A numerical simulation method for diagenesis with multi-field coupling

Abstract

A diagenetic numerical simulation method for multi-field coupling belongs to the technical field of reservoir geology. It involves the classification of diagenetic facies types, the diagenetic characteristics of diagenetic facies, framework minerals, authigenic mineral assemblages and diagenetic differences, a preliminary analysis of the diagenetic mechanism, the chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena, and typical diagenetic phenomena. The present invention collects analytical test data and geological data, conducts the classification of diagenetic facies types of sandstone reservoirs in the target horizon of the target area, the diagenetic characteristics of diagenetic facies, framework minerals, authigenic mineral assemblages and diagenetic differences, a preliminary analysis of the diagenetic mechanism, the chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena, and then conducts a chemical kinetic analysis of typical diagenetic phenomena from the perspective of numerical simulation, establishes a physical model and a numerical simulation model, and reveals and improves the diagenetic mechanism of typical diagenetic facies.

Description

Technical Field

[0001] The present invention relates to a numerical simulation method for diagenesis with multi-field coupling, belonging to the technical fields of computers and reservoir geology. Background Art

[0002] Multi-physical field coupling essentially means that variables are mutually called. In theory, if mutual calls can be achieved, multi-physical field coupling can be realized. Flow-thermal coupling can achieve the coupling of the flow field and the temperature field; the flow field often affects the temperature field through the flow velocity μ, so the coupling is achieved by calling the flow velocity variable in the heat transfer field; considering the influence of temperature on the flow field, the density and viscosity of the fluid are written as functions of temperature. The coupling of flow and mass transfer can be divided into the coupling in free space and the coupling in porous structures, but their coupling mechanisms are the same; mass transfer is mainly the transport of substances, including the transfer of dilute substances, the transfer of concentrated substances, the transfer of dilute substances in porous media, and reaction flows (the coupling of flow and mass transport); the equation for the transfer of dilute substances can be based on the premise of mass conservation. For transient problems, there are time terms, convection terms, reaction source terms, and diffusion terms of Fick's diffusion law; if a chemical reaction occurs in the solution system, a chemical reaction source term can be added; for the transfer of dilute substances in porous media, two additional terms can be added, including adsorption / desorption and dispersion; the transfer of dilute substances in porous media is also realized based on a homogeneous model; when the substance concentration in the solution changes, the change and distribution of the substance concentration can be written as related to the density; that is to say, the solution density may be affected by the substance composition distribution, meaning that the substance concentration distribution and change affect the fluid density and viscosity, thereby affecting the fluid properties.

[0003] Precisely track the position changes of the phase interface using the level set method, phase field method, or moving mesh method; the purposes of the level set, phase field, and moving mesh are the same, which is to track the changes of the phase interface; the level set and phase field methods can simulate topological changes while the moving mesh cannot; the moving mesh moves the mesh nodes, and the moving mesh can simulate the phase interface but cannot handle the process of topological changes of the phase interface. The level set and phase field methods are to solve the problem of phase interface changes; compared with the phase field, the level set method has higher accuracy in characterizing surface tension; however, the phase field method has higher numerical stability and better convergence. The level set method is a pure mathematical method, which is summarized to track the phase interface; its equation is a convection-diffusion equation, including a convection term and a diffusion term. The value range of the level set function is from 0 to 1, and the interface is 0.5. Generally, for the control of fluid properties, less than 0.5 is phase state 1, and greater than 0.5 is phase state 2. The phase field method has practical physical significance and can be extended to multiphase flows; from the perspective of the equation, it is a fourth-order PDE. To be able to solve it, an intermediate variable needs to be introduced, called the phase field auxiliary variable, which is also called the free energy function. By this definition, the fourth-order equation is discretized into two second-order PDEs and then solved; in the phase field function, the value range of the phase field variable is from -1 to 1, the interface is 0, and there are also the mixed energy density, capillary width, mobility (mobility adjustment parameter), and interface thickness control parameter.

[0004] Multiphysics simulation can be applied in thermo-hydro-mechanical-chemical (THMC) coupling analysis, digital core analysis, geological-scale geometric modeling, and multiscale flow simulation. Multiphysics simulation has been widely applied in oil and gas exploitation, such as shale gas seepage field simulation, simulation of the control range of a single fracture in a horizontal well considering fracture sanding parameters, multiphysics coupling of shale gas desorption, seepage mechanism and numerical simulation, quantitative analysis of effective fractures in tight reservoir fracturing development, numerical simulation of coalbed methane-tight gas co-production, numerical calculation of the response of horizontal well array induction logging, stress field simulation during the production process of fractured wells, simulation of wellbore interference during the production process of multi-branch horizontal wells, and development of a seepage model for multi-branch horizontal wells.

[0005] When the development of technology brings it onto the track of multiphysics research, the traditional research methods based on observation and experiment, which are built on the thinking basis of simple and single-physics field analysis, can no longer cope with the complex interactions of multiphysics fields. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a multi-field coupling diagenetic numerical simulation method.

[0007] A diagenetic numerical simulation method for multi-field coupling, comprising the following steps: collecting data, providing the division of diagenetic facies types, diagenetic characteristics of diagenetic facies, framework minerals, authigenic mineral assemblages and diagenetic differences, preliminary analysis of diagenetic mechanisms, chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena, chemical kinetic analysis of typical diagenetic phenomena, physical models, numerical simulation models, revealing and improving the diagenetic mechanism, and jointly revealing and improving the diagenetic mechanism based on the experimental analysis results and numerical simulation results.

[0008] The advantages of the present invention are as follows: Scholars have found that it is difficult to give a convincing theoretical explanation for the experimental analysis results, and the actual scientific research problems faced are mostly the results of the interaction and co-action of multiple physical fields. Therefore, it is necessary to explore a diagenetic numerical simulation method that comprehensively considers the experimental analysis results, the microscopic scale distribution of typical diagenetic phenomena, and the physical models and numerical simulation models of the wider distribution in the sandstone of the target horizon. A diagenetic numerical simulation method for multi-field coupling includes reaction engineering, dilute mass transfer, free and porous medium flow, and level set modules; briefly elaborates the numerical simulation process of the diagenetic mechanism analysis of multi-field coupling, and reveals or improves the diagenetic mechanism of typical diagenetic facies or typical diagenetic phenomena.

