A visualization device for dynamically adjusting wall roughness and branch crack angle

Abstract

This invention belongs to the field of petroleum engineering and fluid mechanics, and relates to a visualization device for dynamically adjusting wall roughness and branch fracture angles. It includes a liquid preparation unit, a sand mixing unit, a fracture simulation unit, a flow monitoring unit, a roughness adjustment unit, and an angle adjustment unit. This invention dynamically switches the wall roughness state, with each adjustment segment's length being greater than or equal to the main fracture length to ensure uniform and stable flow channel wall roughness after switching. Simultaneously, the angle adjustment unit independently drives the branch fractures to rotate relative to the main fracture, achieving continuous and precise adjustment of the branch connection angle. This allows for the systematic simulation of diverse combinations of wall properties and complex fracture network structures on a single experimental device. Combined with real-time sand-carrying fluid flow data acquired by the flow monitoring unit, it enables quantitative research on the evolution of fluid turbulence intensity, proppant settling rate, and diversion transport patterns under the coupled effects of different roughness and branch angles, thereby obtaining high-precision visualization experimental data under the influence of multiple parameters.

Description

Technical Field

[0001] This invention belongs to the field of petroleum engineering and fluid mechanics technology, and relates to a visualization device for dynamically adjusting wall roughness and branch crack angle. Background Technology

[0002] In hydraulic fracturing, unconventional oil and gas development, and subsurface fluid transport studies, the flow patterns within fractures and the effectiveness of proppant placement directly determine the productivity of oil and gas wells. Real formation fractures commonly exhibit rough surfaces and complex branching structures, with strong coupling effects between surface roughness, branching fracture angles, fluid properties, and proppant transport. Therefore, conducting indoor visualization experiments is crucial for revealing the multiphysics mechanisms within fractures and optimizing fracturing operation parameters.

[0003] Currently, the experimental setup used in the study of fracture flow and proppant migration mainly includes a main channel and at least one branch channel. The channel walls are prefabricated with a fixed roughness, and the branch channel and the main channel are at a fixed angle. During the experiment, the proppant-carrying fluid, which is a mixture of proppant and fracturing fluid, is injected into the main channel. When the proppant-carrying fluid flows through the branch area, it is split, and some fluid and proppant enter the branch channel. The fluid flow and proppant placement process are recorded through the observation window to analyze the migration law within the fracture.

[0004] However, since the wall roughness and branch angle are both fixed structures, the experimental parameters are easily narrowly covered, resulting in a lack of systematic comparison of flow patterns under different roughness or branch angles. This limits the development of multi-parameter coupled experiments and thus affects the study of the wall effect on fluid flow and particle transport. Summary of the Invention

[0005] The purpose of this invention is to provide a visualization device for dynamically adjusting wall roughness and branch crack angle, which can expand the range of experimental parameters, ensure the conduct of multi-parameter coupled experiments, and thus accurately reflect the influence of wall effects on fluid flow and particle migration.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A visualization device for dynamically adjusting wall roughness and branch crack angle, comprising: The fluid preparation unit is used to mix the base fluid with additives to obtain fracturing fluid; The sand mixing unit, connected to the fluid preparation unit, is used to mix fracturing fluid and proppant to obtain sand-carrying fluid; The crack simulation unit includes a main crack and at least one branch crack. Both the main crack and the branch crack are hollow strip-shaped transparent structures. The main crack is open at the top and the main crack and the branch crack are set horizontally. One end of the main crack is connected to the outlet of the sand mixing unit. The branch crack is set on one side of the main crack. One end of the branch crack is rotatably connected to the side of the main crack and the two are connected. A flow monitoring unit is installed at the outlet of the sand mixing unit to monitor the flow rate of the sand-carrying fluid entering the main fracture in real time. The roughness adjustment unit includes a slide plate and a horizontal moving component. The slide plate is provided with a sliding seal at the upper opening of the main crack. Multiple adjustment sections are provided at the lower part of the slide plate along its length direction. The roughness of the multiple adjustment sections is different. The length of each adjustment section is greater than or equal to the length of the main crack. The horizontal moving component is used to drive the slide plate to move along the length direction of the main crack to adjust the roughness of the branch crack. An angle adjustment unit, connected to the branch crack, is used to drive the branch crack to rotate in order to adjust the angle of the branch crack.

