A device and method for evaluating the transport performance of dynamic seam width proppant

Abstract

A device and method for evaluating the migration performance of dynamic fracture width proppant, relating to the field of oil and gas development technology, is disclosed. The device includes a measuring assembly formed by front and rear metal shells connected by springs, used to fix a convex glass plate simulating a fracture. When the measuring assembly performs performance evaluation, the device simultaneously withstands external confining pressure and a restoring force generated by the springs. This invention, by introducing a spring structure between the parallel plates simulating a fracture, effectively simulates the stress effect generated by the elastic recovery effect of the fracture itself in actual formations, while considering the application of in-situ stress. This realistically reflects the adaptive adjustment effect of fracture width under actual conditions. Compared to the stress simulation method in the prior art, which only represents the stress condition of fractures by applying in-situ stress to simulate fractures, this method can better restore the actual stress change state of fractures in formations, resulting in more accurate and realistic simulation results.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and specifically to a device and method for evaluating the dynamic joint width proppant migration performance. Background Technology

[0002] Hydraulic fracturing, a crucial technique in unconventional oil and gas reservoir development, relies heavily on the effective migration and placement of proppant within fractures for its success. Currently, laboratories commonly employ visualization simulation devices composed of parallel transparent glass plates to observe proppant migration behavior. However, as unconventional oil and gas reservoir development moves towards deeper, more geologically complex onshore and marine reservoirs, the limitations of existing simulation devices are becoming increasingly apparent. 1. Inability to accurately reproduce the formation fracture opening process in hydraulic fracturing: Existing simulation devices with dynamic fracture opening and closing functions mostly rely on external gas injection pressurization or mechanical structures to forcibly adjust the fracture plate spacing. This method of changing the fracture width through external artificial intervention cannot simulate the real stress relationship between the pumped fluid and the rock fracture wall, ignoring the mechanical evolution characteristics of fractures in actual working conditions, where the internal high-pressure fluid overcomes the minimum principal stress of the formation and thus opens spontaneously.

[0003] 2. Existing devices lack a comprehensive simulation mechanism for the influence of geomechanical parameters on fracture width. Hydraulic fracture width depends not only on the minimum horizontal principal stress of the formation but also significantly on the Young's modulus of the rock. During fracture opening, the fluid pressure within the fracture must overcome the minimum principal stress of the formation and the resistance stress generated by rock deformation to achieve fracture propagation. However, existing visualization simulation devices often treat the fracture walls as rigid bodies, assuming that fracture width changes depend solely on the difference between confining pressure and fluid pressure. In real formations, as fracture width increases, the elastic deformation resistance of the rock also increases, thus limiting unlimited fracture expansion. This complex dynamic fracture width evolution phenomenon is particularly pronounced in the ultra-high pressure environment of deep-sea reservoirs. Although existing devices simulate formation confining pressure through external pressurization, they do not consider elastic constraints. Therefore, if the pumping pressure remains constant, the fracture width will continue to increase once it opens, affecting the accuracy of evaluating proppant migration and placement patterns.

[0004] 3. Neglecting the heat exchange effect under deep geological conditions: Existing equipment typically only preheats the proppant-carrying fluid before pumping it into simulated fractures at room temperature. During this process, as the proppant-carrying fluid moves from the fracture tip to the fracture tip, heat is dissipated to the surroundings, the temperature decreases continuously, and the fluid viscosity gradually increases. However, under actual operating conditions, due to the high temperature of the fracture wall, the temperature of the proppant-carrying fluid should continuously rise and eventually reach thermal equilibrium, and its viscosity should gradually decrease accordingly. For offshore oilfield development, the geothermal gradient in the marine environment is generally higher than that in the terrestrial environment. If this heat exchange effect is ignored, the rheological evolution of the fracturing fluid within the fracture cannot be accurately reflected, leading to a bias in the evaluation of proppant settling behavior.

[0005] Therefore, there is an urgent need for a device that can overcome the above-mentioned defects and achieve an objective and realistic simulation and evaluation of the proppant migration and placement law in cracks. Summary of the Invention

[0006] In view of this, the present invention proposes a device and method for evaluating the dynamic fracture width proppant migration performance, which can accurately reflect the formation stress effect, including the elastic recovery effect of the fracture itself, and significantly improve the accuracy of the simulation.

