Volume fracturing continuous deformation joint network proppant migration experimental simulation device and method

Abstract

The invention relates to a volume fracturing continuous deformation joint network proppant migration experimental simulation device and method, the side wall of a simulation horizontal shaft of the experimental simulation device is connected with an inlet of a visual continuous deformation crack model through a valve, and the outlet direction of the visual continuous deformation crack model is connected with a fracturing fluid recovery container and a pressure gauge through valves; the inlet direction of the simulation horizontal shaft is respectively connected with a pressure gauge, a flowback fluid recovery container and an injection pump through valves; the inlet direction of the injection pump is connected with the fracturing fluid container; the fracturing fluid recovery container is connected with the flowback fluid container and the flowback pump; and the camera device and the pressure gauges are respectively connected with the data acquisition device. The device provided by the invention is reliable in working performance, good in simulation effect, simple in experimental operation and reasonable in design, and the propping agent migration in the extension process of the volume fracturing complex fracture network and the whole subsequent fracturing process can be visually observed.

Description

Technical Field

[0001] The invention relates to the technical field of fracturing and production increase, and in particular to a volume fracturing continuous deformation fracture network proppant migration experimental simulation device and method. Background Art

[0002] Low permeability, ultra-low permeability, and tight oil and gas reservoirs are widely developed in my country. They are characterized by wide distribution areas, diverse reservoir types, and multiple oil and gas-bearing strata. They have gradually become an important resource for stable oil and gas production. Large-scale volume fracturing tests have been carried out on such reservoirs, and the production has been significantly improved. Compared with the general fracturing of a single layer in conventional low-permeability reservoirs, the migration and placement of proppants in volume fracturing present more complex characteristics. The migration of proppants in the process of volume fracturing exists in the continuous stages of opening of complex fracture networks, extension of fracture networks, pumping of sand-carrying fluids, closure of pressure relief fractures, and return of fracturing fluids. During the pumping of sand-carrying fluids, proppants migrate and distribute in different fracture systems as the main fractures gradually extend and the branch fractures open or extend. In the closure stage of the pressure relief fractures, the system pressure in the fractures decreases, and the fractures gradually tend to be closed or semi-closed, and the proppant is squeezed, even broken, and embedded in the wall. During the return process, fluid flow further affects the migration and placement of proppants in the fractures. The impact of this series of stages on proppant migration results in a complex form of proppant laying, which has an important impact on the formation and maintenance of fracture conductivity after fracturing. Existing models and devices are not yet able to simulate the migration of proppant in continuous stages such as the opening of complex fracture networks, fracture network extension, sand-carrying fluid pumping, pressure relief fracture closure, and fracturing fluid backflow; existing devices can only simulate the migration of proppant at a certain fracturing stage, at different locations with the same fracture width (in most devices, the fracture width cannot be changed, and in a few devices, the fracture width can change over time), at different locations with different fracture widths (the model fracture width cannot change over time), etc. In particular, the simulation of proppant migration during the fracture network extension process and the situation where different fracture locations have different fracture widths is difficult, and no device has been established yet.

[0003] For example, Chinese publication number CN202311627947.0 provides a variable fracture proppant transport-closure-backflow simulation experimental device and method, and provides a fracture width adjustment method based on a simple elastic clamp. The elastic clamp is connected to the fracture plate by a sealant to achieve intermediate sealing, but the sealing effect is poor. The proppant entry differences between multiple groups of main fractures and the proppant migration during the entire process of complex fracture network deformation are not characterized, especially the proppant migration during the fracture extension and opening process (different fracture widths in the horizontal direction at different times) cannot be achieved.

[0004] In addition, the proppant migration experiments conducted found that complex fracture combinations are difficult. When the fracture model is squeezed or backflowed, or when the elastic clamp is over-squeezed, it is easy to cause problems such as failure of the complex fracture model seal and leakage of fracturing fluid, which will affect the proppant migration results. A simpler and more effective sealing process is urgently needed.

[0005] In view of this, it is very necessary to design an experimental device and method that can simulate the variable width of fractures in multiple states and can meet the simulation of continuous processes such as fracture opening-fracture extension-proppant delivery-closure-reflux. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned background technology, the present invention proposes a volume fracturing continuous deformation fracture network proppant migration experimental simulation device, which has reliable working performance, good simulation effect, simple experimental operation and reasonable design, and can visually observe the complex fracture network extension process of volume fracturing and the proppant migration in the subsequent whole process of fracturing.

