A method and system for simulating sediments containing natural gas hydrates based on discrete elements

Abstract

The present invention relates to the technical field of hydrate sediment analysis, specifically to a method and system for simulating natural gas hydrate sediments based on discrete elements, the method comprising the following steps: setting a cylindrical space model of a specific size, placing gravel in the space model to obtain an initial arrangement result of the sand particles; introducing a grid method, obtaining the distance between the centers of the particles and a hydrate sample according to the grid method and the initial arrangement result; constructing a hydrate occurrence pattern, adjusting the distance between the centers of the particles according to the occurrence pattern to obtain a target hydrate saturation; and generating a hydrate sediment sample by combining the target hydrate saturation, the hydrate sample and the pure sand sample. Based on the spatial relative position of hydrate and sand particles, the present invention uses different distance thresholds to screen particles, reconstructs the distribution of hydrates and performs simulation analysis to analyze the mechanical behavior of natural gas hydrate sediments, and provides technical support for natural gas extraction and climate change research.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrate sediment analysis, and in particular to a method and system for simulating natural gas hydrate sediments based on discrete elements. Background Art

[0002] Natural gas hydrate sediments are very important in the exploration and development of natural gas resources and the assessment of global climate change. Their mechanical response is deeply affected by the hydrate saturation and occurrence mode. Discrete element method (DEM) is an important analytical method that can reveal the mechanical properties of such sediments at the microscopic scale and their macroscopic manifestations. However, current research using DEM still faces challenges in accurately controlling the occurrence form and saturation of hydrates. At the same time, the physical meaning of the microscopic parameters in the model needs to be further clarified.

[0003] Although DEM provides strong support for understanding and predicting the behavior of gas hydrate sediments, in actual operation, how to accurately set and control the distribution pattern and content of hydrates in sediments, and how to clarify the actual physical meaning of each microscopic parameter in the model are still key problems that need to be overcome in current research. Solving the above problems will help to gain a deeper understanding of the mechanical behavior of gas hydrate sediments, and provide more accurate predictions and guidance for natural gas extraction and climate change research. Summary of the invention

[0004] In view of the defects of existing methods and the shortcomings of practical applications, in order to deeply explore the mechanical properties of hydrate sediments and simulate hydrate sediments in the form of gravel particles, the present invention regulates the relative position between hydrates and sand particles based on the sand particle model, controls the hydrate occurrence mode and saturation, and can not only observe the deformation and destruction process of hydrate sediments from a macroscopic perspective, but also deeply reveal the internal mechanism of its deformation and destruction. In the first aspect, the present invention provides a method for simulating natural gas hydrate sediments based on discrete elements, and the method includes the following steps: setting a cylindrical space model of a specific size, placing gravel in the cylindrical space model to obtain the initial arrangement result of sand particles; introducing a grid method, and obtaining the distance between the centers of particles and hydrate samples according to the grid method and the initial arrangement result of sand particles; constructing a hydrate occurrence mode, and adjusting the distance between the centers of particles according to the hydrate occurrence mode to obtain the target hydrate saturation; and generating a hydrate sediment sample by combining the target hydrate saturation, the hydrate sample and the pure sand sample. The present invention sets a cylindrical space model of a specific size according to specific steps and generates hydrate sediment samples, fully considering the mechanical properties of hydrate sediments in particle form, thereby revealing the macro- and micro-deformation conditions and failure mechanisms of hydrate sediments.

[0005] Optionally, the setting of a cylindrical space model of a specific size and placing gravel in the cylindrical space model to obtain the initial arrangement result of the sand grains includes: introducing an isotropic compression stress method; and setting a cylindrical space model of a specific size based on a predetermined porosity and the isotropic compression stress method. The present invention introduces an isotropic compression stress method and sets a cylindrical space model of a specific size based on a predetermined porosity to obtain the initial arrangement result of the sand grains, which can not only improve the accuracy and reliability of the experimental results, but also promote the in-depth development of sediment mechanics research, and has important practical application value.