[0007] To solve at least one of the above-mentioned technical problems, the present invention provides a dynamic joint width proppant transport performance evaluation device, comprising a water storage tank, a constant flow pump, a pre-liquid tank, a sand-carrying liquid tank, a temperature control component, a confining pressure component, a testing component, a waste liquid tank, and a back pressure pump. The connection or distribution of each component can refer to similar simulation devices in the prior art. The water storage tank is connected to the inlet of the testing component. A branch-connected constant flow pump and a parallel-distributed pre-liquid tank and sand-carrying liquid tank are sequentially arranged on the connecting pipeline. The testing component is also connected to the temperature control component and the confining pressure component. The outlet of the testing component is sequentially connected to the back pressure pump and the waste liquid tank. The testing component includes a front metal shell, a rear metal shell, a spring, a sealing frame, a boss glass plate, a slider, a fixed base, a displacement sensor, and a slide rail base, wherein: Both the front and rear metal shells are cubes with a groove on one side. They are arranged parallel to each other on two sets of strip-shaped sliders with their grooved surfaces facing each other. The front and rear metal shells are connected by multiple sets of symmetrically distributed springs. Two sets of sliders are arranged in parallel and spaced apart on the slide rail base. They can move along the slide rail on the slide rail base, so that the front metal shell and the rear metal shell on the slider can be translated normally. A strip-shaped fixed seat is arranged in parallel between the two sets of sliders. The displacement sensor is set on the slider and can detect the degree of displacement of the slider on the slide rail base. The same protruding glass plate can be installed in the grooves inside the front metal shell and the rear metal shell. The protruding glass plate is a glass structure with a rectangular protrusion on one side. When the two sets of protruding glass plates are installed in the front metal shell and the rear metal shell respectively, they remain parallel and the rectangular protrusions remain facing each other. The sealing frame is a rectangle with a large through hole in the middle, which can fit precisely with the boss of the boss glass plate. The sealing frame is set on the fixed base, parallel to the boss glass plate, and the large through hole of the sealing frame is directly opposite the boss of the two sets of boss glass plates. The sealing frame is also provided with two sets of connecting large through holes and two pairs of sealing frame through holes on the sides. The two sets of sealing frame through holes are on the same horizontal plane and symmetrically distributed along the large through holes. The two sets of sealing frame through holes can be connected to the liquid inlet and outlet of the test component, respectively. When the two sets of boss glass plates move to the point of boss contact, the contact surface of the boss is located on the axis of the sealing frame through hole, and at this time, the multiple sets of springs are exactly in a natural equilibrium state.

[0008] One embodiment of the present invention is that the protruding glass plate is provided with a double-headed bolt hole. When the protruding glass plate is fitted in the front metal shell or the rear metal shell, a double-headed bolt is provided in the double-headed bolt hole that can penetrate the protruding glass plate and the front metal shell or the rear metal shell, and the double-headed bolt is fixed by a locking nut on the surface of the front metal shell or the rear metal shell.

[0009] In one embodiment of the present invention, multiple sets of heating rods are provided on the front metal shell and the rear metal shell, and the heating rods are connected to the temperature control component; a heat insulation layer is also provided on the surfaces of the spring that contact the front metal shell and the rear metal shell respectively.

[0010] One embodiment of the present invention is that the boss side of the boss glass plate is provided with a spherical groove. When two sets of bosses are in contact, the two sets of spherical grooves can form a complete spherical groove that connects to the sealing frame through hole on the inlet side of the test component.

[0011] Furthermore, an observation window is provided on the rear metal shell, and the rear metal shell is fixedly connected to an external support frame. A camera component is provided on the support frame, and the camera component can collect image data between the boss glass plates through the observation window and transfer it to a computer.

[0012] One embodiment of the present invention is that a pressure plate is provided on the outside of the front metal shell, and the pressure plate is connected to the pressure assembly to provide normal pressure to the front metal shell.

[0013] One embodiment of the present invention is that the displacement of the slider is not greater than the thickness of the sealing frame.

[0014] Furthermore, this invention also discloses a method for evaluating the dynamic seam width proppant transport performance based on the above-mentioned device, comprising the following steps: Step S1: Assemble the overall experimental device and test components. The protruding glass plate is embedded into the grooves of the front metal shell and the rear metal shell respectively. The double-headed bolt is inserted into the double-headed bolt hole, passed through the front metal shell and the rear metal shell, and then fixed with a lock nut. At the same time, electric heating rods are set on the front metal shell and the rear metal shell respectively to obtain the front metal shell assembly and the rear metal shell assembly. Step S2: Fix the front metal shell assembly and the rear metal shell assembly onto the two sets of sliders respectively, and make the side of the rear metal shell away from the boss glass plate abut against the support frame to form a fixed constraint, and make the side of the front metal shell away from the boss glass plate abut against the surrounding pressure plate. Step S3: Set the sealing frame on the fixed base and adjust the position of the front metal shell assembly until the two sets of protruding glass plate protruding structures are just in contact inside the sealing frame, so that the spherical groove composed of the spherical groove is connected to the sealing frame through hole on the side near the inlet of the test component. Install symmetrically distributed springs on the heat insulation layer between the front metal shell assembly and the rear metal shell assembly, and ensure that the springs are in a natural balance state. Record the data of the displacement sensor at this time as 0. Step S4: Activate the confining pressure assembly to apply a preset normal pressure to the front metal housing assembly. The glass plates between the protruding surfaces change from being in contact to being under pressure, and the temperature control component heats the glass plates between the protruding surfaces to the simulated temperature. Step S5: The pre-fluid is pumped into the test assembly using a constant flow pump. The fluid enters the test assembly through the spherical groove formed by the spherical groove and is pumped between the two sets of boss glass plates, gradually increasing the pressure. When the pressure is higher than... At this time, the two sets of raised glass plates are opened under pressure, causing the front metal shell assembly and its corresponding slider to move along the slide rail on the slide rail base. The spring changes from a natural equilibrium state to a stretched state. The displacement data of the slider is recorded by the displacement sensor. When the data stabilizes, the displacement sensor data at this time is recorded as the initial crack width. At this point, the pumping pressure is the crack initiation pressure. ; Step S6: Maintain pumping status, switch to the sand-carrying fluid injection path, and set the pumping displacement to [value missing]. The sand-carrying fluid is injected into the simulated fracture channel, and the pumping time is... Record displacement sensor data as crack width The camera module transmits the captured images to the computer via a data cable; Step S7: Turn off the constant flow pump, stop pumping fluid, turn on the back pressure pump to slowly depressurize and simulate the fracturing fluid backflow process. At this time, the front metal shell slowly approaches the rear metal shell under the action of spring restoring force and external confining pressure. After the fluid is backflowed, it enters the waste liquid tank. Step S8: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and set the pump discharge rate to... ,and The pumping time is Record displacement sensor data as crack width And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump to stop the pumping of fluid, turn on the back pressure pump to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank after backflow; Step S9: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and increase the pump discharge rate to... ,and The pumping time is Record displacement sensor data as crack width And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump to stop the pumping of fluid, turn on the back pressure pump to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank after backflow; Step S10: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and reduce the pump discharge rate to... ,and The pumping time is Record displacement sensor data as crack width ,and Simultaneously record the captured images, then turn off the constant flow pump to stop the pumping of fluid, turn on the back pressure pump to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank after backflow.

