Discrete fracture model construction method and device and shale gas reservoir productivity numerical simulation method and device

Abstract

The invention discloses a discrete fracture model construction method and device and a shale gas reservoir productivity numerical simulation method and device. The discrete fracture model construction method comprises the following steps: acquiring geological survey data of a target area, physical parameter data of shale and shale fracture parameters; constructing a three-dimensional stratum model of the target area based on the geological survey data and the physical parameter data of the shale; and constructing a discrete fracture model based on the three-dimensional stratum model and shale fracture parameters, wherein the fracture parameters comprise a fracture angle, fracture area distribution and a fracture network structure. According to the discrete fracture model construction method, during model construction, the influence of the shale fracture parameters on the simulation result of the discrete fracture model is considered, so that the simulation result of the discrete fracture model is closer to the complexity of an actual fracture network, and the accuracy of the simulation result is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas reservoir development, and in particular to a discrete fracture model construction, shale gas reservoir capacity numerical simulation method and device. Background Art

[0002] Shale gas refers to organic-rich, mature dark mud shale or high-carbon mud shale. Due to the adsorption of organic matter or the existence of cracks and matrix pores in the rock, shale stores and preserves certain commercially valuable natural gas of biological origin, pyrolysis origin, and a mixture of the two. It is an unconventional natural gas. Unlike conventional gas reservoirs, shale gas reservoirs are mostly nano-micro pores with low permeability. Due to its complex flow mechanism, it is difficult to exploit. Therefore, production capacity simulation is usually required before exploitation.

[0003] During the hydraulic fracturing process, affected by the original secondary fractures, complex fracture networks are often generated in the fractured formation. Since the opening of the fractures is not uniform, it will change with the extension direction of the fractures. The existence of fractures will affect the movement trajectory of shale gas outflow. In order to improve the accuracy of the numerical simulation of production capacity, the continuous medium hypothesis is introduced in the numerical simulation of production capacity, and a continuous medium model is constructed. Through the fluid seepage law in the fractured oil and gas reservoir, the production capacity of shale gas can be simulated more accurately and intuitively. Later, Warren and Root introduced the dual medium model into the production capacity numerical simulation technology. After decades of development, the discrete fracture model and embedded discrete fracture model were developed from the continuous medium model. The use of discrete fracture models to simulate shale gas production capacity data can reduce the influence of parameters such as fracture size, shape, orientation and direction on the simulation accuracy to a certain extent. Summary of the invention

[0004] The inventors of the present application have found that the existing discrete fracture models do not take into account the influence of shale fracture parameters when they are constructed, so the simulation results of the constructed discrete fracture models have certain errors compared with the actual fracture network.

[0005] In view of the above problems, the present invention is proposed to provide a method and device for constructing a discrete fracture model and numerically simulating the productivity of a shale gas reservoir, which can overcome the above problems or at least partially solve the above problems.

[0006] In a first aspect, an embodiment of the present invention provides a method for constructing a discrete fracture model, including: obtaining geological survey data of a target area, physical parameter data of shale, and shale fracture parameters;

[0007] Constructing a three-dimensional stratigraphic model of a target area based on the geological survey data and the physical parameter data of the shale;

[0008] A discrete fracture model is constructed based on the three-dimensional formation model and shale fracture parameters, wherein the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

[0009] In an optional embodiment, a discrete fracture model is constructed based on a three-dimensional formation model and pre-acquired shale fracture parameters, including:

[0010] Through the discrete fracture simulation method, the three-dimensional formation model and shale fracture parameters are imported into the numerical simulation software for simulation and construction of the initial discrete fracture model;

[0011] The field observation data of the target area is obtained, the simulation results of the initial discrete fracture model are compared with the field observation data of the target area, and the parameters of the initial discrete fracture model are corrected to obtain the discrete fracture model; the simulation results of the initial fracture model include: physical parameters of shale, fracture geometry information and flow parameters.

[0012] In an optional embodiment, field observation data of the target area is obtained, simulation results of the initial discrete fracture model are compared with the field observation data of the target area, and parameter correction is performed on the initial discrete fracture model to obtain a discrete fracture model; including:

[0013] Acquire field observation data of the target area, and obtain fracture geometry information of the target area, shale physical properties of the target area, and fluid properties of the target area according to the field observation data of the target area; the field observation data includes: field fracturing test data, seismic imaging data, and drilling data of the target area;

[0014] Compare and analyze the fracture geometry information simulated by the initial fracture model with the fracture geometry information of the target area, the shale physical properties simulated by the initial fracture model with the shale physical properties of the target area, and the fluid properties simulated by the initial fracture model with the fluid properties of the target area to determine whether the corresponding two meet the consistency requirements;

[0015] If so, a discrete crack model is obtained;

[0016] If not, the parameters of the fracture network model are corrected to change the simulation results of the discrete fracture model, and the comparative analysis steps are continued until the discrete fracture model is obtained.