[0006] Optionally, the obtaining of the distance between the centers of particles and the hydrate sample according to the grid method and the initial arrangement result of the sand particles includes: obtaining a hydrate template based on the grid method and the initial arrangement result of the sand particles; detecting the hydrate template to obtain the distance between the centers of particles in the hydrate sample; optimizing the hydrate template according to the distance between the centers of particles, and obtaining the hydrate sample. The present invention can accurately obtain the relative position information between the sand particles based on detecting the distance between the centers of particles in the hydrate template, which helps to more accurately simulate the stress distribution and deformation behavior inside the sediment.

[0007] Optionally, the construction of the hydrate occurrence mode includes: setting a pore filling mode, a contact cementation mode, a particle coating mode and a skeleton pressure mode; combining the pore filling mode, the contact cementation mode, the particle coating mode and the skeleton pressure mode to construct the hydrate occurrence mode. The occurrence state of hydrates in sediments is diverse. The present invention sets different occurrence modes, which can more accurately describe the specific morphology and distribution of hydrates in sediments, and can more deeply understand the formation mechanism and distribution law of hydrates.

[0008] Optionally, adjusting the distance between the centers of the particles according to the hydrate occurrence mode to obtain the target hydrate saturation includes: analyzing the sand distance thresholds of different occurrence modes according to the hydrate occurrence mode; and adjusting the distance between the centers of the particles according to the sand distance threshold to achieve control of the target hydrate saturation. The present invention analyzes the sand distance thresholds of different occurrence modes to further understand the relationship between the particle center distance and the hydrate saturation under different occurrence modes.

[0009] Optionally, the target hydrate saturation satisfies the following relationship:

[0010]

[0011] in, is the hydrate saturation, is the total volume of hydrate, The relationship of the present invention clearly defines the hydrate saturation, that is, the ratio of the total volume of hydrates to the total volume of the sample pores, which is helpful for the subsequent unified understanding and calculation of hydrate saturation.

[0012] Optionally, the total pore volume of the sample satisfies the following relationship:

[0013]

[0014] in, is the total pore volume of the sample, is the total pore volume of the pure sand sample, The total volume of the sand particles is subtracted from the sample volume. The present invention calculates the total pore volume by the total pore volume of the pure sand sample and the total volume of the sand particles, which can reduce the error caused by directly measuring the pore volume of complex samples, thereby improving the accuracy of the pore volume analysis results.

[0015] Optionally, the generating of the hydrate sediment sample by combining the hydrate target saturation, the hydrate sample and the pure sand sample comprises: obtaining the coordinates of the hydrate target particles by combining the hydrate target saturation and the hydrate sample. The present invention accurately controls the distribution and quantity of hydrate particles, and can more deeply analyze the distribution of hydrates in sediments.

[0016] Optionally, the generating of the hydrate sediment sample by combining the hydrate target saturation, the hydrate sample and the pure sand sample comprises: introducing DEM modeling technology; integrating the hydrate target particle coordinates and the pure sand sample based on the DEM modeling technology to prepare the hydrate sediment sample. The DEM modeling technology of the present invention can accurately simulate the distribution and arrangement of hydrate particles in the pure sand sample, thereby ensuring the accuracy of the hydrate target particle coordinates, and is conducive to accurately controlling the number, size and distribution of hydrate particles to meet specific hydrate target saturation requirements.

[0017] In the second aspect, the present invention also provides a natural gas hydrate sediment simulation system based on discrete elements, which can efficiently execute the natural gas hydrate sediment simulation method based on discrete elements provided by the present invention, the system includes an input device, a processor, an output device and a memory, wherein the input device, the processor, the output device and the memory are interconnected, the memory includes the natural gas hydrate sediment simulation method based on discrete elements as described in the first aspect of the present invention, the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions. The system provided by the present invention has a compact structure, strong applicability, and greatly improves the operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The flowchart of the method for simulating natural gas hydrate-containing sediments based on discrete elements of the present invention;