[0015] The technical effects achieved by this invention are: This invention introduces a spring structure between parallel plates simulating a crack. While considering in-situ stress, it also effectively simulates the stress effect generated by the elastic recovery effect of the crack itself in the actual stratum. It realistically reflects the crack width adaptive adjustment effect under actual conditions. Compared with the stress simulation method in the prior art that only simulates in-situ stress to represent the stress situation of the crack, the simulation method of this invention can better restore the actual stress change state of the crack in the stratum, and the simulation results are more accurate and realistic. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the test components in this invention; Figure 3 This is a schematic diagram of the measurement structure in the test component of the present invention; Figure 4 This is a schematic diagram of the sliding structure in the test component of the present invention; Figure 5 This is a schematic diagram of the distribution structure of the boss glass plate in this invention; Figure 6 This is a schematic diagram of the distribution structure of the sealing frame and the boss glass plate in this invention; In the diagram, 1-Water storage tank, 2-Constant flow pump, 3-Pre-liquid tank, 4-Sand-carrying liquid tank, 5-Temperature control component, 6-Containing pressure component, 7-Test component, 8-Heating rod, 9-Insulation layer, 10-Front metal shell, 11-Rear metal shell, 12-Spring, 13-Sealing frame, 14-Leading glass plate, 15-Support frame, 16-Camera component, 17-Computer, 18-Waste liquid tank, 19-Back pressure pump, 20-Locking nut, 21-Double-ended bolt, 22-Observation window, 23-Slider, 24-Fixed seat, 25-Displacement sensor, 26-Slide rail base, 27-Spherical groove, 28-Sealing frame through hole, 29-Double-ended bolt hole, 30-Containing pressure plate. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0020] See Figure 1A dynamic crack width proppant transport performance evaluation device includes a water storage tank 1, a constant flow pump 2, a pre-fluid tank 3, a sand-carrying liquid tank 4, a temperature control component 5, a confining pressure component 6, a testing component 7, a waste liquid tank 18, a back pressure pump 19, and some flow meters and pressure gauges. The above structure is a conventional setup in existing crack simulation experimental devices. Specifically, the water storage tank 1 is connected to the inlet of the testing component 7. The connecting pipeline is sequentially equipped with a branch-connected constant flow pump 2 and a parallel-distributed pre-fluid tank 3 and sand-carrying liquid tank 4. The type of injected fluid can be adjusted by switching pipelines. The testing component 7 is also connected to the temperature control component 5 and the confining pressure component 6 respectively. Referring to similar devices in the prior art, the experimental temperature and pressure are controlled. The outlet of the testing component 7 is sequentially connected to the back pressure pump 19 and the waste liquid tank 18 to provide the required pressure for the experimental conditions and collect waste liquid. The flow rate and pressure changes at the fluid outlet are monitored in real time by the flow meters and pressure gauges.

[0021] See Figure 3 , Figure 4 The test component 7 includes a front metal shell 10, a rear metal shell 11, a spring 12, a sealing frame 13, a boss glass plate 14, a slider 23, a fixed base 24, a displacement sensor 25, and a slide rail base 26, wherein: Both the front metal shell 10 and the rear metal shell 11 are cubes with a groove on one side. They are arranged parallel to each other on two sets of strip-shaped sliders 23 with their groove faces facing each other. The front metal shell 10 and the rear metal shell 11 are connected by multiple sets of symmetrically distributed springs 12. The same protruding glass plate 14 can be installed in the groove inside the front metal shell 10 and the rear metal shell 11. The protruding glass plate 14 is a glass structure with a rectangular protrusion on one side. When the two sets of protruding glass plates 14 are installed in the front metal shell 10 and the rear metal shell 11 respectively, they remain parallel and the rectangular protrusions remain facing each other.

