Method and system for calculating effective elastic parameters of multi-mineral-component rock

Abstract

The invention discloses a method and a system for calculating effective elastic parameters of multi-mineral-component rock. The method comprises the following steps: S1, presetting types and contents of multi-mineral components; s2, on the basis of the types and contents of the multi-mineral components, constructing a multi-mineral component parameter change digital core model by using a process method; s3, based on an elastic finite element method of a digital rock core, performing numerical simulation on the digital rock core model with multi-mineral component parameter change; s4, calculating effective elastic parameters of the digital core according to a simulation result; and S5, analyzing the relationship between the multi-mineral components and the elastic parameters. Multiple different types and contents of multi-mineral component digital cores are constructed through process method numerical simulation on the basis of a digital core technology, effective elastic parameters of the rock are calculated by applying a finite element numerical simulation method, and the purpose of exploring the elastic change rule of the rock multi-mineral components is achieved. And a theoretical basis is provided for oil and gas reservoir geophysical exploration interpretation.

Description

Technical Field

[0001] The present invention belongs to the field of deep-sea oil and gas reservoir exploration and development, and specifically relates to a method and system for calculating effective elastic parameters of multi-mineral component rocks. Background Art

[0002] In the process of oil and gas reservoir exploration and development, the study of geophysical elastic properties is crucial for the prediction of reservoir physical properties, pore characteristics evaluation and prediction of oil and gas properties. The calculation of reservoir rock elastic parameters is an important part of elastic property research. For sedimentary rocks with the same sedimentary environment, the pore structure and mineral composition of the rocks also show significant differences, which leads to different elastic properties of the rocks. In order to better use geophysical methods to interpret the physical properties of reservoir rocks, it is of great significance to calculate the elastic parameters of multi-mineral rock components.

[0003] The physical properties of rocks are determined by a variety of factors inherent in the rocks themselves. Exploring these properties is important for oil and gas exploration and development. Digital core technology is based on digitized core information and can quantify the pore structure and component information of rocks at the pore scale. It is an effective method for studying the geophysical properties of reservoir rocks. Elastic modulus and wave velocity are important parameters for characterizing elastic properties. The traditional method is to obtain the elastic parameters of rocks through physical experimental tests. The study of rock elastic properties based on digital cores can quantify the relationship between elastic properties and reservoir properties at the microscopic scale, making up for the inability of rock physics experiments to explore microscopic influencing factors.

[0004] Rock elastic properties play an important role in reservoir geological characteristics. The analysis of these properties is usually based on rock physics experiments. Through rock physics experiments, the elastic parameters of reservoir rocks are obtained, and the relationship model between reservoir physical properties and elastic parameters is analyzed, and then the physical properties of oil and gas reservoirs are predicted using the relationship model.

[0005] In the rock physics experiment test, when the rock is brittle or has complex composition, such conventional physical experiments cannot meet the actual requirements; the elastic modulus obtained from the rock physics experiment is the comprehensive result of the entire core test, and it is difficult to analyze the degree and law of influence of various factors on the elastic properties of the rock, making it impossible to deeply understand the elastic properties of the rock. In the numerical simulation of elastic properties based on digital cores, the traditional method sets the solid matrix of the digital core as a single mineral. However, the actual rock usually contains multiple mineral components, which leads to differences between the single mineral component and the actual rock, resulting in inaccurate calculated elastic parameters, and it is impossible to effectively study the elastic properties of the actual rock. It is very necessary to study the elastic properties of multiple mineral components of rocks. Summary of the invention

[0006] In view of the problem that single-mineral component digital cores are unable to characterize the multi-mineral properties of rocks and the elastic modulus calculation of multi-mineral component rocks, the present invention proposes a method and system for calculating the effective elastic parameters of multi-mineral component rocks. Based on digital core technology, multi-mineral component digital cores of various types and contents are constructed through process method numerical simulation, and the finite element numerical simulation method is applied to calculate the effective elastic parameters of rocks, so as to achieve the purpose of exploring the changing laws of the elastic parameters of multi-mineral components of rocks and provide a theoretical basis for the geophysical exploration and interpretation of oil and gas reservoirs.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A method for calculating effective elastic parameters of multi-mineral rock comprises the following steps:

[0009] S1. Type and content of predetermined multi-mineral components;

[0010] S2. Based on the types and contents of multi-mineral components, a digital core model of the parameter changes of multi-mineral components is constructed using a process method;

[0011] S3. Based on the elastic finite element method, numerical simulation of the digital core model with changes in multi-mineral component parameters is performed;

[0012] S4. Calculate the effective elastic parameters of the digital core based on the simulation results.

