A long crack multi-angle sand paving evaluation system and method

Abstract

The present invention provides a long crack multi-angle sand placement evaluation system and method. The evaluation system includes a liquid preparation and sand mixing device, a control device, and a long crack simulation device. Among them, the liquid preparation and sand mixing device can configure a carrying fluid with a predetermined viscosity and inject it into the long crack simulation device; the long crack simulation device can simulate cracks with different lengths, inclination angles, turning angles, and widths; the control device is respectively connected to the liquid preparation and sand mixing device and the long crack simulation device to control the experimental process. The evaluation method conducts experiments by changing the crack length, inclination angle, turning angle, width, fracturing fluid viscosity, pumping displacement, proppant type, proppant particle size, and sand concentration, observes the formation process of the sand dike, collects images during the sand placement process, and records the geometric shape of the sand dike at different times to analyze the migration and settlement law of the proppant in different crack shapes. The present invention has the advantages of being able to simulate cracks with different shapes, different orientations, and different inclination angles, and being able to truly restore the characteristics of formation cracks, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of fracture simulation equipment, and specifically, to a long-fracture multi-angle sand placement evaluation system and method. Background Art

[0002] Horizontal well staged volume fracturing is a key technology for efficient shale gas development. In the proppant-carrying fluid system, the fracturing proppant is the main medium for filling fractures. It has the ability to maintain a relatively high conductivity of the reservoir and provide a high-speed channel for shale gas to flow into the wellbore. Therefore, the distribution pattern of the fracturing proppant in the fracture is an important factor affecting the fracturing effect.

[0003] To study the distribution pattern of the fracturing proppant in the fracture, indoor experimental devices are commonly used for simulation research at home and abroad. The evaluation devices used in Chinese laboratories mainly focus on the simulation of short fractures in the study of formation fractures. In terms of the simulated fracture morphology of the experimental devices, they are mostly single fractures, double fractures or multi-branched fractures, and factors such as wedge-shaped fractures existing in the formation, the inclination angle between the fracture and the ground, and fracture turning are rarely considered, resulting in a large error between the experimental analysis data obtained therefrom and the actual situation. Therefore, it is necessary to design an evaluation system and method that can simulate long formation fractures and can realize changes in fracture morphology and multi-angle changes in fractures to more closely conform to the actual situation of the formation and conduct research on formation fractures. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, one of the purposes of the present invention is to provide a long-fracture multi-angle sand placement evaluation system that can simulate fractures with different morphologies, different orientations, and different inclination angles. Another purpose of the present invention is to provide a long-fracture multi-angle sand placement evaluation method that can simulate fractures with different morphologies, different orientations, and different inclination angles.

[0005] To achieve the above purpose, on the one hand, the present invention provides a long-fracture multi-angle sand placement evaluation system, which includes a liquid preparation and sand mixing device, a control device, and a long-fracture simulation device. Among them,

[0006] The liquid preparation and sand mixing device can prepare a proppant-carrying fluid with a predetermined viscosity and inject the proppant-carrying fluid into the long-fracture simulation device at a predetermined displacement;

[0007] The long-fracture simulation device can simulate fractures with different lengths, inclination angles, turning angles, and widths;

[0008] The control device is respectively connected to the liquid preparation and sand mixing device and the long-fracture simulation device to control the experimental process and record experimental data.

[0009] In an exemplary embodiment of one aspect of the present invention, the liquid preparation and sand mixing device may include a liquid preparation tank, a sand addition tank, a stirring tank, and a screw pump. Among them,

[0010] The liquid preparation tank and the sand addition tank are respectively connected to the stirring tank, and the screw pump pumps the sand-carrying liquid after being evenly stirred in the stirring tank into the inlet of the long crack simulation device;

[0011] The other end of the liquid preparation tank is connected to the outlet of the long crack simulation device through a pipeline.

[0012] In an exemplary embodiment of one aspect of the present invention, the liquid preparation and sand mixing device may further include a sedimentation tank and a drainage trough, and the sedimentation tank is arranged on the pipeline between the outlet of the long crack simulation device and the liquid preparation tank.

[0013] In an exemplary embodiment of one aspect of the present invention, the liquid preparation and sand mixing device may further include a flow meter and a pressure gauge, and the flow meter and the pressure gauge can measure the flow rates at the inlet and outlet of the long crack simulation device and the pressures at the inlet and outlet.

[0014] In an exemplary embodiment of one aspect of the present invention, the control device may include a camera and a PLC control cabinet. Among them,

[0015] The camera is used to collect image data of the sand laying in the long crack simulation device during the experiment;

[0016] The PLC control cabinet is used to control the pumping displacement and sand addition speed of the liquid preparation and sand mixing device, and is used to monitor the flow rate data at the inlet and outlet of the long crack simulation device and the pressure data at the inlet, outlet, and specific positions.

[0017] In an exemplary embodiment of one aspect of the present invention, the long crack simulation device may include a base, a bottom plate, a telescopic rod, and a crack model body. Among them,

[0018] The base is fixedly arranged on the ground, the bottom plate is horizontally arranged on the base and the bottom plate forms a hinge with the base;

[0019] The crack model body is fixedly arranged on the bottom plate along the length direction of the bottom plate and is perpendicular to the bottom plate. The crack model body includes two or more crack models and universal expansion joints connecting adjacent two crack models, and the crack model body is in a curved or straight form with a certain length;

[0020] One end of the telescopic rod is connected to the base, and the other end is connected to the bottom plate to push the bottom plate to rotate relative to the base, so that the simulated crack body is inclined relative to the ground.

[0021] In an exemplary embodiment of one aspect of the present invention, the fracture model may include at least one of a flat fracture model and an irregular fracture model;

[0022] Both the flat fracture model and the irregular fracture model include a box body, two clamping plates, support bars, and bolts, wherein,

[0023] The front and rear sides of the box body are open structures. The two clamping plates are arranged inside the box body and are parallel to the left and right sides of the box body respectively. The two clamping plates can cooperate with each other to form a simulated fracture channel;

[0024] The support bars are fixedly arranged on the outer walls of both sides of the box body. One end of the bolt acts on the two clamping plates, and the other end acts on the support bars.

[0025] In an exemplary embodiment of one aspect of the present invention, at both ends of each of the two clamping plates, there may be provided bent portions protruding towards the same side. Among them, the two clamping plates are matched through the bent portions;

[0026] On the bent portion of one clamping plate, there is provided a groove, and on the bent portion of the other clamping plate, there is provided a protrusion that cooperates with the groove;

[0027] A spring is further provided in the groove, and a spring post is further provided on the protrusion.

[0028] In an exemplary embodiment of one aspect of the present invention, in the flat fracture model, the support bars may be cross - arranged outside the box body. One end of the bolt abuts against the clamping plate, and the distance between the two clamping plates is adjusted by adjusting the screwing - in length of the bolt on the support bar;

[0029] In the irregular fracture model, the support bars may be vertically or parallelly arranged outside the box body. One end of the bolt is fixedly connected to the clamping plate, and the distance between the two clamping plates is controlled by screwing the bolt in and out.

