Visualization method and device for simulating migration rule of proppant in fracture dynamic expansion process

Abstract

The invention discloses a visualization method and device for simulating the migration rule of a proppant in the crack dynamic expansion process, and relates to the technical field of crack expansion and proppant migration. According to the method and device, a crack dynamic expansion visualization model is established, transparent sample plates with different elastic constants are adopted, a finite acute angle crack is reasonably set, and the migration rule of the proppant in the crack dynamic expansion process is simulated. Under the condition that the interface roughness is certain, pressure is applied through the inflatable rubber bag, a crack expansion visual model of a crack flat plate closed layered structure is established, and the dynamic problems of crack initiation expansion and synchronous migration of a propping agent are solved from the overall structure.

Description

Technical Field

[0001] The invention relates to the technical field of crack expansion and proppant migration, and in particular to a visualization method and device for simulating the migration law of proppant during the dynamic expansion of cracks. Background Art

[0002] Hydraulic fracturing is the process of reservoir opening and generating fracture structures as the fracturing fluid is injected. In order to prevent the fractures from closing again under the action of geostress, the fracturing fluid with proppant is injected into the propped fracture channel. The fractures evolve and expand under the filling and supporting action of the proppant particles, maintaining a high conductivity for a long time. Therefore, it is particularly important to study the migration law of proppant while studying the real process of dynamic fracture expansion under formation conditions.

[0003] Existing visualization studies on proppant migration laws mostly use physical simulation experimental devices. The physical models of fracture simulation are all made of flat plates with pre-fabricated gaps and constant length and opening. They are unable to truly simulate the process of gradually carrying proppant into the fracturing fracture while the fracture is dynamically opened. The physical flow field formed does not conform to the actual conditions of the proppant migration law during the fracture initiation and opening process, and there are problems such as high technical difficulty and safety. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention provides a visualization method and device for simulating the migration law of proppant during the dynamic expansion of cracks. The invention establishes a visualization model of dynamic crack expansion, adopts transparent templates with different elastic constants, reasonably sets limited sharp-angle cracks, and applies pressure through an inflatable rubber bag under certain conditions of interface roughness to establish a visualization model of crack expansion with a closed layered structure of a crack flat plate, thereby solving the dynamic problems of crack initiation and expansion and synchronous migration of proppant from the overall structure. To achieve the above purpose, the technical scheme is as follows:

[0005] On the one hand, a visualization method for simulating the migration law of proppant during the dynamic expansion of fractures is provided, and the method comprises:

[0006] S1. Design and produce a visual crack model;

[0007] S2, placing the visualized crack model in an explosion-proof glass window, and checking the sealing of the interface of the explosion-proof glass window;

[0008] S3, placing an inflatable rubber bag in the explosion-proof glass window, compressing the air in the inflatable rubber bag, obtaining the pressure in the inflatable rubber bag and keeping it stable according to the inflatable rubber bag digital pressure sensor, wherein the pressure closes the cracks in the visualized crack model;

[0009] S4, mixing the proppant and the slippery water in a liquid storage container, uniformly stirring with a spiral stirrer and adding a dye to obtain a sand-carrying liquid;

[0010] S5, pumping the sand-carrying liquid into the wellbore simulation component through the liquid inlet pipe at a certain rate and filling the wellbore simulation component, opening the movable baffle, pumping the sand-carrying liquid into the visualized fracture model to form a stable seepage channel, obtaining the crack initiation and expansion rate of the fracture in the visualized fracture model, and obtaining the pressure value in the liquid inlet pipe according to the liquid inlet pipe digital pressure sensor;

[0011] S6. Using a camera to collect the whole process of pumping the sand-carrying fluid into the visualized fracture model in real time, and obtain the fracture initiation and expansion morphology of the visualized fracture model and the laying process of the proppant in the sand-carrying fluid;

[0012] S7, drawing a pressure drop curve according to the pressure value in the liquid inlet pipe and the crack initiation and expansion rate of the visual crack model, and obtaining the crack initiation and expansion law of the visual crack model under different fracturing parameters;

[0013] S8. According to the fracture initiation and expansion morphology of the visualized fracture model and the laying process of the proppant in the sand-carrying fluid, the dynamic fracture initiation and expansion process of the fracture in the visualized fracture model under different fracturing parameters and the migration and settlement law of the proppant in the sand-carrying fluid are obtained;

[0014] S9. Analyze the expansion law of crack initiation and the migration and sedimentation law of the proppant in the sand-carrying fluid under different fracturing parameters of the visualized fracture model to obtain the migration law of the proppant during the dynamic expansion process of the fracture.

