Fracture-cavity oil reservoir water injection displacement analogue simulation method considering leakage
By establishing a simulation method for water injection displacement in fractured-vuggy reservoirs, the problem of leakage in the simulation of displacement in fractured-vuggy reservoirs was solved, the simulation accuracy was improved, and a precise digital simulation of the displacement process in fractured-vuggy reservoirs was realized.
Patent Information
- Application Number
- CN202411156858.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-22
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies fail to effectively consider leakage issues in displacement simulation of fractured-vuggy reservoirs, resulting in low accuracy of simulation results that cannot meet the accuracy requirements of multiphase flow.
The water injection displacement simulation method for fractured-vuggy reservoirs was adopted. A digital model was established, the fractures were simplified to two dimensions and the geometric model was simplified. Numerical simulation was performed using Fluent software, boundary conditions and flow models were set, and the leakage effect was considered.
It improves the accuracy of displacement simulation in fractured-vuggy reservoirs, accurately simulates leakage phenomena during the displacement process, and enhances the guiding significance of the simulation results.
Smart Images
Figure CN121598656A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of reservoir numerical simulation technology, specifically to a simulation method for water injection displacement in fractured-vuggy reservoirs that considers leakage. Background Technology
[0002] Water injection displacement is an important means of improving oil recovery. Because fractured-vuggy reservoirs contain media of different scales such as caverns, fractures, and matrix, the displacement process involves both seepage in the porous media and pipe flow in the fractured-vuggy space, resulting in a complex flow mechanism.
[0003] To understand the flow patterns of multiphase fluids during displacement in fractured-vuggy carbonate reservoirs, physical simulation methods are commonly used. Physical simulation involves designing a physical model based on similarity principles and then simulating the actual system. However, physical simulation studies face challenges such as difficulty in meeting specific temperature and pressure conditions, complex model construction, long experimental cycles, and poor visualization. Furthermore, physical models typically only allow for the study of a particular type of fractured-vuggy unit under specific displacement conditions. Obtaining universally applicable insights and conclusions, or identifying exploitation patterns specific to a new model, often requires extensive physical simulation studies, consuming significant human and material resources.
[0004] In addition, numerical simulation is commonly used in research. Simulation involves establishing a numerical model of the fractured-vuggy reservoir, dividing the region into computational units based on geometric models and accuracy requirements, setting boundary conditions, and conducting multiphase flow numerical simulations based on the Navier-Stokes (NS) equations. This calculates variables such as pressure and velocity in different regions during the flow process, enabling a digital representation and study of the fluid flow process in the fractured-vuggy model, providing an effective tool for studying the flow mechanism of fractured-vuggy reservoirs. However, similar to physical models, most current numerical simulations of displacement in fractured-vuggy reservoirs do not consider leakage caused by fractures in the reservoir, thus affecting the guiding significance of the simulation results.
[0005] Furthermore, in fractured-vuggy reservoirs, there is both porous media seepage and large-space pipe flow, resulting in a complex multi-flow coupled flow pattern that is difficult to apply using traditional numerical simulation methods based on the Darcy equation. According to relevant research and applications, current methods primarily utilize reservoir numerical simulation based on equivalent media models to simulate the displacement process in the physical model of fractured-vuggy reservoirs.