[0019] Figure 2 It is a schematic flow chart of a natural gas hydrate-containing sediment simulation model based on discrete elements in the natural gas hydrate-containing sediment simulation method based on discrete elements of the present invention;

[0020] Figure 3 It is a schematic structural diagram of the discrete element-based natural gas hydrate-containing sediment simulation system of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0022] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0023] See also Figure 1 In order to explore the deformation and destruction mechanism of hydrate sediments at the macro and micro scales, it is necessary to reconstruct the hydrate distribution in real conditions and perform numerical simulation analysis. The present invention provides a method and system for simulating natural gas hydrate sediments based on discrete elements. The method for simulating natural gas hydrate sediments based on discrete elements includes the following steps:

[0024] S1. Set up a cylindrical space model of a specific size and place gravel in the cylindrical space model to obtain the initial arrangement result of the sand particles. The specific implementation steps and related contents are as follows:

[0025] In this embodiment, an isotropic compressive stress method is introduced based on the isotropic compressive stress principle, and a cylindrical space model of a specific size is designed based on a predetermined porosity parameter.

[0026] First, fill the sand into a cylindrical space of a specified size to ensure that the sand layout after filling meets the preset porosity requirements. In order to be closer to the stress environment experienced by sand in nature, the embodiment applies a constant 1 MPa isotropic compressive stress to the sand through isotropic compressive stress technology to simulate the compaction process under actual conditions.

[0027] At the same time, a pure hydrate cube template matching the cylindrical space was also made. Since the size of hydrate particles is quite different from that of matrix sand particles, if full-size hydrate samples are directly prepared, it will bring high costs. Therefore, the embodiment uses the above template to conduct isotropic compression experiments, and also applies a compressive stress of 1 MPa to obtain the initial arrangement results of the sand particles.

[0028] The above implementation process can control economic costs and effectively simulate the mechanical behavior of hydrate sediments under specific stress conditions, laying a solid technical foundation for the simulation method of natural gas hydrate-containing sediments.

[0029] Furthermore, in this embodiment, the method for obtaining the initial arrangement results of sand particles based on the cylindrical space model is only an optional condition of the present invention. In one or some other embodiments, the method for obtaining the initial arrangement results of sand particles can be changed according to the characteristics of the hydrate deposits and the actual simulation requirements. For specific hydrate deposit types and simulation objectives, a suitable sand arrangement method is selected to maximize the efficiency and effect of the simulation experiment, which helps to reveal more details and mechanisms about the mechanical behavior of hydrate deposits.

[0030] S2. Based on the above initial arrangement of sand particles, the distance between particle centers and hydrate samples are obtained. The specific implementation steps and related contents are as follows:

[0031] Firstly, a hydrate template is obtained according to the initial arrangement result of the sand particles.

[0032] According to the initial arrangement of sand particles obtained in step S1, a hydrate template matching it was created. At the same time, the grid method proposed by Duan and Cheng was used to copy the above template layer by layer through MATLAB script to construct a complete hydrate sample. This method not only ensures the precise correspondence between the hydrate sample and the sand particle layout, but also greatly improves the sample preparation efficiency and accuracy.

[0033] According to the initial arrangement of sand particles obtained in step S1, a hydrate template matching it is created. Since the number of hydrates is large, it is impossible to generate them directly in the simulation software at the same size as the sand particles, so the grid method proposed by Duan and Cheng is used. Through the MATLAB script, the hydrate generation process is divided into multiple grid unit operations, thereby simplifying the calculation and speeding up the generation speed. The above method effectively improves the generation efficiency of hydrate samples, while ensuring that the generated hydrates correspond to the sand particle layout.

[0034] The specific implementation steps of the grid method in this embodiment are as follows:

[0035] Meshing: First, the simulation space is divided into a certain number of grid cells. The size of each grid cell is determined by the characteristic size of the hydrate to ensure that the hydrate distribution within each cell can be simplified to appropriate boundary conditions and rules.