[0017] Based on the same inventive concept, an embodiment of the present invention provides a shale gas reservoir productivity numerical simulation method, including:

[0018] The discrete fracture model is meshed using a fine mesh generation method to obtain mesh node data;

[0019] Construct a horizontal well model in the target area. Based on the grid node data, use the equivalent seepage method to embed the horizontal well model into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model.

[0020] Based on the constructed wellbore-shale gas reservoir coupling model, numerical simulation of shale gas reservoir is carried out to obtain the production capacity value of shale gas reservoir;

[0021] Wherein, the discrete fracture model is constructed using the above-mentioned discrete fracture model construction method.

[0022] In an optional embodiment, the discrete fracture model is meshed using a fine meshing method, including:

[0023] Extracting a fracture surface in a three-dimensional space from a discrete fracture model, and projecting the fracture surface in the three-dimensional space onto a preset projection plane to obtain a fracture surface in a two-dimensional plane;

[0024] Perform Delaunay triangulation on the crack surface in the two-dimensional plane to obtain mesh node data in the two-dimensional plane;

[0025] Based on the preset projection plane, the crack surface in the two-dimensional plane is restored to the three-dimensional space, and accordingly, the grid node data in the two-dimensional plane is converted into the three-dimensional space grid node data.

[0026] In an optional embodiment, a horizontal well model of the target area is constructed, and based on the grid node data, the horizontal well model is embedded in the discrete fracture model using the equivalent seepage method to obtain a wellbore-shale gas reservoir coupling model, including:

[0027] The equivalent seepage method is used to construct the flow equation in the wellbore, and its expression is:

[0028]

[0029] Where v is the average flow velocity in the wellbore section, d is the pipe diameter, L is the pipe length, and f p is the friction coefficient of the tube wall under radial flow conditions, is the momentum correction coefficient, v1 is the average flow velocity in the upstream section of the pipeline, and v2 is the average flow velocity in the downstream section of the pipeline;

[0030] The shale gas reservoir equation is constructed, and its expression is:

[0031]

[0032] In the formula, is the pressure gradient, v is the gas velocity, k is the rock permeability, μ is the gas viscosity, ρ is the gas density, β is the Forchheimer coefficient,

[0033] in,

[0034]

[0035] In the formula, k f is the fracture permeability;

[0036] The constructed wellbore flow equation and shale gas reservoir equation are introduced into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model.

[0037] In an optional embodiment, numerical simulation of the shale gas reservoir is performed based on the constructed wellbore-shale gas reservoir coupling model to obtain production capacity simulation data, including:

[0038] The constructed shale gas reservoir equation is numerically discretized using the finite volume method to obtain a numerical discrete equation;

[0039] Performing time and space differentiation on the numerical discrete equation to obtain a differentiated numerical discrete equation;

[0040] The numerical discrete equation after difference is converted into a residual equation, and the shale gas reservoir simulation variables are substituted into the residual equation for solution to obtain the simulated shale gas reservoir production capacity data.

[0041] Based on the same inventive concept, an embodiment of the present invention further provides a device for constructing a discrete fracture model, comprising:

[0042] A data acquisition module is used to obtain geological survey data of the target area, physical parameter data of shale and shale fracture parameters;

[0043] A three-dimensional stratigraphic model building module, which builds a three-dimensional stratigraphic model of a target area based on the geological survey data and the physical parameter data of the shale;

[0044] The first model building module builds a discrete fracture model based on the three-dimensional formation model and shale fracture parameters, wherein the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

[0045] Based on the same inventive concept, an embodiment of the present invention further provides a shale gas reservoir productivity numerical simulation device, comprising:

[0046] Meshing module: Use fine meshing method to mesh the discrete crack model and obtain mesh node data;

[0047] The second model building module: constructs a horizontal well model in the target area. Based on the grid node data, the equivalent seepage method is used to embed the horizontal well model into the discrete fracture model to obtain a wellbore-shale gas reservoir coupling model.

[0048] Capacity simulation module: Based on the constructed wellbore-shale gas reservoir coupling model, numerical simulation of the shale gas reservoir is performed to obtain the capacity value of the shale gas reservoir.

[0049] Based on the same inventive concept, an embodiment of the present invention also provides a computer storage medium, in which computer executable instructions are stored. When the computer executable instructions are executed by a processor, the above-mentioned discrete fracture model construction method and the above-mentioned shale gas reservoir production capacity numerical simulation method are implemented.

[0050] Based on the same inventive concept, an embodiment of the present invention also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the above-mentioned discrete fracture model construction method and the above-mentioned shale gas reservoir production capacity numerical simulation method are implemented.