[0007] The technical solution of the present invention to solve the above problems is:

[0008] A volume fracturing continuous deformation fracture network proppant migration experimental simulation device, which is special in that:

[0009] It includes a visual continuous deformation fracture model, a fracturing fluid container, an injection pump, a flowback fluid recovery container, a simulated horizontal wellbore, a squeeze fluid container, a squeeze pump, a fracturing fluid recovery container, a flowback fluid container, a flowback pump, a hydraulic connection pipeline, a camera device and a data acquisition device;

[0010] The simulated horizontal wellbore side wall is connected to the inlet of the visualized continuous deformation fracture model through a valve, and the outlet direction of the visualized continuous deformation fracture model is connected to the fracturing fluid recovery container and the pressure gauge through a valve; the inlet direction of the simulated horizontal wellbore is respectively connected to the pressure gauge, the return fluid recovery container, and the injection pump through a valve; the inlet direction of the injection pump is connected to the fracturing fluid container; the fracturing fluid recovery container is connected to the return fluid container and the return pump; the camera device and each pressure gauge are respectively connected to the data acquisition device.

[0011] Furthermore, the above-mentioned visualized continuous deformation crack model includes a main crack, a branch crack, an inlet pipeline and an outlet pipeline;

[0012] The main crack and the branch crack both include a crack plate, an input port, an output port, an extrudable sealing ring, a transparent reinforcement sticker, and a filter screen;

[0013] Each group of crack plates of the main crack, each group of crack plates of the branch crack, and the crack plates of the main crack and the branch crack are connected by an extrudable sealing ring; the outside of each group of crack plates and the extrudable sealing ring is wrapped with a transparent reinforcing sticker, and the extrudable sealing ring and the transparent reinforcing sticker perform double sealing on the crack plates; filters are placed outside the input port and the output port.

[0014] Furthermore, a hydraulic device and a bolt squeeze clamp are fixed to the outside of each group of crack plates, and the crack width between each group of crack plates is doubly adjusted by the hydraulic device and the bolt squeeze clamp.

[0015] Furthermore, there are multiple visualized continuous deformation fracture models, and the mesh size of the filter is close to or smaller than the mesh size of the proppant.

[0016] Furthermore, the crack plate is a transparent solid plate, which may be a glass plate, an acrylic plate or other transparent materials.

[0017] Furthermore, the number of bolt compression clamps on the above-mentioned main cracks and branch cracks is not less than 100 respectively.

[0018] Furthermore, the hydraulic device comprises a hydraulic base front plate, a hydraulic base connecting rod, a hydraulic base rear plate, a hydraulic shunt pipeline, a hydraulic rod, and a hydraulic valve;

[0019] The front plate of the hydraulic base and the rear plate of the hydraulic base are connected by a hydraulic base connecting rod. The front plate of the hydraulic base and the rear plate of the hydraulic base are provided with a plurality of hydraulic rods, hydraulic valves are installed on the hydraulic rods, and the hydraulic rods are connected to the extrusion pump through hydraulic shunt pipelines.

[0020] Furthermore, the extrusion pump is connected to an extrusion liquid container; and the number of the hydraulic rods is not less than two.

[0021] In addition, based on the above-mentioned volume fracturing continuous deformation fracture network proppant migration experimental simulation device, the present invention also proposes a volume fracturing continuous deformation fracture network proppant migration experimental simulation method, which is special in that it includes the following steps:

[0022] Step S1: Preparation and device construction. The experimental process is as follows:

[0023] S101 Preparation: Arrange the components required for the experimental device, fracturing fluid 1, fracturing fluid 2, and proppant.

[0024] S102 built a volume fracturing continuous deformation fracture network proppant migration experiment simulation device to conduct sealing tests.

[0025] Step 2: Proppant pumping during the formation of continuous deformation fracture network during volume fracturing:

[0026] S201 adding dyed fracturing fluid 1 and proppant into the simulated fracturing fluid pool to prepare sand-carrying fluid;

[0027] S202 injects the sand-carrying fluid into the simulated horizontal wellbore through the injection pump at a certain pumping displacement, and then enters the visualized continuous deformation fracture model through the input port; the leading edge of the dyed fracturing fluid 1 indicates the injection position of the sand-carrying fluid. As the leading edge of the fracturing fluid 1 moves, the squeezing degree of the hydraulic rod and the bolt squeezing clamp of the hydraulic device at different positions is adjusted to increase the width of the main crack and branch crack at different positions in the visualized continuous deformation fracture model to a certain value in turn, simulating the dynamic expansion and opening of the fracture network; the migration of the proppant is visualized by the camera device to monitor the pressure change.

[0028] S203 When the sand-carrying fluid reaches the output port of the visualized continuous deformation fracture model, the injection pump is stopped.

[0029] Step 3: Crack closure, extrusion and flowback experiment. The experimental process is as follows:

[0030] S301 adjusts the hydraulic device and the bolt extrusion clamp, measures the distance between the crack plates, controls the extrusion degree of the extrudable sealing ring, and closes the width of the main crack and branch crack to a certain value.

[0031] S302 uses a camera to visually observe the proppant migration during the crack plate closing and squeezing process and monitor the pressure changes.