[0030] In an exemplary embodiment of one aspect of the present invention, the clamping plate may be made of a transparent material, and the clamping plate is a transparent organic glass plate or a glass plate injection - molded into an irregular fracture shape.

[0031] In an exemplary embodiment of one aspect of the present invention, the length of the simulated fracture body may be 10 - 30 m, and the inclination angle of the simulated fracture body relative to the ground may be 0 - 90°.

[0032] In an exemplary embodiment of one aspect of the present invention, the simulation device may further include an inlet wellbore and an outlet wellbore, and the inlet wellbore and the outlet wellbore are respectively communicated with both ends of the fracture model body to pump proppant into the fracture model body.

[0033] Another aspect of the present invention provides a method for evaluating sand placement at multiple angles in long fractures. The evaluation method can be implemented by the long fracture multi-angle sand placement evaluation system described in any one of the above, and the evaluation method includes the steps:

[0034] Determine the fracture length, fracture dip angle, fracture turn angle, fracture width, fracturing fluid viscosity, proppant-carrying fluid concentration, pumping rate, proppant type, and proppant particle size required for the experiment;

[0035] Assemble the sand placement evaluation system and detect that the airtightness is qualified;

[0036] Prepare the fracturing fluid with the required viscosity for the experiment, inject the fracturing fluid into the long fracture simulation device at a predetermined displacement, fill it and circulate it;

[0037] Add proppant to the fracturing fluid to form a proppant-carrying fluid with a predetermined viscosity and inject it into the long fracture simulation device;

[0038] During the experiment, observe the formation process of the sand dike, collect images of the sand placement process, and record the geometric shape of the sand dike at different times, as well as the flow rate and pressure data at the inlet and outlet of the long fracture simulation device.

[0039] In an exemplary embodiment of another aspect of the present invention, the method may further include the steps:

[0040] Change the fracture length, fracture dip angle, fracture turn angle, fracture width, fracturing fluid viscosity, proppant-carrying fluid concentration, pumping rate, proppant type, and proppant particle size, and repeat the experiment; use the analytic hierarchy process to analyze the migration and settlement laws of different proppants in long fractures at multiple angles under different fractures and different construction conditions.

[0041] In an exemplary embodiment of another aspect of the present invention, the fracture length of the long fracture in the method can be 10 - 30 m, the fracture dip angle can be 0 - 90°, the fracture turn angle can be 0 - 45°, the fracture width can be 0.6 - 1.2 cm, the viscosity of the fracturing fluid can be 1 - 40 mPa·s, and the pumping rate can be 0 - 180 L / min.

[0042] In an exemplary embodiment of another aspect of the present invention, the migration and settlement law of the proppant may include at least one of the sand dike shape, equilibrium height, equilibrium time, equilibrium flow rate, initial proppant accumulation distance, flow field characteristics near the inlet, and filling degree near the inlet.

[0043] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0044] (1) By adjusting the width and angle of the simulated cracks in the crack model, the present invention can simulate different forms of cracks, such as wedge-shaped cracks and flat cracks. With the design of an irregular crack model, it can simulate the crack morphology in real reservoirs with a higher degree of restoration.

[0045] (2) In the present invention, a universal expansion joint is used to connect the simulated cracks, which can realize the angular change between the crack models and the turning of long cracks for simulating the change of formation crack trend. At the same time, a telescopic rod is used to realize the inclination change of the crack model for simulating the migration of proppants in cracks with different inclinations.

[0046] (3) The crack model of the present invention can be assembled into a long crack (10 - 30 meters) according to experimental requirements, which is closer to the actual situation where the main crack in the reservoir is a long crack. It can eliminate the influence of the inlet and outlet ends on the migration and settlement of proppants in the short crack simulation device, improve the clarity of experimental phenomenon observation, and reduce the possible errors in extracting experimental data due to the small size of the short crack simulation device.

[0047] (4) The long crack multi-angle sand placement evaluation method can quantitatively study the sand dike equilibrium height, equilibrium time, equilibrium flow rate, initial proppant stacking distance, proppant filling degree near the inlet, etc. of proppant migration, and characterize the flow field characteristics near the inlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Through the following description with reference to the drawings, the above and other objects and / or features of the present invention will become clearer, wherein:

[0049] Figure 1 FIG. shows a schematic structural diagram of a long crack multi-angle sand placement evaluation system according to an exemplary embodiment of the present invention;

[0050] Figure 2 FIG. shows Figure 1 a schematic structural diagram of the other side of the long crack simulation device in ;

[0051] Figure 3 FIG. shows a schematic structural diagram of a long crack simulation device according to another exemplary embodiment of the present invention;

[0052] Figure 4 FIG. shows Figure 1 or Figure 3 a schematic structural diagram of an exemplary embodiment of the crack model in ;

[0053] Figure 5 FIG. shows Figure 4 a side view (irregular crack model) of an exemplary embodiment of the crack model in ;

[0054] Figure 6 FIG. shows Figure 4Side view of an exemplary embodiment of the middle crack model (flat crack model);

[0055] Figure 7 Shows Figure 4 Right view of the middle crack model;

[0056] Figure 8 Shows Figure 7 Enlarged schematic view at A in the middle;

[0057] Figure 9 Shows the structural schematic diagram of the plate clamp according to an exemplary embodiment of the present invention;

[0058] Figure 10 Shows the top view of the plate clamp according to an exemplary embodiment of the present invention (flat crack model);

[0059] Figure 11 Shows the top view of the plate clamp according to an exemplary embodiment of the present invention (simulating wedge-shaped cracks with a flat crack model);

[0060] Figure 12 Shows the structural schematic diagram after assembling multiple crack models according to an exemplary embodiment of the present invention;

[0061] Figure 13 Shows the test flow chart according to an exemplary embodiment of the present invention.

[0062] Description of reference numerals:

[0063] 1 - Base, 2 - Bottom plate, 3 - Telescopic rod, 4 - Crack model, 5 - Support plate, 6 - Hinge, 7 - Drainage groove, 8 - Settlement tank, 9 - Liquid mixing tank, 10 - Sand adding tank, 11 - Stirring tank, 12 - Screw pump, 13 - Inlet wellbore, 14 - Outlet wellbore, 15 - Flowmeter, 16 - PLC control cabinet, 17 - Universal expansion joint, 18 - Spring, 19 - Spring column, 20 - Box body, 21 - Sealing rubber, 22 - Clamping plate, 23 - Bolt, 24 - Support bar, 25 - Bending part. Detailed description of the specific implementation

[0064] In the following, the long crack multi-angle sand placement evaluation system and method of the present invention will be described in detail in combination with exemplary embodiments.

[0065] In the first exemplary embodiment of the present invention, the long crack multi-angle sand placement evaluation system mainly includes a liquid mixing and sand mixing device, a control device, and a long crack simulation device.

[0066] Among them, the liquid mixing and sand mixing device can configure a carrying fluid with a predetermined viscosity and inject the carrying fluid into the long crack simulation device at a predetermined displacement for circulation.

