spring, and two ends of the spring are respectively fixed to the protective layer and the crack wall.

[0017] Preferably, an operation method of a proppant transportation simulation device with dynamically changing crack width includes the following steps:

[0018] Respectively, supply the required amount of fracturing fluid and proppant to the mixing and output unit through the fracturing fluid supply unit and the proppant supply unit, and use the mixing and output unit to mix the fracturing fluid and the proppant to form a sand-carrying fluid for standby;

[0019] Open the pressure loading system and supply gas to the two gas chambers simultaneously. By pressurizing on both sides of the two crack walls, the two crack walls move towards each other to adjust the crack chamber to the required width;

[0020] Sequentially open the image capture system and the mixing and output unit. Continuously inject the sand-carrying fluid from the inlet side of the crack chamber through the mixing and output unit and discharge it from the outlet of the crack chamber, and use the image capture system to collect the distribution of the proppant in the crack chamber and the change of the crack chamber width during the injection process of the sand-carrying fluid.

[0021] Compared with the prior art, an apparatus and an operation method for simulating proppant transportation with dynamically changing crack width according to the present invention have the following beneficial effects:

[0022] During the experiment of this device, the mixing and output unit is used to mix the fracturing fluid and the proppant from the fracturing fluid supply unit and the proppant supply unit to form a sand-carrying fluid. The pressure loading system is used to supply gas to the two gas chambers simultaneously to adjust the crack chamber to the required width; then, the sand-carrying fluid is continuously injected from the inlet side of the crack chamber through the mixing and output unit and discharged from the outlet of the crack chamber. The image capture system can clearly collect the dynamic change of the distribution of the proppant in the crack chamber during the injection process of the sand-carrying fluid; thus, by adjusting different widths of the crack chamber in the above manner, the dynamic distribution of the proppant can be accurately reflected. In this way, the distribution of the proppant when the crack chamber is in the process of dynamic width change can be reflected, which has important reference significance for the optimization design of the construction parameters of the sand-carrying fluid in the hydraulic fracturing of unconventional reservoirs, and fully reflects the dynamic change of the crack width under the combined action of the pressure of the sand-carrying fluid in the crack and the crack closing pressure, and is more in line with the actual situation of the post-fracture development of unconventional oil reservoirs. Description of the Drawings

[0023] Figure 1 This is the schematic diagram of the overall structure in the embodiment of the present invention;

[0024] Figure 2 This is the front view of the fracture system in the embodiment of the present invention;

[0025] Figure 3 is Figure 2 the sectional view of the fracture system A-A in

[0026] Figure 4 is Figure 2 the sectional view of the fracture system B-B in

[0027] Figure 5 is Figure 2 the sectional view of the fracture system C-C in.

[0028] Explanation of reference numerals:

[0029] 1. Fracturing fluid storage tank; 2. Liquid pump; 3. Liquid flowmeter; 4. Sand mixing tank; 5. Sand supply pump; 6. Sand outlet valve; 7. Proppant storage tank; 8. Carrying fluid recovery tank; 9. Liquid supply valve; 10. Carrying fluid valve; 11. Screw pump; 12. Carrying fluid pressure gauge; 13. Carrying fluid flowmeter; 14. Gas cylinder; 15. Air pump; 16. Barometer; 17. Fracture system; 18. High-speed camera; 19. Computer; 20. Matrix light source; 21. Injection chamber; 22. Injection chamber wall; 23. Stud; 24. Nut; 25. Protective layer; 26. Gas chamber; 27. Fracture wall; 28. Fracture chamber; 29. Fracture inlet and outlet end plate; 30. Spring; 31. Fracture inlet and outlet; 32. Fracture top and bottom end plate; 33. Discharge chamber. Detailed implementation manners

