CO2 migration dimension reduction simulation method based on plume radius matching

Abstract

The invention discloses a CO2 migration dimension reduction simulation method based on plume migration radius matching, which comprises the following steps: establishing a three-dimensional numerical model of a target reservoir, and simulating CO2 migration at a preset three-dimensional injection rate to obtain a three-dimensional CO2 plume in preset time; based on the three-dimensional CO2 plume, determining the maximum transverse migration radius of CO2; establishing a two-dimensional vertical profile model corresponding to the three-dimensional numerical model; and an equivalent injection rate is determined, so that the transverse migration radius of the CO2 plume formed by the two-dimensional vertical profile model at the same preset time is matched with the maximum transverse migration radius. According to the method, the calculation efficiency can be greatly improved while the simulation precision of the key area is ensured, and an efficient and reliable simulation tool is provided for long-term performance prediction and complex working condition analysis of a CO2 storage project under multi-physics field coupling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of CO2 geological storage, and particularly relates to a dimension reduction simulation method for improving the calculation efficiency of multi-physical field coupling simulation of CO2 migration. BACKGROUND

[0002] CO2 geological storage is a key technical path to achieve the goal of carbon neutrality. Before the implementation of the project, accurate prediction of the migration, distribution and interaction with the surrounding environment of CO2 injected into the underground saline aquifer is a core link to evaluate the long-term safety and effectiveness of the project. Thermal-hydraulic-mechanical-chemical (THMC) fully coupled three-dimensional numerical simulation is recognized as the most accurate prediction tool at present, which can comprehensively consider the complex interaction of temperature field, pore pressure field, geostress field and geochemical reaction field caused by injection. However, the huge advantage of three-dimensional THMC coupling simulation is accompanied by its insurmountable defect: extremely high calculation cost. The control equation set is large and highly nonlinear, and needs to be solved for a three-dimensional geological model containing hundreds of thousands or even millions of grids, resulting in a calculation time of a single simulation condition often in weeks or months. This high time cost seriously restricts the development of project optimization, parameter sensitivity analysis and risk assessment work. In order to solve the problem of calculation efficiency, researchers often use two-dimensional models for simplified simulation, such as two-dimensional radial or profile models. However, the traditional dimension reduction method is usually based on the simple conversion of the total injection amount, such as distributing according to the thickness of the model, to determine the injection rate of the two-dimensional model. This method ignores the "gravity differentiation" effect of CO2 upward migration and expansion at the top of the reservoir in three-dimensional space driven by gravity and buoyancy. As a result, the CO2 plume shape of the two-dimensional simulation, especially the expansion characteristics in the vertical and horizontal directions, is quite different from the true three-dimensional case, which will cause great deviation in the subsequent analysis of the coupled temperature field, stress field, etc., thereby losing its scientific guiding significance. Therefore, there is an urgent need in the art for a new dimension reduction method that can achieve high efficiency of two-dimensional model while ensuring high consistency with three-dimensional model in key physical behaviors. SUMMARY

[0003] The present application provides a CO2 migration dimension reduction simulation method based on plume radius matching, which matches the key spatial characteristics of CO2 plume in three-dimensional and two-dimensional models to determine the equivalent injection parameters of the two-dimensional model, thereby providing an efficient and reliable front-end model for subsequent complex coupling simulation, in order to solve the technical problems in the prior art that three-dimensional multi-physical field coupling simulation has limited practicality due to high calculation cost and long time consumption, and the simulation accuracy of traditional two-dimensional dimension reduction method is seriously insufficient due to excessive simplification of mechanism.

[0004] The technical scheme employed by the present application is as follows: A CO2 migration dimension reduction simulation method based on plume radius matching, comprising the following steps: S1, a three-dimensional numerical model of a target reservoir is established, and a preset three-dimensional injection rate Q 3D CO2 migration is simulated to obtain a three-dimensional CO2 plume at a preset time t; S2, based on the three-dimensional CO2 plume, a maximum lateral migration radius of CO2 is determined ; S3, a two-dimensional vertical profile model corresponding to the three-dimensional numerical model is established; S4, an equivalent injection rate Q 2D is determined, which can make the lateral migration radius of the CO2 plume formed by the two-dimensional vertical profile model at the same preset time t match the maximum lateral migration radius determined in step S2 .

[0005] In the above scheme, the geometric shape of the three-dimensional CO2 plume is assumed to be a cone, and the maximum lateral migration radius of the cone is the radius of the base of the cone.

[0006] In the above scheme, the swept range of the CO2 plume in the two-dimensional vertical profile model is assumed to be a triangle, and the lateral migration radius of the triangle is half the length of the base.

[0007] In the above scheme, in S4, the equivalent injection rate Q 2D is calculated by the following formula:

[0008] wherein, is the equivalent slice thickness of the two-dimensional model; is the maximum lateral migration radius of the matched CO2 plume, and has .