[0032] S303: Put fracturing fluid 2 into the flowback pool, or allow fracturing fluid 1 to enter the flowback pool for gel breaking, to characterize the fracturing fluid gel breaking process; open the valves connecting the flowback fluid container, the flowback pump, and the flowback fluid recovery container; close the valves connecting the injection pump, the fracturing fluid container, and the fracturing fluid recovery container; inject fracturing fluid 2 from the output port of the visualized continuous deformation fracture model through the flowback pump at a certain displacement, and let it flow out from the input port of the visualized continuous deformation fracture model, visualize the migration of the proppant through the camera device, monitor the pressure change, and observe the outflow of fracturing fluid 2; when a certain volume of fracturing fluid 2 is injected, stop the flowback pump; end the experiment and clean the experimental device.

[0033] Step 4: Data analysis and result summary:

[0034] S401 performs analysis based on the measured experimental data, including the flow of proppant in the fracture model, pressure distribution, proppant reflux, etc.; changes the experimental parameters (including the combination form, number and level of main fractures and branch fractures, the type and parameters of fracturing fluid and flowback fluid, proppant parameters, fracture plate length, surface roughness, initial fracture width, extrusion degree, pumping parameters, flowback parameters, etc.) to simulate the proppant migration and laying conditions of the volume fracturing continuous deformation fracture network system formation process (proppant pumping-fracture extension and expansion-closure extrusion-flowback) under different injection processes.

[0035] Furthermore, the above step S102 specifically includes: connecting different components of the visualized continuous deformation fracture model, injecting water into the input port by using an injection pump, and conducting a sealing test to ensure that the system is sealed reliably; connecting the visualized continuous deformation fracture model, the simulated horizontal wellbore, the injection pump, the fracturing fluid container, the pressure gauge, the squeeze liquid container, the squeeze pump, the fracturing fluid recovery container, the valve, the hydraulic connecting pipeline, the camera device, and the data acquisition device; adjusting the hydraulic device and the bolt squeeze clamp to squeeze the width of the main crack and the branch crack in the visualized continuous deformation fracture model to a certain value, and the minimum width can be close to zero; injecting water into the simulated horizontal wellbore by the injection pump, and conducting a sealing test to ensure that the system is sealed reliably; further connecting the return fluid container, the return pump, the return fluid recovery container, and the valve, and injecting water into the output port of the visualized continuous deformation fracture model by the return pump, and conducting a sealing test in the reverse direction to ensure that the system is sealed reliably; after the test is completed, closing the valve connecting the return fluid container, the return pump, and the return fluid recovery container.

[0036] Advantages of the present invention:

[0037] (1) The present invention can adapt to the requirements of different complex fracture combinations and fracture width variations at different times and locations in volume fracturing, and can characterize the continuous migration simulation of proppant in the continuous processes of fracture generation and extension, sand-carrying fluid filling, fracture closure, pressure relief and reflux in the mine;

[0038] (2) The present invention can achieve proppant delivery-closure-backflow simulation for different sizes of fractures, main fractures and branch fractures in a complex fracture network of volume fracturing by adjusting the working parameters of the device;

[0039] (3) The experimental operation of the present invention is simple and convenient, and the cost is low. The present invention provides a visual experimental condition for proppant migration simulation in a volume fracturing continuous deformation fracture network system, and provides a favorable guidance for in-depth understanding of proppant laying rules and post-fracturing capacity prediction;

[0040] (4) The present invention proposes a composite sealing method for the fracture model, which avoids the continuous deformation of the fracture closure and the leakage of the fracturing fluid and proppant at the fracture connection position;

[0041] (5) The present invention provides a mechanical + hydraulic composite extrusion method for a volume fracturing continuous deformation fracture network system, which can flexibly adjust the fracture width at different times and locations. When one extrusion method fails or the extrusion degree is insufficient, another extrusion method can play a supplementary role. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of a simulation device for a proppant migration experiment in a volume fracturing continuous deformation fracture network;

[0043] Figure 2A schematic diagram of the composition of a visualized continuous deformation crack model in a volume fracturing continuous deformation crack network proppant migration experimental simulation device;

[0044] Figure 3 It is a schematic diagram of the appearance of a squeezable sealing ring in a volume fracturing continuous deformation fracture network proppant migration simulation device;

[0045] Figure 4 It is a complex fracture partial combination form applicable to a volume fracturing continuous deformation fracture network proppant migration experimental simulation device.