[0051] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0052] The method for constructing a discrete fracture model provided in an embodiment of the present invention, when constructing a discrete fracture model, uses geological survey data of the target area and physical parameter data of core samples to construct a three-dimensional formation model of the target area, and then constructs a discrete fracture model based on the three-dimensional formation model and the acquired shale fracture parameters. When constructing the discrete fracture model, the fracture parameters of shale are taken into consideration, and the geometric shape, direction, length and connection mode of shale fractures can be more accurately described and simulated. The simulation results of the discrete fracture model are closer to the complexity of the actual fracture network, and the influence of fractures on the mechanical behavior of shale or soil can be more realistically simulated. When using the constructed discrete fracture model to perform numerical simulation of shale gas reservoir production capacity, the accuracy of the numerical simulation of production capacity can be improved.

[0053] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0054] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0056] Figure 1 This is a flow chart of a method for constructing a discrete fracture model in an embodiment of the present invention;

[0057] Figure 2 Flow chart of a shale gas reservoir productivity simulation method in an embodiment of the present invention;

[0058] Figure 3 A schematic diagram of the structure of a discrete crack model construction device in an embodiment of the present invention;

[0059] Figure 4 It is a structural schematic diagram of a shale gas reservoir productivity simulation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0061] There are many methods for numerical simulation of shale gas reservoir productivity in the prior art. For example, the patent application with application number CN202011031095.5 discloses a method for numerical simulation of shale gas reservoir productivity, including establishing a non-structural tetrahedral network model; establishing a matrix system flow equation; establishing a set of equations for solving natural fracture skeleton volume strain and large-scale fracture skeleton volume strain; establishing a shale gas nonlinear seepage model and determining the boundary conditions of the shale gas nonlinear seepage model; obtaining the semi-discrete format of the matrix system flow equation, natural fracture flow equation, and large-scale fracture flow equation; and obtaining the horizontal well production distribution in the target area. This patent introduces skeleton volume strain to construct a non-structural tetrahedral network model, and improves the accuracy of shale gas productivity numerical simulation by adding the influencing parameters of skeleton volume strain on productivity. However, this scheme does not fully take into account the geometry, direction, length, and connection mode of the fractures in the shale gas reservoir productivity numerical simulation area, resulting in limited numerical accuracy of the simulated shale gas productivity.

[0062] Furthermore, the inventors of the present application have discovered that the existing discrete fracture models do not take into account the influence of shale fracture parameters when they are constructed, so the simulation results of the constructed discrete fracture models have certain errors compared with the actual fracture network.

[0063] In order to solve the problems existing in the prior art, an embodiment of the present invention provides a method and device for constructing a discrete fracture model and numerically simulating the productivity of a shale gas reservoir.

[0064] The present invention provides a method for constructing a discrete fracture model. Figure 1 As shown, the following steps are included:

[0065] Step S101: obtaining geological survey data of the target area, physical parameter data of shale and shale fracture parameters;

[0066] Step S102: constructing a three-dimensional stratigraphic model of the target area based on geological survey data and physical parameter data of shale;

[0067] Step S103: constructing a discrete fracture model based on the three-dimensional formation model and shale fracture parameters, where the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

[0068] Among them, the fracture parameters of shale described in the embodiment of the present invention are:

[0069] Fracture angle refers to the angle between the cracks or fractures formed along the inside of the shale rock formation and the horizontal plane. During hydraulic fracturing, high-pressure fluid (usually water and some chemical additives) is injected into the wellbore to create fractures in the rock. These fractures can be vertical, horizontal, or at an angle in between. The choice of fracture angle is very important for maximizing shale oil and gas production and reducing the spread of fractures into unwanted areas.

[0070] Fracture area distribution refers to the size and distribution of cracks or fractures formed in a shale formation. During hydraulic fracturing, the pressure of the injected fluid causes the rock in the shale formation to crack and form multiple fractures with different lengths and widths, i.e., different fracture areas.

[0071] Fracture grid structure refers to the relative position and connection of multiple cracks or fractures in shale. In hydraulic fracturing, the fractures are usually interlaced and connected in a complex way to form a fracture grid structure. The complexity of the fracture grid structure is crucial to determining the flow path and transmission characteristics of oil and gas fluids in the rock.

[0072] Therefore, when constructing a discrete fracture model, taking into account the above-mentioned shale fracture parameters, the obtained discrete fracture model can more accurately describe and simulate the geometric information of shale fractures, such as the geometric shape, direction, length and connection method of the fractures. The simulation results of the discrete fracture model are closer to the complexity of the actual fracture network, and can more realistically simulate the influence of fractures on the mechanical behavior of shale or soil. When using the constructed discrete fracture model to perform numerical simulation of shale gas reservoir production capacity, the accuracy of numerical simulation of production capacity can be improved.

