Fracture-vug type reservoir ground stress prediction method and system based on discrete element and finite element

Abstract

The invention belongs to the technical field of oil and gas field exploration and development, and discloses a fractured-vuggy reservoir ground stress prediction method and system based on discrete elements and finite elements. And taking the obtained boundary stress direction and size as boundary conditions, and combining with a pre-constructed fusion model to obtain the three-dimensional stress of the research area, thereby completing the fracture-vuggy reservoir crustal stress prediction process. The construction process of the fusion model comprises the steps that firstly, a discrete fracture network model and a geomechanical grid model are established, then the discrete fracture network model and the geomechanical grid model are fused, after fusion, three-dimensional heterogeneous parameters are given to the fusion model, and the construction process of the fusion model is completed. The method can accurately and efficiently simulate the three-dimensional distribution rule of the current stress field of the fracture-vug type reservoir, and is of great significance to oil-gas exploration and development.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field exploration and development technology, and relates to a method and system for predicting geostress in fractured-vuggy reservoirs based on discrete element and finite element methods. Background Technology

[0002] In-situ stress is a crucial concept in geology, referring to the forces exerted between different parts of the subsurface rock medium through contact. This force is primarily composed of a combination of factors, including gravitational stress, tectonic stress, thermal stress, and pore pressure. Measuring and studying in-situ stress not only helps in understanding the stress state within the Earth's crust but also provides important data for the prediction and prevention of geological hazards.

[0003] Based on the principles of geostress measurement, methods can be broadly categorized into two types: direct measurement and indirect measurement. Direct measurement primarily focuses on rock fracturing, directly measuring various stresses using instruments. The stress value is then calculated from the relationship between these stresses and the original rock stress. Examples include hydraulic fracturing, stress recovery, and acoustic emission methods. Indirect measurement methods primarily rely on rock deformation and property changes for inverse measurement. By using sensors or media to measure and record changes in physical quantities, the original rock stress value is indirectly obtained through formulas. Examples include stress relief methods and differential strain analysis. Furthermore, discrete element or finite element methods are currently widely used for numerical simulation of tectonic stress fields. These simulations can predict two-dimensional and three-dimensional stress distributions. Under the premise of clearly defining the tectonic stress period, direction, magnitude, and duration, quantitative studies of tectonic stress fields are conducted using geological analysis, experimental testing, and computer numerical simulation. However, the finite element method (FEM) is mainly for continuous media, while the discrete element method (DEM) is mainly for discrete media. The FEM is primarily for reservoirs with relatively underdeveloped fractures or faults, while the DEM is primarily for fractured reservoirs. However, for carbonate rocks, the high complexity, strong heterogeneity, complex fracture system development, and irregular spatial distribution of fractures and cavities make parameter calibration difficult for the DEM stress field simulation method. Furthermore, in the FEM stress field simulation, the influence of large faults on stress is mainly considered. However, when small-scale discrete fractures are densely developed, the fractures will affect the rock mechanical parameters and the distribution of geostress, thus affecting the accuracy of the stress field simulation. These errors will affect well trajectory design, fracturing, and wellbore stability to varying degrees. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method and system for predicting geostress in fractured-vuggy reservoirs based on discrete element and finite element methods. This solves the technical problems of poor geostress measurement accuracy and difficult parameter calibration in the numerical simulation process of stress field in the prior art when facing reservoir conditions with high reservoir complexity, strong heterogeneity, complex fracture system development, and irregular spatial distribution of fractures and cavities.

[0005] This invention is achieved through the following technical solution: A method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods includes the following steps: Obtain the direction and magnitude of the boundary stress in the study area; The obtained boundary stress direction and magnitude are used as boundary conditions, and combined with the pre-built fusion model, the three-dimensional stress of the study area is obtained to complete the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

[0006] Preferably, the construction process of the discrete crack network model is as follows: Select logging curves that affect fracture response characteristics, normalize the logging curves, calculate the mean of the normalized data, and determine the fracture development intensity of a single well. Using the single-well fracture development intensity as a constraint, the three-dimensional fracture intensity development characteristics are controlled by the variation function, the magnitude and direction of the primary and secondary ranges are determined, and a three-dimensional fracture development intensity model is established. A discrete crack network model is established using the three-dimensional morphological parameters of the cracks and the three-dimensional crack development intensity model.