[0007] The invention is further characterized by: The horizontal moving component includes: a fixed platform, positioned above the slide plate; a lead screw, horizontally positioned below the fixed platform, with both ends of the lead screw rotatably connected to the fixed platform; a slider, fixedly positioned above the slide plate, with the lead screw passing through the slider and threadedly connected to it, and the slider slidingly connected to the fixed platform via a guide; and a first motor, positioned below the fixed platform and close to one end of the lead screw, with the output end of the first motor connected to the end of the lead screw.

[0008] The angle adjustment unit includes: a transmission disc, which is horizontally positioned at the lower part of the branch crack and connected to the lower part of the branch crack, with the transmission disc located close to the main crack; and a second motor, which is positioned at the lower part of the transmission disc, with the output end of the second motor connected to the lower edge of the transmission disc, and the connection point between the output end of the second motor and the transmission disc located in the radial direction of the transmission disc close to the main crack.

[0009] A rotating seat is fixed between the transmission disc and the second motor. An angle scale is provided on the upper part of the rotating seat. The output end of the second motor passes through the rotating seat and the angle scale. A pointer is horizontally positioned near the upper part of the angle scale at the output end of the second motor.

[0010] The liquid preparation unit includes at least one liquid preparation tank, and a stirrer is installed inside the liquid preparation tank.

[0011] The sand mixing unit includes a sand mixing tank, the inlet of which is connected to the outlet of the liquid preparation tank via a first delivery pump, and the outlet of the liquid preparation tank is connected to the main fracture via a second delivery pump.

[0012] The flow monitoring unit includes a flow meter, which is located at the outlet of the second delivery pump.

[0013] The flow meter is electrically connected to a control terminal, which is electrically connected to the second delivery pump. The control terminal receives the flow rate value detected by the flow meter and compares the detected flow rate value with the preset flow rate value. Based on the comparison result, the speed of the second delivery pump is adjusted to keep the flow rate of the sand-carrying fluid entering the main fracture constant.

[0014] Both the main crack and the branch cracks are made of transparent acrylic material.

[0015] It also includes a recovery tank, the inlet of which is connected to the other end of the main fissure and the other end of the branch fissure via connecting pipes, and the outlet of the recovery tank is connected to the inlet of the liquid preparation tank via a third transfer pump.

[0016] The visualization device for dynamically adjusting wall roughness and branch crack angle according to the present invention has the following advantages: This invention enables a horizontally moving component to drive a sliding plate along the length of the main crack, allowing multiple adjustment sections with different roughnesses located at the bottom of the sliding plate to move relative to the flow channel inside the main crack, thus dynamically switching the wall roughness state. The length of each adjustment section is greater than or equal to the length of the main crack to ensure that the wall roughness of the flow channel is uniform and stable after switching. At the same time, an angle adjustment unit independently drives the branch cracks to rotate relative to the main crack to achieve continuous and precise adjustment of the branch connection angle. This allows for the systematic simulation of diverse combinations of wall properties and complex crack network structures on a single experimental device. Combined with the real-time sand-carrying fluid flow rate data acquired by the flow monitoring unit, it is possible to quantitatively study the evolution of fluid turbulence intensity, proppant settling rate, and diversion transport laws under the coupling effect of different roughness and branch angles, thereby obtaining high-precision visualized experimental data under the influence of multiple parameters. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 This is a top view of the horizontal moving component in this invention.

[0019] Figure 3 This is a schematic diagram of the angle adjustment unit in this invention.

[0020] Figure label: 1. Main crack, 2. Branch crack, 3. Liquid mixing tank, 4. Agitator, 5. First transfer pump, 6. Sand mixing tank, 7. Flow meter, 8. Slide plate, 9. Valve, 10. Rotary seat, 11. First motor, 12. Lead screw, 13. Control terminal, 14. Recovery tank, 15. Transmission plate, 16. Second motor, 17. Second transfer pump, 18. Third transfer pump. Detailed Implementation

