Deep coalbed gas mixed source identification and quantitative evaluation method

Abstract

The application discloses a deep coalbed gas mixed source identification and quantitative evaluation method and belongs to the technical field of coalbed gas exploration and development and natural gas geochemical evaluation. The application obtains the gas component and stable isotope data of a coalbed gas sample, sequentially carries out genetic type identification, oil-type gas and coal-type gas binary identification, three-end-member gas source subdivision, and establishes a three-end-member identification framework of "oil-type gas-in-situ coal-type gas-high mature coal-type gas"; the range of end members is limited through potential hydrocarbon source rock analysis, and the end member parameters are determined by taking the data of hydrocarbon generation thermal simulation experiment as the preferred basis; quantitative calculation is carried out by adopting a two-step method, the proportion of oil-type gas and total coal-type gas is calculated based on ethane carbon isotope, and the internal proportion of coal-type gas is calculated based on methane carbon isotope. The method improves the accuracy of mixed source identification and quantitative evaluation under complex gas source conditions and is suitable for deep coalbed gas exploration evaluation and reservoir forming process research.

Description

Technical Field

[0001] This invention belongs to the technical fields of coalbed methane exploration and development, unconventional natural gas geochemical evaluation, and stable isotope tracing identification. Specifically, it relates to a method for the identification and quantitative evaluation of mixed-source gas in deep coalbed methane, particularly applicable to the comprehensive identification of biogenic, thermogenic, and mixed-genetic gases in deep coalbed methane, as well as the source identification and contribution ratio calculation under multi-terminal mixing conditions of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas. This invention can be used for deep coalbed methane exploration and evaluation, coalbed methane resource potential analysis, coalbed methane accumulation process reconstruction, deep coal-bearing gas source contribution discrimination, external gas recharge identification, and quantitative evaluation of different types of natural gas in complex coalbed methane systems. Background Technology

[0002] As coalbed methane exploration and development progresses to deeper levels, the sources of deep coalbed methane become more complex due to factors such as source rock type, thermal evolution, and tectonic transport conditions. It often exhibits characteristics such as a mixture of coal-type and oil-type gas, and the superposition of gases at different maturity stages. Currently, gas composition, stable isotopes, and related genetic identification charts are used for the genetic and source analysis of coalbed methane, and can also be used to calculate the contribution ratio of different gas sources. However, in deep coalbed methane-oil mixed systems, existing methods still have the following shortcomings: The causes are not clearly classified, and the identification process often starts directly from the internal source of thermogenic gas, ignoring the influence of biogenic gas, resulting in an incomplete identification process. The identification of the binary relationship between kerosene and oil is insufficient, making it difficult to accurately distinguish the mixing characteristics of oil-type gas and coal-type gas; Endmember segmentation is inaccurate, lacks clear geological basis, and endmember parameters are often selected blindly. The quantitative results lack stability and cannot reliably determine the mixing ratio of the three end-members of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas.

[0003] Therefore, it is necessary to propose a method for the identification and quantitative evaluation of coal-oil mixtures in deep coalbed methane to improve the accuracy of source identification and contribution ratio calculation under complex gas source conditions. Summary of the Invention

[0004] This invention overcomes the technical shortcomings of existing ball gear machining, which relies on five-axis machine tools, is costly, difficult to clamp, and cannot achieve efficient mass production. It provides a novel cyclone milling ball gear machining process that enables low-cost, high-precision, high-efficiency, and mass industrialized machining of ball gears.

[0005] To achieve the above-mentioned objectives, a method for identifying and quantitatively evaluating mixed-source deep coalbed methane includes the following steps: S1: Obtain gas composition data and stable isotope data of the target coalbed methane sample; S2: Based on the gas composition data and stable isotope data, identify the genetic type of the target coalbed methane sample to determine whether it is a biogenic gas, a thermogenic gas, or a mixed-genetic gas. S3: For samples identified as thermogenic gas or mixed-origin gas with thermogenic contribution, conduct binary identification of oil-type gas and coal-type gas to determine whether the sample belongs to kerosene-oil mixture. S4: For samples identified as kerosene-oil mixtures, conduct detailed identification of three-terminal gas sources and establish a three-terminal mixed source identification framework of "oil-type gas - in-situ coal-type gas - highly mature coal-type gas". S5: Analyze potential source rocks in the study area to limit the range of candidate sources for various end-member gases; S6: Determine the end-member parameters for oil-type gas, in-situ coal-type gas, and highly mature coal-type gas; S7: A two-step method was used to quantitatively calculate the contribution ratios of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas in the target coalbed methane sample.