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] In addition, the technical solutions between various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0033] The purpose of hydraulic fracturing is to create channels for high-speed seepage of oil and gas in unconventional reservoirs, increase the control range of oil and gas wells, change the seepage state of reservoir fluids, and thus improve the productivity of unconventional oil and gas wells. During the fracturing process, the fracturing fluid opens fractures in the reservoir, and then the proppant-carrying fluid is used to fill the proppant into the fractures to prevent the fractures from closing under the action of the closing pressure. During this process, the fractures are simultaneously affected by the closing pressure and the pressure of the proppant-carrying fluid in the fractures, and the relative magnitudes of the two pressures directly determine the opening degree of the fractures, that is, the fracture width. Correspondingly, the fracture width directly determines the flow rate and pressure distribution of the proppant-carrying fluid in the fractures. Therefore, experimental equipment that can achieve dynamic changes in fracture width during the flow of the proppant-carrying fluid is of great significance for accurately simulating proppant placement.

[0034] See Figures 1 to 5 As shown, in order to fully reflect the dynamic changes in fracture width under the combined action of the proppant-carrying fluid pressure and the fracture closing pressure, it provides important research and reference for the optimization design of the construction parameters of the proppant-carrying fluid in the hydraulic fracturing of unconventional reservoirs. This embodiment provides a simulation device for proppant transportation with dynamic changes in fracture width, including a proppant-carrying fluid transportation system, a fracture system 17, a pressure loading system, and an image capture system.

[0035] Specifically, the proppant-carrying fluid transportation system includes a fracturing fluid supply unit, a proppant supply unit, and a mixed output unit. The fracturing fluid supply unit is used to quantitatively transport fracturing fluid to the mixed output unit, the proppant supply unit is used to quantitatively transport proppant to the mixed output unit, and the mixed output unit is used to mix the fracturing fluid and the proppant in proportion to form the proppant-carrying fluid; the fracture system 17 includes a protection cavity and two fracture walls 27. The two fracture walls 27 are oppositely arranged in the protection cavity, and both ends of the fracture wall 27 are connected to the side wall of the protection cavity through elastic members. The fracture wall 27 is made of a light-transmitting and highly ductile material, such as tempered glass. Preferably, the elastic member is a spring 30. Both ends of the spring 30 are fixed to the protective layer 25 and the fracture wall 27 respectively by connecting members, and the spring 30 is in a stretched state during use. Furthermore, a fracture chamber 28 is formed between the two fracture walls 27 and the side wall of the protection cavity, and an air chamber 26 is formed between the side of the two fracture walls 27 facing away from the fracture chamber 28 and the side wall of the protection cavity. The fracture chamber 28 has an inlet and an outlet, and the inlet is connected to the mixed output unit for injecting the proppant-carrying fluid into the fracture chamber 28; the output end of the pressure loading system is respectively connected to the two air chambers 26 for simultaneously supplying gas and pressurizing the two air chambers 26 to realize the adjustment of the width of the fracture chamber 28; the image capture system is arranged on one side of the fracture chamber 28 for collecting the distribution of the proppant in the fracture chamber 28 and the change in the width of the fracture chamber 28 during the injection of the proppant-carrying fluid.

[0036] Overall, during the experiment, this device uses the mixed output unit to mix the fracturing fluid and proppant from the fracturing fluid supply unit and the proppant supply unit to form a sand-carrying fluid. The pressure loading system is used to supply gas to the two gas chambers 26 simultaneously to adjust the fracture chamber 28 to the required width. Then, the sand-carrying fluid is continuously injected from the inlet side of the fracture chamber 28 and discharged from the outlet of the fracture chamber 28 through the mixed output unit. The image capture system can clearly collect the distribution of the proppant in the fracture chamber 28 and the change in the width of the fracture chamber 28 during the injection of the sand-carrying fluid. It has important reference significance for the optimization design of the construction parameters of the sand-carrying fluid in the hydraulic fracturing of unconventional reservoirs, fully reflecting the dynamic change of the fracture width under the combined action of the pressure of the in-fracture sand-carrying fluid and the fracture closure pressure, and being more in line with the actual situation of the post-fracture development of unconventional oil reservoirs.