[0073] In step S101, geological survey data of the target area, physical parameter data of shale and shale fracture parameters are obtained; specifically:

[0074] Through field geological surveys, geological profile analysis, core analysis and other geological survey and data collection methods, geological survey data such as rock properties, geological structure, and tectonic stress in the target area are obtained.

[0075] Among them, geological structure and rock properties have an important influence on the formation, distribution and exploitability of mineral resources. Geological structure can control the distribution and morphology of ore deposits, while rock properties affect the grade, mineability and processing properties of ore. Through the study of geological structure and rock properties, we can guide the exploration and development of mineral resources and improve mining efficiency and resource utilization.

[0076] Furthermore, the physical and mechanical parameters of shale include: compressive strength, tensile mechanical properties, shear strength, etc.; obtaining the physical parameters of shale includes: collecting core samples from the target area, conducting laboratory tests on the collected core samples, and determining the physical and mechanical parameters of shale based on the laboratory test results;

[0077] Specifically, the compressive strength of shale can be measured through triaxial compression test, and the cohesion and internal friction angle of shale can also be obtained through triaxial compression test (cohesion reflects the force that breaks shale, and internal friction angle reflects the force that stabilizes shale); the data measured by tensile test can determine the elastic limit, elongation, elastic modulus, proportional limit, area reduction, tensile strength, yield point, yield strength and other tensile mechanical properties of rock; the shear strength of shale can be determined by direct shear test.

[0078] Furthermore, shale fracture parameters can be obtained by:

[0079] 1. Laboratory tests: By conducting rock physics and mechanics tests (such as core profiling tests), the fracture of shale can be observed and recorded. During the test, parameters such as fracture angle and fracture area distribution can be measured and analyzed. For example, in the profiling test, stress is applied to the core sample and the formation, expansion and connection of the cracks are observed and measured.

[0080] 2. Image analysis: Image analysis of the fracture surface of the core sample is performed by using techniques such as microscopy, scanning electron microscopy (SEM) and digital image processing. Image analysis can provide information about the morphology, size and arrangement of the fracture surface. The fracture area distribution and fracture network structure can be determined.

[0081] 3. Seismic imaging technology: Seismic imaging technology, such as seismic reflection and seismic tomography, can be used to observe and interpret the fracture conditions of shale formations. Seismic imaging can provide information about the orientation, density and connectivity of fractures, and infer the fracture angle and fracture network structure of shale.

[0082] Among them, when obtaining shale fracture parameters, the embodiment of the present invention does not specifically limit the specific method of obtaining shale fracture parameters, and technicians in related fields can choose according to actual needs.

[0083] In step S102, the construction of the three-dimensional stratigraphic model may be achieved by geological modeling software. Specifically, the geological modeling software may be Petrel software or GOCAD software, etc. The constructed three-dimensional stratigraphic model includes the stratigraphic conditions in the target area such as shale thickness, stratigraphic distribution, and structural characteristics;

[0084] In an optional embodiment, in step S103, a discrete fracture model is constructed based on the three-dimensional formation model and shale fracture parameters, including:

[0085] Through the discrete fracture simulation method, the three-dimensional formation model and shale fracture parameters are imported into the numerical simulation software for simulation to construct an initial discrete fracture model; wherein, the numerical simulation software used to construct the initial discrete fracture model may be: FLAC3D numerical simulation software or TOUGH2 numerical simulation software, etc., wherein the discrete fracture simulation method may be: Discrete Element Method (DEM): The discrete element method is used to simulate the movement and interaction of solid particles or discrete structures to simulate the fracture and crack formation in rocks, soils or granular materials; or, Discrete Fracture Network (DFN): The DFN method regards rocks or formations as composed of discrete fracture networks, simulating the distribution, direction and properties of faults, fractures and fissures in rocks to study water resource management, underground reservoirs and other issues.

[0086] Obtain the field observation data of the target area, compare and analyze the simulation results of the initial discrete fracture model with the field observation data of the target area, and perform parameter correction on the initial discrete fracture model to obtain the discrete fracture model; the simulation results of the initial fracture model include: physical parameters of shale, fracture geometry information and flow parameters.

[0087] Specifically, fracture geometry information includes: fracture location, direction, length, width, thickness and underground distribution. Physical properties of shale include: data on the physical properties of the rock inside and around the fracture, such as rock porosity, permeability, rock type, elastic modulus, etc. Fluid properties include: fluid density, viscosity, temperature, pressure, etc.