[0006] Furthermore, the cause type identification in step S2 specifically includes: S2-1: Preliminary identification is made based on methane content, non-hydrocarbon gas content, heavy hydrocarbon component content, and dryness coefficient; S2-2: Genetic verification was performed using sequence characteristics of methane carbon isotopes, carbon dioxide carbon isotopes, methane hydrogen isotopes, and alkane carbon isotopes. S2-3: Using Bernard's diagrams and δ 13 C1-δ 13 C-CO2 combination diagram and δ 13 The C-CO2-CDMI chart is used for comprehensive identification, where CDMI is the discriminant index for the origin of carbon dioxide.

[0007] Furthermore, the binary identification of oil-type gas and coal-type gas in step S3 specifically adopts δ 13 C1-δ 13 C2-δ 13 C3 diagram, δ 13 C1-δ 13 The C2 natural gas origin identification chart and the alkane carbon isotope combination relationship are used to identify the source type.

[0008] Furthermore, the detailed identification of the three-terminal gas source in step S4 specifically includes: Combining the sensitivity of methane carbon isotopes to the degree of thermal evolution, δ 13 C1- R Based on empirical relation inversion results, measured coal sample maturity, and anomalous features of alkane carbon isotope sequences, it can be determined whether there is an overlap between in-situ coal-type gas and highly mature coal-type gas within the coal-type gas. When the theoretical maturity is significantly higher than the measured coal and petrology maturity, or when the methane carbon isotope is significantly heavier and accompanied by isotope sequence anomalies, it indicates the involvement of highly mature coal-type gas. When the gas isotope characteristics match the measured maturity and thermal simulation results of the coal-bearing strata in the study area, it is determined to be in-situ coal-type gas.

[0009] Furthermore, the potential source rock analysis described in step S5 specifically includes: Based on the stratigraphic development, organic matter type, maturity, hydrocarbon generation potential, and tectonic transport conditions of the study area and adjacent areas, we analyze the potential source rock formations that may supply gas to the target coalbed methane system. Coal-series source rocks are considered as the main candidate source of in-situ coal-type gas, oil-type source rocks are considered as an important candidate source of oil-type gas, and deep, highly mature or over-mature source rocks are considered as potential sources of highly mature coal-type gas.

[0010] Furthermore, in step S6, the determination of the endmember parameters prioritizes the use of hydrocarbon generation thermal simulation experimental data. When the hydrocarbon generation thermal simulation experimental data is insufficient, the literature survey results of the target strata in the study area and adjacent areas are used to supplement the constraints.

[0011] Furthermore, the two-step quantitative calculation described in step S7 specifically includes: S7-1: Calculation of the ratio of oil-type gas to total coal-type gas based on ethane carbon isotopes: Let the proportion of oil-type gas in the gas mixture be... f oil The total proportion of coal syngas is f coal ,but: f oil + f coal =1 δ 13 C 2,mix = f oil δ 13 C 2,oil + f coal δ 13 C 2,coal Where, δ 13 C 2,mix The measured carbon isotope values ​​of ethane in the sample; δ 13 C 2,oil The carbon isotope end-member values ​​of oil-type ethane gas; δ 13 C 2,coal The carbon isotope end-member values ​​of ethane in coal-type gas; The oil-gas ratio was calculated from this. f oiland the proportion of total coal gas f coal ; S7-2: Calculate the carbon isotope value δ of methane in coal-type gas after removing oil-type gas. 13 C 1,coal-mix : δ 13 C 1,coal-mix =(δ 13 C 1,mix - f oil ×δ 13 C 1,oil ) / f coal Where, δ 13 C 1,mix The measured carbon isotope values ​​of methane in the sample are δ. 13 C 1,oil The carbon isotope end-member values ​​of oil-type gaseous methane; S7-3: Calculation of the proportion of in-situ coal briquette gas and highly mature coal briquette gas in total coal briquette gas based on methane carbon isotopes: Let f be the proportion of in-situ coal briquette gas in the total coal briquette gas. i The proportion of highly mature coal-type gas is f h ,but: f i + f h =1 δ 13 C 1,coal-mix = f i ×δ 13 C 1,i + f h ×δ 13 C 1,h Where, δ 13 C 1,i The carbon isotope end-member value of methane in in-situ coal-type gas, δ 13 C 1,h The carbon isotope end-member value of methane in highly mature coal-type gas; The proportion of in-situ coal briquette gas f is thus calculated. i and the proportion of highly mature coal-type gas f h ; S7-4: Calculate the absolute contribution ratio of the three types of gases in the total mixture: F oil =f oil F i =f coal ×f i F h =f coal ×f h Among them, F oil F i F h These represent the absolute contribution ratios of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas in the total mixed gas, respectively, and satisfy F... oil +F i +F h =1.