[0037] See Figure 1 As shown, further, to ensure the accuracy of the simulation test data, the fracturing fluid is quantitatively transported to the mixed output unit. The fracturing fluid supply unit includes a fracturing fluid storage tank 1, a liquid pump 2, a liquid flowmeter 3, and a liquid supply valve 9. The fracturing fluid storage tank 1 is used to store the fracturing fluid, and its liquid outlet is connected to the mixed output unit through a first delivery pipe. The liquid supply valve 9, the liquid pump 2, and the liquid flowmeter 3 are sequentially arranged on the first delivery pipe in the direction from the fracturing fluid storage tank 1 to the mixed output unit. The liquid pump 2 facilitates the transportation of the fracturing fluid in the fracturing fluid storage tank 1 to the mixed transportation unit. The liquid flowmeter 3 can provide real-time feedback on the fracturing fluid entering the mixed output unit, facilitating quantitative transportation in proportion. At the same time, the feedback of the liquid flowmeter 3 can facilitate the opening and closing of the liquid pump 2 and the liquid supply valve 9.

[0038] See Figure 1 As shown, furthermore, to ensure the accuracy of the simulation test data, the proppant is quantitatively transported to the mixed output unit to achieve the proportional mixing and configuration of the proppant and the fracturing fluid. The proppant supply unit includes a proppant storage tank 7, a sand supply pump 5, and a sand outlet valve 6. When in use, the output port of the proppant storage tank 7 is connected to the mixed output unit through a second delivery pipe. The sand supply pump 5 and the sand outlet valve 6 are sequentially arranged on the second delivery pipe. And the sand outlet valve 6 is located between the sand supply pump 5 and the proppant storage tank 7. The output amount of the proppant can be controlled by using the sand supply pump 5 and the sand outlet valve 6 to achieve quantitative output.

[0039] See Figure 1As shown in the figure, further, to ensure the accuracy of the simulation test data and enable the continuous delivery of proppants to the fracture chamber 28, the mixing and output unit includes a sand mixing tank 4, a carrier fluid valve 10, a screw pump 11, a carrier fluid pressure gauge 12, and a carrier fluid flowmeter 13. The inlet of the sand mixing tank 4 is respectively connected to the first delivery pipe and the second delivery pipe, and the outlet is connected to the fracture chamber 28 through the third delivery pipe; and the carrier fluid valve 10, the screw pump 11, the carrier fluid pressure gauge 12, and the carrier fluid flowmeter 13 are sequentially installed on the third delivery pipe. In addition, a stirrer is installed in the sand mixing tank 4. By rotating the fan blades of the stirrer, the entering fracturing fluid and proppants can be fully mixed to form a carrier fluid. Then, when in use, the proppants and fracturing fluid are first mixed in proportion to form a carrier fluid, and then the carrier fluid valve 10 is opened. The screw pump 11 can efficiently and continuously deliver the carrier fluid into the fracture chamber 28. During the delivery process, the carrier fluid pressure gauge 12 and the carrier fluid flowmeter 13 can be used to monitor the flow pressure and flow rate of the carrier fluid in real time, which is convenient for controlling the screw pump 11 to change the flow pressure and flow rate according to the actual experimental requirements, and at the same time, it is convenient to record the flow pressure and flow data of the carrier fluid during the experiment, providing reliable data for subsequent research and analysis.