[0067] The long crack simulation device can simulate cracks with different lengths, inclination angles, steering angles, and widths.

[0068] The control device is respectively connected to the liquid preparation and sand mixing device and the long crack simulation device to control the experimental process and record experimental data.

[0069] In this exemplary embodiment, the liquid preparation and sand mixing device may include a liquid preparation tank, a sand addition tank, a mixing tank, and a screw pump. Among them, the liquid preparation tank and the sand addition tank are respectively connected to the mixing tank, and the screw pump injects the sand-carrying fluid after being evenly stirred in the mixing tank into the inlet of the long crack simulation device. The other end of the liquid preparation tank is connected to the outlet of the long crack simulation device through a pipeline. Specifically, the liquid preparation tank can configure fracturing fluid with a predetermined viscosity. After the fracturing fluid is configured, it enters the mixing tank. According to the required concentration of the sand-carrying fluid in the experiment, the proppant in the sand addition tank is added to the mixing tank in proportion, and after being evenly stirred, a sand-carrying fluid with a predetermined viscosity and concentration is formed and injected into the inlet of the long crack simulation device through the screw pump. The proppant in the sand-carrying fluid settles in the long crack simulation device, and the excess sand-carrying fluid returns from the outlet to the liquid preparation tank for recycling.

[0070] In this embodiment, further, the liquid preparation and sand mixing device may further include a settling tank and a drainage trough. The settling tank is arranged on the pipeline connecting the outlet of the long crack simulation device and the liquid preparation tank. The sand-carrying fluid coming out of the long crack simulation device first settles out the residual proppant in the settling tank and then enters the liquid preparation tank. The drainage trough is used to receive the excess liquid.

[0071] In this embodiment, further, the liquid preparation and sand mixing device may further include a flowmeter and a pressure gauge. The flowmeter and the pressure gauge can measure the inlet flow rate and outlet flow rate of the long crack simulation device, as well as the inlet pressure and outlet pressure. Here, the pressure gauge and the flowmeter are arranged on the pipelines connecting the liquid preparation and sand mixing device to the inlet and outlet of the long crack simulation device. In addition, pressure gauges are also arranged at specific positions on the long crack simulation device (for example, one pressure gauge is arranged every 2 meters).

[0072] In this exemplary embodiment, the control device may include a camera and a PLC control cabinet. Among them, the camera is used to collect image data of the sand laying in the long crack simulation device during the experimental process. The PLC control cabinet is used to control the pumping displacement and sand addition speed of the liquid preparation and sand mixing device, and is used to monitor the inlet and outlet flow rate data of the long crack simulation device, as well as the pressure data at the inlet, outlet, and specific positions of the long crack simulation device. Here, the PLC control cabinet is respectively connected to the drainage trough, the settling tank, the liquid preparation tank, the sand addition tank, the flowmeter, the pressure gauge, the mixing tank, and the screw pump, etc. to control the liquid preparation and sand mixing device.

[0073] In this exemplary embodiment, the long crack simulation device mainly includes a base, a bottom plate, a telescopic rod, and a crack model body. Among them, the base is fixedly arranged on the ground or a plane and serves to support the bottom plate. The bottom plate is horizontally arranged on the base, and the bottom plate and the base form a hinge connection so that the bottom plate can rotate relative to the base. Here, the hinge connection can be achieved by means of a hinge, a rotating shaft, or a bearing.

[0074] The crack model body is fixedly installed on the bottom plate along the length direction of the bottom plate and is perpendicular to the bottom plate. The crack model body may include more than two crack models and a universal expansion joint connecting adjacent two crack models. Here, by setting the universal expansion joint, adjacent two crack models can form a bent shape. Multiple crack models are set according to experimental requirements, so that the crack model body presents a bent shape, a straight shape, or a shape with a part bent and a part straight with a certain length, so that the simulated long crack is closer to the actual situation of the formation.

[0075] One end of the telescopic rod is connected to the base, and the other end passes through the upper end surface of the base and is connected to the side of the bottom plate that is not hinged to the base to push the bottom plate to rotate relative to the base, thereby driving the simulated crack body to tilt relative to the ground. For example, here the telescopic rod can be a hydraulic cylinder, one end of which is connected to the base, and the other end passes through the upper end surface of the base and is connected to the lower end surface of the side of the bottom plate that is not hinged to the base. By controlling the length of the telescopic rod, the tilt angle of the simulated crack can be controlled. Here, the bottom plate can be a rectangular structure, and the long side on one side of the rectangle can form a hinge connection with the base, and the hinge connection is achieved by means of a hinge.

[0076] In this embodiment, the crack model may include at least one of a flat crack model and an irregular crack model. Both the flat crack model and the irregular crack model may include a box body, two clamping plates, support bars, and bolts.

[0077] Among them, the box body is a flat structure, and the front and rear two side surfaces of the box body are open or there is an opening structure on the upper surface. The two clamping plates are arranged opposite to each other in the box body and are respectively parallel to the left and right two sides of the box body. The two clamping plates can cooperate with each other to form a simulated crack channel; the support bars are fixedly arranged on the outer walls on both sides of the box body, one end of the bolt acts on the two clamping plates, and the other end acts on the support bars. Sealing rubbers are provided at the end faces at both ends of the crack model for sealing the pores between the box body and the clamping plates.

[0078] In this embodiment, further, bent portions protruding to the same side may be provided at both ends of each of the two clamping plates, and the two clamping plates are matched through the bent portions.

[0079] A groove may be provided on the bent portion of one clamping plate, and a protrusion cooperating with the groove may be provided on the bent portion of the other clamping plate. A spring may also be provided in the groove, and a spring post may also be provided on the protrusion, which facilitates the separation of the two clamping plates when the bolt is screwed out. Here, the width of the bent portion may gradually become shorter along the length direction of the clamping plate, so that when the two clamping plates are fitted together, a wedge-shaped crack can be simulated, and at the same time, the wedge-shaped crack is arranged near the inlet wellbore, which can better restore the crack morphology near the wellbore in the real reservoir.

[0080] According to different experimental requirements, the flat crack model and the irregular crack model can be freely combined to form cracks of different shapes.

[0081] In this embodiment, in the flat crack model, the support bars may be cross-arranged outside the box body, and one end of the bolt abuts against the clamping plate. The distance between the two clamping plates is adjusted by adjusting the screwing length of the bolt on the support bar, so as to adjust the width of the crack, thereby forming parallel cracks or wedge-shaped cracks. In the irregular crack model, the support bars may be arranged vertically or parallel to the outside of the box body, and one end of the bolt is fixedly connected to the clamping plate. The vertical or parallel design of the support bars increases the setting density of the bolts on the clamping plate. By screwing in and out the bolts to control the distance between the two clamping plates, an irregular crack shape can be formed between the clamping plates.