[0046] Description of reference numerals:

[0047] 1-Visualized continuous deformation crack model; 111-Main crack; 112-Branch crack; 113-Inlet pipeline;

[0048] 114-export pipeline; 115-input port; 116-output port; 117-transparent reinforcement sticker; 118-crack plate; 119-squeezable sealing ring; 120-filter screen;

[0049] 2-Fracturing fluid container; 3-Injection pump; 4-Flowback fluid recovery container; 5-Pressure gauge; 6-Simulated horizontal wellbore;

[0050] 7-bolt squeeze clamp;

[0051] 8-hydraulic device; 811-hydraulic base front plate; 812-hydraulic base connecting rod; 813-hydraulic base rear plate; 814-hydraulic shunt pipeline; 815-hydraulic rod; 816-hydraulic valve;

[0052] 9-squeeze liquid container; 10-squeeze pump; 11-fracturing fluid recovery container; 12-flowback liquid container; 13-flowback pump; 14-valve; 15-hydraulic connecting pipeline; 16-camera device; 17-data acquisition device. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0054] See also Figure 1A volume fracturing continuous deformation fracture network proppant migration experiment simulation device includes a visualized continuous deformation fracture model 1, a fracturing fluid container 2, an injection pump 3, a backflow fluid recovery container 4, a simulated horizontal wellbore 6, an extrusion fluid container 9, an extrusion pump 10, a fracturing fluid recovery container 11, a backflow fluid container 12, a backflow pump 13, a hydraulic connecting pipeline 15, a camera device 16 and a data acquisition device 17.

[0055] The inlet direction of the visualized continuous deformation fracture model 1 is connected to the valve 14 and the simulated horizontal wellbore 6, and the outlet direction of the visualized continuous deformation fracture model 1 is connected to the fracturing fluid recovery container 11 and the pressure gauge 5 through the valve 14; the inlet direction of the simulated horizontal wellbore 6 is connected to the pressure gauge 5, the backflow fluid recovery container 4, and the injection pump 3 through the valve 14; the inlet direction of the injection pump 3 is connected to the fracturing fluid container 2; the fracturing fluid recovery container 11 is connected to the backflow fluid container 12 and the backflow pump 13; each pressure gauge 5, the camera device 16 is connected to the data acquisition device 17.

[0056] In this embodiment, the number of the visualized continuous deformation crack models 1 is multiple.

[0057] Specifically, see Figure 2 The visualized continuous deformation crack model 1 includes a main crack 111, a branch crack 112, an inlet pipeline 113, and an outlet pipeline 114; the main crack 111 and the branch crack 112 are composed of a crack plate 118, an input port 115, an output port 116, an extrudable sealing ring 119, a transparent reinforcement sticker 117, a bolt extrusion clamp 7, a hydraulic device 8, and a filter screen 120.

[0058] The number of bolt compression clamps 7 on the main crack 111 and the branch crack 112 is not less than 2. The crack plate 118 is a transparent solid plate, which can be a glass plate, an acrylic plate or other transparent materials.

[0059] Each group of crack plates of the main crack 111, each group of crack plates of the branch crack 112, and the crack plates of the main crack 111 and the branch crack 112 are connected by an extrudable sealing ring 119, and the outside of the crack plate 118 and the extrudable sealing ring 119 is wrapped with a transparent reinforcing paste 117, and the extrudable sealing ring 119 and the transparent reinforcing paste 117 perform double sealing on the crack plate 118; a filter screen 120 is placed outside the input port 115 and the output port 116, and the mesh number of the filter screen 120 is close to or less than the mesh number of the proppant; a hydraulic device 8 and a bolt extrusion clamp 7 are fixed to the outside of each group of crack plates, and the seam width between each group of crack plates is doubly adjusted by the hydraulic device 8 and the bolt extrusion clamp 7.

[0060] In some embodiments provided by the present invention, the visualized continuous deformation crack model 1 is an internal and external integrated sealed package, composed of multiple rectangular rough glass plates, including two 40 cm rectangular rough glass plates, multiple 10 cm rectangular rough glass plates, the thickness of the rectangular rough glass plates is 5 mm, the rough glass plates are sealed and connected by an extrudable sealing ring 119, and the outside of the extrudable sealing ring 119 and the connection are further affixed with a transparent reinforcement sticker 117 (6 cm wide) to prevent the fracturing fluid from leaking during transportation-extrusion-return. The diameter of the input port 115 and the output port 116 is 7 mm, the outer diameter of the hose connecting the input port 115 and the output port 116 is 7 mm, and the inner diameter is 5 mm, and the filter screen 120 is made of stainless steel and has a mesh size of 30.

[0061] In some embodiments provided by the present invention, the extrudable sealing ring 119 is a silicone strip, a rubber strip, a cured resin, etc., which has significant elasticity and is not a rigid or weakly extrudable material. The crack width can be adjusted by extruding through the mechanical and hydraulic device 8. After the extrudable sealing ring 119 is extruded, the crack width can be adjusted from the initial thickness of 4-10 mm to the thickness of 0-3 mm after extrusion.

[0062] In some embodiments provided by the present invention, the bolt squeezing clamp 7 is a multi-point angle, such as a two-point or three-point clamp, which applies a certain pressure to the crack plate through the movement of the thread, thereby squeezing the sealing ring 119 to achieve crack squeezing during the fracturing process. The visualized continuous deformation crack model 1 can be installed with multiple bolt squeezing clamps 7. Each group of crack plates of the main crack 111 and the branch crack 112 is placed with no less than 2 bolt squeezing clamps 7 to achieve real-time adjustment of the multi-point crack width.