[0009] The present invention has the characteristics of being operable, having good evaluation effects, and solving practical problems, and has the following innovations: 1) carrying out the division of diagenetic facies types; 2) investigating the diagenetic characteristics of diagenetic facies; 3) conducting a preliminary analysis of the diagenetic mechanism using experimental analysis results; 4) establishing chemical reaction equations and their corresponding kinetic conditions for typical diagenetic phenomena; 5) carrying out chemical kinetic analysis of typical diagenetic phenomena; 6) establishing physical models and numerical simulation models for multi-field coupling; 7) revealing and improving the diagenetic mechanism through numerical simulation results. This method patent meets the solution requirements of the diagenetic mechanism that reflects the essence of typical diagenetic facies or typical diagenetic phenomena, provides a solution for revealing and improving the diagenetic mechanism analysis, and has guiding significance.

[0010] Based on the collected analytical test data and geological data, the present invention conducts the classification of diagenetic facies types of sandstone reservoirs in the target horizon, the diagenetic characteristics of diagenetic facies, framework minerals, authigenic mineral assemblages and differences in diagenetic processes, a preliminary analysis of the diagenetic mechanism, the chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena. Then, from the perspective of numerical simulation, it conducts chemical kinetic analysis of typical diagenetic phenomena, establishes physical models and numerical simulation models, reveals and improves the diagenetic mechanism of typical diagenetic facies, and forms a multi-field coupling diagenetic numerical simulation method. The present invention takes into account the classification of diagenetic facies types, the diagenetic characteristics of diagenetic facies, framework minerals, authigenic diagenetic mineral assemblages and differences in diagenetic processes, and conducts a preliminary analysis of the diagenetic mechanism; based on the data of cast thin sections, scanning electron microscopy and cathodoluminescence thin section images, extracts the diagenetic phenomena of typical diagenetic facies, establishes the chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena, and conducts chemical kinetic analysis of typical diagenetic phenomena; combines the microscopic scale distribution of typical diagenetic phenomena and their distribution in a larger range within the sandstone of the target horizon, establishes a physical model of multiple physical fields, and depicts the input parameters of the numerical simulation model, meeting the research needs of the diagenetic mechanism that reflects the essential problems of typical diagenetic phenomena, revealing and improving the diagenetic mechanism of diagenetic facies, and providing a theoretical basis for the distribution of the diagenetic mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] When considered in conjunction with the accompanying drawings, through reference to the following detailed description, the present invention can be more fully and better understood, and many attendant advantages can be easily known. However, the drawings described herein are used to provide a further understanding of the present invention, form a part of the present invention, and the schematic embodiments and descriptions thereof are used to explain the present invention, and do not constitute an improper limitation of the present invention. As shown in the figures:

[0012] Figure 1 is the evaluation technical flow chart of the present invention.

[0013] Figure 2 is the schematic diagram of the model of calcite formation and distribution of the present invention.

[0014] Figure 3 is the two-dimensional model of calcite formation and distribution of the present invention.

[0015] Figure 4 is the calcite formation and distribution constrained by the laminar flow model of the present invention.

[0016] Figure 5 is the calcite formation and distribution constrained by the free and porous medium flow model of the present invention.

[0017] Figure 6 is the calcite formation and distribution constrained by the Darcy's law model of the present invention.

[0018] Figure 7 The simulation results of the concentration of calcium chloride - 2.34 mol / m 3 sodium carbonate solution injected into the 4-hour calculation domain of the present invention. 3

[0019] Figure 8 The simulation results of the concentration of calcium chloride - 2.34 mol / m 3 sodium carbonate solution injected into the 12-hour calculation domain of the present invention. 3

[0020] Figure 9 The simulation results of the concentration of calcium chloride - 2.34 mol / m 3 sodium carbonate solution injected into the 8-hour calculation domain of the present invention. 3

[0021] Figure 10 The simulation results of the concentration of calcium chloride - 2.34 mol / m 3 sodium carbonate solution injected into the 24-hour calculation domain of the present invention. 3

[0022] Figure 11 The calcite formation and distribution in the porous medium structure of sandstone-mudstone contact of the present invention.

[0023] Figure 12 The calcite formation and distribution in the porous medium structure of sandstone-mudstone contact with fractures of the present invention.

[0024] Figure 13 The calcite formation and distribution in the porous medium structure of sandstone-mudstone contact with two sources of endogenous and exogenous substances of the present invention. Detailed implementation manners

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Obviously, many modifications and variations made by those skilled in the art based on the purpose of the present invention fall within the protection scope of the present invention.

[0027] ​​​​Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the", and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention means the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups. It should be understood that when an element or component is "connected" to another element or component, it can be directly connected to other elements or components, or there may also be intermediate elements or components. The phrase "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0028] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art in the relevant field.

[0029] For the convenience of understanding the embodiments, further explanations will be given below in conjunction with [relevant content], and each embodiment does not constitute a limitation on the present invention.

[0030] Embodiment 1: As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 7 , Figure 7 , Figure 10 , Figure 11 , Figure 12 and Figure 13 shown, a diagenetic numerical simulation method of multi-field coupling, collecting data, providing content such as the classification of diagenetic facies types, the diagenetic characteristics of diagenetic facies, framework minerals, authigenic mineral assemblages and diagenetic differences, a preliminary analysis of diagenetic mechanisms, chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena, chemical kinetic analysis of typical diagenetic phenomena, physical models, numerical simulation models, the revelation and improvement of diagenetic mechanisms, etc., proposes a diagenetic numerical simulation method of multi-field coupling, and the experimental analysis results and numerical simulation results jointly reveal and improve the diagenetic mechanism, including the following steps:

[0031] Step 1), collecting data and information: collecting cast thin sections and their quantitative statistical data, scanning electron microscopy, cathodoluminescence thin sections, and X-ray diffraction analysis data.