[0007] Preferably, the three-dimensional morphological parameters of the crack include crack length, crack width, crack inclination angle, and filling degree.

[0008] Preferably, the construction process of the geomechanical grid model is as follows: Based on the structural characteristics of the study area, the grid size was selected and a geological grid model was established; the porosity attributes obtained by combining well and seismic data were re-acquired into the geological grid to establish a porosity grid model. One-dimensional rock mechanical parameters are calculated using well logging data. Based on these one-dimensional rock mechanical parameters, and using the porosity model as a constraint, a three-dimensional heterogeneous rock mechanical parameter model and a density model are established. The three-dimensional heterogeneous rock mechanical parameter model and density model are then combined with the geological grid model to construct the geomechanical grid model.

[0009] Preferably, the logging data includes P-wave, S-wave, and density; the one-dimensional rock mechanical parameters include Young's modulus and Poisson's ratio.

[0010] Preferably, the discrete fracture network model is fused with the geomechanical grid model, specifically by mapping the fracture attributes in the discrete fracture network model to the corresponding grids in the geomechanical grid model; and integrating the mapped fracture attributes with the porosity, permeability, and rock mechanics parameters in the geomechanical grid model to complete the fusion process.

[0011] A system for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods includes: The data acquisition unit is used to acquire the direction and magnitude of the boundary stress in the study area; The data processing unit is used to take the acquired boundary stress direction and magnitude as boundary conditions, and combine them with a pre-built fusion model to obtain the three-dimensional stress of the study area, thereby completing the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

[0012] A computer device includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described above.

[0013] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described method.

[0014] A computer program product includes a computer program / instructions that, when executed by a processor, implement the steps of the above-described method.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for predicting geostress in fractured-vuggy reservoirs based on discrete element method (DEM) and finite element method (FEM). The method first requires accurately obtaining the direction and magnitude of the boundary stress in the study area, which is the foundation for subsequent numerical simulation of the stress field. Then, the obtained boundary stress direction and magnitude are used as boundary conditions, combined with a fusion model for numerical simulation of the stress field. Through calculation and analysis, the three-dimensional distribution law of the current stress field in the fractured-vuggy reservoir can be obtained. The pre-constructed fusion model integrates a discrete fracture network model and the aforementioned geomechanical grid model. The discrete fracture network model embodies the concept of the discrete element method, which is mainly used to handle discrete media, such as fractures and faults. This model captures the discreteness and irregularity of fractures in the reservoir. The geomechanical grid model is based on the finite element method, which is mainly used to handle continuous media. It analyzes the stress, strain, and deformation of materials by dividing the grid and solving partial differential equations. Integrating the discrete fracture network model into the geomechanical grid model achieves the fusion of the discrete element and finite element models. The fused model includes both the discreteness of fractures and retains the characteristics of the continuous reservoir medium. This method eliminates the difficulty of discrete element parameter calibration, making simulation results more accurate and reliable. Furthermore, by introducing a discrete fracture network system, it can more precisely describe the distribution and characteristics of fractures in the reservoir, thereby improving the precision and accuracy of finite element simulation and solving the problem of finite element accuracy fluctuation. This method can accurately and efficiently simulate the three-dimensional distribution of the current stress field in fractured-vuggy reservoirs, which is of great significance for oil and gas exploration and development. It can help engineers better understand the stress state of reservoirs and provide a scientific basis for drilling, fracturing, and other operations. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a method for predicting geostress in fractured-vuggy reservoirs based on discrete element and finite element methods in Embodiment 1 of the present invention. Figure 2 This is a flowchart of a method for predicting geostress in fractured-vuggy reservoirs based on discrete element and finite element methods in Embodiment 2 of the present invention. Figure 3 This is a schematic diagram of the fracture development intensity in a single well at full depth XX in Embodiment 3 of the present invention; Figure 4 This is a schematic diagram of a three-dimensional fracture development intensity model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of a discrete fracture network model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 6 This is a schematic diagram of the porosity model of a deep oilfield in Embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the Young's modulus model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 8 This is a schematic diagram of the Poisson's ratio model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 9 This is a rose diagram of the induced fracture orientation identified by imaging logging in a deep oilfield in Embodiment 3 of the present invention; Figure 10 This is a schematic diagram of stress analysis of a single well in a deep oilfield in Embodiment 3 of the present invention; Figure 11 This is a schematic diagram of the minimum principal stress model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 12 This is a schematic diagram of the maximum horizontal principal stress model in a deep oilfield area according to Embodiment 3 of the present invention; Figure 13 This is a schematic diagram of the structure of a fractured-vuggy reservoir stress prediction system based on discrete element and finite element methods in one embodiment of the present invention. Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0020] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0022] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 like Figure 1 As shown, this invention discloses a method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods, comprising the following steps: S1: Obtain the direction and magnitude of the boundary stress in the study area; S2: The obtained boundary stress direction and magnitude are used as boundary conditions, and the three-dimensional stress of the study area is obtained by combining the pre-built fusion model to complete the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