[0012] Using the above technical solution, the specific functions of the main components in this invention are as follows: Involute milling cutter: Matches the tooth profile parameters of ball gears, directly mills the formed tooth grooves, ensuring tooth surface accuracy and meshing performance, and reducing tool design and manufacturing costs; Indexing mechanism: Enables precise indexing of the milling mechanism around the circumference of the workpiece. It controls the motor rotation angle by calculating the gear transmission ratio and has a self-locking function to prevent indexing deviation during machining, thereby improving the indexing accuracy of the tooth groove. Feed mechanism (trapezoidal lead screw): realizes radial feed and retraction of the milling cutter, and its self-locking performance ensures stable tooth depth and root circle dimensions without radial movement; Process holes: Eight evenly distributed process holes provide a stable clamping reference, solving the problems of slippage and inaccurate positioning when clamping spherical workpieces, and meeting the requirements of four-clamping processing. Cyclone milling machine: Provides workpiece rotation power, eliminating the need for five-axis linkage function, thus significantly reducing equipment costs.

[0013] In summary, the present invention has the following beneficial effects: 1) This invention incorporates the identification of genetic types, the binary identification of oil-type gas and coal-type gas, and the subdivision of three-terminal gas sources into the same technical process. It first eliminates the interference of biogenic gas, and then gradually analyzes the source of thermogenic gas, avoiding the leaps in the identification process and improving the accuracy of the classification of genetic types.

[0014] 2) This invention introduces potential source rock analysis before end-member selection, which clarifies the geological source of various end-member gases, so that the selection of end-member parameters has a clear geological basis and avoids the deviation of quantitative results caused by blindly selecting end-members.

[0015] 3) This invention employs a two-step method for quantitative calculation. It prioritizes the use of ethane carbon isotopes, which are sensitive to the type of parent material, to distinguish between oil-type gas and total coal-type gas. Then, it uses methane carbon isotopes, which are sensitive to maturity, to distinguish gases at different maturity stages within the coal-type gas. This fully leverages the advantages of different isotope indicators and improves the stability and reliability of the quantitative results.

[0016] 4) This invention establishes a three-terminal mixed source identification framework of "oil-type gas - in-situ coal-type gas - highly mature coal-type gas", which can accurately identify the complex multi-source mixing characteristics in deep coalbed methane, providing a reliable technical means for deep coalbed methane exploration evaluation, resource potential analysis and reservoir formation process research.

[0017] Functions of each step in this invention 1) Step S1 (Data Acquisition): Provides basic data support for the present invention. Gas component data is used to preliminarily identify the gas origin, and stable isotope data is used to finely identify the gas source and perform quantitative calculations.

[0018] 2) Step S2 (Genetic Type Identification): The target coalbed methane is classified into biogenic gas, thermogenic gas, or mixed-genetic gas, and pure biogenic gas samples are excluded. This lays the foundation for subsequent source analysis of thermogenic gas and avoids subsequent analysis errors caused by misclassifying biogenic gas as thermogenic gas.

[0019] 3) Step S3 (Binary identification of oil-type gas and coal-type gas): Identify the source type of thermogenic gas and determine whether there is a mixture of oil-type gas and coal-type gas, providing a prerequisite for subsequent three-terminal subdivision and quantitative calculation.

[0020] 4) Step S4 (Three-terminal gas source subdivision and identification): Further distinguish in-situ coal-type gas from highly mature coal-type gas within the coal-type gas, establish a complete three-terminal gas identification framework, and solve the identification problem of coal-type gas superimposed at different maturity stages.

[0021] 5) Step S5 (Potential source rock analysis): From a geological perspective, the candidate source range of various end-member gases is limited, so that the selection of end-members is combined with the actual geological conditions of the study area, which improves the rationality and applicability of end-member parameters.