[0022] A confining pressure plate 30 is provided on the outside of the metal shell 10. The confining pressure plate 30 is connected to the confining pressure assembly 6 and is used to provide normal pressure to the front metal shell 10. The confining pressure assembly 6 can refer to the confining pressure equipment in the prior art to provide pressure to the confining pressure plate 30 and further drive the front metal shell 10 to move under pressure.

[0023] When the two sets of protruding glass plates 14 move to contact the protruding surfaces, spring 12 is in a state of natural equilibrium. At this time, the protruding glass plates 14 are only subjected to the closing stress provided by the stress loading system. During the experiment, when the pumped fluid pressure is greater than the closing stress, the protruding glass plates 14 gradually open from the closed state to form the simulated crack width. At this time, spring 12 changes from the natural equilibrium state to the tensile state and provides elastic restoring force. At this time, the fluid pressure is greater than the sum of the closing stress and the elastic restoring force. The elastic restoring force further increases due to the continuous stretching of spring 12 as the crack width increases. When the crack width increases to a certain extent, the fluid pressure equals the sum of the closing stress and the elastic restoring force, at which point the crack width remains at a certain size and unchanged. Among the multiple sets of springs 12, the number of springs 12 and the elastic coefficient can be determined according to the Young's modulus of the simulated formation rock.

[0024] In some embodiments, the protruding glass plate 14 is provided with a double-ended bolt hole 29. When the protruding glass plate 14 is fitted into the front metal shell 10 or the rear metal shell 11, a double-ended bolt 21 is provided in the double-ended bolt hole 29, which can penetrate the protruding glass plate 14 and the front metal shell 10 or the rear metal shell 11. The double-ended bolt 21 is fixed by a locking nut 20 on the surface of the front metal shell 10 or the rear metal shell 11. The protruding glass plate 14 is detachably fixed in the front and rear metal shells by the double-ended bolt 21, which is convenient for maintenance and disassembly.

[0025] The protruding glass plate 14 is used to simulate extrusion cracks. After the protruding glass plate 14 is respectively fitted into the front metal shell 10 and the rear metal shell 11, the protruding surfaces of the opposing protruding glass plates 14 can contact or separate when the metal shells move towards each other. Figure 5 As shown, the surface of the boss of the boss glass plate 14 is further provided with a spherical groove 27. When the two sets of bosses are in contact, the two sets of spherical grooves 27 can form a complete spherical groove that connects to the sealing frame through hole 28 on the inlet side of the test component 7. In this way, under the condition that the front metal shell 10 and the rear metal shell 11 are subjected to external confining pressure, the two sets of boss spherical grooves 27 will continue to be in contact, forming a stable spherical groove, which facilitates the introduction of fluid in the sealing frame through hole 28 into it. This allows the fluid to be better guided between the clamped boss surfaces.

[0026] Two sets of sliders 23 are arranged in parallel on the slide rail base 26, and can move along the slide rail on the slide rail base 26, so that the front metal shell 10 and the rear metal shell 11 on the sliders 23 are translated normally. A strip-shaped fixing seat 24 is arranged in parallel between the two sets of sliders 23. The displacement sensor 25 is set on the slider 23 and can detect the degree of displacement of the slider 23 on the slide rail base 26. When the pumping volume is changed, the boss glass plate 14 squeezes the front metal shell 10 and the rear metal shell 11 along the slide rail base 26 due to the change of pumping pressure, resulting in a smooth movement along the normal direction of the metal shell. The displacement sensor 25 will record the displacement change between the slider 23 and the metal shell and convert it into real-time dynamic seam width data.

[0027] See Figure 6 The sealing frame 13 is a rectangle with a large through hole in the middle, which can fit precisely with the boss of the boss glass plate 14. The sealing frame 13 is set on the fixed base 24, parallel to the boss glass plate 14, and the large through hole of the sealing frame 13 is directly opposite the boss of the two sets of boss glass plates 14. The sealing frame 13 is also provided with two sets of connecting large through holes and two pairs of side sealing frame through holes 28. The two sets of sealing frame through holes 28 are on the same horizontal plane and symmetrically distributed along the large through holes. The two sets of sealing frame through holes 28 can be connected to the liquid inlet and outlet of the test component 7, respectively. When the two sets of boss glass plates 14 move to the point of boss contact, the contact surface of the boss is located on the axis of the sealing frame through hole 28. When setting up the experimental device, it should be ensured that the two sets of boss glass plates 14 are in contact in the large through hole of the sealing frame 13, and the spherical groove 27 formed by the two should also be directly opposite the sealing frame through hole 28, that is, the contact surface of the boss is located on the axis of the sealing frame through hole 28. Obviously, to avoid leakage, the allowable displacement of the slider 23 should not exceed the thickness of the sealing frame 13. Meanwhile, to ensure a good seal, a partial sealing structure, such as a rubber sealing ring or sealant, can be provided on the contact surface between the boss glass plate 14 and the sealing frame 13. The entire test assembly 7 can also be housed in a sealed container to prevent losses caused by leakage.