[0063] In some embodiments provided by the present invention, see Figure 2 The hydraulic device 8 includes a hydraulic base front plate 811, a hydraulic base connecting rod 812, a hydraulic base rear plate 813, a hydraulic diversion pipeline 814, a hydraulic rod 815, and a hydraulic valve 816.

[0064] Specifically, the hydraulic base front plate 811 and the hydraulic base rear plate 813 are connected by a hydraulic base connecting rod 812, and a plurality of hydraulic rods 815 are provided on the hydraulic base front plate 811 and the hydraulic base rear plate 813, and a hydraulic valve 816 is installed on the hydraulic rod 815, and the hydraulic rod 815 is connected to the extrusion pump 10 through a hydraulic shunt pipeline 814. The extrusion pump 10 is connected to the extrusion liquid container 9; the number of the hydraulic rods 815 is not less than two.

[0065] In this embodiment, the working principle of the hydraulic device 8 is similar to that of a jack or a syringe. Different hydraulic pressures are applied to the hydraulic rods 815 at different positions of the hydraulic device 8 through the extrusion pump 10, and different confining pressures are further applied to the fracture plates at different positions, thereby controlling the extrusion degree of the extrudable sealing ring 119, realizing the deformation of the fracture plate at different positions and at different times, and truly simulating the migration of the proppant during the entire fracturing process.

[0066] In this embodiment, see Figure 3 The cross-sectional shape of the extrudable sealing ring 119 is a "mountain" character. The protrusions on both sides of the extrudable sealing ring 119 (10-15 mm in height) wrap a group of crack plates 118. The middle protrusion (10-20 mm in height) of the extrudable sealing ring 119 realizes the initial seam width control between a group of crack plates. The bottom width of the groove is 5.1 mm and the top width of the groove is 4.9 mm.

[0067] The device can observe the degree of change of cracks and the laying rules of proppants in cracks from multiple angles, realize multi-faceted observation, control crack width in multiple ways, enhance sealing effect, realize proppant migration in the process of lateral crack extension and opening (different time, different position, different crack width), and also realize proppant migration in continuous stages such as sand-carrying fluid pumping, pressure relief crack closure, and fracturing fluid return.

[0068] The present invention also provides a volume fracturing continuous deformation fracture network proppant migration experimental simulation method, which is implemented according to the volume fracturing continuous deformation fracture network proppant migration experimental simulation device, and includes the following steps:

[0069] Step S1: Preparation and device construction. The experimental process is as follows:

[0070] S101 Preparation: Arrange the components required for the experimental device, fracturing fluid 1, fracturing fluid 2, and proppant.

[0071] S102 Build the device and conduct sealing test: Connect the different components of the visual continuous deformation crack model 1, use the injection pump 3 to inject water into the input port 115, and conduct a sealing test to ensure that the system is sealed reliably; connect the visual continuous deformation crack model 1, the simulated horizontal wellbore 6, the injection pump 3, the fracturing fluid container 2, the pressure gauge 5, the squeezing fluid container 9, the squeezing pump 10, the fracturing fluid recovery container 11, the valve 14, the hydraulic connecting pipeline 15, the camera device 16, and the data acquisition device 17; adjust the hydraulic device 8 and the bolt squeezing clamp 7 to connect the main crack 111 and the branch cracks in the visual continuous deformation crack model 1. The width of the seam 112 is squeezed to a certain value, and the minimum seam width can be close to 0 (the initial seam width is squeezed to 1 mm in the experiment of this embodiment); water is injected into the simulated horizontal wellbore 6 by the injection pump 3, and a sealing test is carried out to ensure that the system is sealed reliably; the backflow liquid container 12, the backflow pump 13, the backflow liquid recovery container 11, and the valve 14 are further connected, and water is injected into the output port 116 of the visualized continuous deformation fracture model 1 by the backflow pump 13, and a sealing test is carried out in the reverse direction to ensure that the system is sealed reliably; after the test is completed, the valve 14 connecting the backflow liquid container 12, the backflow pump 13, and the backflow liquid recovery container 11 is closed.

[0072] In this embodiment, the simulated horizontal well device 6 is connected to multiple visualized continuous deformation fracture models 1 through a valve 14, so that one or more visualized continuous deformation fracture models 1 can be tested simultaneously to observe the migration of proppants in different fracture combinations. Figure 4 The combination of complex fracture networks mainly includes the number and position of main fractures 111, whether there are branch fractures 112, the number and position of branch fractures 112, whether branch fractures 112 are connected to multiple main fractures 111, and the same main fracture 111 has different numbers of branch fractures 112. According to the distribution form of existing volume fracturing complex fracture networks, the main fractures 111 and the branch fractures 112 can also have different spatial extension directions, such as the main fracture is vertical and the branch fracture is vertical, the main fracture is horizontal and the branch fracture is horizontal, the main fracture is vertical and the branch fracture is horizontal, and the main fracture is horizontal and the branch fracture is vertical.