[0088] Further, obtaining field observation data of the target area, comparing the simulation results of the initial discrete fracture model with the field observation data of the target area, and performing parameter correction on the initial discrete fracture model to obtain a discrete fracture model; including:

[0089] Obtaining field observation data of the target area, and obtaining fracture geometry information, shale physical properties and fluid properties of the target area based on the field observation data of the target area; the field observation data include: field fracturing test data, seismic imaging data and drilling data of the target area;

[0090] Compare and analyze the fracture geometry information simulated by the initial fracture model with the fracture geometry information of the target area, the shale physical properties simulated by the initial fracture model with the shale physical properties of the target area, and the fluid properties simulated by the initial fracture model with the fluid properties of the target area to determine whether the corresponding two meet the consistency requirements;

[0091] If so, a discrete crack model is obtained;

[0092] If not, the parameters of the fracture network model are corrected to change the simulation results of the discrete fracture model, and the comparative analysis steps are continued until the discrete fracture model is obtained.

[0093] Specifically, among the field observation data, the fracturing test data of the target area include: the recorded data such as pressure, flow rate, fluid properties, etc. during the fracturing process, and the fluid response data measured in the underground reservoir, such as flow rate and pressure distribution.

[0094] The seismic imaging data of the target area includes: seismic wave data acquired during seismic exploration, which is used to generate an image of the underground structure, including the distribution of fractures.

[0095] The drilling data of the target area includes core data, rock property data and formation information obtained from the drilling process, which can provide detailed information about the underground rocks and fractures.

[0096] That is, the discrete fracture model construction method of the embodiment of the present invention can use numerical fitting and inversion algorithms to fit and optimize the parameters of the discrete fracture model in combination with the field observation data and the simulation results of the initial discrete fracture model;

[0097] For example, the length and width of the cracks in the target area can be obtained based on the flow rate obtained from the on-site fracturing test in the target area. The length and width of the cracks in the target area are compared with the length and width of the cracks simulated by the initial fracture model to see if they match. If they do not match, the parameters of the initial fracture model are adjusted to fine-tune the length and width simulated by the initial fracture model. The simulation results of the fracture model are matched with the on-site observations in the target area, so that the discrete fracture model can better simulate the distribution, size, shape and other characteristics of the cracks in the formation.

[0098] The discrete fracture model constructed by the method provided in the embodiment of the present invention can accurately describe and simulate the geometric shape, direction, length and connection mode of the fracture. Compared with the traditional continuous medium model, the discrete fracture model is closer to the complexity of the actual fracture network, and can more realistically simulate the influence of the fracture on the mechanical behavior of shale or soil, thereby improving the accuracy of the final numerical simulation of shale gas reservoir production capacity.

[0099] Based on the same inventive concept, the embodiment of the present invention also provides a shale gas reservoir productivity model method, referring to Figure 2 As shown, including:

[0100] Step S201: meshing the discrete fracture model using a fine meshing method to obtain mesh node data;

[0101] Step S202: construct a horizontal well model of the target area, and based on the grid node data, use the equivalent seepage method to embed the horizontal well model into the discrete fracture model to obtain a wellbore-shale gas reservoir coupling model;

[0102] Step S203: Based on the constructed wellbore-shale gas reservoir coupling model, numerical simulation of the shale gas reservoir is performed to obtain a production capacity value of the shale gas reservoir;

[0103] The discrete fracture model is constructed using the above-mentioned discrete fracture model construction method.

[0104] In step S201, the discrete fracture model is meshed using a fine meshing method, including:

[0105] Extracting a fracture surface in a three-dimensional space from a discrete fracture model, and projecting the fracture surface in the three-dimensional space onto a preset projection plane to obtain a fracture surface in a two-dimensional plane;

[0106] The crack surface in the two-dimensional plane is divided into Delaunay triangulated meshes to obtain the mesh node data in the two-dimensional plane; wherein, when the crack surface in the two-dimensional plane is divided into Delaunay triangulated meshes, n mesh nodes and m mesh units can be divided, and each mesh unit contains 3 mesh nodes.

[0107] Based on the preset projection plane, the crack surface in the two-dimensional plane is restored to the three-dimensional space, and accordingly, the grid node data in the two-dimensional plane is converted into the three-dimensional space grid node data.

[0108] Compared with the meshing method of the prior art, the fine meshing method provided by the embodiment of the present invention obtains more accurate three-dimensional space node data by converting coordinates between two-dimensional and three-dimensional, provides a high-precision positioning point for the model, and facilitates improving the accuracy of numerical simulation.

[0109] And this subdivision method performs Delaunay triangulation in a two-dimensional plane. Delaunay triangulation can better retain the geometric characteristics of the data. The characteristics of Delaunay triangulation minimize the error of obtaining three-dimensional space node data through interpolation method when performing coordinate transformation. For each node of the two-dimensional crack surface, interpolation calculation can be performed through the adjacent nodes in the Delaunay triangulation to obtain the corresponding three-dimensional space node data. Due to the excellent geometric properties of Delaunay triangulation itself, the interpolation error is small, so the obtained three-dimensional space node data is more accurate.