[0082] In this embodiment, the clamping plate may be made of a transparent material, and the clamping plate may be a transparent organic glass plate or a glass plate injection molded into an irregular crack shape. Specifically, according to the experimental requirements, in the flat crack model, the clamping plate is made of a transparent material such as glass, which is convenient for observing the migration and settlement law of the proppant during the experiment; in the irregular crack model, the clamping plate can be made of materials such as copper plates and aluminum plates that are easy to process and deform. Under the action of the bolts, the two clamping plates can easily form an irregularly shaped crack; the clamping plate can also use a transparent organic glass plate injection molded into an irregular crack shape in advance, which is convenient for observing the migration and settlement law of the proppant during the experiment.

[0083] Figure 1 FIG. shows a schematic structural diagram of a long crack multi-angle sand placement evaluation system according to an exemplary embodiment of the present invention; Figure 2 FIG. shows Figure 1 the structural diagram of the other side of the long crack simulation device in Figure 3 FIG. shows a schematic structural diagram of a long crack multi-angle sand placement evaluation system according to another exemplary embodiment of the present invention; Figure 4 FIG. shows Figure 1 or Figure 3 the structural diagram of an exemplary embodiment of the crack model in Figure 5 FIG. shows Figure 4Side view of an exemplary embodiment of the middle fracture model (irregular fracture model); Figure 6 Shows Figure 4 Side view of an exemplary embodiment of the middle fracture model (flat fracture model); Figure 7 Shows Figure 4 Right view of the middle fracture model; Figure 8 Shows Figure 7 Enlarged schematic view at position A in the middle;

[0084] Figure 9 Shows the structural schematic diagram of a plate clamp according to an exemplary embodiment of the present invention; Figure 10 Top view of a plate clamp according to an exemplary embodiment of the present invention (flat fracture model); Figure 11 Top view of a plate clamp according to an exemplary embodiment of the present invention (simulating a wedge-shaped fracture with a flat fracture model); Figure 12 Shows the structural schematic diagram after assembling multiple fracture models according to an exemplary embodiment of the present invention; Figure 13 Shows the test flow chart according to an exemplary embodiment of the present invention.

[0085] In the second exemplary embodiment of the present invention, as Figures 1 to 12 Shown in the figure, the long fracture multi-angle sand placement evaluation system mainly includes a liquid preparation and sand mixing device, a control device, and a long fracture simulation device.

[0086] Among them, the liquid preparation and sand mixing device can configure a carrying fluid with a predetermined viscosity and inject the carrying fluid into the long fracture simulation device at a predetermined displacement for circulation.

[0087] The long fracture simulation device can simulate fractures with different lengths, lengths, inclination angles, turning angles, and widths.

[0088] The control device is respectively connected to the liquid preparation and sand mixing device and the long fracture simulation device to control the experimental process and record experimental data.

[0089] In this exemplary embodiment, as Figure 1 Shown in the figure, the liquid preparation and sand mixing device may include a liquid preparation tank 9, a sand addition tank 10, a stirring tank 11, and a screw pump 12. Among them, the liquid preparation tank 9 and the sand addition tank 10 are respectively connected to the stirring tank 11, and the screw pump 12 pumps the carrying fluid stirred evenly in the stirring tank 11 into the inlet of the long fracture simulation device. The liquid preparation tank 9 can configure a fracturing fluid with a predetermined viscosity, and after the fracturing fluid is configured, it enters the stirring tank 11. According to the required concentration of the carrying fluid in the experiment, the proppant in the sand addition tank 10 is added to the stirring tank 11 in proportion. After being stirred evenly to form a carrying fluid, it is injected into the inlet of the long fracture simulation device through the screw pump 12. The proppant in the carrying fluid settles in the long fracture simulation device, and the excess carrying fluid returns from the outlet and enters the liquid preparation tank 9 for recycling.

[0090] In this embodiment, further, as shown in Figure 1 , the liquid preparation and sand mixing device may further include a settling tank 8 and a drainage tank 7. The settling tank 8 is arranged on the pipeline between the outlet of the long crack simulation device and the liquid preparation tank 9. The sand-carrying liquid coming out of the long crack simulation device first settles in the settling tank 8 to remove the residual proppant and then enters the liquid preparation tank 9. The drainage tank 7 is used to receive the excess liquid.

[0091] In this embodiment, further, as shown in Figure 1 , the liquid preparation and sand mixing device may further include a flowmeter 15 and a pressure gauge (not shown in Figure 1 ). The flowmeter 15 and the pressure gauge can measure the inlet flow rate and outlet flow rate of the long crack simulation device as well as the inlet pressure and outlet pressure. Here, the pressure gauge and the flowmeter 15 can be arranged on the pipelines connecting the inlet and outlet of the liquid preparation and sand mixing device and the long crack simulation device.

[0092] In this exemplary embodiment, the control device may include a camera (not shown in Figure 1 ) and a PLC control cabinet 16.

[0093] Among them, the camera is used to collect the image data of the sand laying in the long crack simulation device during the experiment. The PLC control cabinet 16 is used to control the pumping displacement and sand addition speed of the liquid preparation and sand mixing device, and is used to monitor the inlet and outlet flow rate data of the long crack simulation device and the pressure data at the inlet, outlet and specific positions of the long crack simulation device. Here, the PLC control cabinet is respectively connected to the drainage tank, the settling tank, the liquid preparation tank, the sand addition tank, the flowmeter, the pressure gauge, the stirring tank and the screw pump, etc. to control the liquid preparation and sand mixing device.

[0094] In this exemplary embodiment, the long crack simulation device mainly includes a base, a bottom plate, a telescopic rod and a crack model body.

[0095] Among them, as shown in Figure 1 , the base 1 is fixedly arranged on the ground or a plane and serves to support the bottom plate 2. The bottom plate 2 is horizontally arranged on the base 1 and the bottom plate 2 forms a hinge with the base 1 so that the bottom plate 2 can rotate relative to the base 1. Here, the hinge can be realized by means of a hinge or a rotating shaft or a bearing.

[0096] The crack model body is fixedly installed on the bottom plate 2 along the length direction of the bottom plate 2 and is perpendicular to the bottom plate 2. The crack model body may include more than two crack models 4 and a universal expansion joint 17 connecting adjacent two crack models. Here, by setting the universal expansion joint 17, adjacent two crack models 4 can form a bent shape. Support plates 5 are provided on one side or both sides of the crack model 4 to prevent the crack model 4 from tipping over during the tilting process. Multiple crack models 4 are set according to experimental requirements, so that the crack model body is in a bent shape or a straight shape or a partially bent and partially straight shape with a certain length, so that the simulated long crack is closer to the actual situation of the formation.

[0097] One end of the telescopic rod 3 is connected to the base 1, and the other end passes through the upper end surface of the base 1 and is connected to the side of the bottom plate 2 that is not hinged to the base 1 to push the bottom plate 2 to rotate relative to the base 1, thereby driving the simulated crack body to tilt relative to the ground. For example, here the telescopic rod can be a hydraulic cylinder, one end of which is connected to the base, and the other end passes through the upper end surface of the base and is connected to the lower end surface of the side of the bottom plate that is not hinged to the base. By controlling the length of the telescopic rod, the tilting angle of the simulated crack is controlled. Here, the length of the simulated crack body can be 10 - 30 m, and the tilting angle of the simulated crack body relative to the ground can be 0 - 90°.