[0032] Step 2), Diagenetic facies type division: Based on the data of casting thin sections, scanning electron microscopy, and cathodoluminescence thin section images, determine the compaction, calcite cementation, quartz cementation, clay mineral transformation, and dissolution experienced by low-permeability tight sandstones; then, classify the low-permeability tight sandstones into various diagenetic facies based on diagenesis and diagenetic minerals.

[0033] Step 3), Diagenetic characteristics research: Based on the casting thin sections and their quantitative statistical data, scanning electron microscopy, cathodoluminescence thin sections, and X-ray diffraction analysis data, investigate the diagenetic characteristics of diagenetic facies.

[0034] Step 4), Preliminary analysis of diagenetic mechanism: Based on the quantitative statistical data of casting thin sections, X-ray diffraction analysis data, and scanning electron microscopy image data, investigate the framework minerals, authigenic diagenetic mineral assemblages, and diagenetic differences of diagenetic facies, and conduct a preliminary analysis of the diagenetic mechanism through experimental analysis results.

[0035] Step 5), Chemical reaction equations and corresponding kinetic conditions of typical diagenetic phenomena: Taking typical diagenetic facies as an example, extract typical diagenetic phenomena, and establish chemical reaction equations reflecting typical diagenetic phenomena and their corresponding kinetic conditions.

[0036] Step 6), Chemical kinetics analysis of typical diagenetic phenomena: Use the "reaction engineering" interface to conduct chemical kinetics analysis of typical diagenetic phenomena in the zero-dimensional model.

[0037] Step 7), Physical model establishment: Analyze the distribution of typical diagenetic phenomena through casting thin sections, scanning electron microscopy, and cathodoluminescence thin section images, and combine the larger-scale distribution of typical diagenetic phenomena in the sandstones of the target layer in the target area to establish a two-dimensional multi-physical field physical model.

[0038] Step 8), Numerical simulation model establishment: Based on the physical model, establish a 2D / 3D space-related model, add free and porous medium flow interfaces, dilute mass transfer interfaces, and level set interfaces, and set the key parameters of the reaction engineering, free and porous medium flow, dilute mass transfer, and level set modules in detail to capture the formation process of typical diagenetic phenomena and reveal and improve the diagenetic mechanism.

[0039] Step 9), Based on the above steps 1), 2), 3), 4), 5), 6), 7), and 8), propose a multi-field coupling diagenetic numerical simulation method. The experimental analysis results and numerical simulation results jointly reveal and improve the understanding of the diagenetic mechanism, and form an evaluation process for the multi-field coupling diagenetic numerical simulation method. Use the 2D model to study the diagenetic mechanism of typical diagenetic phenomena and re-understand its influence on reservoir quality in a larger range.

[0040] Step 3) Study on the diagenetic characteristics of diagenetic facies is as follows:

[0041] Study on diagenetic characteristics: Based on the thin sections of cast slices and their quantitative statistical data, scanning electron microscopy, cathodoluminescence thin sections, and X-ray diffraction analysis data, investigate the diagenetic characteristics of diagenetic facies.

[0042] For example, in the calcite cementation facies, through the thin sections of cast slices, scanning electron microscopy, and cathodoluminescence thin section image data, the distribution of calcite cement mainly presents as early calcite with basal distribution and late ferrocalcite with patchy distribution; the early calcite cement makes the mineral grains present a floating structure, resulting in a decrease in the quality of low-permeability to tight sandstone reservoirs; the late ferrocalcite cement has little influence on the distribution of mineral grains and little influence on the reservoir quality; therefore, the diagenetic characteristics of the calcite cementation facies are the dominant early calcite cementation, underdeveloped secondary pores, a small amount of primary pores, and the contact relationship between grains and cement.

[0043] The innovation of the present invention lies in: Based on data such as thin sections of cast slices, scanning electron microscopy, and cathodoluminescence thin sections, the present invention focuses on the dominant diagenesis, cement distribution, mineral grain distribution, and pore space distribution to study the diagenetic characteristics of diagenetic facies; the diagenetic characteristics analyzed in this way can reflect the dominant diagenesis and pore space distribution experienced during burial diagenesis.

[0044] Step 4) Preliminary analysis of the diagenetic mechanism of diagenetic facies is as follows:

[0045] Preliminary analysis of the diagenetic mechanism: Based on the thin sections of cast slices and their quantitative statistical data, X-ray diffraction analysis data, and scanning electron microscopy image data, investigate the framework minerals, authigenic mineral assemblages, and diagenetic differences of diagenetic facies, and conduct a preliminary analysis of the diagenetic mechanism through the experimental analysis results.

[0046] First, based on the observation of thin sections of cast slices and their petrographic quantitative statistical data, investigate the distribution of framework minerals such as quartz, feldspar, lithic fragments, and argillaceous matrix in the sandstone of the target horizon in the target area.

[0047] Secondly, based on the quantitative statistical data of cast thin-section petrography, X-ray diffraction analysis data, and scanning electron microscope image data, the main authigenic diagenetic minerals in the sandstone of the target horizon in the target area include authigenic quartz microcrystals, quartz secondary enlargement, calcite, ferrocalcite, chlorite films, dispersed flakes, fluffy and rosette-shaped chlorite, flaky, honeycomb-shaped, filamentous and hair-like illite and illite-smectite mixed layers; due to different diagenetic processes and diagenetic evolution processes experienced by different diagenetic facies in the sandstone reservoir of the target horizon, they have different authigenic diagenetic mineral assemblages. For example, the authigenic mineral assemblage of the calcite cementation facies mainly includes calcite and ferrocalcite; the distribution characteristics of these authigenic minerals are that the early calcite cementation occurred in the early diagenetic stage, filling the intergranular pores and showing a basal distribution, and the framework grains presented a floating structure; the late ferrocalcite cementation occurred in the middle and late diagenetic stages, showing a patchy distribution, filling the residual intergranular pores and intragranular dissolution pores, or replacing the early calcite cement.

[0048] Thirdly, based on the images of cast thin-sections, scanning electron microscopes, and cathodoluminescence thin-sections, combined with the burial history-thermal history, the sandstone of the target horizon in the target area has experienced the entire diagenetic evolution process from early diagenesis to burial diagenesis, including compaction, cementation (quartz, calcite, and clay), and dissolution (meteoric freshwater leaching, organic acids, and CO2 acidic fluids); due to different diagenetic processes, different diagenetic facies have different diagenetic differences.