[0040] See Figures 2 to 5 As shown in the figure, further, to ensure the accuracy of the simulation test data, the protection cavity includes two protective layers 25, two fracture inlet and outlet end plates 29, and two fracture top and bottom end plates 32. The two protective layers 25 are rectangular structures and are arranged oppositely. The two fracture walls 27 are inserted into the two protective layers 25. The fracture chamber 28 is parallel to the protective layer 25. The protective layer 25 is made of a light-transmitting high-strength material, such as polycarbonate plate or acrylic plate; the two fracture inlet and outlet end plates 29 and the two fracture top and bottom end plates 32 are sequentially connected end to end around the two protective layers 25. Specifically, the two fracture inlet and outlet end plates 29 are oppositely arranged on the left and right sides of the fracture chamber 28, and the two fracture top and bottom end plates 32 are oppositely arranged on the upper and lower sides of the fracture chamber 28. The fracture inlet and outlet end plates 29 and the fracture top and bottom end plates 32 are both perpendicular to the fracture chamber 28. Fracture inlets and outlets 31 are opened on both of the two fracture inlet and outlet end plates 29. The fracture inlet and outlet 31 on one of the fracture inlet and outlet end plates 29 is connected to the third delivery pipe, and the fracture inlet and outlet 31 on the other fracture inlet and outlet end plate 29 is connected to a carrier fluid recovery tank 8; the fracture top and bottom end plates 32 are made of a transparent material, such as tempered glass. And there are length scale lines in both the horizontal and vertical directions on the fracture top and bottom end plates 32. Due to the pressure change of the carrier fluid along the fracture length direction, the fracture width of the whole fracture may be slightly different along the fracture length direction. The horizontal scale is used to determine the position in the fracture length direction, and the vertical scale is used to determine the fracture width at the corresponding fracture length position. Preferably, both the fracture inlet and outlet end plates 29 and the fracture top and bottom end plates 32 are connected to the two protective layers 25 through stud bolts 23 and nuts 24, which is convenient for installation, disassembly, and adjustment.

[0041] See Figure 4As shown in the figure, further, in order to ensure the accuracy of the simulation test data and improve the full injection effect of the sand-carrying fluid in the fracture chamber 28. A plurality of fracture inlets and outlets 31 are evenly distributed along the length direction of each fracture inlet and outlet end plate 29. And on one side of one fracture inlet and outlet end plate 29 facing away from the fracture chamber 28, an injection chamber 21 is provided, and on one side of the other fracture inlet and outlet end plate 29 facing away from the fracture chamber 28, a discharge chamber 33 is provided. The chamber walls of the injection chamber 21 and the discharge chamber 33 are respectively fixed on the corresponding fracture inlet and outlet end plates 29 to form a sealed cavity therewith. A plurality of fracture inlets and outlets 31 on each fracture inlet and outlet end plate 29 are all communicated with the corresponding injection chamber 21 or discharge chamber 33. Among them, the injection chamber 21 is communicated with the third delivery pipe, and the discharge chamber 33 is communicated with the sand-carrying fluid recovery tank 8. Preferably, the number and arrangement mode of the fracture inlets and outlets 31 on the two fracture inlet and outlet end plates 29 are not limited, and the flow direction of the sand-carrying fluid can be simulated more realistically.

[0042] See Figure 1 As shown in the figure, further, in order to ensure the accuracy of the simulation test data and facilitate pressurizing the fracture wall 27 and adjusting the width of the fracture chamber 28 according to the experimental requirements. The pressure loading system includes a gas cylinder 14, an air pump 15 and a barometer 16. The gas cylinder 14 is communicated with two gas chambers 26 through a gas pipeline; both the air pump 15 and the barometer 16 are arranged on the gas pipeline; and the barometer 16 is arranged between the air pump 15 and the gas chamber 26. The air pump 15 can inflate the gas chamber 26 or deflate the gas chamber 26, so as to adjust the distance between the two fracture walls 27 by changing the gas pressure in the gas chamber 26, and facilitate simulating the actual fracture width. Further, in order to facilitate ensuring the stability of the pressurization in the gas chamber 26, elastic air bags can be placed in the two gas chambers 26, and the elastic air bags are connected with the air pipeline of the air pump 15, which can ensure good airtightness of the gas when it is filled into the gas chamber 26, so as to ensure the stability of the distance between the two fracture walls 27 and improve the accuracy of the experimental data.