[0022] 6) Step S6 (Determination of end-member parameters): To provide accurate end-member parameters for quantitative calculation, priority is given to using hydrocarbon generation thermal simulation experimental data to ensure the theoretical reliability of the end-member parameters, and the results of literature review are used to supplement and ensure the regional applicability of the end-member parameters.

[0023] 7) Step S7 (two-step quantitative calculation): Based on the principle of conservation of stable carbon isotope mass, the contribution ratio of gases from different sources is calculated in two steps, making full use of the advantages of different isotope indices, and realizing the stable determination of the mixing ratio of the three end-members.

[0024] In summary, this invention integrates gas component analysis, stable isotope tracing, multi-map comprehensive identification, potential source rock analysis, and two-step quantitative calculation to form a complete identification and quantitative evaluation method applicable to complex mixed-source systems of deep coalbed methane. This method overcomes the shortcomings of existing technologies, such as incomplete genetic identification, lack of basis for end-member selection, and unstable quantitative results. It can accurately identify the sources and contribution ratios of biogenic gas, thermogenic gas, oil-type gas, in-situ coal-type gas, and highly mature coal-type gas in deep coalbed methane, providing a scientific and reliable geochemical basis for deep coalbed methane exploration and development decisions, resource potential assessment, and hydrocarbon accumulation mechanism research. Attached Figure Description

[0025] Figure 1 This is an overall flowchart of the method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to the present invention; Figure 2 This is a schematic diagram illustrating the principle of the two-step quantitative calculation method of this invention; Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. Example

[0027] This embodiment uses a coalbed methane sample from a deep coalbed methane field in my country as an example to illustrate the specific implementation process of the present invention (e.g., Figure 1 (As shown).

[0028] Step 1: Data Acquisition Coalbed methane samples were collected from 10 wells in the target coalbed methane field. Gas composition data (including methane, carbon dioxide, nitrogen, ethane, propane content, and drying coefficient) and stable isotope data (including δ¹⁸O₂) were obtained. 13 C1, δ 13 C2, δ 13 C3, δ 13 C-CO2, δD-CH4). Test data for some samples are shown in the table below:

[0029] Step 2: Identification of Cause Type Preliminary identification: All samples had a methane content greater than 90% and a drying coefficient greater than 0.96, exhibiting dry gas characteristics; Sample S3 δ 13 C1 is significantly lighter and may contain biogenic gas; S1 and S2 samples have δ 13 C1 is predominantly present, primarily due to thermal origin.

[0030] Isotope verification: δ of sample S3 13 C1 = -42.5‰, δ 13C-CO2 = -15.6‰, consistent with the characteristics of a mixture of biogenic and thermogenic gases; δS1 of samples S2 13 C1 is -38.2‰ and -36.8‰ respectively, δ 13 C2 values ​​were -26.5‰ and -27.2‰, respectively, consistent with the characteristics of thermogenic gases.

[0031] Multi-plot integrated identification: Projecting sample data onto the Bernard plot, δ 13 C1-δ 13 C-CO2 combination diagram and δ 13 The C-CO2-CDMI chart shows that S3 is a mixed-originating gas (biogenic gas + thermogenic gas), while S1 and S2 are thermogenic gases.

[0032] Step 3: Binary Identification of Oil-type Gas and Coal-type Gas The thermal origin data of samples S1, S2, and S3 were plotted onto δ. 13 C1-δ 13 C2-δ 13 C3 diagram and δ 13 C1-δ 13 The C2 natural gas genesis identification chart shows that all three samples fall into the mixed zone of coal-type gas and oil-type gas, indicating the presence of a coal-oil mixed gas.

[0033] Step 4: Detailed Identification of the Three-Terminal Energy Source Based on the measured coal maturity (Ro = 1.2%–1.5%) in the study area, δ0 was used... 13 Theoretical maturity of C1-Ro empirical relation inversion samples: The theoretical maturity Ro of sample S1 is 1.8%, which is significantly higher than the measured coal and petrology maturity, and δ 13 The high C1 concentration indicates the presence of highly mature coal-type gas. The theoretical maturity of sample S2, Ro, is 1.6%, which is slightly higher than the measured coal and petrology maturity, indicating the presence of a small amount of highly mature coal-type gas. The theoretical maturity of the thermal genesis of sample S3 is Ro=1.3%, which is basically consistent with the measured coal and rock maturity, indicating that it is mainly composed of in-situ coal-type gas.