[0006] The equivalent medium model-based numerical simulation method for oil reservoirs uses an equivalent continuous medium model to simulate the coupling effects of fractures, caverns, and the matrix. In this model, the pores of the rock matrix provide the main storage space for fluids, while the main fluid flow occurs in the fracture and cavern media. The basic principle of the equivalent medium model is to use equivalent characterizing units (mesh), treating caverns, fractures, and rock matrix separately within a single unit. That is, a single mesh may simultaneously contain the properties of matrix, fractures, and caverns, and the mass exchange of fluids between different media is characterized by crossflow equations. The equivalent medium model method has the advantages of being intuitive, simple to model, and fast in simulation, and has been well applied in handling reservoir-scale models. However, this method has the following drawbacks: In terms of geometric modeling, this method is designed for actual reservoir-scale models, uses structured meshes, cannot consider the true morphology of fractures and caverns, and has low accuracy; in terms of mathematical modeling, this method is based on the Darcy flow equation instead of the Navier-Stokes equation, resulting in lower accuracy in characterizing multiphase fluid flow and multiphase fluid interfaces, which cannot meet the accuracy requirements of digital experiments. Summary of the Invention
[0007] This invention addresses the problems of low accuracy and leakage in existing fractured-vuggy reservoir displacement simulations, and provides a water injection displacement simulation method for fractured-vuggy reservoirs that takes leakage into account.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0009] A simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage includes the following steps: Step 1: Establish a digital model based on the fractured-vuggy reservoir model to obtain one-dimensional fracture segments; wherein, the fractured-vuggy reservoir model is a one-injection-one-production well group model, which means one water injection well and one production well model; Step 2: Convert the one-dimensional fractures into two dimensions according to the fracture aperture in the digital model to form fracture surfaces; Step 3: Extract the feature points of the fracture-vuggy boundary and simplify the fracture-vuggy geometry model; Step 4: Based on the digital model of the fractured-vuggy reservoir, mesh and generate finite volume calculation cells; Step 5: Set the parameters of the oil-water two-phase fluid involved in the displacement process and set the flow model; Step 6: Set the boundary condition parameters of fracture-vuggy displacement, wherein the boundary condition parameters include inlet, outlet and filtration boundary conditions; Step 7: Based on the boundary condition parameter settings, set the initial conditions of the simplified fracture-vuggy geometry model; Step 8: Solve the simplified fracture-vuggy geometry model using the Fluent simulation solver.
[0010] Based on the above technical solution, further, in step 1, the process of establishing a digital model includes the following steps: Step 11, determine the size range of the fractured-vuggy reservoir model; Step 12, use 2D software to insert an image of the simulated view of the injection-production well group model; Step 13, adjust the image in the image and adjust the comparison image in the image; Step 14, select a spline fitting curve for imitation, merge the line segments, and then perform 3D modeling to complete the establishment of the digital model.
[0011] Based on the above technical solution, further, in step 11, a model size with a 1:1 scale of the real model is adopted.
[0012] Based on the above technical solution, further, in step 2, the two-dimensionalization process includes the following steps: Step 21, setting the crack aperture parameter d; Step 22, setting the endpoint coordinates of each crack one-dimensional line segment, dividing them into P1(x1,y1,z1) and P2(x2,y2,z2), and deriving the corresponding linear equations: In the formula, t is a real number between 0 and 1, representing the position of any point (x, y, z) on the line segment; Step 23: Determine the normal unit vector. (x2-x1)x n +(y2-y1)y n +(z2-z1)z n =0, where n = 1, 2, 3...; Step 24: Translate line segment P1-P2 along the normal direction of the line segment to both sides of the line segment, with a translation amount of d / 2. The coordinates of the line segment after translation are: P 11 (x1+x n d / 2,y1+y n d / 2,z1+z n d / 2); P 21 (x2+x n d / 2,y2+y n d / 2,z2+z n d / 2); P 12 (x1-x n d / 2,y1-y n d / 2,z1-z n d / 2); P 22 (x2-x n d / 2,y2-y n d / 2,z2-z n d / 2); Step 25, P 11 P 21 P 22 P 12 The four points form a two-dimensional crack quadrilateral.
[0013] Based on the above technical solution, further, in step 3, the simplified operation process includes the following steps: Step 31, marking the feature points P of the seam boundary. c Select P c Two adjacent points P t and P r And it satisfies the following characteristics: In the formula, ε is taken as 1e-2; Step 32: retain the feature points that satisfy the feature conditions in step 31 of the slit hole geometric model, delete the remaining non-feature points that do not satisfy the feature conditions, connect all feature points in sequence to obtain the simplified slit hole geometric model; and derive it.
[0014] Based on the above technical solution, the simplified geometric model of the slit hole is further exported as a DWG format file.
[0015] Based on the above technical solution, further, step 4 specifically includes the following steps: Step 41, import the simplified fracture-cavity geometric model into Fluent's built-in mesh generator Meshing module; Step 42, divide the fracture and cave into zones, where the cave area is divided using quadrilateral / triangular meshes, and the fracture area is divided using triangular meshes; Step 43, the engineer or user determines the target mesh number N for the cave area based on the actual situation. gc Calculate the grid resolution L of the karst cave area gc : In the formula, A c It is the area of the karst cave region; Step 44: The engineer or user determines the target grid number N of the crack zone based on the actual situation. gf And calculate the mesh resolution L of the crack zone. gf : In the formula, A f It is the area of the crack region; Step 45: Use Fluent's built-in mesh generator Meshing module to generate a mesh and output the mesh file; Step 46: Start Fluent, select double precision solution based on Fluent's built-in double precision solver, import the mesh file into Fluent, export the mesh file as an msh file, and generate finite volume calculation elements.