[0013] Preferably, based on the types and contents of multiple mineral components, the method for constructing a digital core model of multiple mineral component parameter changes using a process method comprises:

[0014] Simulate the most stable deposition of rock particles under gravity, and establish a deposition model after all particles complete the deposition.

[0015] The compaction of the overlying strata is simulated by the longitudinal downward movement of the sedimentary particles, and the downward movement distance of the particles is controlled according to the set compaction amount. The porosity and density of the digital core model are controlled based on the downward movement distance of the particles.

[0016] By covering the particle surface with a certain thickness of cement, the cementation diagenesis of the particles is simulated, and the thickness of the cementation on the particle surface is controlled according to the set cementation thickness, and the cementation density of the digital core is controlled based on the thickness of the cementation on the particle surface;

[0017] By controlling the type and content of particles and cement, a digital core model with varying parameters of multiple mineral components is established.

[0018] Preferably, the method for numerically simulating the digital core model of multi-mineral component parameter changes based on the elastic finite element method of the digital core includes:

[0019] applying finite element strains to the generated digital rock model;

[0020] Establish elastic energy equation for each voxel;

[0021] Based on the elastic energy equation, the fast conjugate gradient method is used to calculate and minimize the gradient of the total energy relative to the node elastic displacement;

[0022] After obtaining the gradient of the displacement, the average stress and strain in the system and the local stress and strain around the microstructural features are calculated;

[0023] The effective elastic modulus of the entire digital core model is obtained by averaging the calculated physical fields.

[0024] Preferably, the method for calculating the effective elastic parameters of the digital core according to the simulation results includes:

[0025] For the isotropic case, the bulk modulus K and shear modulus µ are calculated as:

[0026] ,

[0027] ,

[0028] In the formula, σ xx , σ yy , σ zz , σ xy , σ xz , σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions;

[0029] Using the calculated bulk modulus K and shear modulus µ, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s The calculation formula is:

[0030] ,

[0031] ,

[0032] Where ρ represents the average density of the digital core, which is obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

[0033] The present invention also provides a multi-mineral component rock effective elastic parameter calculation system, comprising: a preset module, a construction module, a simulation module and a calculation module;

[0034] The preset module is used to preset the types and contents of multiple mineral components;

[0035] The construction module is used to construct a digital core model of multi-mineral component parameter changes based on the types and contents of the multi-mineral components using a process method;

[0036] The simulation module is used to perform numerical simulation on a digital core model of multi-mineral component parameter changes based on an elastic finite element method;

[0037] The calculation module is used to calculate the effective elastic parameters of the digital core according to the simulation results.

[0038] Preferably, the building blocks include: a deposition process unit, a compaction process unit and a diagenesis process unit;

[0039] The sedimentation process unit is used to simulate the most stable sedimentation of rock sedimentary particles under the action of gravity, and a sedimentation model is established after all particles complete the sedimentation;

[0040] The compaction process unit is used to simulate the compaction of the overlying strata by the longitudinal downward movement of the sedimentary particles, control the downward movement distance of the particles according to the set compaction amount, and control the porosity and density of the digital core model based on the downward movement distance of the particles;

[0041] The diagenetic process unit is used to simulate the cementation diagenesis of particles by covering the surface of the particles with a certain thickness of cement, controlling the thickness of the cementation on the surface of the particles according to the set cementation thickness, and controlling the cementation density of the digital core based on the thickness of the cementation on the surface of the particles, thereby establishing a digital core model with changes in multi-mineral component parameters.