[0110] Furthermore, in step S202, a horizontal well model of the target area is constructed, and based on the grid node data, the horizontal well model is embedded in the discrete fracture model using the equivalent seepage method to obtain a wellbore-shale gas reservoir coupling model, including:

[0111] The equivalent seepage method is used to construct the flow equation in the wellbore, and its expression is:

[0112]

[0113] Where v is the average flow velocity in the wellbore section, d is the pipe diameter, L is the pipe length, and f p is the friction coefficient of the tube wall under radial flow conditions, is the momentum correction coefficient, v1 is the average flow velocity in the upstream section of the pipeline, and v2 is the average flow velocity in the downstream section of the pipeline;

[0114] The shale gas reservoir equation is constructed, and its expression is:

[0115]

[0116] In the formula, is the pressure gradient, v is the gas velocity, k is the rock permeability, μ is the gas viscosity, ρ is the gas density, β is the Forchheimer coefficient,

[0117] in,

[0118]

[0119] In the formula, k f is the fracture permeability;

[0120] The constructed wellbore flow equation and shale gas reservoir equation are introduced into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model.

[0121] The existing shale gas reservoir capacity numerical simulation method does not take into account that the flow of shale gas in horizontal wells will affect the permeability, and cannot more accurately simulate the shale gas capacity value. The capacity numerical simulation method provided in the embodiment of the present invention constructs a wellbore-shale gas reservoir coupling model through an equivalent seepage method, and takes into account the flow details of the fluid in the wellbore to improve the accuracy of the simulation value. The equivalent seepage method adopted in this solution does not need to solve the Navier-Stokes equation and the Brinkman equation, and the interface meets the continuity condition, which reduces the amount of calculation when performing capacity numerical simulation, and improves the stability and calculation efficiency of the numerical solution.

[0122] Furthermore, in step S203, numerical simulation of the shale gas reservoir is performed based on the constructed wellbore-shale gas reservoir coupling model to obtain productivity simulation data, including:

[0123] The constructed shale gas reservoir equation is numerically discretized using the finite volume method to obtain a numerical discrete equation;

[0124] Performing time and space differentiation on the numerical discrete equation to obtain a differentiated numerical discrete equation;

[0125] The numerical discrete equation after difference is converted into a residual equation, and the shale gas reservoir simulation variables are substituted into the residual equation for solution to obtain the simulated shale gas reservoir production capacity data.

[0126] Specifically, the constructed shale gas reservoir equation is numerically discretized using the finite volume method to obtain the numerical discrete equation, and the expression of the numerical discrete equation is:

[0127]

[0128] In the formula, η ij is the control volume unit V i The adjacent unit V j A collection of ij For unit V i With adjacent unit V j The interface area between the two, Φ is the flow potential, V i is the volume of unit cell i, q m is the source and sink term of unit cell i, w g is a constant equation, ρ g is the gas density under standard conditions, λ is a constant;

[0129] The numerical discrete equation is differentiated in time and space, and the expression of the numerical discrete equation after differentiation is obtained as follows:

[0130]

[0131] Where n is the previous time tn , n+1 is the current time t n+1 , Δt is the time step t, ij+1 / 2 is a suitable average value of the physical quantity on the interface between adjacent units i and j; γ ij is the conductivity, Q is the source-sink term, which represents the volume of fluid flowing into the control volume V per unit time and unit volume.

[0132] The numerical discrete equation after difference is transformed into the residual equation. The expression of the residual equation is:

[0133]

[0134] In the formula, is a variable, i is the discrete unit number, n is the time step, is the production capacity per unit time of the simulated shale gas reservoir.

[0135] When conducting numerical simulation of production capacity, the shale gas reservoir simulation variables are substituted into the residual equation for solution to obtain the shale gas reservoir production capacity values ​​simulated under different variable conditions; among which, the shale gas reservoir simulation variables are specifically physical variables such as pressure and temperature.

[0136] The embodiment of the present invention constructs a wellbore-shale gas reservoir coupling model through an equivalent seepage method, taking into account the flow details of the fluid in the wellbore to improve the accuracy of the simulation numerical value. The equivalent seepage method adopted in this scheme does not need to solve the Navier-Stokes equation and the Brinkman equation, and the interface satisfies the continuity condition, which reduces the amount of calculation and improves the stability and calculation efficiency of the numerical solution; and the discrete fracture model is used to accurately simulate the fractures in the shale gas reservoir capacity numerical simulation area. The discrete fracture model can accurately describe and simulate the geometry, direction, length and connection mode of the fractures; compared with the traditional continuous medium model, the discrete fracture model is closer to the complexity of the actual fracture network, and can more realistically simulate the influence of the fractures on the mechanical behavior of shale or soil, thereby improving the accuracy of the final shale gas reservoir capacity numerical simulation.

