Proppant conveying simulation device with dynamically changed crack width and operation method

Abstract

The invention belongs to the technical field of petroleum and natural gas engineering, and particularly relates to a crack width dynamic change proppant conveying simulation device and an operation method, and the crack width dynamic change proppant conveying simulation device comprises a sand-carrying fluid conveying system, a crack system, a pressure loading system and an image capturing system. The fracture system is provided with a fracture wall, a gas bin and a fracture bin, in the experimental simulation process, fracturing fluid and a propping agent are mixed through the sand-carrying fluid conveying system to form sand-carrying fluid, the sand-carrying fluid is continuously injected into the fracture bin, and the pressure loading system on the outer side of the fracture wall is used for pressurizing the gas bin to apply closing pressure to the fracture wall; the wall surface of the crack moves under the combined action with the pressure of the sand-carrying fluid in the crack, and an image capturing system is used for collecting the dynamic change condition of the distribution of the propping agent in the flowing process of the sand-carrying fluid in a crack bin, so that the quantitative analysis of the influence of the dynamic crack width on the paving of the propping agent is realized. The method is of great significance to optimization design of sand-carrying fluid construction parameters in hydraulic fracturing of unconventional reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum and natural gas engineering, and in particular relates to a proppant conveying simulation device with dynamic changes in crack width and an operating method. Background Art

[0002] At present, major oil fields in my country have generally entered the middle and late stages of development, and it is becoming increasingly difficult to maintain stable oil and gas production. my country has abundant unconventional oil and gas reserves, and giving full play to its resource advantages plays a vital role in ensuring my country's energy security. However, the porosity and permeability conditions of unconventional reservoirs are extremely poor, and traditional development technologies are difficult to achieve economical and effective utilization of them. With the advancement of oil and gas exploration and development technology, volume fracturing technology has become one of the most core technologies for the development of such oil and gas resources, making unconventional oil and gas gradually become the main force in 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, change the seepage state of oil and gas reservoir fluids, and thus increase the production capacity of unconventional oil and gas wells. During the fracturing process, the fracturing fluid opens cracks in the reservoir, and then the proppant is filled into the cracks with the sand-carrying fluid to prevent the cracks from closing under the action of the closing pressure. In this process, the cracks are simultaneously affected by the closing pressure and the pressure of the sand-carrying fluid in the cracks. The relative size of the two pressures directly determines the degree of opening of the cracks, that is, the crack width. Correspondingly, the crack width directly determines the flow rate and pressure distribution of the sand-carrying fluid in the cracks. Therefore, experimental equipment that can realize the dynamic change of the crack width during the flow of the sand-carrying fluid is of great significance for the accurate simulation of proppant laying.

[0004] However, in the current research on the placement of proppants in fractures after unconventional reservoir fracturing, there is a lack of simulation equipment and methods that can realize the dynamic changes of fracture width during the transportation of sand-carrying fluid. It is impossible to accurately simulate the placement characteristics of proppants in fractures, which restricts the design of unconventional oil and gas fracturing and the formulation of post-fracturing 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 proppant delivery simulation device and an operation method for dynamically changing fracture width. By experimentally simulating the distribution of proppant in the fracture chamber and the change of fracture chamber width, the dynamic change of fracture width under the combined effect of sand-carrying fluid pressure and fracture closure pressure can be fully reflected, which has important reference significance for the optimization design of sand-carrying fluid construction parameters in hydraulic fracturing of unconventional reservoirs.