[0024] The construction process of the discrete crack network model is as follows: Select logging curves that affect fracture response characteristics, normalize the logging curves, calculate the mean of the normalized data, and determine the fracture development intensity of a single well. Using the single-well fracture development intensity as a constraint, the three-dimensional fracture intensity development characteristics are controlled by the variation function, the magnitude and direction of the primary and secondary ranges are determined, and a three-dimensional fracture development intensity model is established. A discrete crack network model is established using the three-dimensional morphological parameters of the cracks and the three-dimensional crack development intensity model. The three-dimensional morphological parameters of the cracks include crack length, crack width, crack dip angle, and degree of filling.

[0025] The process of constructing the geomechanical grid model is as follows: The grid size was selected based on the structural characteristics of the study area, and a geological grid model was established; the porosity attributes obtained by combining well and seismic data were re-acquired into the geological grid, and a porosity grid model was established. One-dimensional rock mechanical parameters are calculated using well logging data. Based on these parameters, and using the porosity model as a constraint, a three-dimensional heterogeneous rock mechanical parameter model and a density model are established. These models are then combined with the geological grid model to construct the geomechanical grid model. The well logging data includes P-wave, S-wave, and density data; the one-dimensional rock mechanical parameters include Young's modulus and Poisson's ratio.

[0026] The fusion of the discrete fracture network model and the geomechanical grid model involves: mapping the fracture attributes in the discrete fracture network model to the corresponding grids in the geomechanical grid model; and integrating the mapped fracture attributes with the porosity, permeability, and rock mechanics parameters in the geomechanical grid model to complete the fusion process.

[0027] Example 2 Currently, stress field simulation is mainly achieved through discrete element method (DEM) or finite element method (FEM). The FEM method is mainly for continuous media, while the DEM method is mainly for discrete media. The former is mainly for reservoirs with relatively underdeveloped fractures or faults, while the latter is mainly for fractured reservoirs. For carbonate rocks, reservoirs are characterized by strong heterogeneity and irregular spatial distribution of fractures and cavities. There is a lack of research on geostress modeling methods in geological backgrounds with complex reservoirs and complex fracture systems. In the process of finite element stress field simulation, the influence of large faults on stress is mainly considered. However, when small-scale discrete fractures are densely developed, the fractures will affect the rock mechanical parameters and the distribution law of geostress, thus affecting the accuracy of stress field simulation. These errors will affect well trajectory optimization design, fracturing stimulation, and wellbore stability to varying degrees.

[0028] To address the above two issues, this invention incorporates a discrete fracture network system into the numerical simulation of the stress field, ultimately achieving a fusion of discrete element modeling and finite element modeling methods. This eliminates the difficulties in discrete element parameter calibration and the inconsistencies in finite element accuracy, accurately and efficiently simulating the current three-dimensional distribution of the stress field in fractured-vuggy reservoirs. The specific solution of this invention is as follows: Step 1: Determine the fracture development intensity of a single well.

[0029] Step 2: Establish a three-dimensional crack development intensity model for the study area.

[0030] Step 3: Establish a discrete crack network model.

[0031] Step 4: Establish porosity properties and geomechanical grid model.

[0032] Step 5: Establish mechanical parameters and density model for heterogeneous rocks.

[0033] Step 6: Predict the three-dimensional geostress in the study area.

[0034] In step 1, well logging curves that show obvious fracture response characteristics are selected, and normalized to eliminate the influence of different units. The average value of the normalized data is used to characterize the fracture development intensity of a single well.

[0035] In step 2, the development intensity of fractures in a single well is used as a constraint, and the three-dimensional fracture intensity development characteristics are controlled by a variation function. The magnitude and direction of the primary and secondary ranges are determined, and a three-dimensional fracture development intensity model is established.