[0073] Step 2: Proppant pumping during the formation of continuous deformation fracture network during volume fracturing:

[0074] S201: Add dyed fracturing fluid 1 and proppant into the simulated fracturing fluid pool to prepare sand-carrying fluid; in this embodiment, slick water fracturing fluid (0.3% gel ratio) and ceramsite (70-140 mesh + 40-70 mesh + 30-50 mesh) are used to prepare 1L of sand-carrying fluid and 20% of sand ratio;

[0075] S202 injects the sand-carrying fluid into the simulated horizontal wellbore 6 through the injection pump 3 at a certain pumping displacement, and then enters the visualized continuous deformation fracture model 1 through the input port 115. In this embodiment, the displacement is set to 120 ml / min; the leading edge of the dyed fracturing fluid 1 indicates the injection position of the sand-carrying fluid. As the leading edge position of the fracturing fluid 1 moves, the squeezing degree of the hydraulic rod 815 of the hydraulic device and the bolt squeezing clamp 7 at different positions is adjusted to increase the width of the main fracture 111 and the branch fracture 112 at different positions in the visualized continuous deformation fracture model to a certain value (in the experiment of this embodiment, the maximum width of the main fracture is 6-8 mm, and the maximum width of the branch fracture is 2-4 mm), simulating the dynamic expansion and opening of the fracture network; the migration of the proppant is visualized by the camera device 16 to monitor the pressure change.

[0076] S203 When the sand-carrying liquid reaches the output port 116 of the visualized continuous deformation crack model 1, the injection pump 3 is stopped; in this embodiment, about 600 ml of the sand-carrying liquid is injected.

[0077] Step 3: Crack closure, extrusion and flowback experiment. The experimental process is as follows:

[0078] S301 adjusts the hydraulic device 8 and the bolt extrusion clamp 7, measures the distance between the crack plates 118, controls the extrusion degree of the extrudable sealing ring 119, and realizes the closure of the width of the main crack 111 and the branch crack 112 to a certain value.

[0079] S302 visualizes the proppant migration during the crack plate closing and squeezing process through the camera device 16 to monitor the pressure change.

[0080] S303: Put fracturing fluid 2 into the backflow liquid pool, or add a debonding agent to fracturing fluid 1 into the backflow liquid pool to break the gel, and characterize the fracturing fluid breaking process; open the valve 14 connecting the backflow liquid container 12, the backflow pump 13, and the backflow liquid recovery container 11; close the valve 14 connecting the injection pump 3, the fracturing fluid container 2, and the fracturing fluid recovery container 11; inject the fracturing fluid 2 from the output port 116 of the visualized continuous deformation fracture model 1 through the backflow pump 13 at a certain displacement (200-350ml / min), and flow out from the input port 115 of the visualized continuous deformation fracture model 1, and visualize the migration of the proppant through the camera device 16, monitor the pressure change, and observe the outflow of the fracturing fluid 2; when a certain volume of fracturing fluid 2 is injected (about 500ml is injected into the backflow in this embodiment), stop the backflow pump 13; end the experiment and clean the experimental device.

[0081] Step 4: Data analysis and result summary:

[0082] S401 performs analysis based on the measured experimental data, including the flow of proppant in the fracture model, pressure distribution, proppant reflux, etc.; changes the experimental parameters (including the combination form, number and level of main fractures and branch fractures, the type and parameters of fracturing fluid and flowback fluid, proppant parameters, fracture plate length, surface roughness, initial fracture width, extrusion degree, pumping parameters, flowback parameters, etc.) to simulate the proppant migration and laying conditions of the volume fracturing continuous deformation fracture network system formation process (proppant pumping-fracture extension and expansion-closure extrusion-flowback) under different injection processes.

[0083] According to the complex formation crack conditions encountered in actual oil and gas production, different types of complex cracks and different crack widths are changed, suitable proppants are selected, and the number and connection form of the rough crack plates in the visualized continuous deformation crack model 1 are changed, so that a complex crack situation simulation device can be established. In this embodiment, the device is built to ensure that the system is sealed reliably. The rough crack plates 118 used in the main crack 111 and the branch crack 112 are consistent, both of which are rectangular rough glass plates. The position and angle between the branch crack 112 and the main crack 111 can be changed to achieve the study of the proppant migration law in the crack based on the position and angle of different secondary cracks. Through the composite form of the bolt extrusion clamp 7 and the hydraulic device 8, the extrusion degree of the extrudable sealing ring 119 on the main crack 111 and the branch crack 112 is adjusted to change the crack width of the main crack 111 and the branch crack 112 at different times and different positions. With the entry of the sand-carrying fluid, the extrusion degree of the extrudable sealing ring 119 is released from left to right in turn, and the extrudable sealing ring 119 is synchronously extruded during the crack closing process. The flow rate of the pump is adjusted to control the flow rate and pressure of the proppant, and the proppant is injected to conduct experiments. During the experiment, the changes in the experimental parameters, including flow rate, pressure, temperature, etc., are continuously monitored, and the experimental data are recorded; and corresponding video recording is performed according to the experimental requirements. When a certain pumping time is reached, the experiment is stopped; the fracturing fluid 2 after gel breaking is injected into the output port 116 of the main fracture and the secondary fracture through the reflux liquid delivery pump, and the fracturing fluid 2 flows from the input port 115 of the main fracture and the branch fracture to the return liquid recovery container 4, and the flow of the proppant in the fracture model is observed.