[0098] In this exemplary embodiment, as Figure 2 shown, the bottom plate 2 can be a rectangular structure, and the long side on one side of the rectangle can form a hinge with the base 1, and the hinge is realized by a hinge 6. Here, the base 1 can be Figure 1 in the shape of a frame, or can be Figure 3 in the shape of a bracket. The telescopic rod 3 can adopt conventional technical means in the art according to the different shapes of the base 1 and the bottom plate 2. Here, the crack model 4 can include at least one of a flat crack model and an irregular crack model.

[0099] In this exemplary embodiment, as Figures 4 to 7 shown, both the flat crack model and the irregular crack model can include a box body 20, two clamping plates 22, support bars 24 and bolts 23.

[0100] Among them, the box body 20 is a flat structure, and the front and rear two side surfaces of the box body 20 are open or there is an opening on the upper surface. The two clamping plates 22 are arranged opposite to each other in the box body 20 and are respectively parallel to the left and right sides of the box body 20. The two clamping plates 22 can cooperate with each other to form a simulated crack channel; the support bars 24 are fixedly arranged on the outer walls on both sides of the box body 20, and one end of the bolt 23 acts on the two clamping plates 22, and the other end acts on the support bars 24. Here, sealing rubbers 21 are provided at the end faces at both ends of the crack model 4 for sealing the pores between the box body 20 and the clamping plates 22.

[0101] In the present exemplary embodiment, as Figures 7 to 10 shown, further, both ends of each of the two clamping plates 22 may be provided with bent portions 25 protruding toward the same side. Among them, the two clamping plates 22 are cooperated through the bent portions 25. Further, a groove may be provided on the bent portion 25 of one clamping plate, and a protruding portion cooperating with the groove may be provided on the bent portion 25 of the other clamping plate. A spring 18 may also be provided in the groove, and a spring post 19 may also be provided on the protruding portion, which is convenient for the two clamping plates to separate when the bolt is screwed out. Here, as Figure 11 shown, the width of the bent portion 25 may gradually become shorter along the length direction of the clamping plate. In this way, when the two clamping plates are fitted together, a wedge-shaped crack can be simulated. At the same time, the wedge-shaped crack is arranged near the inlet wellbore, which can better restore the crack shape near the wellbore in the real reservoir.

[0102] According to different experimental requirements, as Figure 12 shown, the flat fracture model and the irregular fracture model can be freely combined to form fractures of different shapes.

[0103] In the present exemplary embodiment, as Figure 6 shown, in the flat fracture model, the support bars 24 may be cross-arranged outside the left and right planes of the box body 20 (that is, Figure 7 the left and right sides of the box body in ), one end of the bolt 23 abuts against the clamping plate, and the distance between the two clamping plates is adjusted by adjusting the screwing length of the bolt 23 on the support bar 24, so as to adjust the width of the fracture, thereby forming parallel fractures or wedge-shaped fractures.

[0104] In the present exemplary embodiment, as Figure 5 shown, in the irregular fracture model, the support bars 24 may be vertically or parallel arranged outside the left and right planes of the box body 20, and one end of the bolt 23 is fixedly connected to the clamping plate. The vertical or parallel design of the support bars 24 increases the setting density of the bolts 23 on the clamping plate. By screwing in and out the bolts 23 to control the distance between the two clamping plates, an irregular fracture shape can be formed between the clamping plates.

[0105] In the present exemplary embodiment, as Figure 1 shown, the simulation device may further include an inlet wellbore 13 and an outlet wellbore 14. The inlet wellbore 13 and the outlet wellbore 14 are respectively communicated with both ends of the fracture model body to pump proppant into the fracture model body. Specifically, an inlet wellbore 13 and an outlet wellbore 14 are respectively provided on the fracture model 4 at the head and tail of the fracture model body. By pumping proppant and other simulated fracturing fluids into the fracture model 4, the sand-carrying process of the fracturing fluid in the fracture is simulated, and the proppant migration and settlement law and the sand dike formation process under different construction parameters are studied.

[0106] In this exemplary embodiment, the splint may be made of a transparent material, and the splint may be a transparent organic glass plate or a glass plate injection-molded into an irregular crack shape. Specifically, according to experimental requirements, in the flat crack model, the splint is made of a transparent material such as glass, which is convenient for observing the migration and settlement law of proppants during the experiment; in the irregular crack model, the splint can be made of materials such as copper plates and aluminum plates that are easy to process and deform. Under the action of bolts, two splints can easily form an irregularly shaped crack; the splint can also be a transparent organic glass plate injection-molded into an irregular crack shape in advance, which is convenient for observing the migration and settlement law of proppants during the experiment.

[0107] In the third exemplary embodiment of the present invention, the long crack multi-angle sand placement evaluation method can be implemented by the long crack multi-angle sand placement evaluation system described in the above first or second exemplary embodiment, and the evaluation method includes the steps of:

[0108] Determine the crack length, crack inclination angle, crack turning angle, crack width, fracturing fluid viscosity, sand-carrying fluid concentration, pumping displacement, proppant type, and proppant particle size required for the experiment.

[0109] Assemble the sand placement evaluation system and check that the airtightness is qualified.

[0110] Prepare the fracturing fluid with the required viscosity, inject the fracturing fluid into the long crack simulation device at the displacement, fill it and circulate it.

[0111] Add proppants to the fracturing fluid to form a sand-carrying fluid with the experimental concentration and inject it into the long crack simulation device.

[0112] During the experiment, observe the formation process of the sand dike, collect images of the sand placement process, record the geometric morphology of the sand dike at different times, and the flow rate and pressure data at the inlet and outlet of the long crack simulation device.

[0113] In this exemplary embodiment, further, the method may further include the steps of:

[0114] Change the crack length, crack inclination angle, crack turning angle, crack width, fracturing fluid viscosity, sand-carrying fluid concentration, pumping displacement, proppant type, and proppant particle size, and repeat the experiment; use the analytic hierarchy process to analyze the migration and settlement laws of different proppants in long cracks with multi-angle cracks under different crack morphologies and different construction conditions.

[0115] In this exemplary embodiment, for the long crack of the method, the crack length may be 10 - 30 m, the crack inclination angle may be 0 - 90°, the change in the crack turning angle may be 0 - 45°, the crack width may be 0.6 - 1.2 cm, the fracturing fluid viscosity may be 0 - 40 mPa·s, and the pumping displacement of the fracturing fluid may be 0 - 180 L / min.

[0116] In this exemplary embodiment, the migration and settlement law of the proppant may include at least one of the sand dike shape, equilibrium height, equilibrium time, equilibrium flow rate, initial proppant packing distance, flow field characteristics near the inlet, and filling degree near the inlet. Figure 13 FIG. shows a test flow chart according to an exemplary embodiment of the present invention. Specifically, as Figure 13 shown, the multi-angle sand placement evaluation method for a long fracture includes:

[0117] S1. Determine the device parameters: Determine the fracture morphology, fracture length, fracture dip angle, fracture turning angle, and fracture width of the long fracture simulation device.