[0137] Based on the same inventive concept, the embodiment of the present invention also provides a device for constructing a discrete fracture model, referring to Figure 3 As shown, including:

[0138] The data acquisition module 31 is used to acquire geological survey data of the target area, physical parameter data of shale and shale fracture parameters;

[0139] A three-dimensional stratigraphic model building module 32 is used to build a three-dimensional stratigraphic model of a target area based on the geological survey data and the physical parameter data of the shale;

[0140] The first model building module 33 builds a discrete fracture model based on the three-dimensional formation model and shale fracture parameters, wherein the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

[0141] Regarding the discrete fracture model construction device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0142] Based on the same inventive concept, the embodiment of the present invention also provides a shale gas reservoir productivity simulation device, referring to Figure 4 As shown, including:

[0143] Meshing module 41: Meshing the discrete fracture model using a fine meshing method to obtain mesh node data;

[0144] The second model building module 42: constructs a horizontal well model of the target area, and based on the grid node data, uses an equivalent seepage method to embed the horizontal well model into the discrete fracture model to obtain a wellbore-shale gas reservoir coupling model;

[0145] Capacity simulation module 43: Based on the constructed wellbore-shale gas reservoir coupling model, a numerical simulation of the shale gas reservoir is performed to obtain the capacity value of the shale gas reservoir.

[0146] Regarding the shale gas reservoir productivity numerical simulation device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0147] Based on the same inventive concept, an embodiment of the present invention also provides a computer storage medium, in which computer executable instructions are stored. When the computer executable instructions are executed by a processor, the above-mentioned discrete fracture model construction method and the above-mentioned shale gas reservoir production capacity numerical simulation method are implemented.

[0148] Based on the same inventive concept, an embodiment of the present invention also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the above-mentioned discrete fracture model construction method and the above-mentioned shale gas reservoir production capacity numerical simulation method are implemented.

[0149] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0150] Unless otherwise specifically stated, terms such as processing, computing, calculating, determining, displaying, etc. may refer to the actions and / or processes of one or more processing or computing systems, or similar devices, which operate and convert data represented as physical (e.g., electronic) quantities within registers or memories of a processing system into other data similarly represented as physical quantities within memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals may be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0151] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present invention. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0152] In the above detailed description, various features are grouped together in a single embodiment to simplify the invention. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than those clearly stated in each claim. On the contrary, as reflected in the attached claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the attached claims are hereby expressly incorporated into the detailed description, with each claim standing alone as a separate preferred embodiment of the invention.

[0153] Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein may all be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above around their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. A skilled person may implement the described functions in an alternative manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of the present invention.

[0154] The steps of the method or algorithm described in conjunction with the embodiments herein may be directly embodied as hardware, a software module executed by a processor, or a combination thereof. The software module may be located in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a mobile disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor so that the processor can read information from the storage medium and can write information to the storage medium. Of course, the storage medium may also be an integral part of the processor. The processor and the storage medium may be located in an ASIC. The ASIC may be located in a user terminal. Of course, the processor and the storage medium may also be present in a user terminal as discrete components.

[0155] For software implementation, the techniques described in this application can be implemented with modules (e.g., procedures, functions, etc.) that perform the functions described in this application. These software codes can be stored in a memory unit and executed by a processor. The memory unit can be implemented within the processor or outside the processor. In the latter case, it is coupled to the processor in a communication manner via various means, which are well known in the art.

[0156] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. A method for constructing a discrete fracture model, characterized in that: include: Obtain geological survey data of the target area, physical parameter data of shale and shale fracture parameters; Constructing a three-dimensional stratigraphic model of a target area based on the geological survey data and the physical parameter data of the shale; A discrete fracture model is constructed based on the three-dimensional formation model and shale fracture parameters, wherein the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

2. The method for constructing a discrete fracture model according to claim 1, characterized in that: A discrete fracture model is constructed based on the 3D formation model and pre-acquired shale fracture parameters, including: Through the discrete fracture simulation method, the three-dimensional formation model and shale fracture parameters are imported into the numerical simulation software for simulation and construction of the initial discrete fracture model; The field observation data of the target area is obtained, the simulation results of the initial discrete fracture model are compared with the field observation data of the target area, and the parameters of the initial discrete fracture model are corrected to obtain the discrete fracture model; the simulation results of the initial fracture model include: physical parameters of shale, fracture geometry information and flow parameters.

3. The method for constructing a discrete fracture model according to claim 2, characterized in that: Obtaining field observation data of the target area, comparing the simulation results of the initial discrete fracture model with the field observation data of the target area, and performing parameter correction on the initial discrete fracture model to obtain a discrete fracture model; including: Acquire field observation data of the target area, and obtain fracture geometry information of the target area, shale physical properties of the target area, and fluid properties of the target area according to the field observation data of the target area; the field observation data includes: field fracturing test data, seismic imaging data, and drilling data of the target area; Compare and analyze the fracture geometry information simulated by the initial fracture model with the fracture geometry information of the target area, the shale physical properties simulated by the initial fracture model with the shale physical properties of the target area, and the fluid properties simulated by the initial fracture model with the fluid properties of the target area to determine whether the corresponding two meet the consistency requirements; If so, a discrete crack model is obtained; If not, the parameters of the fracture network model are corrected to change the simulation results of the discrete fracture model, and the comparative analysis steps are continued until the discrete fracture model is obtained.