[0021] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0022] like Figure 1 , Figure 2As shown, this invention provides a visualization device for dynamically adjusting wall roughness and branch fracture angle, including a liquid preparation unit, a sand mixing unit, a fracture simulation unit, a flow monitoring unit, a roughness adjustment unit, and an angle adjustment unit. The liquid preparation unit is used to mix the base fluid and additives to obtain fracturing fluid. The sand mixing unit is connected to the liquid preparation unit and is used to mix the fracturing fluid and proppant to obtain proppant-carrying fluid. The fracture simulation unit includes a main fracture 1 and at least one branch fracture 2. Both the main fracture 1 and the branch fracture 2 are hollow, strip-shaped transparent structures. The main fracture 1 is open at the top and the main fracture 1 and branch fracture 2 are horizontally arranged. One end of the main fracture 1 is connected to the outlet of the sand mixing unit. The branch fracture 2 is located on one side of the main fracture 1. One end is rotatably connected to the side of the main crack 1 and the two are in communication. The flow monitoring unit is set at the outlet of the sand mixing unit. The flow monitoring unit is used to monitor the flow rate of the sand-carrying liquid entering the main crack 1 in real time. The roughness adjustment unit includes a slide plate 8 and a horizontal moving component. The slide plate 8 is slidably sealed at the upper opening of the main crack 1. Multiple adjustment sections are set at the lower part of the slide plate 8 along its length direction. The roughness of the multiple adjustment sections is different. The length of each adjustment section is greater than or equal to the length of the main crack 1. The horizontal moving component is used to drive the slide plate 8 to move along the length direction of the main crack 1 to adjust the roughness of the branch crack 2. The angle adjustment unit is connected to the branch crack 2. The angle adjustment unit is used to drive the branch crack 2 to rotate to adjust the angle of the branch crack 2. This invention enables the sliding plate 8 to slide along the length of the main crack 1 via a horizontal moving component, allowing multiple adjustment sections with different roughnesses located at the bottom of the sliding plate 1 to move relative to the flow channel inside the main crack, thus dynamically switching the wall roughness state. The length of each adjustment section is greater than or equal to the length of the main crack to ensure that the wall roughness of the flow channel is uniform and stable after switching. At the same time, the angle adjustment unit independently drives the branch crack 2 to rotate relative to the main crack 1 to achieve continuous and precise adjustment of the branch connection angle. Thus, the invention can systematically simulate the diverse combinations of wall properties and complex crack network structures on a single experimental device. Combined with the real-time sand-carrying fluid flow data acquired by the flow monitoring unit, it can quantitatively study the evolution of fluid turbulence intensity, proppant settling rate, and diversion transport law under the coupling effect of different roughness and branch angles, thereby obtaining high-precision visualized experimental data under the influence of multiple parameters.

[0023] The main crack 1 and the branch crack 2 are connected by a flexible rubber sleeve, which facilitates sealing while ensuring that the branch crack 2 can swing to adjust its angle.

[0024] like Figure 2As shown, the horizontal moving assembly includes: a fixed platform, positioned above the slide plate 8; a lead screw 12, horizontally positioned below the fixed platform, with both ends of the lead screw 12 rotatably connected to the fixed platform; a slider, fixedly positioned above the slide plate 8, with the lead screw 12 passing through the slider and threadedly connected to it, and the slider slidingly connected to the fixed platform via a guide; and a first motor 11, positioned below the fixed platform and close to one end of the lead screw 12, with the output end of the first motor 11 connected to the end of the lead screw 12. By threading the lead screw 12 with the slider and constraining it with the guide, the rotational motion of the first motor 11 can be converted into a smooth linear slide of the slide plate 8 along the length of the main crack 1, thereby achieving precise position switching between the different roughness adjustment sections at the bottom of the slide plate 8 and the internal flow channel of the main crack 1.

[0025] like Figure 3 As shown, the angle adjustment unit includes: a transmission disk 15, which is horizontally disposed at the lower part of the branch crack 2 and connected to the lower part of the branch crack 2, and the position of the transmission disk 15 is close to the main crack 1; a second motor 16, which is disposed at the lower part of the transmission disk 15, and the output end of the second motor 16 is connected to the lower edge of the transmission disk 15. The connection point between the output end of the second motor 16 and the transmission disk 15 is located in the radial direction of the transmission disk 15 close to the main crack 1. By connecting the output end of the second motor 16 to the lower edge of the transmission disk 15 and the connection point being located in the radial direction of the transmission disk 15 close to the main crack 1, a large-angle range of continuous adjustment of the branch crack 2 can be achieved with a small driving torque, while making the drive structure compact and avoiding spatial interference with the main crack 1.