[0042] Preferably, the simulation module includes: an application unit, a construction unit, a first calculation unit, a second calculation unit and a third calculation unit;

[0043] The application unit is used to apply the strain of the digital core model with multiple mineral component parameter variations to the generated digital rock model;

[0044] The construction unit is used to establish an elastic energy equation for each voxel;

[0045] The first calculation unit is used to calculate and minimize the gradient of the total energy relative to the node elastic displacement using the fast conjugate gradient method based on the elastic energy equation;

[0046] The second calculation unit is used to calculate the average stress and strain in the system and the local stress and strain around the microstructural feature after obtaining the gradient of the displacement;

[0047] The third calculation unit is used to obtain the effective elastic modulus of the entire digital core model by averaging the calculated physical field.

[0048] Preferably, the process of calculating the effective elastic parameters of the digital core according to the simulation results includes:

[0049] For the isotropic case, the bulk modulus K and shear modulus µ are calculated as:

[0050] ,

[0051] ,

[0052] In the formula, σ xx , s yy , σ zz , σ xy , σ xz , σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions;

[0053] Using the calculated bulk modulus K and shear modulus µ, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s The calculation formula is:

[0054] ,

[0055] ,

[0056] Where ρ represents the average density of the digital core, which is obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] 1. The present invention calculates the elastic parameters of multi-component rocks based on digital core technology, which can obtain a wider range of rock physical parameter changes without conducting a large number of experimental measurements, saving time costs and manpower and material resources.

[0059] 2. Compared with the traditional digital core modeling method, the digital core constructed by the present invention contains multiple mineral components, and the types and contents of these mineral components can be quantitatively controlled, providing a model basis for calculating the elastic parameters of multiple mineral components.

[0060] 3. The present invention can establish a three-dimensional digital core model with controllable mineral type and content based on digital core technology. The model can better characterize the multi-mineral component characteristics of actual rocks, and the calculated elastic parameter results are closer to the actual ones. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0062] Figure 1 A flow chart of a method for calculating effective elastic parameters of multi-mineral component rocks according to an embodiment of the present invention;

[0063] Figure 2 A schematic diagram of constructing a multi-mineral component three-dimensional digital core model based on a process method according to an embodiment of the present invention;

[0064] Figure 3 It is a schematic diagram of elastic modulus variation based on numerical calculation of a multi-mineral component digital core model according to an embodiment of the present invention;

[0065] Figure 4 It is a schematic diagram of wave velocity variation based on numerical calculation of a multi-mineral component digital core model according to an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] Embodiment 1

[0069] like Figure 1 As shown, the present invention provides a method for calculating effective elastic parameters of multi-mineral component rocks, comprising the following steps:

[0070] S1. Type and content of predetermined multi-mineral components;

[0071] S2. Based on the types and contents of multi-mineral components, a digital core model of the parameter changes of multi-mineral components is constructed using a process method;

[0072] S3. Based on the elastic finite element method, numerical simulation of the digital core model with changes in multi-mineral component parameters is performed;

[0073] S4. Calculate the effective elastic parameters of the digital core based on the simulation results.

[0074] S5. Analyze the relationship between multiple mineral components and elastic parameters.

[0075] In this embodiment, S1, the types and contents of multiple mineral components in digital core modeling are set according to the research objectives:

[0076] In the process of calculating rock elastic parameters based on digital core technology, the first step is to set the type and content of multi-mineral components in the digital core, which has an important impact on the calculated digital core parameters. Traditional digital core modeling usually assumes that the digital core is composed of a solid matrix and pore space, and the solid matrix is ​​composed of a single component mineral, which is significantly different from the mineral composition of the actual rock. Therefore, there is a significant error between the calculated elastic parameters and the actual rock elastic parameters. In terms of digital core modeling, this method constructs a multi-mineral component digital core that is closer to the actual rock mineral composition, and uses numerical methods to reconstruct the digital core, which can achieve rock skeleton simulation containing multiple mineral types and mineral content changes. According to the research purpose and research needs, first set the type of rock to be studied, set the type of minerals in the rock according to the properties of the rock, and quantitatively change the content of different minerals. For example, the main mineral types in sandstone include quartz, feldspar, mica, chlorite, rock fragments, etc. According to the research purpose, set the rock type in advance, and set the type and content changes of minerals in this type of rock, so as to provide basic physical property parameters for multi-mineral component digital core modeling.