[0028] In some embodiments, multiple sets of heating rods 8 are provided on the front metal shell 10 and the rear metal shell 11, and the heating rods 8 are connected to the temperature control component 5; a heat insulation layer 9 is also provided on the surface of the spring 12 that contacts the front metal shell 10 and the rear metal shell 11 respectively. Referring to the heating method in the prior art, the present invention uses detachable heating rods 8 to heat the metal shell and the boss glass plate 14. In order to ensure the heating effect, thermal conductive silicone grease can be applied between the boss glass plate 14 and the front and rear metal shells to improve the heating effect on the boss glass plate 14. The purpose of using the heat insulation layer 9 is to minimize the impact of temperature changes on the material properties of the spring 12 and ensure the accuracy of the test. In addition, the width of the heat insulation layer 9 should not affect the contact between the two sets of boss glass plates 14.

[0029] See Figure 2 , Figure 3 In some embodiments, an observation window 22 is provided on the rear metal shell 11, and the rear metal shell 11 is fixedly connected to an external support frame 15 to provide a reaction force and constrain the movement of the rear metal shell 11. A camera assembly 16 is provided on the support frame 15, which can acquire image data between the boss glass plates 14 through the observation window 22 and transfer it to a computer 17 for real-time reception and storage of images captured by the high-speed photography device.

[0030] Example: Based on the above-mentioned device, the method for evaluating the dynamic joint width proppant transport performance includes the following steps: Step S1: Assemble the overall experimental device and test component 7, wherein the boss glass plate 14 is embedded into the grooves of the front metal shell 10 and the rear metal shell 11 respectively, and the double-headed bolt 21 is inserted into the double-headed bolt hole 29, passing through the front metal shell 10 and the rear metal shell 11 and then fixed with the lock nut 20. At the same time, electric heating rods 8 are set on the front metal shell 10 and the rear metal shell 11 respectively, to obtain the front metal shell 10 assembly and the rear metal shell 11 assembly; Step S2: Fix the front metal shell 10 assembly and the rear metal shell 11 assembly onto the two sets of sliders 23 respectively, and abut the side of the rear metal shell 11 away from the boss glass plate 14 with the support frame 15 to form a fixed constraint, and abut the side of the front metal shell 10 away from the boss glass plate 14 with the surrounding pressure plate 30. Step S3: Set the sealing frame 13 on the fixed base 24, and adjust the position of the front metal shell 10 assembly until the two sets of boss glass plate 14 boss structures are just in contact inside the sealing frame 13, so that the spherical groove 27 formed by the spherical groove is connected to the sealing frame through hole 28 near the inlet side of the test component 7, and install symmetrically distributed springs 12 on the heat insulation layer 9 between the front metal shell 10 assembly and the rear metal shell 11 assembly, ensuring that the springs 12 are in a natural balance state, and record the data of the displacement sensor 25 at this time as 0; In actual formation fracture stress analysis, when the fracture width remains balanced, the main equation is as follows: In the formula, The pressure exerted by the fluid in the crack on the crack is provided by the fluid injected between the boss glass plates in the experimental apparatus of the present invention. This represents the total stress borne by the fractures in the actual formation, which should be balanced with the fluid pressure. The magnitude of the actual geostress experienced by the rock strata is provided by the confining pressure device in the experimental apparatus of this invention. This represents the elastic restoring force of the rock mass where the crack is located. This force is generated at the intact structure of the rock mass where the crack is located (usually at the two ends of the crack) after being squeezed by fluid inside the crack. In the experimental apparatus of this invention, it is provided by a spring.

[0031] For the experimental apparatus in this invention, the confining pressure provided by the confining pressure device (corresponding to the actual ground pressure) and the elastic modulus simulated by the spring (corresponding to the actual ground elastic modulus) are compared to the actual ground pressure. and All of these require equivalent scaling. Therefore, the calculation methods for the confining pressure and the simulated elastic modulus E in the experimental setup are as follows: Based on the simulated spring experiment using the above-mentioned device, the restoring force provided by the spring in the experimental device... It can be represented as: in, n Indicates the number of springs; k This indicates the spring constant of the spring installed between the front and rear metal housing assemblies; This indicates the opening distance of the crack due to fluid compression, i.e., the crack width.

[0032] For the calculation of confining pressure, the elastic modulus of the simulated formation in the experimental setup is first introduced. and stress coefficient C .

[0033] Among them, the elastic modulus of the simulated strata As shown in the following formula: In the formula, v This represents the Poisson's ratio of the rock mass in the target area of ​​the simulation. L This indicates the length of the crack, which is the length of the raised portion of the raised glass plate.