[0015] Optionally, the designing and making of a visual crack model in S1 includes:

[0016] S11, making a visualization plate 1 and making a visualization plate 2;

[0017] S12, prefabricated limited sharp angle cracks;

[0018] S13, using a transparent sealing member to seal the upper, lower and right side gaps of the visualization plate 1 and the visualization plate 2 to obtain the visualization crack model.

[0019] Optionally, the step of compressing the air in the inflatable rubber bag in S3, obtaining the pressure in the inflatable rubber bag and maintaining it stable according to the inflatable rubber bag digital pressure sensor, wherein the pressure closes the cracks in the visualized crack model, comprises:

[0020] S31, filling the inflatable rubber bag with compressed air until it is stretched and expanded to meet the cross-sectional design requirements, and the inflatable rubber bag is pressurized to a fixed value by an air source;

[0021] S32, placing the inflatable rubber airbag between the explosion-proof glass window and the transparent elastic pressure plate, and applying the pressure of the inflatable rubber airbag evenly to the visualized crack model by the transparent elastic pressure plate, so that the cracks of the visualized crack model are closed.

[0022] Optionally, in S5, the sand-carrying fluid is pumped into the wellbore simulation component through the liquid inlet pipe at a certain rate and fills the wellbore simulation component, the movable baffle is opened, and the sand-carrying fluid is pumped into the visualized fracture model to form a stable seepage channel, and the crack initiation and propagation rate of the fracture in the visualized fracture model is obtained, including:

[0023] S51, adjusting the variable flow rate valve to obtain the required injection rate, and injecting the sand-carrying fluid into the wellbore simulation component;

[0024] S52, filling the wellbore simulation component with a sand-carrying fluid pump, opening a movable baffle of the wellbore simulation component, and allowing the sand-carrying fluid to be pumped into the visualized fracture model;

[0025] S53, recording the value of the digital pressure sensor of the liquid inlet pipe, and when the value of the digital pressure sensor of the liquid inlet pipe reaches a certain peak value, the initiation of the crack at the end of the limited acute angle crack is obtained;

[0026] S54. According to the crack initiation at the end of the finite acute angle crack, the pressure is kept substantially unchanged to form a stable seepage channel, and the crack initiation and expansion rate of the crack of the visualized crack model is obtained.

[0027] Optionally, the visual plate 1 is a highly translucent plastic transparent sample with an elastic modulus of 2 to 20 GPa and a Poisson's ratio of 0.15 to 0.3;

[0028] The inner side of the visual plate 1 is a rough wall surface, and the rough wall surface truly simulates the convexity and concavity of the rock crack surface;

[0029] The visual plate 2 is an elastic transparent sample with an elastic modulus of 2-20 MPa and a Poisson's ratio of 0.3-0.5;

[0030] The transparent sealing member is made of nitrile rubber material;

[0031] The viewing flat panel 1 and the viewing flat panel 2 have the same size.

[0032] Optionally, the limited acute-angle crack in S12 has a crack depth of 10 mm and an angle of 30°.

[0033] On the other hand, a visualization device for simulating the migration law of proppant during the dynamic expansion of fractures is provided, the device comprising:

[0034] Visual fracture model module, used to simulate fracture initiation and proppant migration;

[0035] A conveying module, used for conveying sand-carrying fluid to the visual fracture model module;

[0036] An airbag pressure module, used to apply pressure to the visible crack model;

[0037] The numerical control monitoring module is used to monitor the migration process of the proppant in the fracture.

[0038] Optionally, the conveying module comprises:

[0039] A liquid storage container, used for storing sand-carrying liquid;

[0040] A spiral mixer, used for stirring the proppant and the slippery water to obtain the sand-carrying fluid;

[0041] A power pump, used to provide power for conveying the sand-carrying fluid;

[0042] A liquid outlet pipe, used to connect the liquid storage container and the power pump;

[0043] A liquid inlet pipe, used for connecting a variable flow rate valve and a wellbore simulation component;

[0044] The variable flow rate valve is used to adjust the flow rate of the sand-carrying fluid;

[0045] A liquid inlet pipe digital pressure sensor, used to record the pressure inside the liquid inlet pipe;

[0046] The wellbore simulation component is used to inject sand-carrying fluid into the visualized fracture model mold;

[0047] A movable baffle, used for controlling the sand-carrying fluid to flow into the visualized fracture model mold;

[0048] A rectangular connecting component is used to connect the wellbore simulation component and the visualized fracture model.

[0049] Optionally, the airbag pressure module includes:

[0050] An inflatable rubber bladder, used to compress air, provides the air needed to apply pressure;

[0051] Explosion-proof glass windows to provide the enclosed space required to apply pressure;

[0052] A transparent elastic pressure plate, used to connect the inflatable rubber bag and the visual crack model module;

[0053] An inflatable rubber bag digital pressure sensor, used to record the pressure inside the inflatable rubber bag;

[0054] Constant pressure gas source, used to provide stable gas pressure.