[0009] In the above scheme, in S2 and S4, the condition for defining the boundary of the CO2 plume is that the CO2 saturation reaches a preset non-zero threshold.

[0010] In the above scheme, the geological structure, grid division and physical property parameters of the two-dimensional vertical profile model are consistent with the corresponding profile of the injection well in the three-dimensional numerical model.

[0011] In the above scheme, the preset time t is 1-3 months.

[0012] In the above scheme, in S1, the preset three-dimensional injection rate Q 3D is the actual injection rate of engineering design.

[0013] In the above scheme, in S3, the two-dimensional vertical profile model established is a two-dimensional radial model.

[0014] The present application has the following advantages: 1. Unification of efficiency and accuracy: The present method reduces the core transport problem from 3D to 2D, greatly reducing the number of grids and solving complexity, saving valuable computing time for subsequent THMC coupling simulation. At the same time, through the physical constraint of "plume radius matching", the high fidelity of the reduced dimension model in the key indicator of CO2 sweep range is ensured, ensuring the accuracy of the subsequent coupling analysis.

[0015] 2. Clear physical meaning: The present method does not rely on simple flow arithmetic conversion, but ensures the equivalence of the reservoir profile volume swept by the fluid before and after dimension reduction (in two dimensions, it is reflected as area). This can better reflect the comprehensive embodiment of key three-dimensional physical effects such as gravity and buoyancy in the two-dimensional model, and its physical basis is more solid.

[0016] 3. Strong practicability and operability: The steps of the present method are clear, the logic is simple, and it can be implemented based on any mainstream commercial or open source numerical simulation software without modifying the software kernel, and it is easy to popularize and apply in engineering projects and scientific research. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 is a flowchart of the CO2 transport dimension reduction simulation method based on plume radius matching in the embodiments of the present application; Figure 2 is a comparison chart of CO2 transport sweep range of three-dimensional model at three months and two-dimensional model determined by the present method in the embodiments of the present application. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will further describe the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0020] It should be noted that the diagrams provided in the embodiments of the present application only schematically illustrate the basic concepts of the present application, and therefore only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation, the mode, number and proportion of each component in actual implementation can be arbitrarily changed, and the component layout mode can be more complex.

[0021] As shown in Figure 1 , a CO2 migration dimensionality reduction simulation method based on plume radius matching includes the following steps: S1, establishing a three-dimensional model and performing preliminary migration simulation According to the geological, petrophysical and fluid parameters of the target reservoir, a refined three-dimensional numerical model is established. In the model, the CO2 injection process is simulated at the actual injection rate designed by engineering, and a relatively short preset time, such as 1-3 months, is run to obtain the stable initial plume formed by CO2 in three-dimensional space at this time point.

[0022] S2, analyzing the three-dimensional plume and determining the maximum lateral migration radius of CO2 Based on the simulation results of step S1, first, a preset non-zero CO2 saturation threshold (such as 0.0001) is used as the plume boundary. Then, the macroscopic shape of the three-dimensional CO2 plume is geometrically approximated, and it is assumed that the main shape is a circular cone. The cross section of the injection well is extracted, and the maximum lateral migration radius of the three-dimensional CO2 plume is determined accordingly , which corresponds to the radius of the bottom surface of the approximate circular cone.

[0023] S3, establishing a two-dimensional model and assuming the plume shape According to the three-dimensional numerical model, a corresponding two-dimensional vertical profile model (such as a two-dimensional radial model) is constructed, ensuring that its geological structure, grid division and physical property parameters remain consistent with the profile of the injection well in the three-dimensional numerical model. It is assumed that the sweep range of the CO2 plume in the two-dimensional vertical profile model is a triangle.

[0024] S4, radius matching and equivalent injection rate determination Set the core matching criterion: the lateral migration radius of the CO2 plume formed in the two-dimensional vertical profile model at the same preset time t should be equal to the maximum lateral migration radius of the three-dimensional CO2 plume determined in step S2 . This criterion is realized through a mathematical formula derived based on the volume equivalence principle, which establishes the relationship between the three-dimensional injection rate Q 3D and the two-dimensional equivalent injection rate Q 2D :

[0025] By simplifying this formula, we can obtain the formula for directly calculating the two-dimensional equivalent injection rate Q. 2D The final expression:

[0026] In the formula, This refers to the three-dimensional injection rate; Let be the two-dimensional equivalent injection rate to be determined; The maximum lateral transport radius of the matched CO2 plume is determined by step S2; Reservoir thickness; This is the equivalent slice thickness of the two-dimensional model (usually set to 1).

[0027] This method allows us to determine an equivalent injection rate that can accurately reproduce the characteristics of a three-dimensional CO2 plume profile in a two-dimensional model.

[0028] The method of the present invention will be illustrated below through a specific embodiment. This embodiment aims to perform dimensionality reduction processing before THMC fully coupled simulation for a CO2 sequestration project in a deep saline aquifer.