[0026] like Figure 3 As shown, a rotating seat 10 is fixedly arranged between the transmission disk 15 and the second motor 16. An angle scale is provided on the upper part of the rotating seat 10. The output end of the second motor 16 passes through the rotating seat 10 and the angle scale. A pointer is horizontally arranged near the upper part of the angle scale at the output end of the second motor 16. By fixing the rotating seat 10 between the transmission disk 15 and the second motor 16 and making the output end of the second motor 16 pass through the rotating seat 10 and the angle scale, and then horizontally arranging the pointer on its upper part, the real-time rotation angle of the branch crack 2 can be directly read during the driving process of the second motor 16, realizing the integrated integration of driving and angle measurement.

[0027] like Figure 1 As shown, the liquid preparation unit includes at least one liquid preparation tank 3, and a stirrer 4 is installed inside the liquid preparation tank 3.

[0028] like Figure 1 As shown, the sand mixing unit includes: a sand mixing tank 6, the inlet of which is connected to the outlet of the liquid preparation tank 3 via a first transfer pump 5, and the outlet of the liquid preparation tank 3 is connected to the main crack 1 via a second transfer pump 17.

[0029] like Figure 1As shown, the flow monitoring unit includes a flow meter 7, which is located at the outlet of the second delivery pump 17.

[0030] like Figure 1 As shown, the flow meter 7 is electrically connected to the control terminal 13, which is electrically connected to the second delivery pump 17. The control terminal 13 receives the flow rate value detected by the flow meter 7 and compares it with the preset flow rate value. Based on the comparison result, it adjusts the rotation speed of the second delivery pump 17 to keep the flow rate of the sand-carrying fluid entering the main fracture 1 constant. By forming a closed-loop control by electrically connecting the flow meter 7, the control terminal 13, and the second delivery pump 17, the rotation speed of the second delivery pump 17 can be automatically adjusted according to the real-time detected flow rate value and the preset value to keep the flow rate of the sand-carrying fluid entering the main fracture 1 constant, thereby eliminating the interference of flow fluctuations on the experimental results.

[0031] like Figure 1 As shown, both the main fracture 1 and the branch fracture 2 are made of transparent acrylic material. By using transparent acrylic material for both the main fracture 1 and the branch fracture 2, the light transmittance is ≥92%, and it can withstand an experimental pressure of 0.5MPa, ensuring no cracking or leakage during the experiment. At the same time, it has good visualization effect, which is convenient for observing the fluid flow pattern and proppant migration trajectory inside the fracture. The cross-section of the main fracture 1 is rectangular, with a width of 50mm, a height of 10mm, and a length of 500mm. The cross-section of the branch fracture 2 is consistent with the flow channel of the main fracture, with a length of 300mm. Two branch fractures are set, symmetrically arranged on both sides of the main fracture 1, forming a bifurcated flow channel with the main fracture 1, simulating the natural branch fracture structure of the strata.

[0032] Among them, the skateboard 8 is a flat plate made of POM (polyoxymethylene) material with a thickness of 12mm. Its width is adapted to the width of the main crack channel, and it has good wear resistance, rigidity and sliding performance. It is not easily deformed and can be used for a long time.

[0033] like Figure 1 As shown, the present invention provides a visualization device for dynamically adjusting the wall roughness and branch crack angle, which further includes a recovery tank 14. The inlet of the recovery tank 14 is connected to the other end of the main crack 1 and the other end of the branch crack 2 through connecting pipes. The outlet of the recovery tank 14 is connected to the inlet of the liquid preparation tank 3 through a third delivery pump 18. By setting up the recovery tank 14 and connecting its inlet to the outlet of the main crack 1 and the branch crack 2, and its outlet to the inlet of the liquid preparation tank 3, the sand-carrying liquid can be recycled, reducing experimental costs and waste liquid discharge.