[0055] Optionally, the numerical control monitoring module includes:

[0056] A camera, used to record the morphological changes of the visual fracture model module and the migration distribution of the proppant in the sand-carrying fluid in real time;

[0057] Flat surface light source, used to provide the lighting required for video recording.

[0058] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0059] On the one hand, the above scheme can conveniently change the parameters such as sand-carrying fluid injection rate, viscosity, sand-carrying ratio, etc. according to actual conditions, clearly record and observe the initiation and expansion of cracks and the dynamic evolution of effective supporting crack morphology (length and opening), and truly reflect the effective migration and sedimentation laws of proppants during the dynamic opening and expansion of on-site cracks. On the other hand, the above scheme has low technical difficulty and high safety, and can simulate the distribution and migration status of proppants in the initiation of multi-angle and multi-cluster fractures of vertical wells and horizontal wells under visual conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0061] Figure 1 Flowchart of the present invention

[0062] Figure 2 Flowchart for the Visualized Crack Model of the Present Invention

[0063] Figure 3 The crack closure flow chart of the visual crack model of the present invention

[0064] Figure 4 A flow chart of the crack initiation and propagation rate of the visual crack model of the present invention

[0065] Figure 5 A block diagram of a device according to a first embodiment of the present invention

[0066] Figure 6 A front view of the structure of the first embodiment of the present invention

[0067] Figure 7 A top view of the structure of the first embodiment of the present invention

[0068] Figure 8 A three-dimensional view of the structure of the first embodiment of the present invention

[0069] Fig. 9 A schematic diagram of the structure of the second embodiment of the present invention

[0070] Explanation of the numbers in the figure: spiral mixer 1, liquid storage container 2, liquid outlet pipe 3, power pump 4, variable flow rate valve 5, liquid inlet pipe 6, liquid inlet pipe digital pressure sensor 7, movable baffle 8, rectangular connecting component 9, wellbore simulation component 10, inflatable rubber bag digital pressure sensor 11, constant pressure air source 12, camera 13, explosion-proof glass window 14, transparent sealing component 15, visualization plate 116, visualization plate 2 17, transparent elastic pressure plate 18, flat surface light source 19, inflatable rubber bag 20, flange gate valve 21. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0072] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0073] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0074] like Figures 1 to 4 As shown in FIG. 1 , a visualization method of simulating the migration law of proppant during the dynamic expansion of fractures according to the present invention is as follows: Figure 1 As shown, the specific steps of this method are as follows:

[0075] S1. Design and produce a visual crack model;

[0076] Specifically, Figure 2 As shown, the visual crack model is designed and produced in S1, including:

[0077] S11, making a visualization plate 1 16 and making a visualization plate 2 17;

[0078] Furthermore, the visual plate 1 16 is a highly translucent plastic transparent sample with an elastic modulus of 2 to 20 GPa and a Poisson's ratio of 0.15 to 0.3;

[0079] The inner side of the visual plate 1 16 is a rough wall surface, and the rough wall surface truly simulates the convexity and concavity of the rock crack surface;

[0080] The visual plate 2 17 is an elastic transparent sample with an elastic modulus of 2-20 MPa and a Poisson's ratio of 0.3-0.5;

[0081] The visual flat panel 1 16 and the visual flat panel 2 17 are of the same size, and the design and manufacturing dimensions thereof are 600 mm in length, 200 mm in width and 50 mm in thickness;

[0082] S12, prefabricated limited sharp angle cracks;

[0083] Furthermore, the crack depth of the limited acute-angle crack is 10 mm and the angle is 30°;

[0084] S13, using a transparent sealing member 15 to seal the upper, lower and right side gaps of the visualization plate 1 16 and the visualization plate 2 17 to obtain the visualization crack model;

[0085] Furthermore, the transparent sealing member 15 is made of nitrile rubber material.

[0086] S2, placing the visualized crack model in the explosion-proof glass window 14, and checking the sealing of the interface of the explosion-proof glass window 14;

[0087] S3, placing an inflatable rubber bag 20 in the explosion-proof glass window 14, compressing the air in the inflatable rubber bag 20, and obtaining the pressure in the inflatable rubber bag 20 and keeping it stable according to the inflatable rubber bag digital pressure sensor 11, wherein the pressure closes the cracks in the visualized crack model;

[0088] Specifically, Figure 3 As shown, in S3, the air in the inflatable rubber bag 20 is compressed, and the pressure in the inflatable rubber bag 20 is obtained and kept stable according to the inflatable rubber bag digital pressure sensor 11, and the pressure closes the cracks in the visualized crack model, including:

[0089] S31, filling the inflatable rubber bag 20 with compressed air until it is stretched and expanded to meet the cross-sectional design requirements, and the inflatable rubber bag 20 is pressurized to a fixed value by the air source;

[0090] Further, the fixed value is 20Mpa;

[0091] S32, placing the inflatable rubber airbag 20 between the explosion-proof glass window 14 and the transparent elastic pressure plate 18, and the pressure of the inflatable rubber airbag 20 is evenly applied to the visualized crack model by the transparent elastic pressure plate 18, so that the cracks of the visualized crack model are closed.