[0034] Stress coefficient C This represents the ratio of the elastic modulus of the actual strata to the elastic modulus of the simulated strata in the experimental setup. Simultaneously, the ratio of the in-situ stress experienced by the actual strata to the in-situ stress experienced by the simulated strata in the experimental setup also satisfies the stress coefficient. C Therefore, the stress coefficient can be expressed as follows: In the formula, C Indicates the stress coefficient; The elastic modulus of the actual formation can be obtained from well logging or core experiments; This represents the geostress, or confining pressure, experienced by the simulated strata within the experimental setup. This represents the actual in-situ stress experienced by the strata, which can be obtained through well logging or core experiments. The following relationship should be satisfied: As can be seen, once the type of spring is determined for different target geological conditions, the corresponding experimental setup can be calculated. The stress coefficient is calculated by combining the actual elastic modulus E obtained from actual well logging data. C Furthermore, by combining the F-stress obtained from actual well logging data, the required experimental stress can be calculated. .

[0035] Furthermore, to ensure uniform stress distribution, the number of springs should be even and their positions symmetrically distributed. Given the aforementioned geological and spring conditions, the fracture width is examined... By considering the changes in injection pressure, pressure changes before and after proppant injection, and the distribution patterns of proppant, a realistic proppant migration model can be accurately simulated, taking into account the changes in fracture width under the Young's modulus of the formation.

[0036] For conventional experimental setups in existing technologies, they do not include providing The components thus limit existing devices to simple simulation. and Therefore, if the pumping pressure remains greater than the confining pressure and constant, once the crack opens, the crack width will continue to increase unless the pressure is manually changed. In real strata, as the crack width increases, the resistance to elastic deformation of the rock also increases, thus limiting the unlimited expansion of the crack. Therefore, conventional experimental devices in the prior art cannot accurately simulate the stress state in actual strata, and their accuracy in evaluating the proppant migration and placement is lower than that of this invention.

[0037] Step S4: Activate the confining pressure assembly 6 to apply a preset normal pressure to the front metal housing 10 assembly. The protruding glass plates 14 change from being in contact to being under pressure, and the temperature control component 5 heats the protruding glass plates 14 to the simulated temperature.

[0038] Step S5: The pre-fluid is pumped into the test assembly 7 using the constant flow pump 2. The fluid is pumped from the inlet of the test assembly through the spherical groove 27 into the space between the two sets of boss glass plates 14, and the pressure is gradually increased. When the pressure is higher than At this time, the two sets of protruding glass plates 14 are opened under pressure, causing the front metal shell 10 assembly and its corresponding slider 23 to move along the slide rail on the slide rail base 26. The spring 12 changes from a natural equilibrium state to a stretched state. The displacement data of the slider 23 is recorded by the displacement sensor 25. When the data stabilizes, the data of the displacement sensor 25 at this time is recorded as the initial crack width. At this point, the pumping pressure is the crack initiation pressure. .

[0039] Step S6: Maintain pumping status, switch to the sand-carrying fluid injection path, and set the pumping displacement to [value missing]. The sand-carrying fluid is injected into the simulated fracture channel, and the pumping time is... The displacement sensor data 25 was recorded as the crack width. The camera component 16 transmits the captured images to the computer 17 via a data cable.

[0040] At this time, it was observed that when the fracture space is relatively narrow, the proppant particles are prone to frequent contact and collision with the fracture wall during the migration process. The effective carrying effect of the fluid on the particles is limited to a certain extent, and the overall migration speed of the proppant particles in the fracture is relatively slow. Therefore, it is more likely to settle and accumulate at the fracture entrance.

[0041] Step S7: Turn off the constant flow pump 2, stop pumping fluid, turn on the back pressure pump 19 to slowly depressurize and simulate the fracturing fluid backflow process. At this time, the front metal shell 10 slowly approaches the rear metal shell 11 under the action of the spring 12 restoring force and external confining pressure. After the fluid is backflowed, it enters the waste liquid tank 18.

[0042] Step S8: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and set the pump discharge rate to... ,and The pumping time is The displacement sensor data 25 was recorded as the crack width. And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump 2 to stop pumping fluid, turn on the back pressure pump 19 to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank 18 after backflow.

[0043] At this time, it was observed that as the pumping flow rate increased, the crack width W3>W2, the crack space was relatively wide, and the fluid could play a more effective carrying role, so that the particles could maintain a good suspension and transport state in the crack, thus enabling them to migrate to the depth of the crack at a faster speed. Step S9: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and increase the pump discharge rate to... ,and The pumping time is The displacement sensor data 25 was recorded as the crack width. And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump 2 to stop pumping fluid, turn on the back pressure pump 19 to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank 18 after backflow.

[0044] Under hydrodynamic forces, the proppant sand embankment originally deposited at the bottom of the fracture was eroded by high-speed fluid, causing the particles to change from a sedimentary state to a suspended state, accompanied by significant secondary migration. Images show that the proppant accumulation height at the fracture inlet is significantly reduced, and the particles continue to migrate rapidly towards the deeper parts of the fracture, resulting in rapid accumulation and settling at the fracture channel outlet.