[0049] Finally, based on the analysis of the diagenetic characteristics, framework minerals, authigenic mineral assemblages, and diagenetic differences of the diagenetic facies, clarify the types, contents, and occurrence states of siliceous cements, carbonate cements, and authigenic clay minerals that cause reservoir densification, investigate the dissolution periods and associated minerals of feldspar, lithic fragments, and carbonate cements that improve the reservoir pore space, analyze the formation of chlorite films that protect the reservoir pore space, and reveal the diagenetic mechanisms of the diagenetic facies; for example, preliminarily analyze the diagenetic mechanism of the calcite cementation facies through experimental analysis results; the diagenetic mechanism of the calcite cementation facies in the sandstone reservoir of the target horizon in the target area is due to the early calcite cement formed under supersaturated calcium carbonate and alkaline conditions in the sedimentary water medium. The early calcite cementation makes the sandstone framework grains present a floating structure, and the calcite cement shows a basal distribution, blocking and destroying the pore space.

[0050] The innovation of the present invention lies in: based on the cast thin-sections and their quantitative statistical data, X-ray diffraction analysis data, and scanning electron microscope image data, the present invention investigates the framework minerals, authigenic diagenetic mineral assemblages, and diagenetic differences of the diagenetic facies, and conducts a preliminary analysis of the diagenetic mechanism through experimental analysis results; the diagenetic mechanism obtained from the preliminary analysis lays a foundation for chemical reaction equations and their corresponding kinetic conditions and chemical kinetic analysis.

[0051] The chemical reaction equations of typical diagenetic phenomena and their corresponding kinetic conditions in step 5) are as follows:

[0052] Chemical reaction equations of typical diagenetic phenomena and their corresponding kinetic conditions: Taking typical diagenetic facies as an example, typical diagenetic phenomena are extracted, and chemical reaction equations reflecting typical diagenetic phenomena and their corresponding kinetic conditions are established.

[0053] The innovation of the present invention lies in: From experimental research and theoretical analysis, the present invention establishes chemical reaction equations reflecting the essence of typical diagenetic phenomena, and then analyzes the kinetic conditions, which provides a starting point for numerical simulation of diagenesis.

[0054] The chemical kinetic analysis of typical diagenetic phenomena in step 6) is as follows:

[0055] Chemical kinetic analysis of typical diagenetic phenomena: Use the "reaction engineering" interface to conduct chemical kinetic analysis of typical diagenetic phenomena in the zero-dimensional model.

[0056] Reaction engineering is used to simulate several types of chemical reactions and the evolution of chemical reactions over time. Reaction kinetics is an important basis for reaction engineering. Engaging in reaction design of reaction processes without understanding kinetics will always be more or less blind, and even take more detours and fail to achieve the expected goal.

[0057] The kinetic parameters of calcite precipitation were predicted through empirical parameters and parametric scans from literature research. The reaction frequency factor is 10m 3 / (s·mol), the reaction activation energy is 46000 J / mol, and the reaction temperature exponent is 0.

[0058] The innovation of the present invention lies in: The present invention focuses on the chemical kinetic analysis of chemical reaction equations, accurately obtains parameters such as reaction frequency factor, reaction activation energy, and reaction temperature exponent, laying a foundation for numerical simulation research on the analysis of diagenesis mechanism.

[0059] The establishment of the physical model in step 7) is as follows:

[0060] Establishment of the physical model: Analyze the distribution of typical diagenetic phenomena through thin sections of castings, scanning electron microscopy, and cathodoluminescence thin section images, and combine the larger-scale distribution of typical diagenetic phenomena in the sandstone of the target horizon in the target area to establish a physical model of two-dimensional multi-physical fields.

[0061] The innovation of the present invention lies in: The present invention comprehensively considers the microscopic scale distribution of typical diagenetic phenomena and their larger-scale distribution in the sandstone of the target horizon, and establishes a physical model of two-dimensional multi-physical fields; the established physical model provides a spatial field for the numerical simulation model.

[0062] In step 8), a numerical simulation model is established as follows:

[0063] Establishment of the numerical simulation model: Based on the physical model, a 2D / 3D space-related model is established, with the addition of free and porous media flow interfaces, dilute mass transfer interfaces, and level set interfaces. The key parameters of the reaction engineering, free and porous media flow, dilute mass transfer, and level set modules are set in detail to capture the formation process of typical diagenetic phenomena and reveal and improve the diagenesis mechanism;

[0064] Based on the above physical model, a numerical simulation model is established. By integrating the reaction engineering, fluid flow module, dilute mass transfer module, and level set module, the formation and distribution of calcite are described. First, by setting three groups of parallel models and using the same reaction engineering, dilute mass transfer, and level set modules, with each group of models using the laminar flow module, free and porous media flow module, and Darcy's law module respectively, a suitable fluid flow module is screened out; then, a numerical simulation study on multi-field coupled sandstone diagenesis is carried out to capture the formation process of typical diagenetic phenomena.

[0065] Taking the calcite cement phase as an example, the typical diagenetic phenomenon is determined as early calcite cement; then, a project is established, including reaction engineering, dilute mass transfer, free and porous media flow, and level set interfaces; then, based on the data of cast thin sections, scanning electron microscopy, and cathodoluminescence thin section images, the distribution of early calcite cement is determined, and combined with the distribution characteristics of sandstone and mudstone in the target layer of the target area, a physical model is established; then, the key parameters of the reaction engineering, free and porous media flow, dilute mass transfer, and level set modules are set in detail, and a numerical simulation study is carried out to capture the formation process of calcite cement and reveal and improve the diagenesis mechanism.

[0066] The innovation of the present invention lies in: Based on the physical model, the present invention establishes a numerical simulation model, considering the reaction engineering, dilute mass transfer, free and porous media flow, and level set modules, captures the formation process of typical diagenetic phenomena, and reveals and improves the diagenesis mechanism.