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

[0007] A proppant delivery simulation device with dynamically changing crack width, comprising a sand-carrying fluid delivery system, a crack system, a pressure loading system and an image capture system;

[0008] The sand-carrying fluid delivery system comprises a fracturing fluid supply unit, a proppant supply unit and a mixing output unit, wherein the fracturing fluid supply unit is used for quantitatively delivering fracturing fluid to the mixing output unit, the proppant supply unit is used for quantitatively delivering proppant to the mixing output unit, and the mixing output unit is used for mixing the fracturing fluid and the proppant in proportion to form the sand-carrying fluid; the fracture system comprises a protection cavity and two fracture walls, wherein the two fracture walls are arranged oppositely in the protection cavity, and the two ends of the fracture walls are connected to the side wall of the protection cavity through elastic members, a fracture chamber is formed between the two fracture walls and the side wall of the protection cavity, and an air chamber is formed between the side of the two fracture walls away from the fracture chamber and the side wall of the protection cavity, and the fracture chamber has an inlet and an outlet, wherein the inlet is connected to the mixing output unit and is used for injecting the sand-carrying fluid into the fracture chamber; the pressure loading system has its output ends connected to the two air chambers respectively, and is used for simultaneously supplying air and pressurizing the two air chambers to adjust the width of the fracture chamber; the image capture system is arranged on one side of the fracture chamber and is used for collecting the dynamic changes in the distribution of the proppant in the fracture chamber during the injection of the sand-carrying fluid. The above design can accurately reflect the distribution of proppant when the fracture chamber is in the process of dynamic width change, which has important reference significance for the optimization design of sand-carrying fluid construction parameters in hydraulic fracturing of unconventional reservoirs. It fully reflects the dynamic change of fracture width under the combined effect of sand-carrying fluid pressure in the fracture and fracture closure pressure, and is more in line with the actual situation of post-fracturing development of unconventional oil reservoirs.

[0009] Preferably, the fracturing fluid supply unit includes a fracturing fluid storage tank, a liquid pump, a liquid flow meter and a liquid supply valve; the liquid outlet of the fracturing fluid storage tank is connected to the mixed output unit through a first delivery pipe; the liquid pump is arranged on the first delivery pipe; the liquid flow meter 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 mixed delivery unit, and the liquid flow meter can provide real-time feedback of the fracturing fluid entering the mixed output unit, which facilitates proportional quantitative delivery. At the same time, the feedback from the liquid flow meter 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 mixed 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 output amount of the proppant can be controlled by the sand supply pump and the sand outlet valve 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 arranged on the side of one of the protective layers away from the crack wall; the matrix light source is arranged on the side of the other 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, for controlling the opening and closing of the matrix light source and receiving image information taken by the high-speed camera.

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

[0017] Preferably, a method for operating a proppant delivery simulation device with dynamically changing fracture width comprises the following steps:

[0018] The required amount of fracturing fluid and proppant are respectively delivered to the mixing output unit through the fracturing fluid supply unit and the proppant supply unit, and the fracturing fluid and proppant are mixed by the mixing output unit to form a sand-carrying fluid for standby use;

[0019] The pressure loading system is turned on to supply air to the two air chambers at the same time. By applying pressure on both sides of the two crack walls, the two crack walls move toward each other, and the crack chambers are adjusted to the required width;

[0020] The image capture system and the mixed output unit are turned on in sequence. The sand-carrying fluid is continuously injected from the inlet side of the fracture chamber through the mixed output unit and discharged from the outlet of the fracture chamber. The image capture system is used to collect the distribution of the proppant in the fracture chamber and the change of the width of the fracture chamber during the injection of the sand-carrying fluid.

[0021] Compared with the prior art, the proppant delivery simulation device and operation method with dynamic change of crack width of the present invention have the following beneficial effects:

[0022] During the experiment, the device uses a mixing 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, and uses a pressure loading system to supply gas to two gas chambers at the same time to adjust the fracture chamber to a desired width; then the sand-carrying fluid is continuously injected from one side of the inlet of the fracture chamber through the mixing output unit and discharged from the outlet of the fracture chamber, and the image capture system can clearly capture the dynamic changes in the distribution of the proppant in the fracture chamber during the injection of the sand-carrying fluid; thus, the dynamic distribution of the proppant can be accurately reflected by adjusting the different widths of the fracture chamber in the above manner, so that the distribution of the proppant when the fracture chamber is in the process of dynamic width change can be reflected, which has important reference significance for the optimization design of sand-carrying fluid construction parameters in hydraulic fracturing of unconventional reservoirs, fully reflects the dynamic changes in the fracture width under the combined action of the sand-carrying fluid pressure in the fracture and the fracture closure pressure, and is more in line with the actual situation of post-pressure development of unconventional oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 2 It is a front view of the crack system in the embodiment of the present invention;