[0092] S4, mixing the proppant and the slippery water in the liquid storage container 2, using the spiral stirrer 1 to evenly stir and adding a dye to obtain a sand-carrying liquid;

[0093] Furthermore, the ceramsite in the proppant is selected from 20 / 40 mesh, 40 / 70 mesh or 70 / 100 mesh; the viscosity of the slippery water is selected from 0.5 mPa•s, 1 mPa•s or 1.5 mPa•s;

[0094] S5, pumping the sand-carrying liquid into the wellbore simulation component 10 through the liquid inlet pipe 6 at a certain rate and filling the wellbore simulation component 10, opening the movable baffle 8, pumping the sand-carrying liquid into the visualized fracture model to form a stable seepage channel, obtaining the crack initiation and expansion rate of the fracture in the visualized fracture model, and obtaining the pressure value in the liquid inlet pipe according to the liquid inlet pipe digital pressure sensor 7;

[0095] Specifically, Figure 4 As shown, in S5, the sand-carrying fluid is pumped into the wellbore simulation component 10 through the liquid inlet pipe 6 at a certain rate and fills the wellbore simulation component 10, the movable baffle 8 is opened, and the sand-carrying fluid is pumped into the visualized fracture model to form a stable seepage channel, and the crack initiation and expansion rate of the fracture in the visualized fracture model is obtained, including:

[0096] S51, adjusting the variable flow rate valve 5 to obtain the required injection rate, and injecting the sand-carrying fluid into the wellbore simulation component 10;

[0097] Further, the required injection rate may be 0.1 m3 / min, 0.2 m3 / min or 0.3 m3 / min;

[0098] S52, pumping the sand-carrying fluid in the wellbore simulation component 10 full, opening the movable baffle 8 of the wellbore simulation component 10, so that the sand-carrying fluid is pumped into the visualized fracture model;

[0099] S53, recording the value of the digital pressure sensor 7 of the liquid inlet pipe, and when the value of the digital pressure sensor 7 of the liquid inlet pipe reaches a certain peak value, the initiation of the crack at the end of the limited acute angle crack is obtained;

[0100] S54. According to the crack initiation at the end of the finite acute angle crack, the pressure is kept substantially unchanged to form a stable seepage channel, and the crack initiation and expansion rate of the crack of the visualized crack model is obtained.

[0101] S6, using the camera 13 to collect the whole process of the sand-carrying fluid being pumped into the visualized fracture model in real time, to obtain the fracture initiation and expansion morphology of the visualized fracture model and the paving process of the proppant in the sand-carrying fluid;

[0102] S7, drawing a pressure drop curve according to the pressure value in the liquid inlet pipe 6 and the crack initiation and expansion rate of the visualized crack model, and obtaining the crack initiation and expansion law of the visualized crack model under different fracturing parameters;

[0103] S8. According to the fracture initiation and expansion morphology of the visualized fracture model and the paving process of the proppant in the sand-carrying fluid, the dynamic fracture initiation and expansion process of the fracture in the visualized fracture model under different fracturing parameters and the migration and settlement law of the proppant in the sand-carrying fluid are obtained;

[0104] S9, analyzing the expansion law of the crack initiation and the migration and sedimentation law of the proppant in the sand-carrying fluid under different fracturing parameters of the visualized fracture model, and obtaining the migration law of the proppant during the dynamic expansion process of the fracture;

[0105] Specifically, the migration law of the proppant during the dynamic expansion of the fracture can be that when the injection reaches a certain peak value of 15-20MPa, the end of the limited sharp-angle fracture begins to crack, the pressure gradually decreases, and the fracture gradually expands. When it expands to the edge of the visible fracture model, the fracture is completely opened to form a stable seepage channel, and the pressure remains basically unchanged at 0-5 MPa; during the crack initiation and expansion process, the fracture morphology and opening have a certain influence on the migration ability of the proppant in the fracture. The proppant is mainly laid in the area with a larger crack opening near the wellbore simulation component 10. The sand-laying area is small and easy to accumulate at the narrow crack at the front end of the expansion, which hinders the migration of the sand-carrying fluid; increasing the viscosity of the fracturing fluid and reducing the particle size of the proppant can increase the sand-laying area and migration distance of the proppant, increase the effective support fracture length, and thus improve the fracturing transformation effect.

