Quantitative evaluation method for geological storage effect of carbon dioxide in deep coal seam based on three-dimensional geological modeling and numerical simulation

Abstract

The invention discloses a quantitative evaluation method for a deep coal seam carbon dioxide geological sequestration effect based on three-dimensional geological modeling and numerical simulation, and belongs to the technical field of carbon peak reaching and carbon neutralization. The method comprises the following steps: firstly, analyzing geological data of an original coal field, and determining spatial distribution and physical property characteristics of a deep coal reservoir; secondly, a target coal seam three-dimensional geologic model is constructed, and deep coal seam space distribution characteristics are determined in a high-precision and high-resolution mode; then, Eclipse and Comet3 simulation software is fully utilized to construct a carbon dioxide geological sequestration model, and sensitivity analysis of the carbon dioxide sequestration amount and the methane displacement amount is carried out from two aspects of geology and engineering factors; and discussing influence factors influencing the carbon dioxide geological sequestration effect by integrating subjective and objective weights, and determining main control factors. And finally, on the basis of calculating the carbon dioxide sequestration amount, carrying out overall evaluation on the carbon dioxide sequestration effect. Quantitative evaluation of the geological storage effect of the carbon dioxide in the deep coal seam of the target coal-endowed area is realized.

Description

Technical Field

[0001] The present invention belongs to the field of carbon peak and carbon neutrality technology, and specifically relates to a quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation. Background Art

[0002] Carbon dioxide geological storage is expected to become an effective method for carbon emission reduction and has attracted great attention from the world. Carbon negative emission technology represented by CO2 geological storage has become an important way to achieve dual carbon goals in the energy field. With the development of deep earth science and related technologies, deep unconventional reservoirs have become the key target layers for CO2 geological storage. Deep coal reservoirs are characterized by high temperature, high pressure and high free gas content, and have become one of the key targets for breakthroughs in unconventional energy development. At the same time, restricted by the existing production conditions of coal mines, the mining of deep coal seams in coal seam storage areas is limited, and it is difficult to fully utilize the coal seam resources developed in such coal seams. Therefore, deep coal seam CO2 geological storage has become one of the key means to evaluate the resource potential of coal seam storage areas and achieve regional carbon neutrality goals.

[0003] CO2 geological storage is a process with many influencing factors and complex interactions. The use of simple analytical formulas and models to study the storage process may lead to conclusions that are inconsistent with reality. Many previous research results show that numerical simulation technology has obvious advantages in CO2 geological storage research, and can take into account the joint influence of multiple factors at the same time, achieving relatively ideal research results. At present, the focus of numerical simulation research on CO2 geological storage is mainly concentrated on the following four aspects: large-scale CO2 storage site selection and storage potential evaluation, storage state and total storage under different storage mechanisms after CO2 injection, migration and transformation characteristics of CO2 in the reservoir at different time scales, and influencing factors of CO2 geological storage process. With the continuous deepening of research, related research is gradually developing from large-scale storage potential evaluation to the direction of interaction transformation of different storage mechanisms at the storage target level, the influencing factors considered are more comprehensive and comprehensive, and the mathematical model is closer to reality. Compared with foreign countries, my country started late in the research related to numerical simulation of CO2 geological storage, and related research methods and technical means mainly rely on the introduction of existing mature technologies from abroad.

[0004] Although the existing technology has conducted a lot of research on CO2 geological storage methods and calculation of coal-rock CO2 geological storage capacity, there are still the following problems in this field. First, there is a lack of quantitative analysis of factors affecting CO2 geological storage, and a complete evaluation system for coal-bed CO2 geological storage potential has not been established; second, the division principles of CO2 geological storage units have not yet been clarified.