[0025] Figure 3 for Figure 2 Cross-sectional view of the middle crack system AA;

[0026] Figure 4 for Figure 2 Cross-sectional view of the middle crack system BB;

[0027] Figure 5 for Figure 2 Cross-sectional view of the middle crack system CC.

[0028] Description of reference numerals:

[0029] 1. Fracturing fluid storage tank; 2. Liquid pump; 3. Liquid flow meter; 4. Sand mixing tank; 5. Sand supply pump; 6. Sand outlet valve; 7. Proppant storage tank; 8. Sand-carrying fluid recovery tank; 9. Liquid supply valve; 10. Sand-carrying fluid valve; 11. Screw pump; 12. Sand-carrying fluid pressure gauge; 13. Sand-carrying fluid flow meter; 14. Gas cylinder; 15. Gas 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 entrance and exit end plates; 30. Spring; 31. Fracture entrance and exit; 32. Fracture top and bottom end plates; 33. Discharge chamber. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 intended to limit the present invention.

[0031] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

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

[0033] 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, change the seepage state of oil and gas reservoir fluids, and thus increase the production capacity of unconventional oil and gas wells. During the fracturing process, the fracturing fluid opens cracks in the reservoir, and then the proppant is filled into the cracks with the sand-carrying fluid to prevent the cracks from closing under the action of the closing pressure. In this process, the cracks are simultaneously affected by the closing pressure and the pressure of the sand-carrying fluid in the cracks. The relative size of the two pressures directly determines the degree of opening of the cracks, that is, the crack width. Correspondingly, the crack width directly determines the flow rate and pressure distribution of the sand-carrying fluid in the cracks. Therefore, experimental equipment that can realize the dynamic change of the crack width during the flow of the sand-carrying fluid is of great significance for the accurate simulation of proppant laying.

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

[0035] Specifically, the sand-carrying fluid delivery system includes a fracturing fluid supply unit, a proppant supply unit and a mixed output unit, wherein the fracturing fluid supply unit is used to quantitatively deliver fracturing fluid to the mixed output unit, the proppant supply unit is used to quantitatively deliver 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 sand-carrying fluid; the fracture system 17 includes a protective cavity and two fracture walls 27, the two fracture walls 27 are relatively arranged in the protective cavity, and the two ends of the fracture wall 27 are connected to the side wall of the protective cavity through an elastic member, and the fracture wall 27 is made of a light-transmissive high-toughness material, such as tempered glass. Preferably, the elastic member is preferably a spring 30, and the two ends of the spring 30 are respectively fixed to the protective layer 25 and the fracture wall 27 by a connecting member, and the spring 30 is in a stretched state when in use. Then, 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 mixing output unit for injecting the sand-carrying liquid 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 air and pressurizing the two air chambers 26 to adjust 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 sand-carrying liquid.

[0036] On the whole, during the experiment, the device uses a mixing 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, and uses a pressure loading system to supply gas to the two gas chambers 26 at the same time 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 through the mixing output unit and discharged from the outlet of the fracture chamber 28. 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 can be clearly captured by the image capture system; it has important reference significance for the optimization design of sand-carrying fluid construction parameters in unconventional reservoir hydraulic fracturing, fully reflects the dynamic change of the fracture width under the combined action of the sand-carrying fluid pressure in the fracture and the fracture closure pressure, and is more in line with the actual situation of post-pressure development of unconventional oil reservoirs.