[0106] like Fig. 9 As shown, a second embodiment of a visualization method for simulating the migration law of proppant during the dynamic expansion of fractures of the present invention is shown. The second embodiment is an extension of the first embodiment. Multiple visualization fracture models are connected in series through flange gate valves 21, and the number of perforation clusters is further changed to simulate the arrangement of multiple clusters of fractures in horizontal well sections. The effects of wellbore length and cluster spacing on the initiation and expansion of fractures and the dynamic settlement and migration distribution law of proppant between each perforation cluster are studied. The specific steps of the method of the second embodiment are as follows:

[0107] S1. Design and produce 5 sets of visual crack models;

[0108] Specifically, Figure 2 As shown, in S1, 5 sets of visual crack models are designed and produced, including:

[0109] S11, making a visualization plate 1 16 and making a visualization plate 2 17;

[0110] Furthermore, the visual plate 1 16 is a highly translucent plastic transparent sample with an elastic modulus of 2 to 20 GPa and a Poisson's ratio of 0.15 to 0.3;

[0111] The inner side of the visual plate 1 16 is a rough wall surface, and the rough wall surface truly simulates the convexity and concavity of the rock crack surface;

[0112] The visual plate 2 17 is an elastic transparent sample with an elastic modulus of 2-20 MPa and a Poisson's ratio of 0.3-0.5;

[0113] The visual flat panel 1 16 and the visual flat panel 2 17 are of the same size, and the design and manufacturing dimensions thereof are 600 mm in length, 200 mm in width and 50 mm in thickness;

[0114] S12, prefabricated limited sharp angle cracks;

[0115] Furthermore, the crack depth of the limited acute-angle crack is 10 mm and the angle is 30°;

[0116] S13, using a transparent sealing member 15 to seal the upper, lower and right side gaps of the visualization plate 1 16 and the visualization plate 2 17 to obtain the visualization crack model;

[0117] Furthermore, the transparent sealing member 15 is made of nitrile rubber material.

[0118] S2, placing the visualized crack model in the explosion-proof glass window 14, and checking the sealing of the interface of the explosion-proof glass window 14;

[0119] Specifically, the five groups of visualized fracture models are assembled in series by a wellbore simulation component 10 through a flange gate valve 21. The total length of the wellbore simulation component 10 is set to 4 m by opening and closing the flange gate valve 21. The cluster spacing is set to 1 m or 2 m by opening and closing the movable baffle 8 inside the wellbore simulation component 10.

[0120] S3, placing an inflatable rubber bag 20 in the explosion-proof glass window 14, compressing the air in the inflatable rubber bag 20, and obtaining the pressure in the inflatable rubber bag 20 and keeping it stable according to the inflatable rubber bag digital pressure sensor 11, wherein the pressure closes the cracks in the visualized crack model;

[0121] Specifically, Figure 3 As shown, in S3, the air in the inflatable rubber bag 20 is compressed, and the pressure in the inflatable rubber bag 20 is obtained and kept stable according to the inflatable rubber bag digital pressure sensor 11, and the pressure closes the cracks in the visualized crack model, including:

[0122] S31, filling the inflatable rubber bag 20 with compressed air until it is stretched and expanded to meet the cross-sectional design requirements, and the inflatable rubber bag 20 is pressurized to a fixed value by the air source;

[0123] Further, the fixed value is 20Mpa;

[0124] S32, placing the inflatable rubber airbag 20 between the explosion-proof glass window 14 and the transparent elastic pressure plate 18, and the pressure of the inflatable rubber airbag 20 is evenly applied to the visualized crack model by the transparent elastic pressure plate 18, so that the cracks of the visualized crack model are closed.

[0125] S4, mixing the proppant and the slippery water in the liquid storage container 2, using the spiral stirrer 1 to evenly stir and adding a dye to obtain a sand-carrying liquid;

[0126] Furthermore, the ceramsite in the proppant is selected from 20 / 40 mesh, 40 / 70 mesh or 70 / 100 mesh; the viscosity of the slippery water is selected from 0.5 mPa•s, 1 mPa•s or 1.5 mPa•s;

[0127] S5, pumping the sand-carrying liquid into the wellbore simulation component 10 through the liquid inlet pipe 6 at a certain rate and filling the wellbore simulation component 10, opening the movable baffle 8, pumping the sand-carrying liquid into the visualized fracture model to form a stable seepage channel, obtaining the crack initiation and expansion rate of the fracture in the visualized fracture model, and obtaining the pressure value in the liquid inlet pipe according to the liquid inlet pipe digital pressure sensor 7;