[0043] See Figure 1 As shown in the figure, further, in order to ensure the accuracy of the simulation test data and more accurately collect the dynamic distribution of the proppant in the fracture chamber 28 and the dynamic change of the width of the two fracture walls 27 during the flow of the sand-carrying fluid in the fracture chamber 28. The image capture system includes a high-speed camera 18, a matrix light source 20 and a computer 19. The high-speed camera 18 and the matrix light source 20 are oppositely arranged on both sides of the two protective layers 25, and it is recommended that the two be arranged directly opposite to each other. The computer 19 is electrically connected to the high-speed camera 18 and the matrix light source 20 respectively, and is used to control the opening and closing of the matrix light source 20 and receive the image information captured by the high-speed camera 18. In addition, the computer 19 is also electrically connected to other control elements in the device, and is used for intelligent control of the whole device to improve the automation of the device.

[0044] See Figures 1 to 5As shown, according to the design of the proppant transportation simulation device with dynamic change of crack width described above, its operation method during the simulation test includes the following detailed steps:

[0045] Step 1: Prepare the fracturing fluid required for the experiment and inject it into the fracturing fluid storage tank 1;

[0046] Step 2: Select the required proppant and place it in the proppant storage tank 7;

[0047] Step 3: Open the liquid supply valve 9 and the liquid pump 2, inject the required fracturing fluid into the sand mixing tank 4, and then close the liquid pump 2 and the liquid supply valve 9;

[0048] Step 4: Turn on the stirrer in the sand mixing tank 4, and at the same time open the sand outlet valve 6 and the sand supply pump 5, inject the required proppant into the sand mixing tank 4, stir it with the fracturing fluid to form a proppant-carrying fluid, and then close the sand supply pump 5 and the sand outlet valve 6;

[0049] Step 5: Open the gas cylinder 14 and the air pump 15, supply gas to the gas chamber 26, and adjust the crack chamber 28 to the required width;

[0050] Step 6: Turn on the computer 19, the matrix light source 20 and the high-speed camera 18;

[0051] Step 7: Open the proppant-carrying fluid valve 10 and the screw pump 11, send the proppant-carrying fluid from the third transfer pipe through the injection chamber 21 and the crack inlet / outlet 31 on the crack inlet / outlet end plate 29 into the crack chamber 28, and discharge it from the crack inlet / outlet 31 on the other side of the crack inlet / outlet end plate 29 into the proppant-carrying fluid recovery tank 8;

[0052] Step 8: Record the dynamic distribution of the proppant in the crack chamber 28 and the dynamic change of the width of the crack chamber 28 during the transportation of the proppant-carrying fluid;

[0053] Step 9: Turn off the screw pump 11, the proppant-carrying fluid valve 10, the air pump 15, the gas cylinder 14, the matrix light source 20, the high-speed camera 18 and the computer 19 in sequence, dispose of the proppant and the experimental waste liquid, and the experiment ends.

[0054] The proppant transportation simulation device with dynamic change of crack width designed above has the following advantages:

[0055] 1. The device has a simple structure, reasonable design, convenient installation and operation, low investment cost, few ground equipment and small floor area;

[0056] 2. The device can flexibly adjust the ratio of the fracturing fluid and the proppant as well as the crack width, and can conduct in-depth research on the placement of the proppant in the crack during the dynamic change process of the crack width;

[0057] 3. When the device measures the proppant placement in the fracture, it fully reflects the dynamic change of the fracture width under the combined action of the proppant-carrying fluid pressure and the fracture closure pressure in the fracture, which is more in line with the actual situation of post-fracture development in unconventional reservoirs;

[0058] In summary, the scheme design can realize the preparation, transportation, observation and recovery of proppant-carrying fluids with different sand ratios. During the experimental simulation process, the closure pressure is applied to the fracture wall 27 by pressurizing the air chamber 26 outside the fracture wall 27, and the combined action with the proppant-carrying fluid pressure in the fracture causes the movement of the fracture wall 27 surface, realizing the dynamic change of the proppant-carrying fluid in the fracture with the fracture width, so as to realize the quantitative analysis of the influence of the dynamic fracture width on the proppant placement. It is of great significance for the optimization design of the construction parameters of the proppant-carrying fluid in the hydraulic fracturing of unconventional reservoirs.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations.