[0034] like Figure 1As shown, two mixing tanks 3 are preferably connected in parallel. Each mixing tank 3 has a volume of 80L and is made of 304 stainless steel, which has good corrosion resistance and can withstand a working pressure of 0.6MPa, suitable for the scale of routine laboratory experiments and the characteristics of fracturing fluid media (such as those containing acid or polymer additives). The mixing tank adopts a closed pressure-bearing structure with a sealing cap at the tank opening. A rubber sealing ring is used to seal the sealing cap and the tank opening to prevent fracturing fluid evaporation and the entry of external impurities, ensuring the stability of the experimental fluid properties. A chemical dosing port and a vent valve are reserved at the top of the mixing tank. The chemical dosing port is used to add various additives (such as thickeners, crosslinking agents, and breaker agents), and the vent valve is used to balance the pressure inside and outside the tank, avoiding excessive pressure inside the tank that may cause liquid leakage, or excessive pressure that may affect fluid delivery. The inlets of the two liquid preparation tanks 3 are connected to the outlet of the third transfer pump 18, and the outlets of the two liquid preparation tanks 3 are connected to the inlet of the first transfer pump 5. By setting the two liquid preparation tanks 3 in parallel and connecting the third transfer pump 18 to their inlets and the first transfer pump 5 to their outlets, it is possible to achieve alternating preparation and continuous supply of base liquid and additives, avoid interruption and waiting when preparing liquids in a single tank, and improve experimental efficiency.

[0035] Each liquid preparation tank is equipped with a level gauge and a temperature sensor on three sides. The level gauge is used to monitor the liquid level in the tank in real time to prevent overflow due to excessively high liquid level or idling of the pump due to excessively low liquid level. The temperature sensor is used to collect the liquid temperature in the tank in real time. The temperature measurement range is 0℃~150℃ with an accuracy of ±0.5℃. It can promptly report changes in fluid temperature and provide a basis for adjusting experimental parameters.

[0036] The stirrer 4 is driven by a variable frequency speed-regulating motor with a power of 1.5kW and a speed adjustment range of 0r / min to 300r / min. The speed can be flexibly adjusted according to the fluid viscosity and mixing requirements to ensure thorough mixing of the fracturing fluid base and additives, avoiding uneven local concentrations that could affect experimental results. The stirrer's blades adopt a three-blade structure with a diameter of 200mm and a thickness of 5mm, made of stainless steel. Designed to fit snugly against the inner wall of the mixing tank, the gap between the blades and the tank wall is controlled at 5mm to 8mm, effectively preventing fluid adhesion to the tank wall and ensuring uniform mixing. The stirrer and the mixing tank's sealing cover are connected by a mechanical seal, with the sealing surface made of polytetrafluoroethylene (PTFE), possessing excellent wear and corrosion resistance, preventing liquid leakage from the gap between the stirring shaft and the sealing cover during stirring. In this embodiment, when preparing the guar gum fracturing fluid, first inject clean water into the mixing tank, turn on the stirrer to 200 r / min, slowly add guar gum powder, and continue stirring for 30 minutes until the guar gum is completely dissolved. Then, add the crosslinking agent and the breaker through the dosing port, adjust the speed to 150 r / min, and continue stirring for 15 minutes to form a uniform and stable fracturing fluid.

[0037] like Figure 1As shown, each mixing tank 3 has a valve 9 at its inlet, outlet, the first transfer pump 5, the sand mixing tank 6, and the recovery tank 14. These valves are corrosion-resistant ball valves made of 304 stainless steel with a PTFE sealing surface, providing excellent corrosion resistance and sealing performance. They are suitable for various fracturing fluid media, preventing valve corrosion and sealing failure. The valves are mainly located at the inlet and outlet pipes and branch switching points of the mixing tank 3. Through combined valve switching, various operating conditions such as "clean water + base fluid," "base fluid + additives," and "switching between different fracturing fluid formulations" can be achieved. When switching fracturing fluid formulations, simply close the outlet valve of the current mixing tank 3 and open the outlet valve of another mixing tank 3 to quickly switch between different formulations.

[0038] The mixing tank 6, with a volume matching the liquid preparation tank, has an 80L capacity and is made of transparent plexiglass with a light transmittance of ≥92%, facilitating observation of the internal mortar mixing state during experiments and timely detection and adjustment of issues such as proppant settling and stratification. The mixing tank 6 has an inlet and a stirring port at the top; the inlet is for adding proppant, and the stirring port is for installing the stirring mechanism. The bottom has an outlet connected to the pump inlet for transporting the mixed mortar to the pipeline. The mixing tank 6 is equipped with a low-speed stirring mechanism. The stirring motor has a power of 1.0kW, a speed adjustment range of 0r / min to 100r / min, and a three-bladed impeller structure with a blade diameter of 200mm made of stainless steel and a helix angle of 30°. This reduces shear damage to the proppant particles and ensures thorough mixing of the proppant and fracturing fluid, preventing rapid proppant settling and stratification. In this embodiment, 20 / 40 mesh quartz sand was used as the proppant, with a sand-to-liquid mass ratio of 10%. The stirring speed was set to 60 r / min, and continuous stirring was carried out during the experiment to ensure uniform mortar concentration and no particle settling. The inner wall of the sand mixing tank 6 was coated with an anti-fouling coating made of polytetrafluoroethylene, which effectively prevented mortar from adhering to the tank wall, reduced material waste, and facilitated cleaning after the experiment.