[0128] Specifically, Figure 4 As shown, in S5, the sand-carrying fluid is pumped into the wellbore simulation component 10 through the liquid inlet pipe 6 at a certain rate and fills the wellbore simulation component 10, the movable baffle 8 and the flange gate valve 21 are opened, and the sand-carrying fluid is pumped into the visualized fracture model to form a stable seepage channel, and the crack initiation and expansion rate of the fracture in the visualized fracture model is obtained, including:

[0129] S51, adjusting the variable flow rate valve 5 to obtain the required injection rate, and injecting the sand-carrying fluid into the wellbore simulation component 10;

[0130] Further, the required injection rate may be 0.1 m3 / min, 0.2 m3 / min or 0.3 m3 / min;

[0131] S52, pumping the sand-carrying fluid in the wellbore simulation component 10 full, opening the movable baffle 8 and the flange gate valve 21 of the wellbore simulation component 10, so that the sand-carrying fluid is pumped into the visualized fracture model;

[0132] S53, recording the value of the digital pressure sensor 7 of the liquid inlet pipe, and when the value of the digital pressure sensor 7 of the liquid inlet pipe reaches a certain peak value, the initiation of the crack at the end of the limited acute angle crack is obtained;

[0133] S54. According to the crack initiation at the end of the finite acute angle crack, the pressure is kept substantially unchanged to form a stable seepage channel, and the crack initiation and expansion rate of the crack of the visualized crack model is obtained.

[0134] S6, using the camera 13 to collect the whole process of the sand-carrying fluid being pumped into the visualized fracture model in real time, to obtain the fracture initiation and expansion morphology of the visualized fracture model and the paving process of the proppant in the sand-carrying fluid;

[0135] S7, drawing a pressure drop curve according to the pressure value in the liquid inlet pipe 6 and the crack initiation and expansion rate of the visualized crack model, and obtaining the crack initiation and expansion law of the visualized crack model under different fracturing parameters;

[0136] S8. According to the fracture initiation and expansion morphology of the visualized fracture model and the paving process of the proppant in the sand-carrying fluid, the dynamic fracture initiation and expansion process of the fracture in the visualized fracture model under different fracturing parameters and the migration and settlement law of the proppant in the sand-carrying fluid are obtained;

[0137] S9, analyzing the expansion law of the crack initiation and the migration and sedimentation law of the proppant in the sand-carrying fluid under different fracturing parameters of the visualized fracture model, and obtaining the migration law of the proppant during the dynamic expansion process of the fracture;

[0138] Specifically, the migration law of the proppant during the dynamic expansion of the fracture may be that with the increase of the wellbore length, the expansion morphology of each cluster of fractures is non-balanced. In 40 / 70 mesh quartz sand, when the pumping rate is 0.1m3 / min, the uniformity of the uneven perforation clusters is poor, and most of them are settled in the first perforation cluster. As the pumping rate increases, the better the suspension of sand particles, the more they are settled to the more distant perforation clusters. The lower cluster spacing improves the degree of reservoir transformation, but too low cluster spacing is not conducive to the balanced expansion of fractures and the migration of proppant in the fracture, which increases the risk of sand plugging in the fracture. Therefore, it is necessary to consider comprehensive factors to optimize the wellbore length and cluster spacing.

[0139] like Figures 5 to 8 A visualization device for simulating the migration law of proppant during the dynamic expansion of cracks according to an embodiment is provided. The device is used for a visualization method for simulating the migration law of proppant during the dynamic expansion of cracks. The device comprises:

[0140] Visual fracture model module, used to simulate fracture initiation and proppant migration;

[0141] A conveying module, used for conveying sand-carrying fluid to the visual fracture model module;

[0142] Specifically, the conveying module comprises:

[0143] A liquid storage container 2, used for storing sand-carrying liquid;

[0144] A spiral mixer 1 is used to stir the proppant and the slippery water to obtain the sand-carrying fluid;

[0145] A power pump 4, used to provide power for conveying the sand-carrying fluid;

[0146] A liquid outlet pipe 3, used to connect the liquid storage container 2 and the power pump 4;

[0147] A liquid inlet pipe 6, used to connect the variable flow rate valve 5 and the wellbore simulation component 10;

[0148] The variable flow rate valve 5 is used to adjust the flow rate of the sand-carrying liquid;

[0149] A liquid inlet pipe digital pressure sensor 7, used to record the pressure inside the liquid inlet pipe 6;

[0150] The wellbore simulation component 10 is used to inject the sand-carrying fluid into the visual fracture model mold;

[0151] A movable baffle 8, used for controlling the sand-carrying fluid to flow into the visualized fracture model mold;

[0152] The rectangular connecting member 9 is used to connect the wellbore simulation member 10 and the visualized fracture model.