4. A shale gas reservoir productivity model method, It is characterized by; including: The discrete fracture model is meshed using a fine mesh generation method to obtain mesh node data; Construct a horizontal well model in the target area. Based on the grid node data, use the equivalent seepage method to embed the horizontal well model into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model. Based on the constructed wellbore-shale gas reservoir coupling model, numerical simulation of shale gas reservoir is carried out to obtain the production capacity value of shale gas reservoir; Wherein, the discrete fracture model is constructed by using the discrete fracture model construction method as described in any one of claims 1-3.

5. The shale gas reservoir productivity numerical simulation method according to claim 4, characterized in that: The discrete fracture model is meshed using a fine meshing method, including: Extracting a fracture surface in a three-dimensional space from a discrete fracture model, and projecting the fracture surface in the three-dimensional space onto a preset projection plane to obtain a fracture surface in a two-dimensional plane; Perform Delaunay triangulation on the crack surface in the two-dimensional plane to obtain mesh node data in the two-dimensional plane; Based on the preset projection plane, the crack surface in the two-dimensional plane is restored to the three-dimensional space, and accordingly, the grid node data in the two-dimensional plane is converted into the three-dimensional space grid node data.

6. The shale gas reservoir productivity numerical simulation method according to claim 4, characterized in that: Construct a horizontal well model in the target area. Based on the grid node data, use the equivalent seepage method to embed the horizontal well model into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model, including: The equivalent seepage method is used to construct the flow equation in the wellbore, and its expression is: Where v is the average flow velocity in the wellbore section, d is the pipe diameter, L is the pipe length, and f p is the friction coefficient of the tube wall under radial flow conditions, is the momentum correction coefficient, v1 is the average flow velocity in the upstream section of the pipeline, and v2 is the average flow velocity in the downstream section of the pipeline; The shale gas reservoir equation is constructed, and its expression is: In the formula, is the pressure gradient, v is the gas velocity, k is the rock permeability, μ is the gas viscosity, ρ is the gas density, β is the Forchheimer coefficient, in, In the formula, k f is the fracture permeability; The constructed wellbore flow equation and shale gas reservoir equation are introduced into the discrete fracture model to obtain the wellbore-shale gas reservoir coupling model.

7. The shale gas reservoir productivity numerical simulation method according to claim 6, characterized in that: Numerical simulation of shale gas reservoirs is performed based on the constructed wellbore-shale gas reservoir coupling model to obtain production capacity simulation data, including: The constructed shale gas reservoir equation is numerically discretized using the finite volume method to obtain a numerical discrete equation; Performing time and space differentiation on the numerical discrete equation to obtain a differentiated numerical discrete equation; The numerical discrete equation after difference is converted into a residual equation, and the shale gas reservoir simulation variables are substituted into the residual equation for solution to obtain the simulated shale gas reservoir production capacity data.

8. A device for constructing a discrete fracture model, characterized in that: include: A data acquisition module is used to obtain geological survey data of the target area, physical parameter data of shale and shale fracture parameters; A three-dimensional stratigraphic model building module, which builds a three-dimensional stratigraphic model of a target area based on the geological survey data and the physical parameter data of the shale; The first model building module builds a discrete fracture model based on the three-dimensional formation model and shale fracture parameters, wherein the fracture parameters include fracture angle, fracture area distribution and fracture network structure.

9. A shale gas reservoir productivity numerical simulation device, characterized in that: include: Meshing module: Use fine meshing method to mesh the discrete crack model and obtain mesh node data; The second model building module: constructs a horizontal well model in the target area. Based on the grid node data, the equivalent seepage method is used to embed the horizontal well model into the discrete fracture model to obtain a wellbore-shale gas reservoir coupling model. Capacity simulation module: Based on the constructed wellbore-shale gas reservoir coupling model, numerical simulation of the shale gas reservoir is performed to obtain the capacity value of the shale gas reservoir.

10. A computer storage medium, characterized in that: The computer storage medium stores computer executable instructions, which, when executed by a processor, implement the method for constructing a discrete fracture model as described in any one of claims 1 to 3 and the method for numerically simulating the productivity of a shale gas reservoir as described in any one of claims 4 to 7.

11. A computer device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for constructing a discrete fracture model as described in any one of claims 1 to 3 and the method for numerically simulating the productivity of a shale gas reservoir as described in any one of claims 4 to 7 are implemented.

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