[0039] The flow meter 7 is an electromagnetic flow meter with an accuracy class of 0.5 and a measurement range of 0 L / min to 50 L / min. It can monitor the instantaneous and cumulative flow of fluid in real time, with a measurement error of ≤±0.5%, meeting the quantitative control requirements of the experiment. The electromagnetic flow meter adopts a flange connection, and its installation position is ≥1.5m away from the outlet of the second transfer pump 17 to avoid the vibration of the second transfer pump 17 affecting the flow measurement accuracy. The flow meter 7 is connected to the control terminal 13 via an RS485 bus, which can transmit the real-time acquired flow signal to the control terminal 13. The preset flow value for the routine experiment is 10 L / min. When the flow meter 7 detects a flow deviation exceeding ±5%, the control terminal 13 immediately sends a signal to adjust the speed of the second transfer pump 17 until the flow rate returns to the target value.

[0040] Limit switches are installed at the lower part of the fixed platform near both ends of the slide plate 8 and near the position between two adjacent adjustment sections. A stop block is installed on the upper part of the slide plate 8 near one of the limit switches. Multiple limit switches are electrically connected to the control terminal. When the control terminal 13 issues a command to start the first motor 11 to drive the slide plate 8 to slide, the stop block fixed on the upper part of the slide plate 8 moves synchronously with the slide plate 8. When the stop block moves to the position of a certain limit switch, the stop block triggers the limit switch, and the triggered limit switch sends a positioning signal to the control terminal 13. The control terminal 13 identifies the current position of the slide plate 8 according to the received signal and controls the first motor 11 to stop rotating, so that the adjustment section of the lower part of the slide plate 8 corresponding to the roughness is exactly stopped at the flow channel position of the main crack 1. The limit switches installed at the lower part of the fixed platform near both ends of the slide plate 8 are used to limit the extreme stroke of the slide plate 8 to prevent the slide plate 8 from exceeding the sliding range. The limit switches installed near the position between two adjacent adjustment sections are used to realize the precise positioning and automatic switching of different roughness adjustment sections.

[0041] The limit switch is a magnetic proximity switch, model TL-Q5MC1, which can adapt to sandy and humid experimental conditions, can work stably for a long time, and is not easily damaged.

[0042] Among them, the control terminal 13 is a PLC controller, which is a Siemens S7-1200 series, model 1214C DC / DC / DC.

[0043] Working principle: First, the base fluid and additives are mixed evenly in the mixing tank 3 by the agitator 4 to form fracturing fluid. The fracturing fluid is then transported to the sand mixing tank 6 by the first delivery pump 5. In the sand mixing tank 6, the fracturing fluid is mixed with proppant to form proppant-carrying fluid. The proppant-carrying fluid is then transported to the main fracture 1 by the second delivery pump 17 via the flow meter 7. The flow meter 7 detects the flow rate in real time and feeds it back to the control terminal 13. The control terminal 13 compares the detected value with the preset value and adjusts the speed of the second delivery pump 17 to keep the flow rate of the proppant-carrying fluid entering the main fracture 1 constant. After the proppant-carrying fluid enters the main fracture 1, part of the proppant-carrying fluid flows directly along the main fracture 1 to the other end, while part of the proppant-carrying fluid is diverted at the connection node between the branch fracture 2 and the main fracture 1 and enters the branch fracture 2. The flow of the proppant-carrying fluid and the proppant placement process are observed through the main fracture 1 and the branch fracture 2, which are made of transparent acrylic material.

[0044] During the experiment, the first motor 11 drives the lead screw 12 to rotate, and the lead screw 12 drives the slider and slide plate 8 to slide along the length of the main crack 1, so that the adjustment section with different roughness at the bottom of the slide plate 8 is opposite to the internal flow channel of the main crack 1, thereby dynamically switching the roughness of the wall of the main crack 1. The second motor 16 drives the transmission disk 15 to rotate, and the transmission disk 15 drives the branch crack 2 to rotate relative to the main crack 1. At the same time, the output end of the second motor 16 passes through the rotating seat 10 and the angle scale to drive the pointer to rotate. The real-time angle of the branch crack 2 is read by the position indicated by the pointer on the angle scale. The sand-carrying fluid flowing through the main crack 1 and the branch crack 2 finally flows into the recovery tank 14 respectively, and the fluid in the recovery tank 14 is returned to the liquid distribution tank 3 for recycling.