[0067] By combining and innovating in steps 1), 2), 3), 4), 5), 6), 7), and 8), an evaluation process of a multi-field coupled diagenetic numerical simulation method is formed, providing a solution for revealing and improving the diagenesis mechanism analysis, which helps to reveal and improve the diagenesis mechanism.

[0068] A multi-field coupled diagenetic numerical simulation method is achieved through the classification of diagenetic phase types, diagenetic characteristics of diagenetic phases, preliminary analysis of diagenetic mechanisms, chemical reaction equations of typical diagenetic phenomena and their corresponding kinetic conditions, chemical kinetic analysis of typical diagenetic phenomena, physical models, numerical simulation models, and the revelation and improvement of diagenetic mechanisms, and then the diagenetic mechanisms are revealed and improved by combining experimental analysis results and numerical simulation results.

[0069] Innovations have been made in the study of diagenetic numerical simulation methods and diagenetic mechanism research, and a multi-field coupled diagenetic numerical simulation method has been formed by comprehensively considering reaction engineering, dilute material transfer, free and porous media flow, and level set modules. An innovative multi-field coupled diagenetic numerical simulation method and process framework have been developed, and the numerical simulation results and experimental analysis results are combined to reveal and improve the diagenetic mechanism. The present invention provides a multi-field coupled diagenetic numerical simulation method and forms a set of multi-field coupled diagenetic numerical simulation evaluation processes; this can provide technical service support for revealing and improving the diagenetic mechanism.

[0070] Example 2: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 7 , Figure 7 , Figure 10 , Figure 11 , Figure 12 and Figure 13 As shown in the figure, a multi-field coupled diagenetic numerical simulation method provides technical support for the analysis of the diagenetic mechanism of typical diagenetic phases.

[0071] Collect data and information based on analysis of test data and geological data, mainly including the classification of diagenetic phase types, diagenetic characteristics of diagenetic phases, differences in skeleton minerals, own mineral groups and diagenesis, preliminary distribution of diagenetic mechanisms, chemical reaction equations of typical diagenetic phenomena and their corresponding kinetic conditions, chemical kinetic analysis of typical diagenetic phenomena, establishment of physical models, establishment of numerical simulation models, revelation and improvement of diagenetic mechanisms, etc.

[0072] This implementation method provides an evaluation technology flow chart of a multi-field coupled diagenetic numerical simulation method ( Figure 1 ), including the following steps:

[0073] (1) Taking the sandstone reservoir in the target layer of the XX Sag in the XX Basin as an example, cast thin sections and their quantitative statistical data, scanning electron microscopy, cathodoluminescence thin sections, and X-ray diffraction analysis data were collected.

[0074] (2) Classification of diagenetic facies types: Based on thin-section casting, scanning electron microscopy, and cathodoluminescence thin-section image data, determine the compaction, calcite cementation, quartz cementation, clay mineral transformation, and dissolution experienced by low-permeability tight sandstone; then, classify the low-permeability tight sandstone into multiple diagenetic facies based on diagenesis and diagenetic minerals.

[0075] (3) Study of diagenetic characteristics: Based on thin-section casting and its quantitative statistical data, scanning electron microscopy, cathodoluminescence thin-section, and X-ray diffraction data, investigate the diagenetic characteristics of diagenetic facies.

[0076] For example, in the calcite cementation facies, through thin-section casting, scanning electron microscopy, and cathodoluminescence thin-section image data, the distribution of calcite cement mainly presents as early calcite with a basal distribution and late ferrocalcite with a patchy distribution; the early calcite cement makes the mineral grains present a floating structure, resulting in a decrease in the reservoir quality of low-permeability tight sandstone; the late ferrocalcite cement has little influence on the distribution of mineral grains and has little influence on the reservoir quality; therefore, the diagenetic characteristics of the calcite cementation facies are dominated by early calcite cementation, underdeveloped secondary pores, a small amount of primary pores, and the contact relationship between grains and cement.

[0077] (4) Preliminary analysis of diagenesis mechanism: Based on the quantitative statistical data of thin-section casting, X-ray diffraction analysis data, and scanning electron microscopy image data, investigate the framework minerals, authigenic diagenetic mineral assemblages, and diagenetic differences of diagenetic facies, and conduct a preliminary analysis of the diagenesis mechanism through the experimental analysis results.

[0078] First, based on the observation of thin-section casting and its petrographic quantitative statistical data, investigate the distribution of framework minerals such as quartz, feldspar, lithic fragments, and argillaceous matrix in the sandstone of the target horizon in the target area.

[0079] Second, based on the petrographic quantitative statistical data of thin-section casting, X-ray diffraction analysis data, and scanning electron microscopy image data, the main authigenic diagenetic minerals in the sandstone of the target horizon in the target area include authigenic quartz microcrystals, quartz secondary enlargement, calcite, ferrocalcite, chlorite films, dispersed flakes, globular and rosette chlorite, flaky, honeycomb-like, filamentous, and hair-like illite, and illite-montmorillonite mixed layers; due to different diagenesis and diagenetic evolution processes experienced by different diagenetic facies in the sandstone reservoir of the target horizon, they have different authigenic diagenetic mineral assemblages. For example, the authigenic mineral assemblage of the calcite cementation facies mainly includes calcite and ferrocalcite; the distribution characteristics of these authigenic minerals are that early calcite cementation occurs in the early diagenetic stage, filling the intergranular pores, showing a basal distribution, and the framework grains presenting a floating structure; late ferrocalcite cementation occurs in the middle diagenetic stage and the late diagenetic stage, showing a patchy distribution, filling the residual intergranular pores and intragranular dissolution pores, or replacing the early calcite cement.

[0080] Thirdly, based on the thin sections of cast rocks, scanning electron microscopy, and cathodoluminescence thin section image data, combined with the burial history - thermal history, the sandstones in the target horizon have experienced the entire diagenetic evolution process from early diagenesis to burial diagenesis, including compaction, cementation (quartz, calcite, and clay), and dissolution (meteoric freshwater leaching, organic acids, and CO2 acidic fluids); due to the different diagenetic processes, different diagenetic facies have different diagenetic differences.