[0084] The migration experiment simulation method carried out by this experimental device realizes the function of observing the migration law of proppant in the whole process of complex fracture network extension and subsequent fracturing of volume fracturing and in different complex fracture combinations of volume fracturing. Complex fractures involve different combinations of main fractures and branch fractures, which can more realistically simulate the proppant migration characteristics of the formation-extension-filling-closure-flowback process of complex fractures in volume fracturing in the formation. The experimental operation is simple and the design is reasonable, which provides theoretical support for predicting the proppant laying state and production capacity change law in the fractures after fracturing.

[0085] Matters not covered by the present invention are known technologies.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can still adjust the technical solutions described in the above embodiments or replace some of the technical features by equivalents. Therefore, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A volume fracturing continuous deformation fracture network proppant migration experimental simulation device, which is special in that: It includes a visualized continuous deformation fracture model (1), a fracturing fluid container (2), an injection pump (3), a flowback fluid recovery container (4), a simulated horizontal wellbore (6), an extrusion fluid container (9), an extrusion pump (10), a fracturing fluid recovery container (11), a flowback fluid container (12), a flowback pump (13), a hydraulic connection pipeline (15), a camera device (16) and a data acquisition device (17); The side wall of the simulated horizontal wellbore (6) is connected to the inlet of the visualized continuous deformation fracture model (1) through a valve, and the outlet direction of the visualized continuous deformation fracture model (1) is connected to the fracturing fluid recovery container (11) and the pressure gauge through a valve; the inlet direction of the simulated horizontal wellbore (6) is respectively connected to the pressure gauge, the backflow fluid recovery container (4), and the injection pump (3) through a valve; the inlet direction of the injection pump (3) is connected to the fracturing fluid container (2); the fracturing fluid recovery container (11) is connected to the backflow fluid container (12) and the backflow pump (13); the camera device (16) and each pressure gauge are respectively connected to the data acquisition device (17).

2. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 1 is special in that: The visualized continuous deformation crack model (1) comprises a main crack (111), a branch crack (112), an inlet pipeline (113) and an outlet pipeline ((114); The main crack (111) and the branch crack (112) each include a crack plate (118), an input port (115), an output port (116), an extrudable sealing ring (119), a transparent reinforcement sticker (117), and a filter screen (120); Each group of crack plates of the main crack (111), each group of crack plates of the branch crack (112), and the crack plates of the main crack (111) and the crack plates of the branch crack (112) are connected via an extrudable sealing ring (119); the outside of each group of crack plates (118) and the extrudable sealing ring (119) is wrapped with a transparent reinforcing sticker (117), and the extrudable sealing ring (119) and the transparent reinforcing sticker (117) perform a double seal on the crack plates (118); and a filter screen (120) is placed outside the input port (115) and the output port (116).

3. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 2 is special in that: A hydraulic device (8) and a bolt extrusion clamp (7) are fixed to the outside of each group of slit plates, and the slit width between each group of slit plates is doubly adjusted by the hydraulic device (8) and the bolt extrusion clamp (7).

4. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 3 is special in that: The cross-sectional shape of the extrudable sealing ring (119) is a "mountain" shape, the protrusions on both sides of the extrudable sealing ring (119) wrap a group of crack plates (118), and the middle protrusion of the extrudable sealing ring (119) realizes the initial seam width control between the group of crack plates.

5. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 4 is special in that: The crack plate (118) is a transparent solid plate; the number of the visualized continuous deformation crack models (1) is multiple, and the mesh number of the filter screen (120) is close to or smaller than the mesh number of the proppant.

6. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 5 is special in that: The number of bolt compression clamps (7) on the main crack (111) and the branch crack (112) is no less than 2 respectively.

7. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 6 is special in that: The hydraulic device (8) comprises a hydraulic base front plate (811), a hydraulic base connecting rod (812), a hydraulic base rear plate (813), a hydraulic flow distribution pipeline (814), a hydraulic rod (815), and a hydraulic valve (816); The hydraulic base front plate (811) and the hydraulic base rear plate (813) are connected via a hydraulic base connecting rod (812); a plurality of hydraulic rods (815) are provided on the hydraulic base front plate (811) and the hydraulic base rear plate (813); hydraulic valves (816) are installed on the hydraulic rods (815); and the hydraulic rods (815) are connected to the extrusion pump (10) via a hydraulic shunt pipeline (814).

8. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 7 is special in that: The extrusion pump (10) is connected to the extrusion liquid container (9); the number of hydraulic rods (815) on the hydraulic base front plate (811) and the hydraulic base rear plate (813) is not less than two.

9. A volume fracturing continuous deformation fracture network proppant migration experimental simulation method, according to the volume fracturing continuous deformation fracture network proppant migration experimental simulation device according to claim 8, which is special in that it includes the following steps: Step S1: Preparation and device construction. The experimental process is as follows: S101 Preparation: Arrange the components required for the experimental device, fracturing fluid 1, fracturing fluid 2, and proppant; S102 built a volume fracturing continuous deformation fracture network proppant migration simulation device and conducted a sealing test; Step 2: Proppant pumping during the formation of continuous deformation fracture network during volume fracturing: S201 adding dyed fracturing fluid 1 and proppant into the simulated fracturing fluid pool to prepare sand-carrying fluid; S202 injects the sand-carrying fluid into the simulated horizontal wellbore (6) through the injection pump (3) at a certain pumping displacement, and then enters the visualized continuous deformation fracture model (1) through the input port (115); the leading edge of the dyed fracturing fluid 1 indicates the injection position of the sand-carrying fluid, and as the leading edge position of the fracturing fluid 1 moves, the squeezing degree of the hydraulic rod (815) of the hydraulic device and the bolt squeezing clamp (7) at different positions is adjusted to increase the crack widths of the main crack (111) and the branch crack (112) at different positions in the visualized continuous deformation fracture model (1) to certain values ​​in sequence, simulating a dynamically expanded and opened crack network; and the migration of the proppant is visualized and the pressure change is monitored through the camera device (16); S203: when the sand-carrying fluid reaches the output port (116) of the visualized continuous deformation fracture model (1), the injection pump (3) is stopped; Step 3: Crack closure, extrusion and flowback experiment. The experimental process is as follows: S301 adjusts the hydraulic device (8) and the bolt squeeze clamp (7), measures the distance between the crack plates, controls the squeezing degree of the squeezing seal ring (119), and closes the width of the main crack (111) and the branch crack (112) to a certain value; S302 visually observes the proppant migration during the crack plate closing and squeezing process through a camera device (16) to monitor the pressure change; S303: Put fracturing fluid 2 into the flowback liquid pool; open the valves connecting the flowback liquid container (12), the flowback pump (13), and the flowback liquid recovery container (4); close the valves connecting the injection pump (3), the fracturing fluid container (2), and the fracturing fluid recovery container (11); inject fracturing fluid 2 from the output port (116) of the visualized continuous deformation fracture model (1) through the flowback pump (13) at a certain displacement, and let it flow out from the input port (115) of the visualized continuous deformation fracture model (1); visualize the migration of the proppant through the camera device (16), monitor the pressure change, and observe the outflow of fracturing fluid 2; when a certain volume of fracturing fluid 2 is injected, stop the flowback pump (13); end the experiment and clean the experimental device; Step 4: Data analysis and results summary: S401 performs analysis based on the measured experimental data, including the flow of proppant in the fracture model (1), pressure distribution, and proppant reflux; changes the experimental parameters to simulate the proppant migration and placement during the formation of a volume fracturing continuous deformation fracture network system under different injection processes.

10. The volume fracturing continuous deformation fracture network proppant migration experimental simulation device method according to claim 9 is special in that: Step S102 specifically includes: Connect different components of the visualized continuous deformation fracture model (1), use the injection pump (3) to inject water into the input port (115), conduct a sealing test, and ensure that the system is sealed reliably; connect the visualized continuous deformation fracture model (1), the simulated horizontal wellbore (6), the injection pump (3), the fracturing fluid container (2), the pressure gauge, the squeeze fluid container (9), the squeeze pump (10), the fracturing fluid recovery container (11), the valve, the hydraulic connection pipeline (15), the camera device (16), and the data acquisition device; adjust the hydraulic device (8) and the bolt squeeze clamp (7) to close the main fracture ( 111), the width of the branch fracture (112) is squeezed to a certain value, and the minimum width of the fracture can be close to zero; water is injected into the simulated horizontal wellbore (6) by the injection pump (3), and a sealing test is carried out to ensure that the system is sealed reliably; the return fluid container (12), the return pump (13), the return fluid recovery container (4), and the valve are further connected, and water is injected into the output port (116) of the visualized continuous deformation fracture model (1) by the return pump (13), and a sealing test is carried out in the reverse direction to ensure that the system is sealed reliably; after the test is completed, the valve connecting the return fluid container (12), the return pump (13), and the return fluid recovery container (4) is closed.

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