[0036] Layered generation: Hydrate samples are generated layer by layer through MATLAB scripts. In each layer, the number of hydrates in the grid cells is determined according to the layout and distribution of the sand particles. Since the grid method only generates hydrates, the position and size of the sand particles are only used as a reference to ensure that the overall layout of the hydrates matches the overall structure of the sand particles.

[0037] Sample splicing: The system gradually generates a complete three-dimensional hydrate sample by copying and splicing the hydrate distribution in the grid cells. The grid method can significantly reduce the amount of calculation and improve the generation efficiency by reducing the complex calculation of each unit.

[0038] Structural optimization: After generating the hydrate sample, the script optimizes the entire sample to ensure that the hydrate structure between each grid unit is continuous and unbroken, avoiding problems such as structural defects caused by splicing.

[0039] Through the above-mentioned grid method, hydrate samples can be generated quickly and efficiently without being directly generated with the same size as sand particles, and the precise correspondence between the hydrate and sand particle layout is ensured, which not only solves the technical problem that a large number of hydrates cannot be directly generated, but also improves the overall preparation efficiency and accuracy of the sample. The hydrate template is tested to obtain the distance between the centers of the particles in the hydrate sample; and the hydrate template is optimized according to the distance between the centers of the particles to obtain the hydrate sample.

[0040] In the process of preparing hydrate samples, the above hydrate templates are first tested to accurately measure the distance between the centers of particles in the sample. Subsequently, the hydrate templates are optimized based on the relevant distance data. This optimization step is aimed at ensuring that the arrangement between particles is both tight and reasonable, and avoiding overlap and other phenomena.

[0041] Specifically, the method of accurately locating particles is adopted in the embodiment, and the distance between the centers of particles is strictly monitored. If the distance between two particles is found to be less than the sum of their respective radii, it indicates that the two particles overlap, and one of the overlapping particles will be immediately removed to ensure that the hydrate structure in the pore space remains dense and orderly, thereby obtaining and obtaining the hydrate sample of the embodiment.

[0042] Through the above method, hydrate samples that meet the predetermined porosity requirements and have good mechanical properties are prepared, providing strong experimental and data support for subsequent work.

[0043] Furthermore, in the present embodiment, the method for obtaining the hydrate sample is only an optional condition of the present invention. In one or some other embodiments, the method for obtaining the hydrate sample can be adjusted according to the actual situation of the hydrate and the simulation requirements, and the method for obtaining the hydrate sample can be adjusted, so that the present invention can better adapt to various complex and changeable hydrate characteristics, thereby ensuring the accuracy and reliability of the simulation results.

[0044] S3. Construct a hydrate occurrence model and adjust the distance between particle centers according to the hydrate occurrence model to obtain the target hydrate saturation. The specific implementation steps and related contents are as follows:

[0045] The pore filling mode, contact cementation mode, particle coating mode and skeleton pressure mode are set, and the hydrate occurrence mode is constructed by combining the pore filling mode, contact cementation mode, particle coating mode and skeleton pressure mode. The specific contents are as follows:

[0046] When constructing the hydrate occurrence mode, four modes are mainly set in the embodiment: pore filling type, contact cementation type, particle coating type and skeleton pressure type. Different modes reflect the different existence modes of hydrate in sandy environment.

[0047] The pore filling mode can simulate the pore space filled by hydrates in sandy materials under natural conditions. In order to accurately simulate the process of methane gas migrating through the pores of sand under specific pressure and temperature conditions and forming hydrates in the pores, the hydrate particles with a radius equal to the surface of the sand particles, which can be set to within 0.1 mm in the simulation test, are further deleted. The above processing method helps to better understand the formation and distribution of hydrates in pores.

[0048] The contact cementation model focuses on the formation of hydrates at the contact points of sand particles, and plays a role in enhancing the mechanical strength of the sand structure. In the examples, by deleting hydrate particles far away from the particle contact points, the formation process of hydrates as a binder at the particle contact points under natural conditions is simulated, which helps to reveal the influence of hydrates on the overall mechanical properties of sandy materials.