[0037] See also Figure 1 As shown, further, in order to ensure the accuracy of the simulation test data, the fracturing fluid is quantitatively delivered to the mixed output unit, and the fracturing fluid supply unit includes a fracturing fluid storage tank 1, a liquid pump 2, a liquid flow meter 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 first delivery pipe is sequentially provided with a liquid supply valve 9, a liquid pump 2 and a liquid flow meter 3 from the fracturing fluid storage tank 1 to the mixed output unit. The liquid pump 2 facilitates the delivery of the fracturing fluid in the fracturing fluid storage tank 1 to the mixed delivery unit. The liquid flow meter 3 can provide real-time feedback of the fracturing fluid entering the mixed output unit, which is convenient for quantitative delivery in proportion. At the same time, the feedback of the liquid flow meter 3 can facilitate the opening and closing of the liquid pump 2 and the liquid supply valve 9.

[0038] See also Figure 1 As shown, further, in order to ensure the accuracy of the simulation test data, the proppant is quantitatively delivered to the mixed output unit to achieve the proportionate mixing 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 7 output ports of the proppant storage tank are 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 the sand supply pump 5 and the sand outlet valve 6 to achieve quantitative output.

[0039] See also Figure 1As shown, further, in order to ensure the accuracy of the simulation test data, the proppant can be continuously transported to the fracture chamber 28, and the mixed output unit includes a sand mixing tank 4, a sand carrying liquid valve 10, a screw pump 11, a sand carrying liquid pressure gauge 12 and a sand carrying liquid flow meter 13. The inlet of the sand mixing tank 4 is connected to the first delivery pipe and the second delivery pipe respectively, and the outlet is connected to the fracture chamber 28 through the third delivery pipe; and the sand carrying liquid valve 10, the screw pump 11, the sand carrying liquid pressure gauge 12 and the sand carrying liquid flow meter 13 are sequentially installed on the third delivery pipe. In addition, an agitator is installed in the sand mixing tank 4. The rotation of the agitator blades can fully mix the incoming fracturing fluid and proppant to form a sand-carrying fluid. When in use, the proppant and fracturing fluid are first mixed in proportion to form a sand-carrying fluid, and then the sand-carrying fluid valve 10 is opened. The screw pump 11 can be used to efficiently and continuously transport the sand-carrying fluid to the fracture chamber 28. During the transportation process, the sand-carrying fluid pressure gauge 12 and the sand-carrying fluid flow meter 13 can be used to monitor the flow pressure and flow rate of the sand-carrying fluid in real time, so as to control the screw pump 11 to change the flow pressure and flow rate according to actual experimental needs, and at the same time, it is convenient to record the flow pressure and flow data of the sand-carrying fluid during the experiment, so as to provide reliable data for subsequent research and analysis.

[0040] See also Figures 2 to 5 As shown, further, in order to ensure the accuracy of the simulation test data, the protection cavity includes a protection layer 25, a crack inlet and outlet end plate 29, and a crack top and bottom end plate 32, and two of each are provided. Furthermore, the two protection layers 25 are rectangular structures and are arranged opposite to each other, two crack walls 27 are inserted in the two protection layers 25, and the crack chamber 28 is parallel to the protection layer 25. The protection layer 25 is a light-transmissive high-strength material, such as a polycarbonate plate or an acrylic plate; the two crack inlet and outlet end plates 29 and the two crack top and bottom end plates 32 are connected end to end in sequence and surround the two protection layers 25. Specifically, two crack inlet and outlet end plates 29 are relatively arranged on the left and right sides of the crack bin 28, and two crack top and bottom end plates 32 are relatively arranged on the upper and lower sides of the crack bin 28. The crack inlet and outlet end plates 29 and the crack top and bottom end plates 32 are perpendicular to the crack bin 28. Crack inlet and outlet 31 are opened on the two crack inlet and outlet end plates 29. The crack inlet and outlet 31 on one crack inlet and outlet end plate 29 is connected to the third conveying pipe, and the crack inlet and outlet 31 on the other crack inlet and outlet end plate 29 is connected to the sand-carrying liquid recovery tank 8; the crack top and bottom end plates 32 are made of transparent materials, such as tempered glass. And the crack top and bottom end plates 32 have length scale lines in the horizontal and vertical directions. Due to the pressure change of the sand-carrying liquid along the crack length direction, the crack width of the entire crack may be slightly different along the crack length direction. The horizontal scale is to determine the position in the crack length direction, and the vertical scale is to determine the crack width at the corresponding crack length position. The preferred crack entry and exit end plates 29 and crack top and bottom end plates 32 are connected to the two protective layers 25 via studs 23 and nuts 24 for easy installation, disassembly and adjustment.