[0045] Step S10: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and reduce the pump discharge rate to... ,and The pumping time is The displacement sensor data 25 was recorded as the crack width. ,and Simultaneously record the captured images, then turn off the constant flow pump 2 to stop pumping fluid, turn on the back pressure pump 19 to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank 18 after backflow.

[0046] Observations revealed that, compared to the pump injection displacement of... Under these conditions, the proppant particles extend further horizontally and have a more uniform vertical placement. Compared to a pump injection displacement of... Under these conditions, the proppant accumulation and settlement at the fracture channel outlet is significantly reduced. Therefore, the pump injection rate is controlled at... This can reduce the non-uniform accumulation of proppant during propagation in the fracture channel, ensuring that the fracture has a continuous and stable high conductivity. Therefore, the pumping displacement is... At the optimal fluid displacement, the proppant can be evenly distributed inside the crack channel, and the local accumulation phenomenon is significantly reduced.

[0047] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dynamic joint width proppant transport performance evaluation device, comprising a water storage tank (1), a constant flow pump (2), a pre-liquid tank (3), a sand-carrying liquid tank (4), a temperature control component (5), a confining pressure component (6), a testing component (7), a waste liquid tank (18), and a back pressure pump (19), wherein the water storage tank (1) is connected to the inlet of the testing component (7), and the connecting pipeline is sequentially provided with a branch-connected constant flow pump (2) and a parallel-distributed pre-liquid tank (3) and a sand-carrying liquid tank (4), the testing component (7) is also connected to the temperature control component (5) and the confining pressure component (6), and the outlet of the testing component (7) is sequentially connected to the back pressure pump (19) and the waste liquid tank (18), characterized in that, The test assembly (7) includes a front metal shell (10), a rear metal shell (11), a spring (12), a sealing frame (13), a boss glass plate (14), a slider (23), a fixed base (24), a displacement sensor (25), and a slide rail base (26), wherein: The front metal shell (10) and the rear metal shell (11) are both cubes with a groove on one side. They are arranged in parallel on two sets of strip-shaped sliders (23) with the grooves facing each other. The front metal shell (10) and the rear metal shell (11) are connected by multiple sets of symmetrically distributed springs (12). Two sets of sliders (23) are arranged in parallel on the slide rail base (26), and can move along the slide rail on the slide rail base (26), so that the front metal shell (10) and the rear metal shell (11) on the slider (23) are translated in the normal direction; a strip-shaped fixing seat (24) is arranged in parallel between the two sets of sliders (23), and a displacement sensor (25) is set on the slider (23) to detect the degree of displacement of the slider (23) on the slide rail base (26); The same protruding glass plate (14) can be installed in the grooves inside the front metal shell (10) and the rear metal shell (11). The protruding glass plate (14) is a glass structure with a rectangular protrusion on one side. When the two sets of protruding glass plates (14) are installed in the front metal shell (10) and the rear metal shell (11) respectively, they remain parallel and the rectangular protrusions remain facing each other. The sealing frame (13) is a rectangle with a large through hole in the middle. Its large through hole can fit exactly with the boss of the boss glass plate (14). The sealing frame (13) is set on the fixed seat (24). The sealing frame (13) is parallel to the boss glass plate (14) and the large through hole of the sealing frame (13) is directly opposite the boss of the two sets of boss glass plates (14). The sealing frame (13) is also provided with two sets of connecting large through holes and two pairs of sealing frame through holes (28) on the sides. The two sets of sealing frame through holes (28) are on the same horizontal plane and are symmetrically distributed along the large through hole. The two sets of sealing frame through holes (28) can be connected to the liquid inlet and outlet of the test component (7) respectively. When the two sets of boss glass plates (14) move to the boss contact, the contact surface of the boss is located on the axis of the sealing frame through hole (28), and at this time, the multiple sets of springs (12) are just in a natural balance state.

2. The dynamic seam width support transport performance evaluation device according to claim 1, characterized in that: The protruding glass plate (14) is provided with a double-headed bolt hole (29). When the protruding glass plate (14) is fitted into the front metal shell (10) or the rear metal shell (11), the double-headed bolt hole (29) is provided with a double-headed bolt (21) that can penetrate the protruding glass plate (14) and the front metal shell (10) or the rear metal shell (11), and the double-headed bolt (21) is fixed by a locking nut (20) on the surface of the front metal shell (10) or the rear metal shell (11).

3. The dynamic seam width support transport performance evaluation device according to claim 1, characterized in that: Multiple sets of heating rods (8) are provided on the front metal shell (10) and the rear metal shell (11), and the heating rods (8) are connected to the temperature control component (5); a heat insulation layer (9) is also provided on the surface of the spring (12) that contacts the front metal shell (10) and the rear metal shell (11) respectively.

4. The dynamic seam width support transport performance evaluation device according to claim 1, characterized in that: The boss glass plate (14) has a spherical groove (27) on the side of the boss. When the two sets of bosses are in contact, the two sets of spherical grooves (27) can form a complete spherical groove to connect the sealing frame through hole (28) on the inlet side of the test component (7).