[0016] Based on the above technical solution, further, in step 46, the mesh generation quality of the slit hole geometric model is checked. If a negative volume appears, the process returns to step 42 to re-mesh the slit hole.
[0017] Based on the above technical solution, further, step 5 includes the following steps: Step 51: Import the discretized cavity geometry model and mesh into Fluent, and set the gravitational acceleration in the Y direction; Step 52: Set the volume fraction parameter to an explicit discretization format; Step 53: Select a multiphase flow model; Step 54: Set the number of phases according to the actual fluid types and quantities used in the displacement process; Step 55: Set the density and viscosity of each phase fluid; Step 56: Set the interfacial tension coefficients, where the oil-water interfacial tension is 0.072 N / m and the gas-liquid interfacial tension is 0.02 N / m; Step 57: Set the flow model to a k-ω model.
[0018] Based on the above technical solution, further, in step 53, the multiphase flow model is the Euler model and the interface type is the Sharp type.
[0019] Based on the above technical solution, further, in step 6, the inlet adopts Neumann boundary conditions; the inlet Ω is set. inlet The injection rate is q inlet The unit is m 3 / s, will q inlet Convert to linear velocity v inlet The unit is m / s: Among them, A inlet It is the area of the entrance boundary.
[0020] Based on the above technical solution, further, in step 6, the outlet adopts the Dirichlet boundary condition for the absolute pressure at the outlet. Will Converted to relative pressure: Among them, P sc That is the standard pressure.
[0021] Based on the above technical solution, further, in step 6, the filtration boundary condition adopts the Dirichlet boundary condition, for the outlet absolute pressure. Will Converted to relative pressure: Among them, P sc That is the standard pressure.
[0022] Based on the above technical solution, further, step 7 includes the following steps: Step 71, setting the initial pressure distribution for the simplified slit geometry model, characterized by: In the formula, P init It is the initial pressure; P sc It is standard pressure; The initial gauge pressure is used; Step 72: Set the initial fluid distribution for the simplified cavity geometry model, either by model partitioning or by setting it according to model coordinates; Step 73: Set the initial velocity distribution for the simplified cavity geometry model, where the velocity field is zero: v(x,y,z)=0.
[0023] Based on the above technical solution, further, step 8 includes the following steps in the solution process: Step 81, import the mesh .msh format file generated in step 46 into Fluent; Step 82, select a 2D or 3D solver according to the established model, check the imported mesh, and if the mesh has negative volume, it needs to be re-meshed; Step 83, select the solver format and solver type; Step 84, determine the material physical properties; Step 85, set the operating environment; Step 86, define each boundary condition in step 6; Step 87, set the control parameters; Step 88, initialize the flow field; Step 89, run the numerical calculation solution using Fluent.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] This invention proposes a simulation method for fracture-vuggy reservoirs that considers leakage. By establishing a fracture model connecting the fractured-vuggy carbonate reservoir to bottom water, the method involves multiple steps, including digitizing the fracture model, creating a two-dimensional fracture model, simplifying the geometric model, and setting boundary parameters. Fluent software is then used to simulate the water injection and displacement process. This method can simulate the impact of leakage during displacement, improving the accuracy of simulations for fracture-vuggy reservoir displacement. Attached Figure Description
[0026] Figure 1 This is a flowchart of the simulation method of the present invention;
[0027] Figure 2 This is a schematic diagram of a two-dimensional reservoir model in the simulation method of this invention;
[0028] Figure 3 This is a schematic diagram of the digital model in the simulation method of the present invention;
[0029] Figure 4 This is a schematic diagram of the crack after two-dimensionalization in the simulation method of the present invention;
[0030] Figure 5 This is a simplified schematic diagram of the geometric model of the crack in the simulation method of this invention;
[0031] Figure 6 This is a schematic diagram illustrating the generation of unstructured meshes and the setting of boundary conditions in the simulation method of this invention.