[0036] In step 3, the characteristics of fracture development are clarified by using field and core observation results, including fracture length, fracture width, fracture dip angle and filling degree. Based on these, the three-dimensional morphological parameters of the fracture are accurately assigned. Combined with the three-dimensional fracture development intensity model, a discrete fracture network model is established.

[0037] In step 4, based on the structural characteristics of the study area, an appropriate grid size is selected to establish a geological grid model. The porosity attributes derived from well-seismic analysis are then re-acquired into the geological grid to establish a porosity grid model. Based on the three-dimensional geological grid model, it is then transformed into a geomechanical grid model with consistent dimensions.

[0038] In step 5, one-dimensional rock mechanical parameters are calculated using P-wave, S-wave, and density logging data, mainly including Young's modulus and Poisson's ratio. Based on the one-dimensional rock mechanical parameters and density, a three-dimensional heterogeneous rock mechanical parameter model and density model are established using a porosity model as constraints.

[0039] In step 6, the discrete fracture network model is integrated into the geomechanical grid model to establish a geomechanical grid model under the discrete fracture network. Based on this integrated model, three-dimensional heterogeneous parameters are assigned to the model, including three-dimensional heterogeneous Young's modulus, three-dimensional heterogeneous Poisson's ratio and three-dimensional heterogeneous density. The direction of boundary stress is determined by imaging logging data, and the stress of a single well is used as the boundary condition. Finally, the three-dimensional stress is calculated.

[0040] This invention integrates discrete element modeling and finite element modeling methods by incorporating a discrete fracture network system into the numerical simulation of the stress field. This eliminates the difficulties in calibrating discrete element parameters and the inconsistencies in finite element accuracy, enabling accurate and efficient simulation of the current three-dimensional distribution of stress field in fractured-vuggy reservoirs.

[0041] Example 3 To further explain the technical solution of this invention, the following embodiments are provided: This invention uses the Yijianfang Formation and Yingshan Formation reservoirs in a certain oilfield as an example to illustrate the specific implementation process of the invention. This area is a superimposed basin composed of a surrounding Cenozoic foreland basin and a Paleo-Mesozoic craton basin, exhibiting a broad and gentle intracraton uplift tectonic pattern. A thick Sinian-Quaternary sedimentary rock series develops on the pre-Sinian metamorphic basement, among which Cambrian-Ordovician marine carbonate rocks are developed, which are the main target layers for oil and gas exploration and development in the basin area. The main tectonic units include the Kuqa Depression, the North Tarim Uplift, the Northern Depression (Awati Depression, Aman Transition Zone, and Manjiaer Depression), the Central Uplift (Bachu Uplift, Central Tarim Uplift, and East Tarim Low Uplift), and the Southwest Tarim Depression. The oilfield is situated between the Tarim North Uplift and the Tarim Central Uplift, bordered by the Manjiaer Depression to the east and the Awati Depression to the west, exhibiting a saddle-shaped distribution. Its Ordovician formations, specifically the Yijianfang and Yingshan Formations, possess the lithological basis for developing high-quality reservoirs and are the primary target formations for exploration and development. The reservoir type is predominantly porosiform. The oilfield features a highly developed NNE and NNE-trending fault system, located at the intersection of different fault zones. Influenced by the regional tectonic location and stress field, the fault types are diverse and complex, exhibiting characteristics of east-west zoning, north-south segmentation, vertical stratification, and phased activity.

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The illustrative examples and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0043] Step 1: Determine the fracture development intensity of a single well.

[0044] Step 2: Establish a three-dimensional crack development intensity model for the study area.

[0045] Step 3: Establish a discrete crack network model.

[0046] Step 4: Establish porosity properties and geomechanical grid model.

[0047] Step 5: Establish mechanical parameters and density model for heterogeneous rocks.

[0048] Step 6: Predict the three-dimensional geostress in the study area.

[0049] Step 1: Determine the fracture development intensity of a single well. Select well logging curves that can reflect fracture development in the study area, such as caliper logging (CAL) and sonic transit time (DT) curves. Normalize these curves to eliminate the influence of different units, ensuring that high values ​​after normalization represent areas of fracture development and low values ​​represent areas of underdeveloped fractures. Calculate the average value of the normalized well logging curves; the magnitude of this value represents the intensity of fracture development (e.g., ...). Figure 3 (As shown).