[0049] The particle coating mode specifically refers to that, in certain natural environments, hydrates often form a coating layer around sand particles. This coating layer will change the surface characteristics of the sand particles and their geotechnical engineering properties. In order to simulate relevant natural phenomena, the embodiments retain hydrate particles within a certain distance from the surface of the sand particles to simulate the close bonding between the hydrates and the surface of the sand particles, which helps to deeply understand the influence of the hydrate coating layer on the mechanical properties of the sand particles.

[0050] The skeleton pressure mode is similar to the pore filling mode, but it focuses more on simulating the cluster structure formed by hydrates under sand load, and the contribution of related structures to the mechanical stability of the sand structure. When selecting hydrate particles, a method similar to the pore filling mode is used in the embodiment, but the sample is pre-loaded so that the hydrate clusters can play a role in load transfer in the sand matrix, which helps to reveal the load transfer mechanism of hydrates in sandy materials and its impact on the overall mechanical properties.

[0051] By combining the above four modes, the hydrate occurrence mode of the embodiment can be obtained. The above hydrate occurrence mode not only improves the depth and breadth of the understanding of the occurrence state of hydrates in sandy environments, but also provides a reference for the mechanical behavior under complex geological conditions. Based on this, it is possible to more comprehensively and systematically explore the distribution law, stability characteristics of hydrates and their potential impact on surrounding formations, thereby providing more accurate and reliable basis and guidance for key links such as risk assessment, resource exploitation, and geological disaster prevention in engineering applications.

[0052] The sand grain distance thresholds of different occurrence modes are analyzed according to the hydrate occurrence mode; at the same time, the distance between the particle centers is adjusted according to the sand grain distance threshold to achieve the control of the hydrate target saturation.

[0053] Firstly, the sand particle distance thresholds under different hydrate occurrence modes were analyzed according to the hydrate occurrence modes. The thresholds corresponding to different modes are helpful to understand the distribution of hydrates in sandy environments. Based on the distance thresholds of different modes, the distance between particle centers can be further adjusted to ensure that the predetermined hydrate target saturation can be achieved.

[0054] In the process of regulating the distribution of hydrates, a method related to the sand grain distance threshold is used in the embodiment. The distribution of hydrates in sediment particles is adjusted according to the thresholds of different modes to keep it consistent with the four common occurrence modes in the natural environment. For hydrate particles that do not meet the requirements of a specific occurrence mode, removal measures are taken. This method can systematically and randomly delete hydrate particles that do not meet the requirements, thereby achieving precise control of hydrate saturation.

[0055] The above hydrate target saturation satisfies the following relationship:

[0056]

[0057] in, is the hydrate saturation, is the total volume of hydrate, is the total pore volume of the sample.

[0058] Furthermore, the total pore volume of the above samples satisfies the following relationship:

[0059]

[0060] in, is the total pore volume of the sample, is the total pore volume of the pure sand sample, The total volume of the sand is subtracted from the sample volume.

[0061] Furthermore, in the present embodiment, the control method of the target hydrate saturation is only an optional condition of the present invention. In one or some other embodiments, the control method of the target hydrate saturation can be optimized according to the actual application of the natural gas hydrate deposition simulation method and the target requirements of hydrates. The present invention can better adapt to various complex and changeable natural gas hydrate deposition characteristics and different hydrate saturation requirements, thereby ensuring the accuracy and reliability of experimental or application results.

[0062] S4. Combine the above hydrate target saturation, hydrate sample and pure sand sample to generate hydrate sediment sample. The specific implementation steps and related contents are as follows:

[0063] First, on the basis of achieving the preset hydrate target saturation standard, a series of cutting-edge computing technologies and precise analytical tools are used, while the physical properties and chemical characteristics of the hydrate samples are comprehensively considered, so that the specific positions of the target hydrate particles can be accurately identified and located.