[0005] This shows that the prior art needs to be further improved. Summary of the invention

[0006] The purpose of the present invention is to provide a quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation. It fully mines traditional coalfield geological data and maximizes the use of preliminary exploration and evaluation results through the combination of three-dimensional geological modeling and numerical simulation. It can realize the reuse of original data and help achieve the dual carbon goals of regional coal-bearing areas.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation includes the following steps:

[0009] a. Analyze the comprehensive geological characteristics of the target coal seam coal-bearing area, and on this basis, clarify the distribution law of the remaining reserves of the target coal seam;

[0010] b. Calculate the critical depth of carbon dioxide geological storage in the target coal seam based on the temperature and pressure gradient of the coal-bearing strata, and clarify the spatial distribution law of the target coal seam at the critical depth;

[0011] c. Based on the spatial distribution law of the target coal seam, the Petrol modeling software is used to construct a three-dimensional geological model of the target coal seam to further clarify the spatial distribution characteristics of the target coal seam;

[0012] d. Use COMET3 and Eclipse reservoir simulation software to build a numerical model for geological storage of carbon dioxide. Consider the characteristics of coal reservoirs and working systems, design different engineering schemes according to the principle of statistical optimization, select different influencing factors under numerical simulation calculations as the main consideration indicators, and gradually realize the sensitivity analysis of various influencing factors;

[0013] e. Based on the sensitivity analysis of various influencing factors, analyze the effects of carbon dioxide injection and methane output under different schemes, use statistical methods to achieve quantitative evaluation of various influencing factors, and determine the main controlling factors according to the principle of combining qualitative and quantitative evaluation;

[0014] f. Combined with the three-dimensional geological model of the target coal seam, the CO2 injection effect within the target coal seam is evaluated; the linkage reaction of CO2 injection volume, injection pressure and sealing properties is discussed in detail to further determine the optimal area for CO2 geological storage.

[0015] In the above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step a, the comprehensive geological characteristics of the coal-bearing area of ​​the target coal seam refer to basic geological characteristics, coal petrology characteristics, adsorption and storage characteristics, reservoir physical properties characteristics and fluid characteristics, wherein the basic geological characteristics refer to the tectonic environment, spatial distribution characteristics, coal seam roof and floor and hydrogeological characteristics of the target coal seam; coal petrology characteristics refer to the coal rock type and metamorphic degree of the reservoir; adsorption and storage characteristics and reservoir physical properties characteristics mainly refer to the gas content, adsorption and desorption characteristics, pore and fracture distribution and permeability development of the coal seam; fluid characteristics refer to the characteristics, composition and physical properties of gas and water.

[0016] The above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation conducts theoretical model research and basic data analysis on the basis of the comprehensive geological characteristics of the target coal seam coal-bearing area, and establishes a coal seam model, a reservoir physical property model and a gas content model.

[0017] In the above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step b, if the formation temperature and pressure gradient corresponding to the target coal seam are higher than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is good; if the formation temperature and pressure gradient corresponding to the target coal seam are lower than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is poor; the carbon dioxide storage effect of the target coal seam is further judged in combination with the remaining coal resources at the critical depth, and the calculation formula of the remaining coal resources is shown in formula (1):

[0018] Q = S *M *D (1);

[0019] In formula (1), Q is the remaining resource reserves of the target coal seam; S is the area of ​​the target coal seam; and M is the average thickness of the target coal seam.

[0020] In the above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step c, a three-dimensional integrated visualization scene of carbon dioxide geological storage above ground and underground is established, and a three-dimensional animation model of key technical principles and working scenes in different typical well development projects is designed and developed.

[0021] In the above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step d, the coal reservoir characteristics mainly include coal rank, organic microscopic components, permeability, physical and mechanical properties and water content, and the working system includes CO2 injection rate, injection pressure and injection time.

[0022] The above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step e, through the sensitivity analysis of various influencing factors, find out the single factors with strong significance and their interaction relationships, on the basis of the sensitivity analysis, take the selected influencing factors as independent variables, take the average methane production, the cumulative methane production and the cumulative CO2 storage as dependent variables, and correct the subjective weights obtained by the hierarchical analysis method through the entropy method and the principal component analysis method, and finally screen and determine the main controlling factors affecting the displacement and storage effects.

[0023] In the above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, in step f, the evaluation of the carbon dioxide injection effect within the target coal seam range is as follows: clarify the linkage changes of carbon dioxide injection amount, methane output and reservoir pressure change with time and space during carbon dioxide injection; while determining the optimal area for carbon dioxide geological storage effect, according to the principles, construction technology and development process of carbon dioxide geological storage, in accordance with the development mode, key nodes and construction technology principles of carbon dioxide geological storage, design and establish a three-dimensional animation model of the whole process of carbon dioxide geological storage, a three-dimensional animation model of key process principles, and a three-dimensional animation model of construction principles and processes; respectively, for different development modes of vertical single well development, horizontal well and cluster well, and for key technical nodes of drilling, fracturing and drainage, establish three-dimensional animations; use animation videos with text and explanation to show the development scene of carbon dioxide geological storage in deep coal seams in the target coal-bearing area.