[0077] In this embodiment, S2, the process method is a specific method in the digital core technology, which is used to realize multi-mineral component three-dimensional digital core modeling:

[0078] The process method is an effective method for simulating and establishing digital cores. This method simulates the formation process of rocks to establish digital cores with quantitative changes in pore structure and mineral components, providing a model basis for elastic parameter calculation. The process method mainly includes three main steps: sedimentation process, compaction process and diagenesis process. By using the MATLAB programming language to simulate these processes, a digital core model with changes in multi-mineral component parameters is established. The following introduces the sedimentation process, compaction process and diagenesis process of digital cores constructed by the process method. The sedimentation process simulates the deposition of mineral particles in a complex geological environment. First, the range of deposition is set, and mineral particles can only be deposited in this area. At the same time, the size distribution, type and content of mineral particles need to be set. This information can be obtained by scanning real rock samples, or it can be customized according to the research objectives. For example, the type and content of multi-mineral particles are pre-set in step S1 according to the research objectives, and the particle shape can be set as regular spheres or irregular shapes. Then the deposition particles begin to deposit, one after another, and the next particle deposition begins only after the previous particle deposition is stable. It is assumed that the current deposition particle satisfies the maximum direction of global gravitational potential energy, that is, the most stable deposition, until all deposition particles complete the deposition process. This process is implemented using the MATLAB programming language.

[0079] The compaction process simulates the compaction of deposited particles under the gravity of the overlying strata. Due to the influence of the gravity of the overlying strata, all deposited particles will be subject to the vertical downward gravity, which will cause downward compaction, resulting in a reduction in pore space and a closer interaction between particles. Due to the different thicknesses of the overlying strata, the compaction effect will also be different. The compaction effect of the overlying strata is simulated by performing different degrees of compaction on all deposited particles. This process is implemented in the MATLAB programming language. The control of the compaction amount of different particles is achieved according to the vertical coordinate position of each particle. The process is described by the formula:

[0080] (1)

[0081] In the formula, Z o represents the initial vertical position of the particle center, Z p It indicates the vertical position of the center of the particle after compaction, and λ indicates the set compaction amount to control the compaction density.

[0082] The diagenesis process simulates a series of physical, chemical and biological changes in mineral particles after compaction and stabilization. This process affects the type and content of mineral components in the rock, as well as the changes in the pore structure of the rock. The cementation process is an important process in the diagenesis process. By simulating the formation process of cements of different components and shapes on the surface of mineral particles, the cementation of rocks is simulated. This process is implemented using the MATLAB nominal language. In the cementation process, considering the size of the particles and the growth rate in different directions, it can be described by the formula:

[0083] (2)

[0084] Where ∆(r) represents the thickness of cement formed on the particle surface in the r direction, represents the average radius of the particles, R0 represents the initial radius of a particle, l(r) represents the distance from the surface of a mineral particle to the surface of another mineral particle along the r direction, β represents the parameter controlling the cementation type, and α represents the parameter affecting the particle radius.

[0085] According to the set mineral type, the mineral component type of the particles to be deposited is pre-set, and according to the set content of different mineral components, the number of particles to be deposited is pre-set, for example, different proportions of particles are set to represent quartz, feldspar and rock fragments respectively. Then, the process method is used to construct a multi-component mineral three-dimensional digital core, for example Figure 2 The three-dimensional digital core model of different mineral types and contents is displayed. Different gray values ​​represent different mineral types, and the proportion of different gray values ​​represents the content changes of different mineral components. A digital core model of multi-mineral component parameter changes is constructed based on the process method.

[0086] In this embodiment, S3, numerical simulation of elastic finite element method based on digital core is carried out:

[0087] The finite element method is a method for numerically calculating the elastic properties of three-dimensional digital images. Based on the three-dimensional digital core model reconstructed by the process method, the strain is applied to the generated digital rock model, and the stress-strain effect of the rock is simulated by using the finite element method to calculate the elastic modulus parameters.

[0088] The digital core model consists of voxels with different phases, including pore space and solid matrix with different mineral components. In the numerical calculation, each voxel is regarded as a trilinear unit, so the entire digital core model can be regarded as a finite element mesh. For each voxel, its elastic energy E obeys the variational principle and can be expressed as:

[0089] (3)

[0090] In the formula, ε pq represents the strain tensor, C pqrsrepresents the elastic modulus tensor, the subscripts r and s represent the grid node positions, the subscripts p and q represent the digital core coordinate positions, and d 3 r represents triple integration.