[0118] S2. Determine the experimental parameters: Fracturing fluid viscosity, pumping displacement, proppant-carrying fluid concentration, pumping process.

[0119] S3. Assemble the long fracture simulation device, and connect the long fracture simulation device, the liquid preparation and sand mixing device, and the control device to form an evaluation system.

[0120] S4. According to the experimental requirements, prepare a fracturing fluid with a certain viscosity that meets the experimental requirements in the liquid preparation tank, and prepare the proppant used in the experiment.

[0121] S5. Inject the prepared fracturing fluid into the multi-angle long fracture simulation device at a predetermined displacement, fill it and circulate it, check the sealing performance of the device. After confirming the sealing, check the cleanliness inside the device to ensure that there are no impurities in the fracture that affect the experimental results.

[0122] S6. Turn on the camera and keep it on to prepare for collecting images during the sand placement process.

[0123] S7. Turn on the control device to start the experiment. There are a pumping displacement button, a sand addition speed button, and an image collection button in the control device. The sand addition speed is calculated from the pumping displacement and the target sand concentration. During the experiment, the sand addition tank uniformly adds the proppant to the mixing tank and mixes it evenly, and the screw pump injects the evenly mixed proppant-carrying fluid into the multi-angle long fracture simulation device.

[0124] S8. During the experiment, observe the formation process of the sand dike, record the geometric morphology of the sand dike at different times, the equilibrium height and equilibrium time of the sand dike, the initial proppant packing distance, the flow field characteristics near the inlet, etc.

[0125] S9. After the experiment is completed, stop the pump and clean the experimental device.

[0126] S10. Adjust the fracture turning angle, fracture dip angle, and fracture width in the long-fracture multi-angle fracture model according to experimental requirements, change the pumping rate, fracturing fluid viscosity, proppant type, and proppant particle size. Repeat steps S1 - S8, and use the analytic hierarchy process to analyze the migration and settlement laws of proppants in the long-fracture multi-angle fracture under different fracture morphologies and different construction conditions, including the geometric shape of the sand embankment, the equilibrium height and equilibrium time of the sand embankment, the initial stacking distance of proppants, and the flow field characteristics near the inlet, etc.

[0127] To better understand the above exemplary embodiments of the present invention, the following further illustrates them with specific examples.

[0128] Example 1: Sand-laying evaluation system and evaluation method considering fracture turning

[0129] 1. Determine the specific parameters of the fracture model in the sand-laying evaluation system: the fracture is 20 meters long, a regular fracture, fractures at 10 meters with a turning angle of 30 degrees, the fracture is at 90 degrees to the horizontal plane, and the fracture width is 10 mm; the length of a single fracture model is 2 meters and the height is 0.6 meters.

[0130] 2. A total of 10 fracture models are required for this evaluation system. Adjust the distance between the two splints by adjusting the screwing length of the bolts on the support bars to achieve a fracture width of 10 mm; connect 5 single fracture models to form the first 10-meter fracture model, then add an expansion joint, and adjust the expansion joint to make the fracture turning angle 30 degrees; then connect the subsequent 10-meter fracture model.

[0131] 3. The experimental liquid is slickwater with a viscosity of 2 mPa·s, the pumping rate is 90 L / min, the sand-carrying fluid concentration is 160 kg / m 3 , continuous sand addition mode, and the proppant is 40 / 70 quartz sand.

[0132] 4. Connect the entire long-fracture multi-angle sand-laying evaluation system.

[0133] 5. Prepare slickwater with a viscosity of 2 mPa·s and 40 / 70 quartz sand.

[0134] 6. Inject slickwater with a viscosity of 2 mPa·s into the fracture simulation device and determine the airtightness of the device.

[0135] 7. Turn on the camera so that it is in the open state.

[0136] 8. Open the pumping rate button, sand addition button, and image acquisition button in the control device, control the experimental displacement to 90 L / min, the sand addition speed to 14.4 kg / min, and start the experiment.

[0137] 9. During the experiment, record the geometric shape of the sand dike at different times, the equilibrium height and equilibrium time of the sand dike, the initial packing distance of the proppant, the flow field characteristics near the inlet, etc.

[0138] 10. After the experiment, stop the pump.

[0139] 11. Clean the entire multi-angle sand placement evaluation device for long fractures.

[0140] Example 2: Sand Placement Evaluation System and Evaluation Method Considering Variable Inclination Angle of Fractures

[0141] 1. Determine the specific parameters of the fracture model in the sand placement evaluation system: the fracture length is 20 meters, the fracture is inclined at 30 degrees to the horizontal plane, and the fracture width is 10 mm; the length of a single multi-angle fracture model for long fractures is 2 meters and the height is 0.6 meters.

[0142] 2. A total of 10 fracture models are required for this evaluation system. By adjusting the screwing length of the bolts on the support bars, the distance between the two clamping plates is adjusted to achieve a fracture width of 10 mm; after connecting the 10 fracture models at one time, by controlling the length of the telescopic rod, one side of the bottom plate is rotated along one side of the base 1, thereby driving the multi-angle fracture model for long fractures to tilt at an angle of 30°, which is used to simulate the inclined fracture.

[0143] 3. The experimental liquid is slickwater with a viscosity of 2 mPa·s, the pumping displacement is 120 L / min, the concentration of the sand-carrying fluid is 160 kg / m 3 , continuous sand addition mode, and the proppant is 40 / 70 ceramic proppant.

[0144] 4. Connect the entire multi-angle sand placement evaluation device for long fractures.

[0145] 5. Prepare slickwater with a viscosity of 2 mPa·s and 40 / 70 ceramic proppant.

[0146] 6. Inject the slickwater with a viscosity of 2 mPa·s into the fracture simulation device to determine the airtightness of the device.

[0147] 7. Turn on the camera so that it is in the open state.

[0148] 8. Open the pumping displacement button, sand addition button, and image acquisition button in the control device, control the experimental displacement to be 120 L / min, the sand addition speed to be 19.2 kg / min, and start the experiment.

[0149] 9. During the experiment, record the geometric shape of the sand dike at different times, the equilibrium height and equilibrium time of the sand dike, the initial packing distance of the proppant, the flow field characteristics near the inlet, etc.

[0150] 10. After the experiment, stop the pump.

[0151] 11. Clean the entire long crack multi-angle sand placement evaluation device.

[0152] Example 3: Sand placement evaluation system and evaluation method considering fracture diversion and fracture variable dip angle

[0153] 1. Determine the specific parameters of the fracture model in the sand placement evaluation system: the fracture length is 20 meters, the fracture is a regular fracture, the fracture turns at an angle of 15 degrees at 10 meters, the fracture is inclined at an angle of 30 degrees to the horizontal plane, and the fracture width is 10 mm; the length of a single long fracture multi-angle fracture model is 2 meters and the height is 0.6 meters.