[0024] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0025] (1) The present invention provides a quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation. It implements a quantitative evaluation of the geological storage effect of carbon dioxide in deep coal seams in target coal-bearing areas by following a step-by-step research approach of spatial distribution of target coal seams - physical property characteristics - three-dimensional modeling - geological storage model construction - determination of main controlling factors - storage effect evaluation.

[0026] (2) The high-precision deep coal seam carbon dioxide geological storage effect evaluation and three-dimensional animation design based on three-dimensional geological modeling provided by the present invention create a good theoretical basis and technical guidance for deep coal seam carbon dioxide geological storage projects.

[0027] (3) Specifically, the present invention first analyzes the original coalfield geological data to clarify the spatial distribution and physical properties of deep coal reservoirs; secondly, the three-dimensional geological model of the target coal seam is constructed using modeling software such as Petrol, and the spatial distribution characteristics of the deep coal seam are clarified with high precision and high resolution; then, professional simulation software such as Eclipse and Comet3 are fully utilized to construct the carbon dioxide geological storage model, and the sensitivity analysis of the carbon dioxide storage amount and the methane displacement amount is carried out from the two aspects of geological and engineering factors. At the same time, the subjective and objective weights are comprehensively considered to explore the factors affecting the effect of carbon dioxide geological storage, and the main control factors are determined. Finally, based on the calculation of the carbon dioxide storage amount, the hierarchical analysis-fuzzy evaluation method is comprehensively used to evaluate the overall effect of carbon dioxide storage. The present invention can ultimately form a high-precision deep coal seam carbon dioxide geological storage effect evaluation based on three-dimensional geological modeling; at the same time, a comprehensive consideration of the deep coal seam carbon dioxide geological storage process is formed, and a set of three-dimensional animation design that fully considers the actual carbon dioxide geological storage project is established. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] Figure 1 is a gas-water relative permeability curve diagram used in the numerical simulation of the present invention;

[0030] Figure 2 is a capillary pressure curve diagram used in the numerical simulation of the present invention;

[0031] Figure 3 It is a diagram for constructing a vertical well group geological model in the ECLIPSE software of the present invention;

[0032] Figure 4 This is a schematic diagram of the hierarchical analysis of factors affecting CO2 displacement and storage;

[0033] Figure 5 3D animation of geological storage of carbon dioxide in coal fields;

[0034] Figure 6 Screenshot of the deep coal reservoir dynamic simulation and display platform;

[0035] Figure 7 Provide 3D animation of the whole process of CO2 injection and gas extraction;

[0036] Figure 8 A 3D animation of horizontal drilling and fracturing. DETAILED DESCRIPTION

[0037] The present invention proposes a quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation. In order to make the advantages and technical solutions of the present invention clearer and more specific, the present invention is further described below in conjunction with specific embodiments.

[0038] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0039] In the description of the present application, "includes," "includes," and "has," and any variations thereof, are intended to cover a non-exclusive inclusion.

[0040] The specific use methods of the Petrol modeling software, COMET3 and Eclipse reservoir simulation software described in the present invention can be realized by those skilled in the art by referring to the existing technology.

[0041] The present invention provides a quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, comprising the following steps:

[0042] a. Analyze the comprehensive geological characteristics of the target coal seam coal-bearing area, and on this basis, clarify the distribution law of the remaining reserves of the target coal seam; the comprehensive geological characteristics of the target coal seam coal-bearing area refer to the basic geological characteristics, coal petrology characteristics, adsorption and storage characteristics, reservoir physical properties characteristics and fluid characteristics, among which the basic geological characteristics refer to the tectonic environment, spatial distribution characteristics, coal seam roof and floor and hydrogeological characteristics of the target coal seam; coal petrology characteristics refer to the coal rock type and metamorphic degree of the reservoir; adsorption and storage characteristics and reservoir physical properties characteristics mainly refer to the gas content, adsorption and desorption characteristics, pore and fracture distribution and permeability development of the coal seam; fluid characteristics refer to the characteristics, composition and physical properties of gas and water.