[0091] The elastic modulus tensor gives the relationship between stress and strain, which is linked to each other by Hooke's law. The strain at a voxel in the digital core is equal to the displacement gradient, which indicates how fast the displacement u changes in the material. Assuming linear interpolation of the elastic displacements of the mesh nodes and summing over repeated subscripts, the elastic energy using periodic boundary conditions can be rewritten as:

[0092] (4)

[0093] In the formula, u i and u j represents the elastic displacement of the mesh node, b i represents the linear term matrix, c represents the constant term, D ij represents the stiffness matrix.

[0094] The above elastic energy equation is established for each voxel, and the gradient of the total energy with respect to the elastic displacement of the node is calculated and minimized using the fast conjugate gradient method. After obtaining the displacement, the average stress and strain of the entire three-dimensional digital core are calculated. Then, the effective elastic modulus of the entire digital core model is derived by averaging the calculated physical fields.

[0095] In this embodiment, S4, calculating the effective elastic parameters of the digital core according to the simulation results:

[0096] The finite element method is used to calculate the effective elastic parameters of the digital core model, and the code of this method is written in Fortran. In order to calculate the effective elastic parameters of the digital core model, the model needs to be divided into non-overlapping finite element units, each voxel is set as a basic unit, and periodic boundary conditions are adopted. In addition, macroscopic strains are applied in the principal stress direction and the shear stress direction. The finite element method is used to numerically simulate the elastic properties of the digital core. The elastic potential energy of the digital core is obtained by calculating the elastic displacement vector of each node. The finite element method can be used to calculate stresses and strains in six directions. For the isotropic case, the bulk modulus K and shear modulus µ can be obtained by the following equations:

[0097] (5)

[0098] (6)

[0099] In the formula, σ xx , σ yy , σ zz , σ xy , σ xz, σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions.

[0100] Using the calculated bulk modulus and shear modulus, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s It can be calculated by the following formula:

[0101] (7)

[0102] (8)

[0103] Where ρ represents the average density of the digital core, and the average density can be obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

[0104] In this embodiment, S5, analyzing the relationship between multiple mineral components and elastic parameters:

[0105] Based on this method, the elastic parameters of multi-mineral rock are calculated, and the bulk modulus and shear modulus of the digital core model are calculated using Formula 3 and Formula 4. The variation of the elastic modulus with the mineral composition is analyzed, such as Figure 3 The variation of the elastic modulus and quartz content of the digital core model is shown. The variation of the elastic modulus of rock is affected by the combined effects of the types and contents of multiple mineral components. For example, sandstone is usually composed of mineral components such as feldspar, quartz and rock fragments. These minerals have different elastic properties and have different effects on the elastic properties of rocks. The bulk modulus of quartz and feldspar minerals is higher, while the bulk modulus of rock fragments is lower. The shear modulus of quartz is higher, followed by the shear modulus of feldspar, and the shear modulus of rock fragments is the smallest. Figure 3 It can be seen that with the increase of quartz content, both bulk modulus and shear modulus gradually increase, the change trend is approximately linear, and the increase of shear modulus is greater than that of bulk modulus. These changes reflect the influence of multi-component mineral type and content changes on rock elastic parameters. The wave velocity of the multi-mineral component digital core model is calculated using formula 5 and formula 6. Figure 4 The relationship between wave velocity and quartz content is shown. It can be seen from the figure that with the increase of quartz content, both the longitudinal wave velocity and the shear wave velocity gradually increase and change approximately linearly. This method constructs a three-dimensional digital core with multiple mineral components based on digital core technology, and explores the influence of multiple mineral components on elastic parameters through numerical simulation, providing theoretical data for geophysical interpretation of oil and gas reservoir exploration and development.

[0106] In this embodiment, the technology is widely used in geophysical exploration and development of oil and gas, and is of great significance in the fine interpretation of reservoir physical properties by geophysical logging. 1. In terms of the characterization of multi-mineral components in reservoirs, this method can establish a three-dimensional digital core model with controllable mineral types and contents based on digital core technology, so as to better characterize the multi-mineral component characteristics of actual rocks. 2. In terms of seismic interpretation of oil and gas reservoirs, this method can analyze the changing laws of multi-mineral components and elastic parameters, and provide data support for the accurate interpretation of reservoir physical properties. 3. Physical experiments consume a lot of manpower and material resources. This method is based on digital core technology and conducts rock physics numerical simulation research, which can obtain a wider range of rock physical parameter changes and provide technical support for the interpretation of complex oil and gas reservoirs.