[0050] Step 2: Establish a three-dimensional fracture development intensity model for the study area. Using the fracture development intensity of a single well as a constraint, a variogram is used to control its distribution. Since the wells in the study area are far apart, larger principal and secondary ranges are needed. The principal range of this variogram is 10026m, the secondary range is 8437m, the vertical range is 15.8m, and the direction is 50.2°. After determining the specific values ​​of each term in the variogram, Gaussian sequential simulation is used to assign values ​​to the three-dimensional fracture development intensity, thereby clarifying the three-dimensional fracture development intensity (e.g., Figure 4 (As shown).

[0051] Step 3: Establish a discrete fracture network model. Perform structural interpretation of the faults in the target segment of the study area. The structurally interpreted faults are large-scale fractures. The main faults interpreted in this study are F... Ⅰ 17. Faults along the fault zone and surrounding areas were used to construct a fault model for the target layer. Using the three-dimensional fracture development intensity as a constraint, and combining fracture development characteristics observed in the field and in core samples, parameters such as fracture shape, size, dip angle, and aperture were determined and used as input data. This data, combined with the three-dimensional fracture development intensity model, led to the construction of a small-scale fracture model. Finally, the large-scale fault model and the small-scale fracture model were coupled to form a discrete fracture network model (e.g., Figure 5 (As shown).

[0052] Step 4: Establish porosity attributes and a geomechanical grid model. A suitable area is selected on the plane as the boundary of the geological model, with the top and bottom of the target layer as the interface to determine the top and bottom of the geological model. The target layers in the study area are the Yijianfang Formation and Yingshan Formation of the Ordovician System; therefore, the top of the Yijianfang Formation and the bottom of the Yingshan Formation are selected as the top and bottom structural layers. The geological model is subdivided into appropriate sizes on the plane and vertically. Based on the actual situation, the grid size is 50m × 50m × 10m. The porosity attribute volume (such as...) obtained by combining well and seismic analysis is then used... Figure 6 (As shown) The data was re-acquired onto the geological grid model according to the geological grid size. Based on the geological model, the boundary range and depth range of the model were appropriately widened to avoid stress concentration, and it was then converted into a geomechanical grid model.

[0053] Step 5: Establish mechanical parameters and density model for heterogeneous rocks.

[0054] Dynamic rock mechanics parameters were calculated using density, P-wave, and S-wave logging data. Using the rock mechanics parameters and density of a single well as hard data, and employing a porosity grid model acquired from a geological grid model as a constraint, a three-dimensional heterogeneous density grid model and a three-dimensional heterogeneous rock mechanics parameter grid model were established under the constraint of the porosity model using sequential Gaussian simulation.

[0055] The calculation of dynamic rock mechanics parameters using well logging data refers to: (1) (2) In formulas (1)~(2), μ d Let be the dynamic Poisson's ratio of the rock, which is dimensionless; E d Let be the dynamic Young's modulus of the rock, in GPa; ρ b Rock density interpreted for well logging, g / cm³ 3 ;Δ t p P-wave transit time of the rock, μs / ft; Δ t s denoted as shear wave transit time of the rock, μs / ft, and β as the conversion factor, 9.290304 × 10⁻⁶. 7 .

[0056] Step 6: Predict the three-dimensional geostress in the study area. The discrete fracture network model is integrated into the geomechanical mesh model to establish a geomechanical mesh model under the discrete fracture network. Based on this integrated model, three-dimensional heterogeneous parameters are assigned to the model, including the three-dimensional heterogeneous Young's modulus (e.g., ...). Figure 7 As shown), three-dimensional heterogeneous Poisson's ratio (e.g.) Figure 8 (as shown) and three-dimensional heterogeneous density. Utilizing induced seams (such as...) Figure 9 (as shown in A) or well wall collapse (such as...) Figure 9 Information such as (as shown in B) can determine the current direction of geostress. Imaging logging data in the study area shows that the induced fracture direction is 20° northeast (e.g., as shown in B). Figure 9 As shown in C), the direction of the current maximum horizontal principal stress is 20° northeast. Using parameters such as Young's modulus, Poisson's ratio, and density, the magnitude of the one-dimensional current geostress is calculated. Based on the calculation results, the boundary stress conditions are determined. The applied boundary horizontal maximum principal stress is 168 MPa, and the applied horizontal minimum principal stress is 139 MPa (as shown in C). Figure 10 As shown). Based on the integrated discrete crack network model, the model is given three-dimensional heterogeneous parameters, and after applying actual boundary conditions, the three-dimensional stress in the study area is simulated (e.g., Figures 11-12 (As shown).