[0034] This leads to the establishment of a three-terminal mixed-source identification framework for "oil-type gas - in-situ coal-type gas - highly mature coal-type gas".

[0035] Step 5: Analysis of potential source rocks Three sets of source rocks were developed in the study area and adjacent areas: The Carboniferous-Permian coal-bearing source rocks have an organic matter type of III and a maturity of Ro = 1.2%–1.5%, making them the main source of in-situ coal-type gas. The Ordovician carbonate source rocks have organic matter of type I-II and maturity Ro = 1.0%–1.3%, and are the main source of oil-type gas. The deep Cambrian coal-bearing source rocks have an organic matter type of III and a maturity of Ro = 2.0%–2.5%, making them the main source of highly mature coal-type gas.

[0036] Step 6: Determine endmember parameters By conducting hydrocarbon generation thermal simulation experiments on the above three sets of source rocks, stable isotope parameters of various end-member gases were obtained: Oil-type gas end-member: δ 13 C1 = -45.0‰, δ 13 C2 = -32.0‰; In-situ coal-type gas end-member: δ 13 C1 = -40.0‰, δ 13 C2 = -25.0‰; Highly mature coal-type gas end-member: δ 13 C1 = -35.0‰, δ 13 C2 = -24.0‰.

[0037] Step 7: Two-step quantitative calculation, such as... Figure 2 As shown, Quantitative calculations were performed using sample S1 as an example: Step 1: Calculate the ratio of oil-based gas to total coal-based gas. Given δ 13 C 2，mix =-26.5‰, δ 13 C 2，oil =-32.0‰, δ 13 C 2，coal The weighted average of the ethane carbon isotopes of in-situ coal-type gas and highly mature coal-type gas is taken (here, the arithmetic mean minus 24.5‰ is taken as the preliminary calculation). Substitute into the formula: -26.5=f oil ×(-32.0)+(1-f oil )×(-24.5) Solving for f, we get: oil =0.267, f coal =0.733 That is, the proportion of oil-based gas is 26.7%, and the proportion of total coal-based gas is 73.3%.

[0038] Step 2: Calculate the carbon isotope values ​​of methane in coal-form gas after removing oil-form gas. Given δ 13 C 1，mix =-38.2‰, δ 13 C 1，oil =-45.0‰ Substitute into the formula: δ 13 C 1，coal- mix =(-38.2-0.267×(-45.0)) / 0.733≈-35.72‰ Step 3: Calculate the ratio of in-situ coal briquette gas to highly mature coal briquette gas. Given δ 13 C 1，i =-40.0‰, δ 13 C 1，h =-35.0‰ Substitute into the formula: -35.72=f i ×(-40.0)+(1-f i )×(-35.0) Solving for f, we get: i =0.144, f h =0.856 That is, the proportion of in-situ coal syngas in the total coal syngas is 14.4%, and the proportion of highly mature coal syngas is 85.6%.

[0039] Step 4: Calculate the absolute contribution ratio F oil =0.267=26.7% F i =0.733 × 0.144 ≈ 0.106 = 10.6% F h =0.733 × 0.856 ≈ 0.627 = 62.7% Verification: 26.7% + 10.6% + 62.7% = 100%, which meets the requirements.

[0040] Similarly, the contribution ratios of sample S2 were calculated as follows: oil-type gas 18.2%, in-situ coal-type gas 32.5%, and highly mature coal-type gas 49.3%; the contribution ratios of sample S3 were as follows: oil-type gas 12.5%, in-situ coal-type gas 75.8%, and highly mature coal-type gas 11.7%.

[0041] The results of this embodiment show that the coalbed methane in this deep coalbed methane field mainly originates from highly mature coal-type gas, followed by oil-type gas and in-situ coal-type gas, which is consistent with the geological background of the study area and verifies the accuracy and reliability of the method of the present invention.