[0041] See also Figure 4As shown, further, in order to ensure the accuracy of the simulation test data and improve the effect of full injection of the sand-carrying liquid in the crack bin 28. Each crack inlet and outlet end plate 29 is evenly distributed with multiple crack inlets and outlets 31 along the length direction, and one of the crack inlet and outlet end plates 29 is provided with an injection bin 21 on the side away from the crack bin 28, and the other crack inlet and outlet end plate 29 is provided with a discharge bin 33 on the side away from the crack bin 28. The bin wall of the injection bin 21 and the bin wall of the discharge bin 33 are respectively fixed on the corresponding crack inlet and outlet end plate 29 to form a closed cavity therewith, and the multiple crack inlets and outlets 31 on each crack inlet and outlet end plate 29 are connected with the corresponding injection bin 21 or the discharge bin 33, wherein the injection bin 21 is connected with the third delivery pipe, and the discharge bin 33 is connected with the sand-carrying liquid recovery tank 8. It is preferred that the number and arrangement of the crack inlets and outlets 31 on the two crack inlet and outlet end plates 29 are not limited, so that the flow direction of the sand-carrying liquid can be simulated more realistically.

[0042] See also Figure 1 As shown, further, in order to ensure the accuracy of the simulated test data, it is convenient to pressurize the crack wall 27 and adjust the width of the crack 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 connected to the two gas chambers 26 through a gas pipeline; the air pump 15 and the barometer 16 are both 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 the gas chamber 26 can be deflated, so as to adjust the distance between the two crack walls 27 by changing the gas pressure in the gas chamber 26, so as to simulate the actual crack width. Further, in order to ensure 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 and the gas pipeline of the air pump 15 are connected to ensure good sealing of the gas in the gas chamber 26, so as to ensure the stability of the distance between the two crack walls 27 and improve the accuracy of the experimental data.

[0043] See also Figure 1 As shown, further, in order to ensure the accuracy of the simulation test data, more accurately collect the dynamic distribution of the proppant in the fracture chamber 28 and the dynamic changes in 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 relatively arranged on both sides of the two protective layers 25, and it is recommended that the two be arranged oppositely. 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 taken by the high-speed camera 18. In addition, the computer 19 is also electrically connected to other control elements in the device, which is used to intelligently control the entire device and improve the automation of the device.

[0044] See also Figures 1 to 5As shown, according to the design of the above-mentioned proppant delivery simulation device with dynamic change of fracture width, its operation method during the simulation test process 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 close the liquid pump 2 and the liquid supply valve 9;

[0048] Step 4: Turn on the agitator 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, mix it with the fracturing fluid to form a sand-carrying fluid, and 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 into 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 sand-carrying liquid valve 10 and the screw pump 11, and deliver the sand-carrying liquid from the third delivery pipe to the crack chamber 28 through the injection chamber 21 and the crack inlet and outlet 31 on the crack inlet and outlet end plate 29 in sequence, and discharge it from the crack inlet and outlet 31 on the other side of the crack inlet and outlet end plate 29 to the sand-carrying liquid recovery tank 8;

[0052] Step 8, recording the dynamic distribution of the proppant in the fracture chamber 28 and the dynamic change of the width of the fracture chamber 28 during the sand-carrying fluid transportation process;

[0053] Step nine, close the screw pump 11, the sand-carrying liquid 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 is finished.