[0043] The above-mentioned quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation conducts theoretical model research and basic data analysis on the basis of the comprehensive geological characteristics of the target coal seam coal-bearing area, and establishes a coal seam model, a reservoir physical property model and a gas content model.

[0044] b. Calculate the critical depth of carbon dioxide geological storage in the target coal seam in combination with the temperature and pressure gradient of the coal-bearing strata, and clarify the spatial distribution law of the target coal seam at the critical depth; in step b, if the formation temperature and pressure gradient corresponding to the target coal seam are higher than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is good; if the formation temperature and pressure gradient corresponding to the target coal seam are lower than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is poor; further judge the carbon dioxide storage effect of the target coal seam in combination with the remaining coal resources at the critical depth, and the calculation formula of the remaining coal resources is shown in formula (1):

[0045] Q = S *M *D (1);

[0046] In formula (1), Q is the remaining resource reserves of the coal seam (unit: 10,000 tons); S is the area of ​​the coal seam (unit: square meters); M is the average thickness of the coal seam (unit: meters); and D is the apparent density of coal (unit: tons / cubic meters). In the calculation process, it is worth noting that the calculation of the coal seam area: according to the different inclinations of the coal seams, select the appropriate area calculation method and ensure the accuracy of the measurement results. Determination of the thickness of the coal seam: considering the interlayer of the coal seam, calculate the adopted thickness of the coal seam according to the regulations, and determine the coal points involved in the average thickness calculation. Selection of the apparent density of coal: select the appropriate apparent density value according to the type and properties of the coal.

[0047] c. Based on the spatial distribution law of the target coal seam, the Petrol modeling software is used to construct a three-dimensional geological model of the target coal seam, establish a three-dimensional integrated visualization scene of carbon dioxide geological storage above and below the ground, and design and develop key technical principles and three-dimensional animation models of working scenes in different typical well development projects.

[0048] d. A numerical model for geological storage of carbon dioxide is constructed by combining COMET3 and Eclipse reservoir simulation software. Considering the characteristics of coal reservoirs and working systems, a preliminary analysis and summary of the influencing factors in the process of CO2 geological storage and displacement are conducted. Different engineering schemes are designed according to the principle of statistical optimization. Different influencing factors under numerical simulation calculations are selected as the main consideration indicators, and sensitivity analysis of various influencing factors is gradually realized. The characteristics of coal reservoirs mainly include coal rank, organic micro-components, permeability, physical and mechanical properties, water content, etc. The working system mainly involves the injection rate, injection pressure and injection time of CO2.

[0049] e. Based on the sensitivity analysis of various influencing factors, analyze the effects of carbon dioxide injection and methane output under different schemes, use statistical methods such as grey correlation analysis, fuzzy comprehensive evaluation or hierarchical analysis to achieve quantitative evaluation of various influencing factors, and determine the main controlling factors according to the principle of combining qualitative and quantitative evaluation.

[0050] In this step, the research simulation work is divided into three parts. The first part, factor sensitivity analysis, is the basis for the subsequent experimental analysis, and its purpose is to find out the single factors and interactive relationships with strong significance. On the basis of sensitivity analysis, the selected influencing factors are used as independent variables, and the average gas production / cumulative gas production of methane and the cumulative storage of CO2 are used as dependent variables. The subjective weights obtained by the hierarchical analysis method are corrected by the entropy method / principal component analysis method, and finally the main controlling factors affecting the displacement and storage effects are screened and determined.

[0051] f. Combined with the three-dimensional geological model of the target coal seam, evaluate the CO2 injection effect within the target coal seam; focus on the linkage reaction of CO2 injection volume, injection pressure and sealing performance, and further determine the optimal area for CO2 geological storage effect; in this step, based on the three-dimensional geological modeling, simulate the CO2 geological storage in the entire area to clarify the linkage changes of CO2 injection volume and methane output as well as reservoir pressure changes with time and space during CO2 injection. Divide the study area into block units based on structure and burial depth as division parameters. Statistically analyze the CO2 storage volume and methane output in different units during the simulation period, and give priority to the area with the optimal CO2 geological storage effect. At the same time, according to the principles, construction technology and development process of carbon dioxide geological storage, and in accordance with the development mode, key nodes and construction technology principles of carbon dioxide geological storage, a three-dimensional animation model of the entire process of carbon dioxide geological storage, a three-dimensional animation model of key process principles, and a three-dimensional animation model of construction principles and processes are designed and established. Targeting different development modes such as vertical single well development, horizontal wells, cluster wells (directional wells), and establishing three-dimensional animations for key technical nodes such as drilling, fracturing, and production, the animation video is used with text and explanation to display the development scene of carbon dioxide geological storage in deep coal seams in the target coal-bearing area.