[0154] 2. A total of 10 long fracture multi-angle fracture models are required for this evaluation system. By adjusting the screwing length of the bolts on the support bars, the distance between the two splints is adjusted to achieve a fracture width of 10 mm; after assembling the first 10-meter long fracture model, an expansion joint is added and the angle of the expansion joint is adjusted to make it 15 degrees; then the last 10-meter fracture model is connected; by controlling the length of the telescopic rod, one side of the bottom plate rotates along one side of the base, thereby driving the long fracture multi-angle fracture model to tilt at an angle of 30°, for simulating the inclined fracture.

[0155] 3. The experimental liquid is high-viscosity slickwater with a viscosity of 10 mPa·s, the pumping displacement is 150 L / min, the concentration of the sand-carrying fluid is 160 kg / m 3 , continuous sand addition mode, and the proppant is 40 / 70 ceramic proppant.

[0156] 4. Connect the entire long fracture multi-angle sand placement evaluation system.

[0157] 5. Prepare slickwater with a viscosity of 10 mPa·s and 40 / 70 ceramic proppant.

[0158] 6. Inject slickwater with a viscosity of 10 mPa·s into the fracture simulation device to determine the airtightness of the device.

[0159] 7. Turn on the camera to make it in the open state.

[0160] 8. Open the pumping displacement button, sand addition button, and image acquisition button in the control device, control the experimental displacement to be 150 L / min, the sand addition speed to be 24.0 kg / min, and start the experiment.

[0161] 9. During the experiment, record the geometric shape of the sand dike at different times, the equilibrium height and equilibrium time of the sand dike, the initial stacking distance of the proppant, the flow field characteristics near the inlet, etc.

[0162] 10. After the experiment, stop the pump.

[0163] 11. Clean the entire long fracture multi-angle sand placement evaluation device.

[0164] Example 4: Evaluation System and Evaluation Method for Multi-angle Sand Deposition in Long Fractures Considering Wedge-shaped Fractures

[0165] 1. Determine the specific parameters of the fracture model in the sand deposition evaluation system: the fracture length is 20 meters, the fracture is at a 90-degree angle to the horizontal plane, and the entire fracture model is a wedge-shaped fracture; the length of a single fracture model is 2 meters and the height is 0.6 meters.

[0166] 2. A total of 10 long fracture multi-angle fracture models are required for this evaluation system. By adjusting the screwing-in lengths of the upper and lower bolts on the support bars, the spacing between the two splints is adjusted to form a wedge-shaped fracture, controlling the upper fracture width to be 10 mm and the lower fracture width to be 6 mm, thus forming a wedge-shaped fracture.

[0167] 3. The experimental liquid is slickwater with a viscosity of 2 mPa·s, the pumping displacement is 100 L / min, the concentration of the sand-carrying fluid is 160 kg / m 3 , slug sand addition mode, and the proppant is 40 / 70 ceramic proppant.

[0168] 4. Connect the entire long fracture multi-angle sand deposition evaluation system.

[0169] 5. Prepare slickwater with a viscosity of 2 mPa·s and 40 / 70 ceramic proppant.

[0170] 6. Inject slickwater with a viscosity of 2 mPa·s into the fracture simulation device to determine the airtightness of the device.

[0171] 7. Turn on the camera so that it is in the open state.

[0172] 8. Open the pumping displacement button, sand addition button, and image acquisition button in the control device, and start the experiment. Control the experimental displacement to be 100 L / min, add pure liquid for 10 minutes, add sand-carrying fluid for 10 minutes, and repeat 5 times. During the process of adding sand-carrying fluid, the sand addition speed is 16.0 kg / min.

[0173] 9. During the experiment, record the geometric shape of the sand dike, the equilibrium height and equilibrium time of the sand dike, the initial stacking distance of the proppant, the flow field characteristics near the inlet, etc. at different times.

[0174] 10. After the experiment, stop the pump.

[0175] 11. Clean the entire long fracture multi-angle sand deposition evaluation device.

[0176] Example 5: Evaluation System and Evaluation Method for Sand Deposition Considering Irregular Fractures

[0177] 1. Determine the specific parameters of the crack model in the sand-laying evaluation system: the crack length is 20 meters, the first 10 meters are regular cracks, the last 10 meters are irregular cracks, the width of the regular crack is 10 mm, and the width of the irregular crack is 6 - 10 mm; the length of the multi-angle crack model of a single long crack is 2 meters and the height is 0.6 meters.

[0178] 2. A total of 10 multi-angle crack models of long cracks are required for this evaluation system. For the first 5 multi-angle crack models of long cracks, the distance between the two splints is adjusted by adjusting the screwing length of the bolts on the support bar, so as to achieve a crack width of 10 mm; after assembling the first 10-meter long crack model, the splints of the last 5 crack models adopt transparent organic glass plates pre-injected into the shape of irregular cracks to form irregular cracks.

[0179] 3. The experimental liquid is slickwater with a viscosity of 2 mPa·s, the pumping displacement is 80 L / min, the concentration of the sand-carrying fluid is 160 kg / m 3 , continuous sand addition mode, and the proppant is 40 / 70 quartz sand.

[0180] 4. Connect the entire multi-angle sand-laying evaluation system for long cracks.

[0181] 5. Prepare slickwater with a viscosity of 2 mPa·s and 40 / 70 quartz sand.

[0182] 6. Inject slickwater with a viscosity of 2 mPa·s into the crack simulation device to determine the airtightness of the device.

[0183] 7. Turn on the camera so that it is in the open state.

[0184] 8. Open the pumping displacement button, sand addition button, and image acquisition button in the control device, control the experimental displacement to be 80 L / min, the sand addition speed to be 12.8 kg / min, and start the experiment.

[0185] 9. During the experiment, record the geometric shape of the sand dike, the equilibrium height and equilibrium time of the sand dike, the initial stacking distance of the proppant, the flow field characteristics near the inlet, etc. at different times.

[0186] 10. After the experiment, stop the pump.

[0187] 11. Clean the entire multi-angle sand-laying evaluation device for long cracks.

[0188] In summary, the beneficial effects of the present invention include at least one of the following:

[0189] (1) By adjusting the width and angle of the simulated cracks in the crack model, the present invention can simulate cracks of different shapes, such as wedge-shaped cracks and flat cracks; the design of the irregular crack model can simulate the crack morphology in the real reservoir with higher reduction degree;

[0190] (2) In the present invention, a universal expansion joint is used to connect between the simulated fractures, which can achieve the angular change between the fracture models, realize fracture turning, and be used to simulate the change of the formation fracture trend. At the same time, a telescopic rod is used to achieve the inclination angle change of the fracture model, and simulate the migration of proppants in fractures with different inclination angles.

[0191] (3) The fracture model of the present invention can be assembled into a long fracture with a longer length (10 - 30 meters) according to the experimental requirements, which is closer to the actual situation that the main fracture in the reservoir is a long fracture. It can eliminate the influence of the inlet and outlet ends on the migration and settlement of proppants in the short fracture simulation device, improve the clarity of observing experimental phenomena, and reduce the possible errors in extracting experimental data due to the small size of the short fracture simulation device.