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

[0055] 1. The device has a simple structure, reasonable design, easy installation and operation, low investment cost, less ground equipment and small footprint;

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

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

[0058] In summary, the scheme design can realize the preparation, transportation, observation and recovery of sand-carrying fluids with different sand ratios. In the experimental simulation process, the gas chamber 26 outside the fracture wall 27 is pressurized to apply closing pressure to the fracture wall 27, and the combined effect of the pressure of the sand-carrying fluid in the fracture causes the surface movement of the fracture wall 27, so as to realize the dynamic change of the sand-carrying fluid with the fracture width during the flow in the fracture, thereby realizing the quantitative analysis of the influence of the dynamic fracture width on the proppant laying. It is of great significance to the optimization design of the construction parameters of the sand-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 equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A proppant transport simulation device with dynamic change of fracture width, characterized in that: include: A sand-carrying fluid delivery system, comprising a fracturing fluid supply unit, a proppant supply unit and a mixing output unit, wherein the fracturing fluid supply unit is used to quantitatively deliver fracturing fluid to the mixing output unit, the proppant supply unit is used to quantitatively deliver proppant to the mixing output unit, and the mixing output unit is used to mix the fracturing fluid and the proppant in proportion to form a sand-carrying fluid; A crack system (17), comprising a protection cavity and two crack walls (27), wherein the two crack walls (27) are arranged opposite to each other in the protection cavity, and the two ends of the crack walls (27) are connected to the side walls of the protection cavity through elastic members, a crack chamber (28) is formed between the two crack walls (27) and the side walls of the protection cavity, and an air chamber (26) is formed between the sides of the two crack walls (27) facing away from the crack chamber (28) and the side walls of the protection cavity, and the crack chamber (28) has an inlet and an outlet, and the inlet is connected to the mixing output unit and is used to inject sand-carrying liquid into the crack chamber (28); A pressure loading system, the output ends of which are respectively connected to the two gas bins (26) for simultaneously supplying gas and pressurizing the two gas bins (26) to adjust the width of the crack bin (28); An image capture system is arranged on one side of the fracture chamber (28) and is used to collect dynamic changes in the distribution of the proppant in the fracture chamber (28) during the injection of the sand-carrying fluid.

2. A proppant transport simulation device with dynamic change of crack width according to claim 1, characterized in that: The fracturing fluid supply unit comprises: A fracturing fluid storage tank (1), the fluid outlet of which is connected to the mixing output unit via a first delivery pipe; A liquid pump (2), arranged on the first delivery pipe; A liquid flow meter (3) is arranged on the first delivery pipe and is located on a side of the liquid pump (2) away from the fracturing fluid storage tank (1); A liquid supply valve (9) is located between the fracturing fluid storage tank (1) and the liquid pump (2), and is installed on the first delivery pipe.

3. A proppant transport simulation device with dynamic change of crack width according to claim 2, characterized in that: The proppant supply unit comprises: A proppant storage tank (7), the output port of which is connected to the mixing output unit via a second delivery pipe; A sand supply pump (5), arranged on the second delivery pipe; The sand outlet valve (6) is arranged on the second delivery pipe and is located between the sand supply pump (5) and the proppant storage tank (7).

4. A proppant transport simulation device with dynamic change of fracture width according to claim 3, characterized in that: The hybrid output unit comprises: A sand mixing tank (4), the inlet of which is respectively connected to the first delivery pipe and the second delivery pipe, and the outlet of which is connected to the crack chamber (28) through a third delivery pipe; A sand-carrying liquid valve (10) is arranged at one end of the third delivery pipe close to the sand mixing tank (4); A screw pump (11) is arranged on the third delivery pipe and is located between the sand-carrying liquid valve (10) and the fracture chamber (28); A sand-carrying liquid pressure meter (12) and a sand-carrying liquid flow meter (13) are sequentially arranged on the third delivery pipe between the crack chamber (28) and the screw pump (11).