Claims

1. A proppant transportation simulation device with dynamically changing crack widths, characterized in that, Comprising: A proppant-carrying fluid delivery system, including a fracturing fluid supply unit, a proppant supply unit, and a mixing and output unit. The fracturing fluid supply unit is used to quantitatively deliver fracturing fluid to the mixing and output unit. The proppant supply unit is used to quantitatively deliver proppant to the mixing and output unit. The mixing and output unit is used to mix the fracturing fluid and the proppant in proportion to form a proppant-carrying fluid; A fracture system (17), including a protection cavity and two fracture walls (27). The two fracture walls (27) are oppositely arranged in the protection cavity, and both ends of the fracture walls (27) are connected to the side wall of the protection cavity through elastic members. A fracture chamber (28) is formed between the two fracture walls (27) and the side wall of the protection cavity. Gas chambers (26) are formed between the sides of the two fracture walls (27) facing away from the fracture chamber (28) and the side wall of the protection cavity. The fracture chamber (28) has an inlet and an outlet. The inlet is communicated with the mixing and output unit for injecting the proppant-carrying fluid into the fracture chamber (28); A pressure loading system, whose output ends are respectively connected to the two gas chambers (26), and is used to supply gas and pressurize the two gas chambers (26) simultaneously to realize the adjustment of the width of the fracture chamber (28); An image capture system, arranged on one side of the fracture chamber (28), and is used to collect the dynamic change of the distribution of the proppant in the fracture chamber (28) during the injection process of the proppant-carrying fluid.

2. The proppant transportation simulation device with dynamically changing crack width according to claim 1, wherein The fracturing fluid supply unit includes: A fracturing fluid storage tank (1), whose liquid outlet is connected to the mixing and output unit through a first delivery pipe; A liquid pump (2), arranged on the first delivery pipe; A liquid flowmeter (3), arranged on the first delivery pipe and located on the side of the liquid pump (2) away from the fracturing fluid storage tank (1); A liquid supply valve (9), located between the fracturing fluid storage tank (1) and the liquid pump (2) and installed on the first delivery pipe.

3. The proppant transportation simulation device with dynamically changing crack width according to claim 2, characterized in that, The proppant supply unit includes: A proppant storage tank (7), whose output port is connected to the mixing and output unit through a second delivery pipe; A sand supply pump (5), arranged on the second delivery pipe; A sand outlet valve (6), arranged on the second delivery pipe and located between the sand supply pump (5) and the proppant storage tank (7).

4. A proppant transportation simulation device with dynamically changing crack widths according to claim 3, characterized in that, The mixing and output unit includes: A sand mixing tank (4), whose inlet is respectively communicated with the first delivery pipe and the second delivery pipe, and the outlet is communicated with the fracture chamber (28) through a third delivery pipe; A proppant-carrying fluid valve (10), arranged at one end of the third delivery pipe close to the sand mixing tank (4); A screw pump (11), arranged on the third delivery pipe and located between the proppant-carrying fluid valve (10) and the fracture chamber (28); A proppant-carrying fluid pressure gauge (12) and a proppant-carrying fluid flowmeter (13), which are sequentially arranged on the third delivery pipe between the fracture chamber (28) and the screw pump (11).