[0081] Finally, based on the analysis of the diagenetic characteristics, framework minerals, authigenic mineral assemblages, and diagenetic differences of the diagenetic facies, clarify the types, contents, and occurrence states of the siliceous cements, carbonate cements, and authigenic clay minerals that lead to reservoir densification, investigate the dissolution stages and associated minerals of feldspar, lithic fragments, and carbonate cements that improve the reservoir pore space, analyze the formation of chlorite films that protect the reservoir pore space, and reveal the diagenetic mechanisms of the diagenetic facies; for example, preliminarily analyze the diagenetic mechanism of the calcite cementation facies through experimental analysis results; the diagenetic mechanism of the calcite cementation facies in the sandstone reservoir of the target horizon in the study area is that the early calcite cement is formed due to the supersaturation of calcium carbonate and alkaline conditions in the sedimentary water medium. The early calcite cementation makes the sandstone framework particles show a floating structure, and the calcite cement shows a basal distribution, blocking and destroying the pore space.

[0082] (5) Chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena: Taking typical diagenetic facies as an example, extract typical diagenetic phenomena and establish chemical reaction equations reflecting typical diagenetic phenomena and their corresponding kinetic conditions.

[0083] (6) Chemical kinetic analysis of typical diagenetic phenomena: Use the "reaction engineering" interface to conduct chemical kinetic analysis of typical diagenetic phenomena in the zero - dimensional model.

[0084] The kinetic parameters of calcite precipitation were predicted through empirical parameters and parametric scans from literature research. The reaction frequency factor is 10m 3 / (s·mol), the reaction activation energy is 46000 J / mol, and the reaction temperature exponent is 0.

[0085] (7) Physical model establishment: Investigate the distribution of typical diagenetic phenomena through thin sections of cast rocks, scanning electron microscopy, and cathodoluminescence thin section image data, and combine the wider - range distribution of typical diagenetic phenomena in the sandstones of the target horizon in the study area to establish a two - dimensional multi - physical - field physical model.

[0086] Figure 2 The schematic diagram of the model showing the formation and distribution of calcite is presented; Figure 3 The two - dimensional model showing the formation and distribution of calcite is presented.

[0087] Such as Figure 2 and Figure 3As shown, a physical model of two-dimensional multi-physics fields is established, and the model length (L) × height (H) is 4 cm × 5 cm. Among them, computational domain 1 is the sandstone layer, with a length of 4 cm and a height of 3.45 cm; computational domain 2 is the mudstone layer, which is composed of two rectangles. One rectangle has a length of 2 cm and a height of 1.55 cm, and the other rectangle has a length of 2 cm and a height of 1.4 cm. The model can be divided into two parts. The part where y < 1.55 cm is the mudstone part, and the part where y > 1.55 cm is the sandstone part. The fluid inlet and outlet are located at the bottom and top of the micromodel respectively; the lengths of fluid inlet 1 are 2 cm (y = 0 cm) and 2 cm (y = 0.15 cm) respectively; the width of the fluid outlet is about 4 cm (y = 5 cm).

[0088] The particle diameter range in the physical model is about 0.1 mm - 1.0 mm (0.25 mm, 0.5 mm, and 1 mm). The particles in this study are regular and moderately to well sorted in the physical model.

[0089] (8) Establishment of numerical simulation model: Based on the physical model, a 2D / 3D space-related model is established, adding free and porous media flow interfaces, dilute mass transfer interfaces, and level set interfaces, and the key parameters of reaction engineering, free and porous media flow, dilute mass transfer, and level set modules are set in detail to capture the formation process of typical diagenetic phenomena and reveal and improve the diagenesis mechanism.

[0090] The formation and distribution of calcite under the laminar flow model, free and porous media flow, and Darcy's law constraint are compared and analyzed. Figure 4 The formation and distribution of calcite under the laminar flow model constraint are shown. Figure 5 The formation and distribution of calcite under the free and porous media flow model constraint are shown. Figure 6 The formation and distribution of calcite under the Darcy's law constraint are shown; the results show that the formation and distribution of calcite under the Darcy's law model constraint are in good agreement with the observation results of experimental studies; this is mainly attributed to the following three reasons: First, large thick sandstone layers and thin mudstone layers are developed in the study area, and the burial depths of these sandstones and mudstones are between 3500 m - 4500 m, which are low-permeability - tight sandstones and also porous media materials, so they are applicable to the Darcy's law interface; second, the applicable conditions of Darcy's law include slow flow in saturated porous media, the addition of gravity effects, preset head, pressure head and other boundary conditions, anisotropic permeability, Kozeny-Carman model, Non-Darcian model; third, the formation and distribution of calcite simulated using the Darcy's law interface are more consistent with the calcite distribution observed in thin section and scanning electron microscope images.

[0091] The simulation results of different calcium chloride - sodium carbonate solution concentrations were comparatively analyzed. The formation and distribution of calcite increased with the increase in the concentration of the injected solution. The main controlling factor for the dependence of the kinetics of calcite formation and distribution on the solution concentration is the interaction between flow, diffusion, and reaction kinetics. The numerical simulation captured the main characteristics of calcite formation and distribution. In the experiment, for five solution concentrations of calcium chloride - sodium carbonate, namely 1.4 mol / m 3 calcium chloride - 1.26 mol / m 3 sodium carbonate, 1.7 mol / m 3 calcium chloride - 1.53 mol / m 3 sodium carbonate, 2.0 mol / m 3 calcium chloride - 1.8 mol / m 3 sodium carbonate, 2.3 mol / m 3 calcium chloride - 2.07 mol / m 3 sodium carbonate, 2.6 mol / m 3 calcium chloride - 2.34 mol / m 3 sodium carbonate, the model predicted very similar trends among the five simulations.