5. A proppant transport simulation device with dynamic change of fracture width according to claim 4, characterized in that: The protective cavity comprises: The two protective layers (25) are rectangular in structure and are arranged opposite to each other. The two crack walls (27) are inserted in the two protective layers (25). The crack chamber (28) is parallel to the protective layers (25). The protective layers (25) are made of a light-transmissive high-strength material. Two crack inlet and outlet end plates (29) are arranged on the left and right sides of the crack bin (28) and are detachably connected to the two protective layers (25); the crack inlet and outlet end plates (29) are perpendicular to the crack bin (28); crack inlets and outlets (31) are provided on the two crack inlet and outlet end plates (29); the crack inlet and outlet (31) on one of the crack inlet and outlet end plates (29) is connected to the third conveying pipe, and the crack inlet and outlet (31) on the other crack inlet and outlet end plate (29) is connected to a sand-carrying liquid recovery tank (8); Two crack top and bottom end plates (32) are arranged oppositely on the upper and lower sides of the crack chamber (28) and are detachably connected to the protective layer (25).

6. A proppant transport simulation device with dynamic change of fracture width according to claim 5, characterized in that: The crack inlet and outlet end plate (29) is evenly distributed with a plurality of crack inlets and outlets (31) along the length direction; an injection bin (21) is fixedly connected to a side of one crack inlet and outlet end plate (29) facing away from the crack bin (28); a discharge bin (33) is fixedly connected to a side of another crack inlet and outlet end plate (29) facing away from the crack bin (28); the injection bin (21) and the discharge bin (33) are respectively connected to the crack inlets and outlets (31) on the corresponding crack inlet and outlet end plate (29); the injection bin (21) is connected to the third conveying pipe; and the discharge bin (33) is connected to the sand-carrying liquid recovery tank (8).

7. The proppant transport simulation device with dynamic change of fracture width according to claim 1, characterized in that: The pressure loading system comprises: A gas cylinder (14) is connected to the two gas bins (26) via a gas pipeline; An air pump (15) is arranged on the gas pipeline; A barometer (16) is arranged on the gas pipeline between the air pump (15) and the gas chamber (26).

8. The proppant transport simulation device with dynamic change of fracture width according to claim 5, characterized in that: The image capture system comprises: A high-speed camera (18) is arranged on a side of one of the protective layers (25) facing away from the crack wall (27); A matrix light source (20) is arranged on a side of the other protective layer (25) away from the crack wall (27), and the matrix light source (20) is directly opposite to the high-speed camera (18); 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 image information captured by the high-speed camera (18).

9. The proppant transport simulation device with dynamic change of fracture width according to claim 5, characterized in that: The elastic member comprises a spring (30), and two ends of the spring (30) are respectively fixed to the protective layer (25) and the crack wall (27).

10. The method for operating a proppant delivery simulation device with dynamically changing fracture width according to any one of claims 1 to 9, characterized in that: The following steps are involved: The required amount of fracturing fluid and proppant are respectively delivered to the mixing output unit through the fracturing fluid supply unit and the proppant supply unit, and the fracturing fluid and proppant are mixed by the mixing output unit to form a sand-carrying fluid for standby use; The pressure loading system is turned on to supply air to the two air chambers (26) at the same time, and by applying pressure on both sides of the two crack walls (27), the two crack walls (27) move towards each other, and the crack chamber (28) is adjusted to a desired width; The image capture system and the mixed output unit are sequentially turned on, and the sand-carrying fluid is continuously injected from one side of the inlet of the fracture chamber (28) and discharged from the outlet of the fracture chamber (28) through the mixed output unit. 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 are collected using the image capture system.

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