[0064] Next, the self-written MATLAB code is used to process the above-identified hydrate particle position information and export it in the form of coordinate data. MATLAB in the embodiment is an efficient programming tool with powerful data processing and numerical calculation capabilities, and can accurately process complex spatial data and geometric arrangements. By writing a special script, the position information of hydrate particles in three-dimensional space can be automatically read and converted into a standard coordinate format (such as CSV or TXT file) for subsequent experimental verification, simulation analysis and industrial application.

[0065] The implementation process for obtaining the position of hydrate particles is as follows:

[0066] Hydrate particle information reading: Use MATLAB script to read the initial position information of hydrate particles from the stored 3D data file. The reading process includes but is not limited to parsing the data file and extracting the 3D coordinates of the particles. , and perform preliminary normalization on the relevant data to ensure that the units and formats of all data points are consistent.

[0067] Coordinate data conversion and export: After reading and processing the hydrate particle data, the MATLAB code will store and export the position information of these particles in a standard coordinate format. The exported coordinate data file can be in CSV, TXT or other common file formats for subsequent use and analysis. Each data point corresponds to the three-dimensional coordinates of a hydrate particle. The data structure in the embodiment is clear, which is helpful for further processing and analysis.

[0068] Data visualization: In order to more intuitively display the distribution of hydrate particles, the MATLAB code can also visualize the exported coordinate data. Through the built-in graphics function of MATLAB, a three-dimensional scatter plot or other geometric figures can be generated to show the distribution of hydrate particles in three-dimensional space. The above visualization process can help researchers understand the spatial relationship between hydrates and sand particles more intuitively.

[0069] Data optimization and correction: Before data export, the MATLAB code also provides data cleaning and optimization functions to ensure that the exported coordinate data does not contain errors or anomalies. In an optional embodiment, isolated, invalid or duplicate particle data is automatically detected and removed to ensure that the exported data has high accuracy and completeness.

[0070] The equipment support content is as follows: Computer hardware: In this embodiment, the position information processing and exporting of hydrate particles are performed on a standard high-performance computer. The computer configuration includes but is not limited to a 64-bit processor, at least 16GB of memory and 500GB of hard disk space to ensure the smoothness of large-scale data processing.

[0071] Software environment: MATLAB 2021b and its related toolkits, mainly including the data processing toolbox and the graphics visualization toolbox, are the core software platform of this embodiment, responsible for the automated processing and calculation of the entire process from reading to exporting.

[0072] In this embodiment, the coordinate information of the hydrate target particles is first obtained through precise measurement and calculation. The above information records the precise position of each hydrate particle in three-dimensional space in detail to ensure the accuracy and completeness of the data, providing a reliable basis for subsequent research and application. At the same time, according to the specific experimental or application requirements, the coordinate information is properly processed and analyzed to obtain more valuable hydrate particle position information.

[0073] Based on this, the coordinates of the hydrate target particles were effectively combined with the target saturation of the hydrate sample to generate the final hydrate target particle coordinate data. The above data provides strong support for subsequent research, simulation analysis and industrial application.

[0074] In order to effectively integrate hydrate particles into pure sand samples and further prepare hydrate sediment samples, this embodiment introduces the discrete element method (DEM) modeling technology. DEM technology is a numerical method for simulating the behavior of granular materials, and is particularly suitable for simulating the microscopic movement and contact behavior of particles. In the present invention, DEM technology is used to accurately simulate the interaction between hydrate particles and sand particles, ensuring that the generated hydrate sediment samples have good structural stability and real physical properties.

[0075] The specific implementation steps are as follows:

[0076] 1. Set initial conditions:

[0077] First, the coordinate data of the hydrate target particles generated by MATLAB were imported into the DEM simulation environment. At the same time, a pure sand sample with uniform mass was selected as the matrix material, and its initial layout was set according to the experimental requirements to ensure that the hydrate particles and sand particles can be reasonably distributed in the same space. The pure sand sample has uniform physical and chemical properties, which provides a stable foundation for the subsequent modeling and integration process.