[0052] The present invention will be further described below in conjunction with the embodiments.

[0053] Embodiment 1:

[0054] Take a mine in Ningdong Coalfield as an example.

[0055] The quantitative evaluation method of the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation of the present invention is adopted, and the specific steps are as follows:

[0056] 1.1. Analyze the comprehensive geological characteristics of the target coal-bearing area, and on this basis, clarify the distribution law of the remaining coal seam reserves. According to the mine exploration report, the thickness of the main mineable coal seams in the Taiyuan Group of this mine is relatively stable. Among them, 12 coals are located at the top of the third section of the Taiyuan Group and are distributed in the mine field. The coal seam thickness is 0.78~3.09m and the average thickness is 1.44m. The probability of mining this coal seam area in the mine field is 97.58%, which is a mineable coal seam in the entire mine field. The area with a coal seam thickness of 1.31~3.09m accounts for 69.19% of the mineable range, and the coal seam thickness changes little. The coal seam thickness of the thin coal section that exists locally is about 1 meter.

[0057] Shanxi Group 4 coal is located in the lower part of Shanxi Group. It is common and stable in the mine field. The coal seam thickness is 0.43 to 7.08m, with an average thickness of 1.87m. The average distance from the Taiyuan Group 12 coal below is 195.19m. The probability of mining the coal seam area in the mine field is 97.26%, which is a mineable coal seam in the whole mine field. The 4 coal seams in the mine field with a thickness of 1.31 to 3.50m account for 61.71% of the mineable range, which is a relatively stable medium-thick coal seam.

[0058] The geological structure of the mine is relatively complex. The main fold structure of the mine field is a west-dipping monocline, connected to the Wei 1 mine field in the north and the Wei 3 mine field in the southwest. The stratum dips gently, and is only slightly steep in the shallow part of the concealed outcrop. Faults are well developed within the mine field, mainly a group of "X"-shaped faults in the northwest and northwest (nearly north-south) and a group of faults in the northwest, and there are very few east-west faults. The northwest fault is a later fault. The two groups of oblique faults cut the coal-bearing strata in the mine field into many blocks of varying sizes, and the integrity and continuity of the coal-bearing strata have suffered severe damage.

[0059] There are 40 faults in the well field, 29 of which are faults that interrupt both the Taiyuan and Shanxi coal seams, 9 faults that interrupt only the Shanxi coal seams, and 2 faults that interrupt only the Taiyuan coal seams. According to the nature of the faults, there are 22 reverse faults and 18 normal faults; according to the direction of the faults, there are 20 faults with northwest and north-northwest orientation, 9 faults with north-south orientation, 10 faults with northeast and north-northeast orientation, and 1 fault with east-west orientation.

[0060] The boundaries of the mine field, the boundaries of the preliminary mining, and the locations of the boreholes were sorted and mapped. From the schematic diagram of the mine boundary and the locations of the boreholes, it can be seen that the existing borehole data are mainly concentrated near the first mining area. There are few coalfield geological boreholes at the south and north ends of a mine. In view of the spatial distribution characteristics of the above-mentioned borehole data, if a three-dimensional geological model of the coal seam within the scope of a mine is established based on this, it is obvious that the uncertainty of the model will increase at the north and south ends of the mine field due to the scarcity of boreholes. Therefore, a three-dimensional geological model within the preliminary scope of a mine will be established as a typical model of the mine field.

[0061] In the 3D geological modeling software, the borehole coordinates and the stratified data of the coal-bearing strata of a mine are extracted and imported into the software to obtain the 3D model of the borehole data. According to the structural outline map of a mine and the exploration report of the mine field, with the previous boundary range of a mine as a reference, the faults with large extension length and high degree of identification in the mine field are selected as the main modeling objects to establish the 3D model of the fault.