[0032] Figure 7This is a schematic diagram of the initial condition settings in the simulation method of the present invention;
[0033] Figure 8 This is a schematic diagram of the simulation results in the simulation method of the present invention;
[0034] Figure 9 This is a schematic diagram of the simulation results in the simulation method of the present invention without considering leakage.
[0035] Figure 10 This is a schematic diagram comparing the water displacement effect in the simulation method of this invention. Detailed Implementation
[0036] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.
[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Technical features in the various embodiments of the present invention can be combined accordingly without mutual conflict.
[0038] Example
[0039] Combination Figures 1-10 As shown in the figure, this embodiment provides a simulation method for water injection displacement in fractured-vuggy reservoirs that considers leakage. It should be noted that... Figures 3-9 The black lines indicating the location of the cracks show their distribution. And combined with... Figures 6-9 Different color levels correspond to Figure 2 The different colors indicated represent oil leaks, water seepage, pressure increases, and leakage. Among them, Figure 3 and Figure 4 The text also indicates the length of the area, such as 170m or 700m.
[0040] The specific method includes the following steps:
[0041] Step 1: Establish a digital model based on the fractured-vuggy reservoir model to obtain a one-dimensional fracture segment; wherein, the fractured-vuggy reservoir model is a one-injection-one-production well group model, which means a water injection well and an oil production well model.
[0042] In this embodiment, the process of establishing a digital model includes the following steps: Step 11, determine the size range of the fractured-vuggy reservoir model; Step 12, using 2D software, click "Attach Image" to insert an image of the simulated view of an injection-production well group model, wherein CAD software is preferred; Step 13, insert the image or, right-click the mouse, select the "Adjust" option in the image, and adjust the contrast image to make the lines in the image more obvious; Step 14, select "Spline Fitting Curve" for tracing, then input the "PE" command and merge the line segments, select "3D Modeling," input the "SU" command to delete the two middle faces, and complete the establishment of the digital model. Since it is a digital model, no similarity transformation is required, and the model size is usually adopted at a 1:1 scale with the real model.
[0043] Combination Figure 2 The fractured-vuggy reservoir model shown has cavern size and fracture aperture (2mm) that match the actual reservoir, eliminating the need for similarity analysis and simulation parameter adjustments. However, the presence of fractures communicating with the bottom water in the model results in significant water leakage (approximately 58%), leading to low waterdrive efficiency. It should be noted that... Figure 2 The black straight lines indicate the location of the cracks, which involves descriptions of oil displacement, water channeling, pressure increase, and leakage.
[0044] Step 2: Divide the one-dimensional fracture into two dimensions based on the fracture opening to form a fracture surface. Since the fracture opening (i.e., width) usually only has size, which is very different from the reservoir model size (more than 1:10000), the fracture obtained in step 1 is only a one-dimensional line segment and does not have an opening.
[0045] Specifically, in this embodiment, the two-dimensionalization process includes the following steps: Step 21, setting the crack aperture parameter d; Step 22, setting the endpoint coordinates of each crack one-dimensional line segment, dividing them into P1(x1,y1,z1) and P2(x2,y2,z2), and deriving the corresponding linear equations: In the formula, t is a real number between 0 and 1, representing the position of any point (x, y, z) on the line segment; Step 23: Determine the normal unit vector. (x2-x1)x n +(y2-y1)y n +(z2-z1)z n =0, where n = 1, 2, 3...; Step 24: Translate line segment P1-P2 along the normal direction of the line segment to both sides of the line segment, with a translation amount of d / 2. The coordinates of the line segment after translation are: P 11(x1+xnd2,y1+ynd2,z1+znd2; P21x2+xnd2,y2+ynd2,z2+znd2; P12x1-xnd2,y1-ynd2,z1-znd2; P 22 (x2-x n d / 2,y2-y n d / 2,z2-z n d / 2); Step 25, P 11 P 21 P 22 P 12 The four points form a two-dimensional crack quadrilateral.
[0046] Step 3: Extract the feature points of the crevice boundary and simplify the crevice geometry model. Since the crevice geometry model is drawn using spline fitting curves, the original points are very dense, which is not conducive to mesh generation. Therefore, simplification is required.