5. The dynamic seam width support transport performance evaluation device according to claim 4, characterized in that: The rear metal shell (11) is provided with an observation window (22). The rear metal shell (11) is fixedly connected to the external support frame (15). The support frame (15) is provided with a camera component (16). The camera component (16) can collect image data between the boss glass plate (14) through the observation window (22) and transfer it to the computer (17).

6. The dynamic seam width support transport performance evaluation device according to claim 1, characterized in that: The front metal shell (10) is provided with a confining pressure plate (30) on its outside. The confining pressure plate (30) is connected to the confining pressure assembly (6) and is used to provide normal pressure to the front metal shell (10).

7. The dynamic seam width support transport performance evaluation device according to claim 1, characterized in that: The displacement that the slider (23) is allowed to move is no greater than the thickness of the sealing frame (13).

8. A method for evaluating the transport performance of dynamic seam width proppant, characterized in that, Performed using the apparatus described in any one of claims 1 to 7, comprising the following steps: Step S1: Assemble the overall experimental device and test components (7), wherein the boss glass plate (14) is embedded into the grooves of the front metal shell (10) and the rear metal shell (11) respectively, and the double-headed bolt (21) is inserted into the double-headed bolt hole (29), and after passing through the front metal shell (10) and the rear metal shell (11), it is fixed with a lock nut (20). At the same time, electric heating rods (8) are set on the front metal shell (10) and the rear metal shell (11) respectively, to obtain the front metal shell (10) assembly and the rear metal shell (11) assembly; Step S2: Fix the front metal shell (10) assembly and the rear metal shell (11) assembly onto the two sets of sliders (23) respectively, and make the side of the rear metal shell (11) away from the boss glass plate (14) abut against the support frame (15) to form a fixed constraint, and make the side of the front metal shell (10) away from the boss glass plate (14) abut against the confining plate (30); Step S3: Set the sealing frame (13) on the fixed seat (24) and adjust the position of the front metal shell (10) assembly until the two sets of boss glass plate (14) boss structures are in contact inside the sealing frame (13), so that the spherical groove (27) formed by the spherical groove is connected to the sealing frame through hole (28) near the inlet side of the test component (7), and install symmetrically distributed springs (12) on the heat insulation layer (9) between the front metal shell (10) assembly and the rear metal shell (11) assembly, ensuring that the springs (12) are in a natural balance state, and record the data of the displacement sensor (25) at this time as 0; Step S4: Activate the confining pressure assembly (6) to apply a preset normal pressure to the forward metal shell (10) assembly. The protruding glass plates (14) change from just contact to being under pressure, and the temperature control component (5) heats the protruding glass plates (14) to the simulated temperature. Step S5: The pre-fluid is pumped into the test assembly (7) by a constant flow pump (2). The fluid is pumped from the inlet of the test assembly through the spherical groove (27) into the space between the two sets of boss glass plates (14) and the pressure is gradually increased. When the pressure is higher than At this time, the two sets of protruding glass plates (14) are opened under pressure, which drives the front metal shell (10) assembly and its slider (23) to move along the slide rail on the slide rail base (26). The spring (12) changes from a natural equilibrium state to a stretched state. The displacement data of the slider (23) is recorded by the displacement sensor (25). When the data stabilizes, the data of the displacement sensor (25) at this time is recorded as the initial crack width. At this point, the pumping pressure is the crack initiation pressure. ; Step S6: Maintain pumping status, switch to the sand-carrying fluid injection path, and set the pumping displacement to [value missing]. The sand-carrying fluid is injected into the simulated fracture channel, and the pumping time is... The displacement sensor (25) data was recorded as the crack width. The camera component (16) transmits the captured image to the computer (17) via a data cable. Step S7: Turn off the constant flow pump (2), stop pumping fluid, turn on the back pressure pump (19) to slowly depressurize and simulate the fracturing fluid backflow process. At this time, the front metal shell (10) slowly approaches the rear metal shell (11) under the action of the spring (12) restoring force and external confining pressure. After the fluid is backflowed, it enters the waste liquid tank (18). Step S8: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and set the pump discharge rate to... ,and The pumping time is The displacement sensor (25) data was recorded as the crack width. And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump (2), stop pumping fluid, turn on the back pressure pump (19) to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank (18) after backflow. Step S9: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and increase the pump discharge rate to... ,and The pumping time is The displacement sensor (25) data was recorded as the crack width. And the width of the crack Simultaneously record the captured images, then turn off the constant flow pump (2), stop pumping fluid, turn on the back pressure pump (19) to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank (18) after backflow. Step S10: Repeat steps S3-S5, switch to the sand-carrying fluid injection path, and reduce the pump discharge rate to... ,and The pumping time is The displacement sensor (25) data was recorded as the crack width. ,and Simultaneously record the captured images, then turn off the constant flow pump (2), stop pumping fluid, turn on the back pressure pump (19) to gently depressurize and simulate the fracturing fluid backflow process, and the fluid enters the waste liquid tank (18) after backflow.

Images