[0062] The 3D geological model of the early mining section of a mine is established through the above-mentioned 3D model of drilling data and 3D model of faults. Slicing the 3D geological structure model can clearly reflect the coal seam, fault structure and spatial position relationship of the early mining section of a mine. The 3D model of Shanxi Group 4 coal and Taiyuan Group 12 coal in the early mining section of a mine.

[0063] 1.2. Based on the actual situation of the study area, a numerical model for CO2 geological storage was constructed by combining COMET3 and Eclipse reservoir simulation software.

[0064] This study assumes that the caprock is perfectly sealed without exceeding the pressure limit, and the boundary condition is set to no flow. The BHP (bottom hole pressure) parameter is used in the simulation to control the upper limit of the reservoir pressure. In practice, this pressure value is related to parameters such as the fracture pressure that destroy the reservoir sealing property. Figure 1 is the gas-water relative permeability curve used in the numerical simulation. Figure 2 This is the capillary pressure curve used in the numerical simulation.

[0065] Eclipse reservoir simulation software uses as few restrictive assumptions as possible in the process of numerical simulation of coalbed methane, so that the simulation results can better match the actual situation. In the process of building the model, the following basic assumptions are used:

[0066] (1) The reservoir temperature remains constant.

[0067] (2) The flow of gas and water in the fracture system satisfies Darcy's law and can be reflected by relative permeability.

[0068] (3) The coal matrix blocks in the same finite difference grid are all homogeneous, but the size of the matrix blocks, gas adsorption time and certain parameters can be set differently in different grid blocks.

[0069] (4) Based on the Warren-Root hypothesis, at any time, the diffusion process of fluid from the coal matrix block to the fracture system is quasi-steady state, that is, the methane concentration decreases at the same rate in each matrix block unit.

[0070] On the basis of fully drawing on the relevant research and achievements of predecessors, the spatial distribution characteristics, gas content and other conditions of the coal reservoirs in the two test areas were summarized and analyzed in detail. Based on the actual needs of the simulation software, the relevant parameters were preliminarily determined in order to provide actual reference data for the subsequent analysis of the main controlling factors (Table 1).

[0071] Table 1 Range of numerical simulation parameters in the test area

[0072]

[0073] The numerical simulation output results in this study include daily gas production, cumulative gas production, injection rate, cumulative injection volume, and formation pressure. The daily gas production / cumulative gas production reflects the effect of coalbed methane displacement during the drainage stage, the injection rate / cumulative injection volume reflects the CO2 storage effect during the entire injection stage, and the formation pressure parameter reflects the overall stability of the formation during the entire injection and drainage stage.

[0074] The basic reservoir physical parameters, fluid parameters, and grid parameter settings of the vertical well group numerical simulation model are the same as those of the vertical single well model. In the Eclipse reservoir simulation software, a vertical well group model is established, such as Figure 3 shown.

[0075] 1.3. Sensitivity analysis of factors affecting CO2 geological storage and methane displacement. _ There are many factors affecting the effects of ECBM and CCS, such as fracture pressure, adsorption parameters, gas content, coal seam thickness, coal seam burial depth, reservoir pressure, porosity, permeability, and formation temperature. Based on the relevant literature, the factors affecting CO2 displacement and storage are divided into two aspects, namely reservoir geological conditions and engineering injection conditions, for analysis and discussion, based on the geological data of the study area and the actual simulation needs. For example, Figure 4 shown.

[0076] The multi-factor objectives of this study include: fracture pressure, thickness, burial depth, gas content, permeability, porosity, bottom hole pressure, well spacing and injection volume, a total of 9 factor tests, the factors involved are shown in Table 2 (the value of each factor is based on the specific actual situation of the study area). The value range and type of each influencing factor are shown in Table 3.

[0077] Table 2 Range of factors affecting experimental design

[0078]

[0079] Table 3 Types and values ​​of influencing factors in the experiment

[0080] factor Data Types Minimum Median Maximum Burst pressure Classification 10MPa 40MPa thickness continuous 1m 5m Buried Depth continuous 1000m 1500m Gas content continuous <![CDATA[10m 3 / t]]> <![CDATA[30m 3 / t]]> Permeability Classification 0.01md 1md Porosity continuous 0.75％ 6％ Bottom hole pressure Classification 0.5Mpa 1.5MPa Well spacing Classification 100m 400m Injection volume Classification <![CDATA[1000m 3 / t]]> <![CDATA[8000m 3 / t]]>

[0081] The simulation work of this study is divided into three parts: the first part of the factor sensitivity analysis is the basis for the subsequent experimental analysis, the purpose is to find out the single factors and interactive relationships with strong significance. This part conducted 4×9 simulation experiments. On the basis of sensitivity analysis, 9 influencing factors were used as independent variables, and the average gas production / cumulative gas production and cumulative CO2 storage were used as dependent variables. The subjective weights obtained by the hierarchical analysis method were corrected by the entropy method / principal component analysis method, and finally the main influencing factors affecting the displacement and storage effects of coalbed methane were screened and determined.