[0047] In this embodiment, the simplified operation process includes the following steps: Step 31, marking the feature point P of the seam boundary. c Select P c Two adjacent points P t and P r And it satisfies the following characteristics: In the formula, ε is taken as 1e-2; Step 32: retain the feature points that satisfy the feature conditions in step 31 of the gap hole geometric model, delete the other non-feature points that do not satisfy the feature conditions, connect all feature points in sequence to obtain a simplified gap hole geometric model; and export the model as a DWG format file.
[0048] In this embodiment, it should be noted that steps 2 and 3 are parallel processes, and their order can be interchanged. Step 2 mainly addresses the crack, transforming it from a line into a surface, while step 3 mainly addresses the geometric shape of the crack segment, reducing geometric complexity.
[0049] Step 4: Based on the digital model of the fractured-vuggy reservoir, mesh the data and generate finite volume computational cells; that is, perform the operation of generating unstructured networks.
[0050] Specifically, in this embodiment, the steps are as follows: Step 41: Import the simplified geometric model of the fissure into the Meshing module of Fluent's built-in mesh generator; Step 42: Divide the fissure and the cave into separate parts to improve computational efficiency. The cave area is divided into quadrilateral / triangular meshes, and the fissure area is divided into triangular meshes; Step 43: Determine the target number of meshes N for the cave area. gc Calculate the grid resolution L of the karst cave area gc : In the formula, Ac It is the area of the cave region; Step 44: Determine the target grid number N of the fissure zone. gf And calculate the mesh resolution L of the crack zone. gf : In the formula, A f This refers to the area of the crack region; Step 45: Use Fluent's built-in Meshing module to generate a mesh, i.e., generate finite volume calculation elements, and export the mesh as an msh format file; Step 46: Start Fluent, select double precision solution based on Fluent's built-in double precision solver, and import the mesh file into Fluent; Check the quality of the model mesh to prevent negative volumes from causing solution failure. If negative volumes occur, the mesh needs to be regenerated.
[0051] Step 5: Set the parameters of the oil-water two-phase fluid involved in the displacement process, and set the flow model and related parameters;
[0052] In this embodiment, step 5 includes the following steps: Step 51, import the discretized geometries and meshes into Fluent, and set the gravitational acceleration to -9.81 m / s². 2 Step 52: Set the volume fraction parameter to explicit discrete format; Step 53: Select multiphase flow model: To obtain a more accurate phase interface, select the Euler model, and the interface type is Sharp; Step 54: Set the number of phases according to the actual fluid types and quantities used in the displacement process, such as oil, water, and air, and set the main phase as oil; Step 55: Set the density and viscosity of each phase fluid; Step 56: Set the interfacial tension coefficient, where the oil-water interfacial tension is 0.072 N / m and the gas-liquid interfacial tension is 0.02 N / m; Step 57: Set the flow model to k-ω model.
[0053] Step 6: Based on the generated unstructured mesh, set the boundary condition parameters for slot displacement, including inlet, outlet, and filtering boundary conditions.
[0054] In this embodiment, the inlet adopts Neumann boundary conditions; the inlet Ω is set. inlet The injection rate is q inlet The unit is m 3 / s, will q inlet Convert to linear velocity v inlet The unit is m / s: Among them, A inlet It is the area of the entrance boundary.
[0055] The outlet uses Dirichlet boundary conditions, typically employing relative pressure (gauge pressure). For the outlet absolute pressure... Will Converted to relative pressure: Among them, P sc That is the standard pressure.
[0056] The filtration boundary condition adopts the Dirichlet boundary condition (connected bottom water), generally using relative pressure (gauge pressure), while the outlet absolute pressure is used. Will Converted to relative pressure: Among them, P sc That is the standard pressure.
[0057] Step 7: Based on the boundary condition parameter settings, set the initial conditions for the simplified slit geometry model; that is, set the initial conditions for the model.
[0058] In this embodiment, the process includes the following steps: Step 71, setting the initial pressure distribution of the simplified slit geometry model, using the same relative pressure as in Step 6, and the characterization method is as follows: In the formula, P init Psc is the initial pressure; Psc is the standard pressure. The initial gauge pressure is used; Step 72: Set the initial fluid distribution for the simplified slotted geometry model. This can be done by model partitioning or by setting the model coordinates. Specifically, based on the distribution of the water, oil, and gas phases in the actual physical model, measure the Z-coordinates of the water-oil horizontal boundary and the oil-gas horizontal boundary to divide the model into a gas phase region (top), an oil phase region (middle), and a water phase region (bottom); Step 73: Set the initial velocity distribution for the simplified slotted geometry model. The initial flow field can be considered to be stationary, and the velocity field is zero at this time: v(x,y,z)=0.