[0153] An airbag pressure module, used to apply pressure to the visible crack model;

[0154] Specifically, the airbag pressure module includes:

[0155] An inflatable rubber bag 20, used for compressing air and providing the air required for applying pressure;

[0156] An explosion-proof glass window 14 is used to provide a closed space required for applying pressure;

[0157] Transparent elastic pressurizing device 18, used to connect the inflatable rubber bag 20 and the visual crack model module;

[0158] An inflatable rubber bag digital pressure sensor 11 is used to record the pressure inside the inflatable rubber bag;

[0159] The constant pressure gas source 12 is used to provide a stable gas pressure.

[0160] The numerical control monitoring module is used to monitor the migration process of the proppant in the fracture.

[0161] Specifically, the numerical control monitoring module includes:

[0162] The camera 13 is used to record the morphological changes of the visual fracture model module and the migration distribution of the proppant in the sand-carrying fluid in real time;

[0163] The flat surface light source 19 is used to provide the illumination required for video recording.

[0164] The present invention provides a visualization method and device for simulating the migration law of proppant during the dynamic expansion of cracks. The invention establishes a visualization model of dynamic crack expansion, adopts transparent samples with different elastic constants, reasonably sets finite sharp-angle cracks, applies pressure through an inflatable rubber bag under the condition of certain interface roughness, and establishes a crack expansion visualization model of a closed layered structure of a crack flat plate, thereby solving the dynamic problem of crack initiation and expansion and synchronous migration of proppant from the overall structure.

[0165] It is to be understood that the present invention is described by the above embodiments and should not be construed as limiting the embodiments of the present invention and the scope of the present invention. It is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A visualization method for simulating the migration law of proppant during the dynamic expansion of fractures, characterized in that: The method comprises: S1. Design and produce a visual crack model; S2, placing the visualized crack model in an explosion-proof glass window, and checking the sealing of the interface of the explosion-proof glass window; S3, placing an inflatable rubber bag in the explosion-proof glass window, compressing the air in the inflatable rubber bag, obtaining the pressure in the inflatable rubber bag and keeping it stable according to the inflatable rubber bag digital pressure sensor, wherein the pressure closes the cracks in the visualized crack model; S4, mixing the proppant and the slippery water in a liquid storage container, uniformly stirring with a spiral stirrer and adding a dye to obtain a sand-carrying liquid; S5, pumping the sand-carrying liquid into the wellbore simulation component through the liquid inlet pipe at a certain rate and filling the wellbore simulation component, opening the movable baffle, pumping the sand-carrying liquid into the visualized fracture model to form a stable seepage channel, obtaining the crack initiation and expansion rate of the fracture in the visualized fracture model, and obtaining the pressure value in the liquid inlet pipe according to the liquid inlet pipe digital pressure sensor; S6. Using a camera to collect the whole process of pumping the sand-carrying fluid into the visualized fracture model in real time, and obtain the fracture initiation and expansion morphology of the visualized fracture model and the laying process of the proppant in the sand-carrying fluid; S7, drawing a pressure drop curve according to the pressure value in the liquid inlet pipe and the crack initiation and expansion rate of the visual crack model, and obtaining the crack initiation and expansion law of the visual crack model under different fracturing parameters; S8. According to the fracture initiation and expansion morphology of the visualized fracture model and the laying process of the proppant in the sand-carrying fluid, the dynamic fracture initiation and expansion process of the fracture in the visualized fracture model under different fracturing parameters and the migration and settlement law of the proppant in the sand-carrying fluid are obtained; S9. Analyze the expansion law of crack initiation and the migration and sedimentation law of the proppant in the sand-carrying fluid under different fracturing parameters of the visualized fracture model to obtain the migration law of the proppant during the dynamic expansion process of the fracture.

2. The method for visualizing the migration law of simulating proppant during the dynamic expansion of fractures according to claim 1, characterized in that: The visual crack model is designed and produced in S1, including: S11, making a visualization plate 1 and making a visualization plate 2; S12, prefabricated limited sharp angle cracks; S13, using a transparent sealing member to seal the upper, lower and right side gaps of the visualization plate 1 and the visualization plate 2 to obtain the visualization crack model.