[0082] 1.4. Determination of the main controlling factors of carbon dioxide geological storage potential. Based on the hierarchical analysis, the report uses the principal component analysis method (corrected by the grey correlation method) to quantitatively determine the correlation between each influencing factor and production capacity from the perspective of mathematical statistics using relevant data, compare the relative size of the correlation of each factor, and more intuitively analyze the importance of these factors, thereby supporting the results obtained by the hierarchical analysis method.

[0083] The PCA model is fed with the original data to be processed using the principal component analysis method, and the data is screened and sorted. The sorted original data is dimensionlessly processed in a standardized manner to obtain the correlation matrix. Then, the eigenvalues, characteristic equations, and cumulative contribution rates of the correlation coefficient matrix are obtained according to the calculation formulas in the above text, and a new data set containing only the principal components is determined. By comparing the weight values ​​(Table 4), the well spacing has the highest weight, with a weight value of 1 / 4; the burial depth, permeability, bottom hole pressure, and injection rate are second; the porosity, fracture pressure, and thickness have the smallest weights.

[0084] Table 4

[0085]

[0086] 1.5. Based on the above, the CO2 geological storage units in the mine are divided according to the distribution law of the main controlling factors. The mine is divided into 6 CO2 storage areas according to the fault structure, and the CO2 storage capacity is calculated for each area. On this basis, the burial depth parameter is used to divide Block 1 into 15 storage units, and the CO2 geological storage capacity is calculated for each area.

[0087] 1.6. According to the engineering principles, construction technology and development process of carbon dioxide geological storage development, and in accordance with the development mode, key nodes and construction technology principles, design and establish a three-dimensional animation model of the entire process of carbon dioxide geological storage, a three-dimensional animation model of key process principles, and a three-dimensional animation model of construction principles and processes. For different development modes such as vertical single well development, horizontal wells, cluster wells (directional wells) for gas drainage, and for key technical nodes such as drilling, fracturing, and drainage, establish three-dimensional animations. Use animated videos with text and explanations to display the development scenes of carbon dioxide geological storage.

[0088] Combining 3D geological models, coal seam and development well models, dynamic simulation of reservoirs of different well types, comprehensive scene display platform angle design and development scene 3D animation, key information such as geological background of carbon dioxide geological storage, spatial morphology of coalbed methane, different coalbed methane well types, brief construction process, dynamic changes of reservoirs, etc. are visualized. Figure 5 , Figure 6 , Figure 7 shown.

[0089] A special animation is designed to demonstrate the basic principles and construction process of carbon dioxide geological storage. Taking the vertical single well development of coalbed methane as an example, a three-dimensional animation of the entire process of vertical single well development from drilling to coalbed methane drainage is established, reflecting the process principles and construction process of key technical nodes such as drilling, completion, perforation, fracturing, drainage, gathering and transportation.

[0090] According to the construction method of coalbed methane horizontal well development, a 3D animation model is established for the drilling and fracturing links of horizontal well development to display the construction process animation of horizontal drilling, cementing, perforating and fracturing links, such as Figure 8 shown.

[0091] Parts not described in the present invention can be implemented by referring to the existing technology.