[0078] 2. Define particle properties:

[0079] In the DEM modeling process, the physical properties of hydrate particles and sand particles need to be defined separately. The above properties include but are not limited to particle diameter, density, Young's modulus, Poisson's ratio, friction coefficient and contact cementation bond strength. The physical parameters can be set according to actual data from experiments or literature to ensure the accuracy of the modeling process.

[0080] 3. Set the interface contact model:

[0081] In DEM modeling, the key step is to define the contact model between particles. This embodiment uses a parallel cementation-softening contact model to simulate the contact mechanical behavior between hydrate particles and sand particles. The above model can accurately describe the normal force and tangential force when the particles are in contact, as well as the cementation of hydrate particles and the strength softening behavior when they are destroyed. By setting the contact model, it can be ensured that the interaction between particles conforms to the actual physical laws.

[0082] 4. Generate particle integration and sediment:

[0083] In the DEM simulation environment, hydrate particles and sand particles are gradually integrated through gravity and contact force. In this process, hydrate particles will settle in the pure sand sample and form a stable sediment structure. DEM technology can accurately track the movement trajectory of each particle to ensure that the relative position of hydrate particles and sand particles remains consistent, thereby simulating the natural sedimentation process of the entire sample.

[0084] 5. Fine integration and simulation analysis:

[0085] After entering the core link of DEM modeling software, according to the coordinates of hydrate target particles, hydrate particles are integrated into the three-dimensional model of pure sand samples one by one in a virtual form. The above process requires not only extremely high accuracy, but also in-depth understanding and proficiency in DEM modeling technology to ensure that each hydrate particle can be accurately placed in the predetermined position while maintaining its original physical and chemical properties. In this process, the powerful simulation capability of DEM modeling technology is fully utilized to simulate and analyze the interaction between hydrate particles and pure sand matrix, which helps to gain a deeper understanding of the distribution law of hydrates in sediments and their interaction mechanism with the surrounding environment.

[0086] 6. Simulation results output and optimization:

[0087] Finally, through careful integration and simulation, hydrate sediment samples that meet specific requirements were generated. The above samples not only accurately show the distribution of hydrate particles, but also retain the original characteristics of pure sand samples, providing a valuable technical basis for subsequent experimental research and industrial applications.

[0088] By introducing DEM modeling technology, this example successfully achieved the efficient integration of hydrate target particle coordinates and pure sand samples, and prepared hydrate sediment samples that meet specific needs. This process not only demonstrated the great potential of DEM modeling technology in geological and material science research, but also provided strong support for future in-depth research and industrial applications.

[0089] The simulation method of natural gas hydrate sediments proposed in this embodiment uses the Particle Flow Code (PFC) software. PFC is a numerical simulation tool based on the discrete element method (DEM), which is widely used in the simulation of mechanical behavior of granular materials. The software can effectively simulate the contact, collision, friction and stress transfer between particles, and is suitable for simulating the movement and interaction of granular materials. In the embodiment, the PFC software is used to generate and simulate the distribution of hydrate particles in natural gas hydrate sediments, and then integrate them with pure sand matrix particles. By using the PFC software, the natural gas hydrate sediment simulation method in this embodiment not only significantly improves the modeling efficiency, but also ensures that the distribution of hydrate particles conforms to the physical laws in the actual geological environment. The powerful particle simulation capability of the PFC software enables the interaction between hydrates and sand particles to be accurately simulated, reducing the time and workload required for repeated trials and adjustments in the traditional random addition method, and greatly accelerating the process of natural gas hydrate sediment simulation. At the same time, the discrete element method (DEM) is also combined in this embodiment, which can explore the mechanical effects of different hydrate distribution forms in engineering practice, ranging from fine morphology at the pore scale, such as various occurrence modes, to heterogeneous structures at the macro level, including but not limited to layered, nodular or vein-like structures. The simulation method of natural gas hydrate-containing sediments based on discrete elements helps to deeply understand and predict the mechanical behavior of hydrate sediments.