[0107] Embodiment 2

[0108] The present invention also provides a multi-mineral component rock effective elastic parameter calculation system, comprising: a preset module, a construction module, a simulation module and a calculation module;

[0109] The preset module is used to predetermine the type and content of multiple mineral components;

[0110] The construction module is used to construct a digital core model of multi-mineral component parameter changes based on the types and contents of multi-mineral components using a process method;

[0111] The simulation module is used to perform numerical simulation on the digital core model with multi-mineral component parameter changes based on the elastic finite element method of the digital core;

[0112] The calculation module is used to calculate the effective elastic parameters of the digital core according to the simulation results.

[0113] In this embodiment, the building blocks include: a deposition process unit, a compaction process unit, and a diagenesis process unit;

[0114] The sedimentation process unit is used to simulate the most stable sedimentation of rock particles under the action of gravity, and the sedimentation model is established after all particles complete the sedimentation.

[0115] The compaction process unit is used to simulate the compaction of the overlying strata by the longitudinal downward movement of the sedimentary particles, control the downward movement distance of the particles according to the set compaction amount, and control the porosity and density of the digital core model based on the downward movement distance of the particles;

[0116] The diagenetic process unit is used to simulate the cementation diagenesis of particles by covering the surface of the particles with a certain thickness of cement. The thickness of the cementation on the particle surface is controlled according to the set cementation thickness. The cementation density of the digital core is controlled based on the thickness of the cementation on the particle surface, and then a digital core model with changes in multi-mineral component parameters is established.

[0117] In this embodiment, the simulation module includes: an application unit, a construction unit, a first calculation unit, a second calculation unit, and a third calculation unit;

[0118] The application unit is used to apply the strain of the digital core model with the variation of multi-mineral component parameters to the generated digital rock model;

[0119] The building block is used to establish the elastic energy equation for each voxel;

[0120] The first calculation unit is used for calculating and minimizing the gradient of the total energy relative to the node elastic displacement by using the fast conjugate gradient method based on the elastic energy equation;

[0121] The second calculation unit is used to calculate the average stress and strain in the system and the local stress and strain around the microstructural feature after obtaining the gradient of the displacement;

[0122] The third calculation unit is used to obtain the effective elastic modulus of the entire digital core model by averaging the calculated physical field.

[0123] In this embodiment, the process of calculating the effective elastic parameters of the digital core according to the simulation results includes:

[0124] For the isotropic case, the bulk modulus K and shear modulus µ are calculated as:

[0125] ,

[0126] ,

[0127] In the formula, σ xx , σ yy , σ zz , σ xy , σ xz , σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions;

[0128] Using the calculated bulk modulus K and shear modulus µ, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s The calculation formula is:

[0129] ,

[0130] ,

[0131] Where ρ represents the average density of the digital core, which is obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

[0132] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for calculating effective elastic parameters of multi-mineral rock, characterized in that: The following steps are involved: S1. Type and content of predetermined multi-mineral components; S2. Based on the types and contents of multi-mineral components, a digital core model of the parameter changes of multi-mineral components is constructed using the process method; S3. Based on the elastic finite element method, numerical simulation of the digital core model with changes in multi-mineral component parameters is performed; S4, calculating effective elastic parameters of the digital core according to the simulation results; Based on the types and contents of multi-mineral components, the method of constructing a digital core model of multi-mineral component parameter changes using a process method includes: Simulate the most stable deposition of rock particles under gravity, and establish a deposition model after all particles complete the deposition. The compaction of the overlying strata is simulated by the longitudinal downward movement of the sedimentary particles, and the downward movement distance of the particles is controlled according to the set compaction amount. The porosity and density of the digital core model are controlled based on the downward movement distance of the particles. By covering the particle surface with a certain thickness of cement, the cementation diagenesis of the particles is simulated, and the thickness of the cementation on the particle surface is controlled according to the set cementation thickness, and the cementation density of the digital core is controlled based on the thickness of the cementation on the particle surface; By controlling the type and content of particles and cement, a digital core model with varying parameters of multiple mineral components is established.