[0059] Step 8: Use the Fluent simulation solver to solve the simplified geometric model of the crack, and then fill the digital model and the geometric model of the crack into the corresponding positions in the Fluent software.
[0060] In this embodiment, the solution process includes the following steps: Step 81, import the mesh .msh format file generated in step 45 into Fluent; Step 82, select a 2D or 3D solver according to the established simplified gap geometry model, check the imported mesh, and if the mesh has negative volume, it needs to be re-meshed; Step 83, select the solver format and solver type; Step 84, determine the material physical properties; Step 85, set the operating environment; Step 86, define the boundary conditions in step 6; Step 87, set control parameters, such as setting the calculation time step; Step 88, initialize the flow field; Step 89, run the numerical calculation solution using Fluent.
[0061] Combination Figure 10It can be seen that during the water injection displacement process, the model with leakage is defined as the leakage model. The recovery rate of the leakage model is 45.68%, while the recovery rate of the non-leakage model is 60.77%, with a leakage ratio close to 60%, showing a high degree of agreement. Compared with the numerical simulation results without considering leakage, the simulation results using the method of this invention have higher accuracy.
[0062] In this embodiment, it should be noted that the fractured-vuggy reservoir model is a model in the actual physical world, the fractured-vuggy geometric model is the geometric part of the fractured-vuggy model, the digital model is the digitalization of the fractured-vuggy reservoir model, and the flow model is the model used to describe and simulate fluid flow among the above models, including fluid models, mathematical models, etc. The boundary conditions in these models generally do not consider leakage. This solution incorporates leakage, therefore, the corresponding model is called the leakage model.
[0063] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.
Claims
1. A simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, characterized in that: Includes the following steps: Step 1: Establish a digital model based on the fractured-vuggy reservoir model to obtain a one-dimensional fracture segment; wherein, the fractured-vuggy reservoir model is a one-injection-one-production well group model; Step 2: Based on the crack aperture in the digital model, the one-dimensional crack is converted into a two-dimensional crack surface. Step 3: Extract the feature points of the crevice boundary and simplify the geometric model of the crevice. Step 4: Based on the digital model of the fractured-vuggy reservoir, mesh the data and generate finite volume calculation cells; Step 5: Set the parameters of the oil-water two-phase fluid involved in the displacement process, and set the flow model; Step 6: Set the boundary condition parameters for the crack displacement, including the inlet, outlet, and filtration boundary conditions. Step 7: Based on the boundary condition parameter settings, set the initial conditions for the simplified slit geometry model; Step 8: Use the Fluent simulation solver to solve the simplified geometric model of the crack.
2. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 1, the process of building a digital model, includes the following steps: Step 11: Determine the size range of the fractured reservoir model; Step 12: Using 2D software, insert an image of the simulation view of the injection-production well group model; Step 13: Adjust the image in the picture, and adjust the contrast in the image; Step 14: Select a spline fitting curve for imitation, merge the line segments, and then perform 3D modeling to complete the establishment of the digital model.
3. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 2, is characterized in that: In step 11, a model size with a 1:1 scale of the real model is used.
4. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 2, the two-dimensionalization process includes the following steps: Step 21: Set the crack aperture parameter d; Step 22: Define the endpoint coordinates of each crack one-dimensional line segment, designated as P1(x1,y1,z1) and P2(x2,y2,z2), and derive the corresponding line equations: In the formula, t is a real number between 0 and 1, representing the position of any point (x, y, z) on the line segment; Step 23: Determine the unit vector of the normal direction. (x2-x1)x n +(y2-y1)y n +(z2-z1)z n =0; where n = 1, 2, 3...; Step 24: Translate line segment P1-P2 along the normal direction of the line segment to both sides by a translation amount of d / 2. The coordinates of the line segment after translation are as follows: P 11 (x1+x n d / 2,y1+y n d / 2,z1+z n d / 2)? P 21 (x2+x n d / 2,y2+y n d / 2,z2+z n d / 2); P 12 (x1–x n d / 2,y1-y n d / 2.z1-z n d / 2)? P 22 (x2-x n d / 2,y2-y n d / 2,z2-z n d / 2); Step 25, P 11 P 21 P 22 P 12 The four points form a two-dimensional crack quadrilateral.
5. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 3, the process of simplifying the operation includes the following steps: Step 31: Mark the feature point P of the seam boundary. c Select P c Two adjacent points P t and P r And it satisfies the following characteristics: In the formula, ε is taken as 1e-2; Step 32: Retain the feature points that satisfy the feature conditions in Step 31 of the slit geometry model, delete the remaining non-feature points that do not satisfy the feature conditions, connect all feature points in sequence to obtain a simplified slit geometry model, and then export it.
6. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 5, is characterized in that: The exported simplified slit geometry model is a DWG file.
7. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 4 specifically includes the following steps: Step 41: Import the simplified slit geometry model into Fluent's built-in Meshing module; Step 42: Divide the cracks and caves into zones. The cave area is divided into quadrilateral / triangular grids, and the cracks are divided into triangular grids. Step 43: Determine the target grid number N for the karst cave area. gc Calculate the grid resolution L of the karst cave area gc : In the formula, A c It refers to the area of the cave region. Step 44: Determine the target mesh number N in the crack zone. gf And calculate the mesh resolution L of the crack zone. gf : In the formula, A f It is the area of the cracked region; Step 45: Use Fluent's built-in Meshing module to generate a mesh, i.e., generate finite volume calculation cells, and export the mesh as an msh format file; Step 46: Start Fluent, select double precision solver based on Fluent's built-in double precision solver, and import the mesh file into Fluent.
8. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 7, is characterized in that: In step 46, check the mesh quality of the slit geometry model. If a negative volume is found, return to step 42 and re-mesh the model.
9. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 5 includes the following steps: Step 51: Import the discretized slit geometry model and mesh into Fluent, and set the gravitational acceleration in the Y direction; Step 52: Set the volume fraction parameter to an explicit discrete format; Step 53: Select a multiphase flow model; Step 54: Set the number of phases according to the actual types and quantities of fluids used in the displacement process; Step 55: Set the density and viscosity of each phase fluid; Step 56: Set the interfacial tension coefficients, where the oil-water interfacial tension is 0.072 N / m and the gas-liquid interfacial tension is 0.02 N / m; Step 57: Set the flow model to the k-ω model.
10. A simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 9, characterized in that: In step 53, the multiphase flow model is the Euler model, and the interface type is Sharp.
11. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: In step 6, Neumann boundary conditions are applied to the inlet; the inlet Ω is set. inlet The injection rate is q inlet The unit is m 3 / s, will q inlet Convert to linear velocity v inlet The unit is m / s: Among them, A inlet It is the area of the entrance boundary.
12. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: In step 6, the Dirichlet boundary condition is applied to the outlet, and the outlet absolute pressure is... Will Converted to relative pressure: Among them, P sc That is the standard pressure.
13. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: In step 6, the Dirichlet boundary condition is used for the filtration boundary condition, and the outlet absolute pressure is... Will Converted to relative pressure: Among them, P sc That is the standard pressure.
14. The simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 1, is characterized in that: Step 7 includes the following steps: Step 71: Set the initial pressure distribution for the simplified geometries of the cracks, characterized as follows: In the formula, P init It is the initial pressure; P sc It is standard pressure; This is the initial gauge pressure; Step 72: Set the initial fluid distribution for the simplified slit geometry model; Step 73: Set the initial velocity distribution for the simplified slit geometry model, where the velocity field is zero: v(x,y,z)=0.
15. A simulation method for water injection displacement in fractured-vuggy reservoirs considering leakage, as described in claim 7, characterized in that: Step 8, the solution process includes the following steps: Step 81: Import the mesh MSH format file generated in Step 45 into Fluent; Step 82: Select a 2D or 3D solver based on the simplified geometric model of the slit, check the imported mesh, and if the mesh has negative volume, it needs to be re-meshed. Step 83: Select the solver format and solver type; Step 84: Determine the physical properties of the material; Step 85: Set up the operating environment; Step 86: Define the boundary conditions from Step 6; Step 87: Set control parameters; Step 88: Initialize the flow field; Step 89: Use Fluent to run numerical calculations to solve the problem.