[0192] (4) The multi-angle sand placement evaluation method for long fractures can quantitatively study the sand dike equilibrium height, equilibrium time, equilibrium flow rate, initial proppant accumulation distance, proppant filling degree near the inlet, etc. of the proppant migration, and characterize the flow field characteristics near the inlet.

[0193] Although the present invention has been described above in conjunction with exemplary embodiments and the accompanying drawings, those of ordinary skill in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A long crack multi-angle sand laying evaluation system, characterized in that, the evaluation system includes a liquid preparation and sand mixing device, a control device and a long crack simulation device, wherein, the liquid preparation and sand mixing device can configure a carrying fluid with a predetermined viscosity and inject the carrying fluid into the long crack simulation device; the long crack simulation device can simulate cracks with different lengths, inclination angles, turning angles and widths; the control device is respectively connected to the liquid preparation and sand mixing device and the long crack simulation device to control the experimental process and record experimental data; the long crack simulation device includes a base, a bottom plate, a telescopic rod and a crack model body. Among them, the base is fixedly arranged on the ground, the bottom plate is horizontally arranged on the base and the bottom plate forms a hinge with the base; the crack model body is fixedly arranged on the bottom plate along the length direction of the bottom plate and is perpendicular to the bottom plate. The crack model body includes more than two crack models and a universal expansion joint connecting adjacent two crack models. The crack model body is in a bent or straight form with a certain length; one end of the telescopic rod is connected to the base, and the other end is connected to the bottom plate to push the bottom plate to rotate relative to the base, so that the crack model body is inclined relative to the ground; the crack model includes at least one of a flat crack model and an irregular crack model; both the flat crack model and the irregular crack model include a box body, two clamping plates, support bars and bolts. Among them, the front and rear sides of the box body are open structures, the two clamping plates are arranged in the box body and are respectively parallel to the left and right sides of the box body. The two clamping plates can cooperate with each other to form a simulated crack channel; the support bars are fixedly arranged on the outer walls on both sides of the box body, and one end of the bolt acts on the two clamping plates, and the other end acts on the support bars; In the flat crack model, the support bars are cross-arranged outside the box body, one end of the bolt abuts against the clamping plate, and the distance between the two clamping plates is adjusted by adjusting the screwing length of the bolt on the support bar; in the irregular crack model, the support bars are vertically or parallel arranged outside the box body, one end of the bolt is fixedly connected to the clamping plate, and the distance between the two clamping plates is controlled by screwing in and out the bolt; under the action of the bolt, the clamping plate can be deformed to form an irregularly shaped crack.

2. The long crack multi-angle sand laying evaluation system according to claim 1, characterized in that, the liquid preparation and sand mixing device includes a liquid preparation tank, a sand adding tank, a stirring tank and a screw pump, wherein, the liquid preparation tank and the sand adding tank are respectively connected to the stirring tank, and the screw pump pumps the carrying fluid stirred evenly by the stirring tank into the inlet of the long crack simulation device; the other end of the liquid preparation tank is connected to the outlet of the long crack simulation device through a pipeline.

3. The long crack multi-angle sand laying evaluation system according to claim 2, characterized in that, the liquid preparation and sand mixing device further includes a sedimentation tank and a drainage trough, and the sedimentation tank is arranged on the pipeline between the outlet of the long crack simulation device and the liquid preparation tank.

4. The long crack multi-angle sand laying evaluation system according to claim 2, characterized in that, The liquid preparation and sand mixing device further includes a flow meter and a pressure gauge, and the flow meter and the pressure gauge can measure the inlet and outlet flow rates and the inlet and outlet pressures of the long fracture multi-angle sand placement evaluation system.

5. The long fracture multi-angle sand placement evaluation system according to claim 1, wherein, the control device includes a camera and a PLC control cabinet, wherein, the camera is used to collect image data of the sand placement in the long fracture simulation device during the experiment; the PLC control cabinet is used to control the pump injection displacement and the sand addition speed of the liquid preparation and sand mixing device, and is used to monitor the inlet and outlet flow rate data of the long fracture simulation device, as well as the pressure data at the inlet, outlet and specific positions.

6. The long fracture multi-angle sand placement evaluation system according to claim 1, wherein, bending portions protruding to the same side are provided at both ends of each of the two clamping plates, and wherein, the two clamping plates are fitted through the bending portions; a groove is provided on the bending portion of one clamping plate, and a protruding portion cooperating with the groove is provided on the bending portion of the other clamping plate; a spring is further provided in the groove, and a spring post is further provided on the protruding portion.

7. The long fracture multi-angle sand placement evaluation system according to claim 1, wherein, the clamping plate is made of a transparent material.

8. The long fracture multi-angle sand placement evaluation system according to claim 1, wherein, the length of the fracture model body is 10 - 30 m, and the inclination angle of the fracture model body relative to the ground is 0 - 90°.

9. The long fracture multi-angle sand placement evaluation system according to claim 7, wherein, the simulation device further includes an inlet wellbore and an outlet wellbore, and the inlet wellbore and the outlet wellbore are respectively communicated with both ends of the fracture model body to pump proppant into the fracture model body.

10. A long fracture multi-angle sand placement evaluation method, wherein, the evaluation method is implemented by the long fracture multi-angle sand placement evaluation system according to any one of claims 1 - 9, and the evaluation method includes the steps: Determine the required fracture length, fracture dip angle, fracture turn angle, fracture width, fracturing fluid viscosity, proppant-carrying fluid concentration, pump injection displacement, proppant type and proppant particle size for the experiment; Assemble the sand placement evaluation system and detect that the airtightness is qualified; Prepare the fracturing fluid with the required viscosity for the experiment, inject the fracturing fluid into the long fracture simulation device at a predetermined displacement, fill it and circulate it; Add proppant to the fracturing fluid to form a proppant-carrying fluid with a predetermined viscosity and inject it into the long fracture simulation device; During the experiment, observe the formation process of the sand dike, collect images of the sand placement process, record the geometric shape of the sand dike at different times, and the flow rate and pressure data at the inlet and outlet of the long fracture simulation device.

11. The long fracture multi-angle sand placement evaluation method according to claim 10, wherein, the method further includes the steps: Change the fracture length, fracture dip angle, fracture turning angle, fracture width, fracturing fluid viscosity, proppant-carrying fluid concentration, pumping rate, proppant type, and proppant particle size, and repeat the experiment; use the analytic hierarchy process to analyze the migration and settlement laws of different proppants in long fractures with multiple angles under different fractures and different construction conditions.

12. The long fracture multi-angle sand placement evaluation method according to claim 10, characterized in that the fracture length of the long fracture in the method is 10-30 m, the fracture dip angle is 0-90°, the fracture turning angle is 0-45°, the fracture width is 0.6-1.2 cm, the viscosity of the fracturing fluid is 1-40 mPa·s, and the displacement of the fracturing fluid is 0-180 L / min.

13. The long fracture multi-angle sand placement evaluation method according to claim 10, characterized in that the migration and settlement law of the proppant includes at least one of the sand dike shape, equilibrium height, equilibrium time, equilibrium flow rate, initial proppant packing distance, flow field characteristics near the inlet, and filling degree near the inlet.

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