[0092] Figure 7 The simulation results of injecting a 2.6 mol / m 3 calcium chloride - 2.34 mol / m 3 sodium carbonate solution concentration in the computational domain for 4 hours are shown; Figure 8 The simulation results of injecting a 2.6 mol / m 3 calcium chloride - 2.34 mol / m 3 sodium carbonate solution concentration in the computational domain for 12 hours are shown; Figure 9 The simulation results of injecting a 2.6 mol / m 3 calcium chloride - 2.34 mol / m 3 sodium carbonate solution concentration in the computational domain for 18 hours are shown; Figure 10 The simulation results of injecting a 2.6 mol / m 3 calcium chloride - 2.34 mol / m 3 sodium carbonate solution concentration in the computational domain for 24 hours are shown. In the simulation with a calcium chloride concentration of 2.6 mol / m 3 and a sodium carbonate concentration of 2.34 mol / m 3 , a calcite cement layer with a thickness of 2.1 cm - 2.8 cm was observed throughout the sandstone - mudstone interface ( Figures 7 to 10) The thickness of the calcite cement layer is captured through the level set module, coupling reaction engineering, Darcy's law, and the dilute species transport module, which also captures the formation and distribution of calcite. At the end of the numerical simulation, i.e., 24 hours, the thickness of the calcite cement layer reaches 2.8 cm. It is comparable to the experimental image data obtained from thin sections and cathodoluminescence thin sections. As calcite forms and develops, the concentrations of the discharged Ca 2+ and CO3 2- ions decrease. In the simulation, the formation and distribution of calcite show four different stages: slow growth of calcite crystals from the start to ~4 hours ( Figure 7 ); within 4 - 12 hours, the calcite crystals grow rapidly, and the distribution of calcite is 10 - 20 times that at 4 hours ( Figure 8 ); slow growth of calcite crystals from 12 - 18 hours, mainly due to the lateral connection and contact of locally formed calcite ( Figure 9 ); rapid growth of calcite crystals from 18 - 24 hours, and the distribution of calcite is about 2 times that at 18 hours ( Figure 10 ).

[0093] The above research analysis shows that the main controlling factor for the dependence of calcite formation on solution concentration is the interaction between flow, diffusion, and reaction kinetics. However, the porous medium structure affected by complex precipitation mechanisms has a non - negligible impact on the formation and distribution of calcite. The precipitate structure is mainly controlled by local transport, and the formation and distribution of calcite have a complex dependence on the porous medium structure. Figure 11 shows the formation and distribution of calcite in the porous medium structure of sandstone - mudstone contact; Figure 12 shows the formation and distribution of calcite in the porous medium structure of fractured sandstone - mudstone contact; Figure 13 shows the formation and distribution of calcite in the porous medium structure of sandstone - mudstone contact with two material sources, endogenous and exogenous.

[0094] Figure 11 shows the formation and distribution of calcite in the porous medium structure of sandstone - mudstone contact; this model shows that a calcite cement layer is formed at the sandstone - mudstone contact interface.

[0095] Figure 12 shows the formation and distribution of calcite in the porous medium structure of fractured sandstone - mudstone contact; the simulation results show that calcite crystals are more distributed in the fracture zone, which may be because the diffusion coefficient of the fracture is lower than that of the surrounding medium, making it easy to become crystal nucleation sites, and under such continuous conditions, the crystals continue to grow in the fractures and become calcite veins.

[0096] Figure 13 shows the formation and distribution of calcite in sandstone - mudstone contact with two material sources, endogenous and exogenous; when Ca2+ and CO3 2- When the ions are from internal and external sources respectively, calcite crystals appear as locally or sporadically distributed in the porous medium structure.

[0097] For the simulation of the porous medium structure model of sandstone - mudstone contact, the amount of calcite precipitate is significantly higher, mainly distributed along the sandstone - mudstone contact interface; for the simulation of the porous medium structure model of fractured sandstone - mudstone contact, the amount of calcite precipitate is moderate, mainly distributed along the micro - fractures; for the simulation of the porous medium structure model of sandstone - mudstone contact with both endogenous and exogenous material sources, the amount of calcite precipitate is less.

[0098] The above - mentioned research mainly involves reaction kinetics, velocity field, porous medium structure and reaction mechanism. Generally, chemical reactions and the factors affecting them are studied first. After a sufficient understanding of them, kinetics is studied. After the applicability of the obtained empirical rate expression and the numerical simulation experiment process is tested, then the reaction mechanism is analyzed. A lot of feedback test data information will be obtained through numerical simulation experiments and adjusted accordingly. The formation and distribution of calcite may change according to the obtained kinetic data, and then the form of the kinetic equation itself is optimized, and modified according to the research and feedback understanding of the reaction mechanism.

[0099] (9), Based on the above (1), (2), (3), (4), (5), (6), (7) and (8), a multi - field coupled diagenetic numerical simulation method is proposed. The experimental analysis results and numerical simulation results jointly reveal and improve the diagenetic mechanism, and form an evaluation process for the multi - field coupled diagenetic numerical simulation method. Use the 2D model to study the diagenetic mechanism of typical diagenetic phenomena and re - understand its influence on reservoir quality in a larger range.

[0100] A multi - field coupled diagenetic numerical simulation method and framework can incorporate the mechanism descriptions of more diagenetic facies, which will provide necessary information for revealing or improving the analysis of the diagenetic mechanism.

[0101] As described above, the embodiments of the present invention have been described in detail. However, as long as it does not substantially deviate from the inventive points and effects of the present invention, there can be many deformations, which are obvious to those skilled in the art. Therefore, such deformation examples are also all included in the protection scope of the present invention.