[0092] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation, characterized in that: The following steps are involved: a. Analyze the comprehensive geological characteristics of the target coal seam coal-bearing area, and on this basis, clarify the distribution law of the remaining reserves of the target coal seam; b. Calculate the critical depth of carbon dioxide geological storage in the target coal seam based on the temperature and pressure gradient of the coal-bearing strata, and clarify the spatial distribution law of the target coal seam at the critical depth; c. Based on the spatial distribution law of the target coal seam, the Petrol modeling software is used to construct a three-dimensional geological model of the target coal seam to further clarify the spatial distribution characteristics of the target coal seam; d. Use COMET3 and Eclipse reservoir simulation software to build a numerical model for geological storage of carbon dioxide. Consider the characteristics of coal reservoirs and working systems, design different engineering schemes according to the principle of statistical optimization, select different influencing factors under numerical simulation calculations as the main consideration indicators, and gradually realize the sensitivity analysis of various influencing factors; e. Based on the sensitivity analysis of various influencing factors, analyze the effects of carbon dioxide injection and methane output under different schemes, use statistical methods to achieve quantitative evaluation of various influencing factors, and determine the main controlling factors according to the principle of combining qualitative and quantitative evaluation; f. Combined with the three-dimensional geological model of the target coal seam, the CO2 injection effect within the target coal seam is evaluated; the linkage reaction of CO2 injection volume, injection pressure and sealing properties is discussed in detail to further determine the optimal area for CO2 geological storage.

2. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step a, the comprehensive geological characteristics of the target coal seam coal-bearing area refer to basic geological characteristics, coal petrology characteristics, adsorption and reservoir characteristics, reservoir physical properties characteristics and fluid characteristics, among which, basic geological characteristics refer to the tectonic environment, spatial distribution characteristics, coal seam roof and floor and hydrogeological characteristics of the target coal seam; coal petrology characteristics refer to the coal rock type and metamorphic degree of the reservoir; adsorption and reservoir characteristics and reservoir physical properties characteristics mainly refer to the gas content, adsorption and desorption characteristics, pore and fracture distribution and permeability development of the coal seam; fluid characteristics refer to the characteristics, composition and physical properties of gas and water.

3. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 2 is characterized by: Based on the comprehensive geological characteristics of the target coal seam and coal-bearing area, theoretical model research and basic data analysis are carried out to establish coal seam model, reservoir physical property model and gas content model.

4. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step b, if the formation temperature and pressure gradient corresponding to the target coal seam are higher than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is good; if the formation temperature and pressure gradient corresponding to the target coal seam are lower than the critical point, the carbon dioxide storage effect of the target coal seam at this depth is poor; the carbon dioxide storage effect of the target coal seam is further judged by combining the remaining coal resources at the critical depth. The calculation formula of the remaining coal resources is shown in formula (1): Q = S *M *D (1); In formula (1), Q is the remaining resource reserves of the target coal seam; S is the area of ​​the target coal seam; and M is the average thickness of the target coal seam.

5. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step c, a three-dimensional integrated visualization scene of carbon dioxide geological storage above and below ground is established, and three-dimensional animation models of key technical principles and working scenes in different typical well type development projects are designed and developed.

6. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step d, the coal reservoir characteristics mainly include coal rank, organic microscopic components, permeability, physical and mechanical properties and water content, and the working system includes CO2 injection rate, injection pressure and injection time.

7. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step e, a sensitivity analysis of each influencing factor is performed to find out the single factors with strong significance and their interaction relationships. On the basis of the sensitivity analysis, the selected influencing factors are used as independent variables, and the average methane production, cumulative methane production and cumulative CO2 storage are used as dependent variables. The subjective weights obtained by the hierarchical analysis method are corrected through the entropy method and principal component analysis method, and finally the main controlling factors affecting the displacement and storage effects are screened and determined.

8. The quantitative evaluation method for the geological storage effect of carbon dioxide in deep coal seams based on three-dimensional geological modeling and numerical simulation according to claim 1 is characterized by: In step f, the evaluation of the carbon dioxide injection effect within the target coal seam is as follows: clarify the linkage changes of the carbon dioxide injection amount, methane output and reservoir pressure changes with time and space during the carbon dioxide injection period; while determining the optimal area for carbon dioxide geological storage effect, according to the principles, construction technology and development process of carbon dioxide geological storage, in accordance with the development mode, key nodes and construction technology principles of carbon dioxide geological storage, design and establish a three-dimensional animation model of the entire process of carbon dioxide geological storage, a three-dimensional animation model of key process principles, and a three-dimensional animation model of construction principles and processes. For different development modes of vertical single well development, horizontal well and cluster well, three-dimensional animations are established for key technical nodes of drilling, fracturing and drainage. The animation video is presented in the form of text and explanation to display the development scene of carbon dioxide geological storage in deep coal seams in the target coal-bearing area.

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