[0057] The formula for calculating the current geostress using single-well information is as follows: (3) (4) In formulas (3) to (4), S Hmax For the maximum horizontal principal stress, S hmin For the minimum principal stress in the horizontal direction, μ For the static Poisson's ratio, σ v Where α is the pressure of the overlying strata, α is the Biot elastic coefficient, and P is the overlying strata pressure. p Let E be the pore pressure, E be the static Young's modulus, and ε be the pore pressure. x and ε y These represent the strains in the directions of the minimum and maximum horizontal principal stresses, respectively.

[0058] Example 4 In addition, this invention also discloses a geostress prediction system for fractured-vuggy reservoirs based on discrete element and finite element methods, comprising: The data acquisition unit is used to acquire the direction and magnitude of the boundary stress in the study area; The data processing unit is used to take the acquired boundary stress direction and magnitude as boundary conditions, and combine them with a pre-built fusion model to obtain the three-dimensional stress of the study area, thereby completing the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

[0059] Additionally, a schematic diagram of a terminal device according to an embodiment of the present invention is provided. This terminal device includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0060] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0061] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0062] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0063] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0064] If the modules / units integrated into the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods, characterized in that, Includes the following steps: Obtain the direction and magnitude of the boundary stress in the study area; The obtained boundary stress direction and magnitude are used as boundary conditions, and combined with the pre-built fusion model, the three-dimensional stress of the study area is obtained to complete the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

2. The method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods according to claim 1, characterized in that, The construction process of the discrete crack network model is as follows: Select logging curves that affect fracture response characteristics, normalize the logging curves, calculate the mean of the normalized data, and determine the fracture development intensity of a single well. Using the single-well fracture development intensity as a constraint, the three-dimensional fracture intensity development characteristics are controlled by the variation function, the magnitude and direction of the primary and secondary ranges are determined, and a three-dimensional fracture development intensity model is established. A discrete crack network model is established using the three-dimensional morphological parameters of the cracks and the three-dimensional crack development intensity model.

3. The method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods according to claim 2, characterized in that, The three-dimensional morphological parameters of the crack include crack length, crack width, crack inclination angle, and degree of filling.

4. The method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods according to claim 1, characterized in that, The process of constructing the geomechanical grid model is as follows: The grid size was selected based on the structural characteristics of the study area, and a geological grid model was established; the porosity attributes obtained by combining well and seismic data were re-acquired into the geological grid, and a porosity grid model was established. One-dimensional rock mechanical parameters are calculated using well logging data. Based on these one-dimensional rock mechanical parameters, and using the porosity model as a constraint, a three-dimensional heterogeneous rock mechanical parameter model and a density model are established. The three-dimensional heterogeneous rock mechanical parameter model and density model are then combined with the geological grid model to construct the geomechanical grid model.

5. The method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods according to claim 4, characterized in that, The logging data includes P-wave, S-wave, and density; the one-dimensional rock mechanics parameters include Young's modulus and Poisson's ratio.

6. The method for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods according to claim 1, characterized in that, The fusion of the discrete fracture network model and the geomechanical grid model involves: mapping the fracture attributes in the discrete fracture network model to the corresponding grids in the geomechanical grid model; and integrating the mapped fracture attributes with the porosity, permeability, and rock mechanics parameters in the geomechanical grid model to complete the fusion process.

7. A system for predicting in-situ stress in fractured-vuggy reservoirs based on discrete element and finite element methods, characterized in that, include: The data acquisition unit is used to acquire the direction and magnitude of the boundary stress in the study area; The data processing unit is used to take the acquired boundary stress direction and magnitude as boundary conditions, and combine them with a pre-built fusion model to obtain the three-dimensional stress of the study area, thereby completing the geostress prediction process of the fractured-vuggy reservoir. The construction process of the fusion model is as follows: First, a discrete fracture network model and a geomechanical grid model are established. Then, the discrete fracture network model and the geomechanical grid model are fused. After fusion, three-dimensional heterogeneous parameters are assigned to the fusion model to complete the construction process of the fusion model.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method as described in any one of claims 1 to 6.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method as described in any one of claims 1 to 6.

Images