Claims

1. A numerical simulation method for diagenesis with multi-field coupling, characterized in that, It includes the following steps: Step 1), collecting data and information: collecting thin sections of cast bodies and their quantitative statistical data, scanning electron microscopy, thin sections of cathodoluminescence, X-ray diffraction analysis data; Step 2), dividing diagenetic facies types: based on the thin sections of cast bodies, scanning electron microscopy and thin section images of cathodoluminescence, determining the compaction, calcite cementation, quartz cementation, clay mineral transformation and dissolution experienced by low-permeability and tight sandstones; then, dividing the low-permeability and tight sandstones into various diagenetic facies based on diagenesis and diagenetic minerals; Step 3), studying diagenetic characteristics: based on the thin sections of cast bodies and their quantitative statistical data, scanning electron microscopy, thin sections of cathodoluminescence, X-ray diffraction analysis data, investigating the diagenetic characteristics of diagenetic facies; Step 4), preliminary analysis of diagenetic mechanism: first, based on the observation of thin sections of cast bodies and their petrographic quantitative statistical data, investigating the distribution of framework minerals such as quartz, feldspar, lithic fragments and argillaceous matrix in the sandstones of the target horizon in the target area; Secondly, based on the petrographic quantitative statistical data of thin sections of cast bodies, X-ray diffraction analysis data, scanning electron microscopy image data, the authigenic diagenetic minerals in the sandstones of the target horizon in the target area include authigenic quartz microcrystals, quartz secondary enlargement, calcite, ferrocalcite, chlorite film, dispersed flakes, flocculent and rosette chlorite, flakes, honeycomb, filamentous and hair-like illite and illite-smectite mixed layer; due to different diagenetic processes and diagenetic evolution processes experienced by different diagenetic facies in the sandstone reservoir of the target horizon, they have different authigenic diagenetic mineral assemblages. The authigenic mineral assemblage of the calcite cementation facies includes calcite and ferrocalcite; the distribution characteristics of these authigenic minerals are that early calcite cementation occurs in the early diagenetic stage, filling the intergranular pores and showing a basal distribution, and the framework grains show a floating structure; late ferrocalcite cementation occurs in the middle diagenetic stage and the late diagenetic stage, showing a patchy distribution, filling the residual intergranular pores and intragranular dissolution pores, or replacing the early calcite cement; Thirdly, based on the thin sections of cast bodies, scanning electron microscopy and thin section images of cathodoluminescence, combined with the burial history-thermal history, the sandstones of the target horizon in the target area experience the entire diagenetic evolution process from early diagenesis to burial diagenesis, including compaction, cementation and dissolution; due to different diagenetic processes, different diagenetic facies have different diagenetic differences; Finally, based on the analysis of the diagenetic characteristics, framework minerals, authigenic mineral assemblages and diagenetic differences of diagenetic facies, clarifying the types, contents and occurrence states of siliceous cements, carbonate cements and authigenic clay minerals that cause reservoir tightness, investigating the dissolution periods and associated minerals of feldspar, lithic fragments and carbonate cements that improve the reservoir pore space, analyzing the formation of chlorite films that protect the reservoir pore space, and revealing the diagenetic mechanism of diagenetic facies; Preliminarily analyze the diagenetic mechanism of calcite cement phase through experimental analysis results; the diagenetic mechanism of calcite cement phase in the sandstone reservoir of the target horizon in the target area is due to the early calcite cement formed by supersaturation of calcium carbonate and alkaline conditions in the sedimentary water medium. The early calcite cementation makes the sandstone framework particles present a floating structure, and the calcite cement presents a basal distribution, clogging and destroying the pore space; Step 5), Chemical reaction equations and their corresponding kinetic conditions of typical diagenetic phenomena: Taking typical diagenetic facies as an example, extract typical diagenetic phenomena, and establish chemical reaction equations reflecting typical diagenetic phenomena and their corresponding kinetic conditions; Step 6), Chemical kinetic analysis of typical diagenetic phenomena: Use the "reaction engineering" interface to conduct chemical kinetic analysis of typical diagenetic phenomena in the zero-dimensional model; Step 7), Establishment of physical model: Analyze the distribution of typical diagenetic phenomena through thin sections of cast specimens, scanning electron microscopy and cathodoluminescence thin section image data, and combine the wider distribution of typical diagenetic phenomena in the sandstone of the target horizon in the target area to establish a physical model of two-dimensional multi-physical fields; Step 8), Establishment of numerical simulation model: On the basis of the physical model, establish a 2D / 3D spatial correlation model, add free and porous media flow interfaces, dilute mass transfer interfaces and level set interfaces, and set the key parameters of reaction engineering, free and porous media flow, dilute mass transfer and level set modules to capture the formation process of typical diagenetic phenomena and reveal and improve the diagenetic mechanism.

2. The diagenetic numerical simulation method with multi-field coupling according to claim 1, wherein The study of the diagenetic characteristics of the diagenetic facies in Step 3) is as follows: Study of diagenetic characteristics: Based on thin sections of cast specimens and their quantitative statistical data, scanning electron microscopy, cathodoluminescence thin sections, and X-ray diffraction analysis data, investigate the diagenetic characteristics of diagenetic facies; Through thin sections of cast specimens, scanning electron microscopy and cathodoluminescence thin section image data of the calcite cement phase, the distribution of calcite cement presents early calcite with a basal distribution and late ferrocalcite with a patchy distribution; the early calcite cement makes the mineral particles present a floating structure, resulting in a decrease in the quality of low-permeability to tight sandstone reservoirs; the late ferrocalcite cement has little effect on the distribution of mineral particles and little effect on the reservoir quality; therefore, the diagenetic characteristics of the calcite cement phase are dominant early calcite cementation, underdeveloped secondary pores, a small amount of primary pores, and the contact relationship between particles and cement.

3. A diagenetic numerical simulation method of multi-field coupling according to claim 1, characterized in that The chemical kinetic analysis of typical diagenetic phenomena in Step 6) is as follows: Chemical kinetic analysis of typical diagenetic phenomena: Use the "reaction engineering" interface to conduct chemical kinetic analysis of typical diagenetic phenomena in the zero-dimensional model; reaction engineering is used to simulate several types of chemical reactions and the evolution of chemical reactions over time; The kinetic parameters of calcite precipitation were predicted by empirical parameters and parametric scanning from literature research. The reaction frequency factor is 10m 3 / (s·mol), the reaction activation energy is 46000 J / mol, and the reaction temperature exponent is 0.

4. A numerical simulation method for diagenesis with multi-field coupling according to claim 1, characterized in that The establishment of the numerical simulation model in Step 8) is as follows: Based on the physical model, a numerical simulation model is established, integrating reaction engineering, fluid flow module, dilute mass transfer module, and level set module to describe the formation and distribution of calcite. First, by setting up three groups of parallel models, using the same reaction engineering, dilute mass transfer, and level set modules, and the three groups of models using laminar flow module, free and porous medium flow module, and Darcy's law module respectively, a suitable fluid flow module is screened out; then, a multi-field coupled numerical simulation study of sandstone diagenesis is carried out to capture the formation process of typical diagenetic phenomena and reveal and improve the diagenetic mechanism.

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