[0090] In this example, by considering the relative layout of hydrate and sand particles in space, using differentiated distance thresholds as the basis for particle selection, the real hydrate distribution pattern is efficiently reconstructed under the three-dimensional discrete element simulation technology, and further numerical simulation analysis is carried out. For details, please refer to Figure 2 .

[0091] See also Figure 3 In an optional embodiment, in order to efficiently execute the natural gas hydrate-containing sediment simulation method based on discrete elements provided by the present invention, the present invention also provides a natural gas hydrate-containing sediment simulation system based on discrete elements, the natural gas hydrate-containing sediment simulation system based on discrete elements includes a processor, an input device, an output device and a memory, the processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, the computer program includes program instructions, the processor is configured to call the program instructions, and execute the natural gas hydrate-containing sediment simulation method based on discrete elements and the specific steps of the related embodiments provided by the present invention. The natural gas hydrate-containing sediment simulation system based on discrete elements of the present invention has a complete structure and is objectively stable.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for simulating natural gas hydrate-containing sediments based on discrete elements, characterized in that: The steps include: Setting a cylindrical space model of a specific size, placing gravel in the cylindrical space model to obtain an initial arrangement result of the gravel; A grid method is introduced, and the distance between the centers of the particles and the hydrate sample are obtained according to the grid method and the initial arrangement result of the sand particles; constructing a hydrate occurrence pattern, and adjusting the distance between the centers of the particles according to the hydrate occurrence pattern to obtain a target hydrate saturation; generating a hydrate sediment sample by combining the hydrate target saturation, the hydrate sample and the pure sand sample; The step of setting a cylindrical space model of a specific size and placing gravel in the cylindrical space model to obtain an initial arrangement result of the gravel comprises: Introducing the isotropic compressive stress method; A cylindrical space model of a specific size is set based on a predetermined porosity and isotropic compressive stress method; The obtaining of the distance between the centers of particles and the hydrate sample according to the grid method and the initial arrangement result of the sand particles comprises: Based on the initial arrangement of the sand particles, a hydrate template matching the overall structure of the sand and gravel is created, and the template is replicated layer by layer using the grid method to construct a complete hydrate sample. Detecting the hydrate template to obtain the distance between the centers of particles in the hydrate sample; The hydrate template is optimized according to the distance between the centers of the particles, and a hydrate sample is obtained.

2. The method for simulating natural gas hydrate-containing sediments based on discrete elements according to claim 1, characterized in that: The constructing of the hydrate occurrence mode comprises: Set pore filling mode, contact bonding mode, particle coating mode and skeleton pressure bearing mode; The hydrate occurrence model is constructed by combining the pore filling model, the contact cementation model, the particle coating model and the skeleton pressure-bearing model.

3. The method for simulating natural gas hydrate-containing sediments based on discrete elements according to claim 2, characterized in that: The adjusting the distance between the centers of the particles according to the hydrate occurrence mode to obtain the target hydrate saturation includes: Analyze the sand distance thresholds of different occurrence modes according to the hydrate occurrence mode; The distance between the centers of the particles is adjusted according to the sand grain distance threshold to achieve control of the target hydrate saturation.

4. The method for simulating natural gas hydrate-containing sediments based on discrete elements according to claim 3, characterized in that: The target hydrate saturation satisfies the following relationship: ， in, is the hydrate saturation, is the total volume of hydrate, is the total pore volume.

5. The method for simulating natural gas hydrate-containing sediments based on discrete elements according to claim 1, characterized in that: The step of combining the hydrate target saturation, the hydrate sample and the pure sand sample to generate a hydrate sediment sample comprises: combining the hydrate target saturation and the hydrate sample to obtain the coordinates of the hydrate target particles; Introducing DEM modeling technology; The hydrate target particle coordinates and the pure sand sample are integrated based on the DEM modeling technology to generate a hydrate sediment sample.

6. A natural gas hydrate sediment simulation system based on discrete elements, characterized in that: The system includes a processor, an input device, an output device and a memory, wherein the processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions to execute the discrete element-based natural gas hydrate sediment simulation method as described in any one of claims 1 to 5.

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