3. The method for visualizing the migration law of simulating proppant during the dynamic expansion of fractures according to claim 1, characterized in that: The step S3 compresses the air in the inflatable rubber bag, obtains the pressure in the inflatable rubber bag and keeps it stable according to the inflatable rubber bag digital pressure sensor, and the pressure closes the cracks in the visualized crack model, including: S31, filling the inflatable rubber bag with compressed air until it is stretched and expanded to meet the cross-sectional design requirements, and the inflatable rubber bag is pressurized to a fixed value by an air source; S32, placing the inflatable rubber airbag between the explosion-proof glass window and the transparent elastic pressure plate, and applying the pressure of the inflatable rubber airbag evenly to the visualized crack model by the transparent elastic pressure plate, so that the cracks of the visualized crack model are closed.

4. The method for visualizing the migration law of simulating proppant during the dynamic expansion of fractures according to claim 1, characterized in that: In S5, the sand-carrying liquid is pumped into the wellbore simulation component through the liquid inlet pipe at a certain rate and fills the wellbore simulation component, the movable baffle is opened, and the sand-carrying liquid is pumped into the visualized fracture model to form a stable seepage channel, and the crack initiation and expansion rate of the fracture in the visualized fracture model is obtained, including: S51, adjusting the variable flow rate valve to obtain the required injection rate, and injecting the sand-carrying fluid into the wellbore simulation component; S52, filling the wellbore simulation component with a sand-carrying fluid pump, opening a movable baffle of the wellbore simulation component, and allowing the sand-carrying fluid to be pumped into the visualized fracture model; S53, recording the value of the digital pressure sensor of the liquid inlet pipe, and when the value of the digital pressure sensor of the liquid inlet pipe reaches a certain peak value, the initiation of the crack at the end of the limited acute angle crack is obtained; S54. According to the crack initiation at the end of the finite acute angle crack, the pressure is kept substantially unchanged to form a stable seepage channel, and the crack initiation and expansion rate of the crack of the visualized crack model is obtained.

5. The method for visualizing the migration law of simulating proppant during the dynamic expansion of fractures according to claim 2, characterized in that: The visual plate 1 is a highly translucent plastic transparent sample with an elastic modulus of 2-20 GPa and a Poisson's ratio of 0.15-0.3; The inner side of the visual plate 1 is a rough wall surface, and the rough wall surface truly simulates the convexity and concavity of the rock crack surface; The visual plate 2 is an elastic transparent sample with an elastic modulus of 2-20 MPa and a Poisson's ratio of 0.3-0.5; The transparent sealing member is made of nitrile rubber material; The viewing flat panel 1 and the viewing flat panel 2 have the same size.

6. The method for visualizing the migration law of simulating proppant during the dynamic expansion of fractures according to claim 2, characterized in that: The crack depth of the limited acute-angle crack in S12 is 10 mm and the angle is 30°.

7. A visualization device for simulating the migration law of proppant during the dynamic expansion of fractures, characterized in that: The device comprises: Visual fracture model module, used to simulate fracture initiation and proppant migration; A conveying module, used for conveying sand-carrying fluid to the visual fracture model module; An airbag pressure module, used to apply pressure to the visible crack model; The numerical control monitoring module is used to monitor the migration process of the proppant in the fracture.

8. The visualization device for simulating the migration law of proppant during the dynamic expansion of fractures according to claim 7, characterized in that: The conveying module comprises: A liquid storage container, used for storing sand-carrying liquid; A spiral mixer, used for stirring the proppant and the slippery water to obtain the sand-carrying fluid; A power pump, used to provide power for conveying the sand-carrying fluid; A liquid outlet pipe, used to connect the liquid storage container and the power pump; A liquid inlet pipe, used for connecting a variable flow rate valve and a wellbore simulation component; The variable flow rate valve is used to adjust the flow rate of the sand-carrying fluid; A liquid inlet pipe digital pressure sensor, used to record the pressure inside the liquid inlet pipe; The wellbore simulation component is used to inject sand-carrying fluid into the visualized fracture model mold; A movable baffle, used for controlling the sand-carrying fluid to flow into the visualized fracture model mold; A rectangular connecting component is used to connect the wellbore simulation component and the visualized fracture model.

9. The visualization device for simulating the migration law of proppant during the dynamic expansion of fractures according to claim 7, characterized in that: The airbag pressure module comprises: An inflatable rubber bladder, used to compress air, provides the air needed to apply pressure; Explosion-proof glass windows to provide the enclosed space required to apply pressure; A transparent elastic pressure plate, used to connect the inflatable rubber bag and the visual crack model module; An inflatable rubber bag digital pressure sensor, used to record the pressure inside the inflatable rubber bag; Constant pressure gas source, used to provide stable gas pressure.

10. The visualization device for simulating the migration law of proppant during the dynamic expansion of fractures according to claim 7, characterized in that: The numerical control monitoring module comprises: A camera, used to record the morphological changes of the visual fracture model module and the migration distribution of the proppant in the sand-carrying fluid in real time; Flat surface light source, used to provide the lighting required for video recording.

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