[0029] S1. Establish a three-dimensional model and conduct preliminary transport simulation. A three-dimensional geological model representing the target reservoir was constructed at a depth of 1178 meters. The model is 775 meters long and 775 meters wide, divided into 155 grids in each direction. The model height is 200 meters, divided into 100 grids, each 2 meters high. From top to bottom, the model consists of 41 grids representing the caprock and 59 grids representing the reservoir. The reservoir is further subdivided into 8 smaller segments with thicknesses of 18 meters, 32 meters, 12 meters, 6 meters, 8 meters, 6 meters, 14 meters, and 22 meters. The injection well is located at the center of the model along its length, with perforation depths of 1322-1326 meters and 1336-1340 meters. The actual CO2 injection rate was set at 70,000 tons per day. A three-month CO2 injection and migration simulation was conducted using the multiphase flow simulation software TOUGH2.

[0030] S2. Analyze the three-dimensional plume and determine the maximum lateral transport radius. After the simulation, three-dimensional CO2 saturation field data at 3 months were exported. The data were then visualized using post-processing software. The region with a CO2 saturation of 0.0001 was defined as the plume boundary. Observations revealed that the plume body exhibited a conical shape, wider at the top and narrower at the bottom. The maximum lateral migration radius of this plume at the top of the reservoir was measured, yielding... = 65.21m.

[0031] S3. Establish a two-dimensional model and assume the plume morphology. Based on the aforementioned 3D model, the central profile of the wellbore was extracted, and a 2D radial model with a radial length of 775 meters and a vertical thickness of 200 meters was established. The meshing, geological stratification, and physical property parameters of this 2D model are completely consistent with those of the 3D model.

[0032] S4. Perform radius matching and determine the two-dimensional equivalent injection rate. The two-dimensional equivalent injection rate is determined using the direct calculation formula provided by this invention. :

[0033] Substitute the known parameters into: where =70,000 tons / year =65.21m, =1m (unit thickness of the two-dimensional radial model).

[0034] The equivalent injection rate of the two-dimensional model was obtained through calculation. =512.79 kg / day.

[0035] This The simulation was performed using a two-dimensional model, and the results are shown in the attached figure. Figure 2 As shown, the CO2 migration range of the two-dimensional model basically matches the migration range of the corresponding cross-section of the three-dimensional model (the red part is the CO2 migration range), verifying the effectiveness of this method.

[0036] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0037] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0038] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for dimensionality reduction simulation of CO2 transport based on plume radius matching, characterized in that, Includes the following steps: S1. Establish a three-dimensional numerical model of the target reservoir and inject it at a preset three-dimensional rate Q. 3D Simulate CO2 transport to obtain a three-dimensional CO2 plume at a preset time t; S2. Based on the three-dimensional CO2 plume, determine the maximum lateral transport radius of CO2. ; S3. Establish a two-dimensional vertical profile model corresponding to the three-dimensional numerical model; S4. Determine an equivalent injection rate Q 2D This rate enables the lateral transport radius of the CO2 plume formed by the two-dimensional vertical profile model at the same preset time t to be increased. Compared with the maximum lateral transport radius determined in step S2 Matching.

2. The CO2 transport dimensionality reduction simulation method based on plume radius matching according to claim 1, characterized in that, The geometry of the three-dimensional CO2 plume is assumed to be a cone, with a maximum lateral transport radius of... Let be the radius of the base of the cone.

3. The CO2 transport dimensionality reduction simulation method based on plume radius matching according to claim 1, characterized in that, In the two-dimensional vertical profile model, the sweep area of ​​the CO2 plume is assumed to be triangular, with a lateral transport radius of... It is half the length of the base of the triangle.

4. The CO2 transport dimensionality reduction simulation method based on plume radius matching according to claim 1, characterized in that, In S4, the equivalent injection rate Q 2D Calculated using the following formula: In the formula, The equivalent slice thickness of the two-dimensional model; The maximum lateral transport radius of the matched CO2 plume, and has .

5. The CO2 transport dimension reduction simulation method based on plume radius matching according to claim 1, characterized in that, In S2 and S4, the condition used to define the CO2 plume boundary is that the CO2 saturation reaches a preset non-zero threshold.

6. The CO2 transport dimension reduction simulation method based on plume radius matching according to claim 1, characterized in that, The geological structure, mesh division, and physical property parameters of the two-dimensional vertical profile model are consistent with the corresponding profile of the injection well in the three-dimensional numerical model.

7. The CO2 transport dimension reduction simulation method based on plume radius matching according to claim 1, characterized in that, The preset time t is 1-3 months.

8. The CO2 transport dimension reduction simulation method based on plume radius matching according to claim 1, characterized in that, In S1, the preset three-dimensional injection rate Q 3D Take the actual injection rate designed in the engineering process.

9. The CO2 transport dimension reduction simulation method based on plume radius matching according to claim 1, characterized in that, In S3, the established two-dimensional vertical profile model is a two-dimensional radial model.

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