[0045] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A visualization device for dynamically adjusting wall roughness and branch crack angle, characterized in that, include: The fluid preparation unit is used to mix the base fluid with additives to obtain fracturing fluid; The sand mixing unit, connected to the fluid preparation unit, is used to mix fracturing fluid and proppant to obtain sand-carrying fluid; The crack simulation unit includes a main crack and at least one branch crack. Both the main crack and the branch crack are hollow, transparent strip structures. The main crack is open at the top and the main crack and the branch crack are arranged horizontally. One end of the main crack is connected to the outlet of the sand mixing unit. The branch crack is located on one side of the main crack and one end of the branch crack is rotatably connected to the side of the main crack and the two are in communication. A flow monitoring unit is installed at the outlet of the sand mixing unit to monitor the flow rate of the sand-carrying fluid entering the main fracture in real time. The roughness adjustment unit includes a sliding plate and a horizontal moving component. The sliding plate is slidably sealed at the upper opening of the main crack. The lower part of the sliding plate is provided with multiple adjustment sections along its length direction. The roughness of the multiple adjustment sections is different. The length of each adjustment section is greater than or equal to the length of the main crack. The horizontal moving component is used to drive the sliding plate to move along the length direction of the main crack to adjust the roughness of the branch crack. An angle adjustment unit, connected to the branch crack, is used to drive the branch crack to rotate in order to adjust the angle of the branch crack.

2. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 1, characterized in that, The horizontal moving assembly includes: a fixed platform, disposed above the slide plate; a lead screw, horizontally disposed below the fixed platform, with both ends of the lead screw rotatably connected to the fixed platform; a slider, fixedly disposed above the slide plate, with the lead screw passing through the slider and threadedly connected to the slider, and the slider being slidably connected to the fixed platform via a guide; and a first motor, disposed below the fixed platform and positioned close to one end of the lead screw, with the output end of the first motor connected to the end of the lead screw.

3. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 1, characterized in that, The angle adjustment unit includes: a transmission disc, horizontally disposed at the lower part of the branch crack and connected to the lower part of the branch crack, the transmission disc being positioned close to the main crack; and a second motor, disposed at the lower part of the transmission disc, the output end of the second motor being connected to the lower edge of the transmission disc, the connection point between the output end of the second motor and the transmission disc being located in the radial direction of the transmission disc close to the main crack.

4. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 3, characterized in that, A rotating base is fixedly installed between the transmission disc and the second motor. An angle scale is provided on the upper part of the rotating base. The output end of the second motor passes through the rotating base and the angle scale. A pointer is horizontally installed at the output end of the second motor near the upper part of the angle scale.

5. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 1, characterized in that, The liquid preparation unit includes at least one liquid preparation tank, and a stirrer is provided inside the liquid preparation tank.

6. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 5, characterized in that, The sand mixing unit includes a sand mixing tank, the inlet of which is connected to the outlet of a liquid preparation tank via a first delivery pump, and the outlet of the liquid preparation tank is connected to the main crack via a second delivery pump.

7. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 6, characterized in that, The flow monitoring unit includes a flow meter, which is located at the outlet of the second delivery pump.

8. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 7, characterized in that, The flow meter is electrically connected to a control terminal, which is electrically connected to the second delivery pump. The control terminal receives the flow rate value detected by the flow meter, compares the detected flow rate value with a preset flow rate value, and adjusts the speed of the second delivery pump according to the comparison result to keep the flow rate of the sand-carrying fluid entering the main fracture constant.

9. The visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 1, characterized in that, Both the main crack and the branch cracks are made of transparent acrylic material.

10. A visualization device for dynamically adjusting wall roughness and branch crack angle according to claim 1, characterized in that, It also includes a recovery tank, the inlet of which is connected to the other end of the main fissure and the other end of the branch fissure via connecting pipes, and the outlet of the recovery tank is connected to the inlet of the liquid preparation tank via a third transfer pump.

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