2. The method for calculating effective elastic parameters of multi-mineral rock according to claim 1, characterized in that: Based on the elastic finite element method, the method of numerically simulating the digital core model with the variation of multi-mineral component parameters includes: applying finite element strains to the generated digital rock model; Establish elastic energy equation for each voxel; Based on the elastic energy equation, the fast conjugate gradient method is used to calculate and minimize the gradient of the total energy relative to the node elastic displacement; After obtaining the gradient of the displacement, the average stress and strain in the system and the local stress and strain around the microstructural features are calculated; The effective elastic modulus of the entire digital core model is obtained by averaging the calculated physical fields.

3. The method for calculating effective elastic parameters of multi-mineral rock according to claim 1, characterized in that: Methods for calculating effective elastic parameters of digital cores based on simulation results include: For the isotropic case, the bulk modulus K and shear modulus µ are calculated as: ， ， In the formula, σ xx , σ yy , σ zz , σ xy , σ xz , σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions; Using the calculated bulk modulus K and shear modulus µ, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s The calculation formula is: ， ， Where ρ represents the average density of the digital core, which is obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

4. A multi-mineral rock effective elastic parameter calculation system, characterized in that: include: Preset modules, construction modules, simulation modules and calculation modules; The preset module is used to preset the types and contents of multiple mineral components; The construction module is used to construct a digital core model of multi-mineral component parameter changes based on the types and contents of the multi-mineral components using a process method; The simulation module is used to perform numerical simulation on a digital core model of multi-mineral component parameter changes based on an elastic finite element method; The calculation module is used to calculate the effective elastic parameters of the digital core according to the simulation results.

5. The multi-mineral component rock effective elastic parameter calculation system according to claim 4, characterized in that: The building blocks include: a deposition process unit, a compaction process unit and a diagenesis process unit; The sedimentation process unit is used to simulate the most stable sedimentation of rock sedimentary particles under the action of gravity, and a sedimentation model is established after all particles complete the sedimentation; The compaction process unit is used to simulate the compaction of the overlying strata by the longitudinal downward movement of the sedimentary particles, control the downward movement distance of the particles according to the set compaction amount, and control the porosity and density of the digital core model based on the downward movement distance of the particles; The diagenetic process unit is used to simulate the cementation diagenesis of particles by covering the surface of particles with a certain thickness of cement, control the thickness of the cementation on the surface of particles according to the set cementation thickness, and control the cementation density of the digital core based on the thickness of the cementation on the surface of particles; By controlling the type and content of particles and cement, a digital core model with varying parameters of multiple mineral components is established.

6. The multi-mineral component rock effective elastic parameter calculation system according to claim 4, characterized in that: The simulation module includes: an application unit, a construction unit, a first calculation unit, a second calculation unit and a third calculation unit; The application unit is used to apply the finite element strain to the generated digital rock model; The construction unit is used to establish an elastic energy equation for each voxel; The first calculation unit is used to calculate and minimize the gradient of the total energy relative to the node elastic displacement using the fast conjugate gradient method based on the elastic energy equation; The second calculation unit is used to calculate the average stress and strain in the system and the local stress and strain around the microstructural feature after obtaining the gradient of the displacement; The third calculation unit is used to obtain the effective elastic modulus of the entire digital core model by averaging the calculated physical field.

7. The multi-mineral component rock effective elastic parameter calculation system according to claim 4, characterized in that: The process of calculating the effective elastic parameters of the digital core based on the simulation results includes: For the isotropic case, the bulk modulus K and shear modulus µ are calculated as: ， ， In the formula, σ xx , σ yy , σ zz , σ xy , σ xz , σ yz Represents stress in 6 directions; ε xx , ε yy , ε zz , ε xy , ε xz , ε yz Represents strain in 6 directions; Using the calculated bulk modulus K and shear modulus µ, the longitudinal wave velocity V of the 3D digital core p and shear wave velocity V s The calculation formula is: ， ， Where ρ represents the average density of the digital core, which is obtained by calculating the density of each mineral component and multiplying it by the corresponding volume fraction.

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