5. The proppant transportation simulation device with dynamically changing crack widths according to claim 4, characterized in that, The protection cavity includes: Two protective layers (25), which are rectangular structures and are arranged oppositely. Two of the crack walls (27) are inserted into the two protective layers (25). The crack chamber (28) is parallel to the protective layer (25). The protective layer (25) is made of a light-transmitting high-strength material; Two crack inlet / outlet end plates (29), which are arranged oppositely on the left and right sides of the crack chamber (28) and are detachably connected to the two protective layers (25). The crack inlet / outlet end plates (29) are perpendicular to the crack chamber (28). Crack inlets / outlets (31) are provided on both of the two crack inlet / outlet end plates (29). The crack inlet / outlet (31) on one of the crack inlet / outlet end plates (29) is communicated with the third delivery pipe, and the crack inlet / outlet (31) on the other crack inlet / outlet end plate (29) is connected to a sand-carrying fluid recovery tank (8); Two crack top / bottom end plates (32), which are arranged oppositely on the upper and lower sides of the crack chamber (28) and are detachably connected to the protective layer (25).

6. The proppant transportation simulation device with dynamically varying crack widths according to claim 5, characterized in that, A plurality of the crack inlets / outlets (31) are evenly distributed along the length direction of the crack inlet / outlet end plate (29). An injection chamber (21) is fixedly connected to the side of one crack inlet / outlet end plate (29) facing away from the crack chamber (28), and a discharge chamber (33) is fixedly connected to the side of the other crack inlet / outlet end plate (29) facing away from the crack chamber (28). The injection chamber (21) and the discharge chamber (33) are respectively communicated with the crack inlets / outlets (31) on the corresponding crack inlet / outlet end plates (29), and the injection chamber (21) is communicated with the third delivery pipe, and the discharge chamber (33) is communicated with the sand-carrying fluid recovery tank (8).

7. A proppant transportation simulation device with dynamically changing crack widths according to claim 1, characterized in that The pressure loading system includes: An air cylinder (14), which is communicated with the two air chambers (26) through an air delivery pipe; An air pump (15), which is arranged on the air delivery pipe; A barometer (16), which is arranged on the air delivery pipe between the air pump (15) and the air chamber (26).

8. A proppant transportation simulation device with dynamically changing crack widths according to claim 5, characterized in that, The image capturing system includes: A high-speed camera (18), which is arranged on the side of one of the protective layers (25) facing away from the crack wall (27); A matrix light source (20), which is arranged on the side of the other protective layer (25) facing away from the crack wall (27), and the matrix light source (20) is directly opposite to the high-speed camera (18); A computer (19), which is electrically connected to the high-speed camera (18) and the matrix light source (20) respectively, and is used for controlling the opening and closing of the matrix light source (20) and receiving the image information captured by the high-speed camera (18).

9. The simulation device for proppant transportation with dynamically changing crack width according to claim 5, wherein, The elastic member includes a spring (30). Two ends of the spring (30) are respectively fixed to the protective layer (25) and the crack wall (27).

10. The operating method of a proppant transportation simulation device with dynamically changing crack widths according to any one of claims 1-9, characterized in that, It includes the following steps: Respectively deliver the required amounts of fracturing fluid and proppant to the mixing and output unit through the fracturing fluid supply unit and the proppant supply unit, and use the mixing and output unit to mix the fracturing fluid and the proppant to form a sand-carrying fluid for standby; The opening pressure loading system supplies gas to the two gas chambers (26) simultaneously. By applying pressure on both sides of the two fracture walls (27), the two fracture walls (27) move towards each other to adjust the fracture chamber (28) to the required width; The image capture system and the hybrid output unit are turned on in sequence. The proppant-carrying fluid is continuously injected from the inlet side of the fracture chamber (28) and discharged from the outlet of the fracture chamber (28) through the hybrid output unit. The image capture system is used to collect the distribution of the proppant in the fracture chamber (28) and the change in the width of the fracture chamber (28) during the injection of the proppant-carrying fluid.

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