Claims

1. A method for identifying and quantitatively evaluating mixed sources of deep coalbed methane, characterized in that: Includes the following steps: S1: Obtain gas composition data and stable isotope data of the target coalbed methane sample; S2: Based on the gas composition data and stable isotope data, identify the genetic type of the target coalbed methane sample to determine whether it is a biogenic gas, a thermogenic gas, or a mixed-genetic gas. S3: For samples identified as thermogenic gas or mixed-origin gas with thermogenic contribution, conduct binary identification of oil-type gas and coal-type gas to determine whether the sample belongs to kerosene-oil mixture. S4: For samples identified as kerosene-oil mixtures, conduct detailed identification of three-terminal gas sources and establish a three-terminal mixed source identification framework of "oil-type gas - in-situ coal-type gas - highly mature coal-type gas". S5: Analyze potential source rocks in the study area to limit the range of candidate sources for various end-member gases; S6: Determine the end-member parameters for oil-type gas, in-situ coal-type gas, and highly mature coal-type gas; S7: A two-step method was used to quantitatively calculate the contribution ratios of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas in the target coalbed methane sample.

2. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: The cause type identification in step S2 specifically includes: S2-1: Preliminary identification is made based on methane content, non-hydrocarbon gas content, heavy hydrocarbon component content, and dryness coefficient; S2-2: Genetic verification was performed using sequence characteristics of methane carbon isotopes, carbon dioxide carbon isotopes, methane hydrogen isotopes, and alkane carbon isotopes. S2-3: Using Bernard's diagrams and δ 13 C1-δ 13 C-CO2 combination diagram and δ 13 The C-CO2-CDMI chart is used for comprehensive identification, where CDMI is the discriminant index for the origin of carbon dioxide.

3. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: The binary identification of oil-type gas and coal-type gas in step S3 specifically adopts δ 13 C1-δ 13 C2-δ 13 C3 diagram, δ 13 C1-δ 13 The C2 natural gas origin identification chart and the alkane carbon isotope combination relationship are used to identify the source type.

4. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: The detailed identification of the three-terminal gas source in step S4 specifically includes: Combining the sensitivity of methane carbon isotopes to the degree of thermal evolution, δ 13 C1- R Based on empirical relation inversion results, measured coal sample maturity, and anomalous features of alkane carbon isotope sequences, it can be determined whether there is an overlap between in-situ coal-type gas and highly mature coal-type gas within the coal-type gas. When the theoretical maturity is significantly higher than the measured coal and petrology maturity, or when the methane carbon isotope is significantly heavier and accompanied by isotope sequence anomalies, it indicates the involvement of highly mature coal-type gas. When the gas isotope characteristics match the measured maturity and thermal simulation results of the coal-bearing strata in the study area, it is determined to be in-situ coal-type gas.

5. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: The potential source rock analysis in step S5 specifically includes: Based on the stratigraphic development, organic matter type, maturity, hydrocarbon generation potential, and tectonic transport conditions of the study area and adjacent areas, we analyze the potential source rock formations that may supply gas to the target coalbed methane system. Coal-series source rocks are considered as the main candidate source of in-situ coal-type gas, oil-type source rocks are considered as an important candidate source of oil-type gas, and deep, highly mature or over-mature source rocks are considered as potential sources of highly mature coal-type gas.

6. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: In step S6, the determination of the endmember parameters is primarily based on hydrocarbon generation thermal simulation experimental data. When hydrocarbon generation thermal simulation experimental data is insufficient, supplementary constraints are provided by literature survey results of the target strata in the study area and adjacent areas.

7. The method for identifying and quantitatively evaluating mixed sources of deep coalbed methane according to claim 1, characterized in that: The two-step quantitative calculation described in step S7 specifically includes: S7-1: Calculation of the ratio of oil-type gas to total coal-type gas based on ethane carbon isotopes: Let the proportion of oil-type gas in the gas mixture be... f oil The total proportion of coal syngas is f coal ,but: f oil + f coal =1 d 13 C 2,mix = f oil d 13 C 2,oil + f coal d 13 C 2,coal Where, δ 13 C 2,mix The measured carbon isotope values ​​of ethane in the sample; δ 13 C 2,oil The carbon isotope end-member values ​​of oil-type ethane gas; δ 13 C 2,coal The carbon isotope end-member values ​​of ethane in coal-type gas; The oil-gas ratio was calculated from this. f oil and the proportion of total coal gas f coal ; S7-2: Calculate the carbon isotope value δ of methane in coal-type gas after removing oil-type gas. 13 C 1,coal-mix : d 13 C 1,coal-mix =(δ 13 C 1,mix - f oil ×d 13 C 1,oil ) / f coal Where, δ 13 C 1,mix The measured carbon isotope values ​​of methane in the sample are δ. 13 C 1,oil The carbon isotope end-member values ​​of oil-type gaseous methane; S7-3: Calculation of the proportion of in-situ coal briquette gas and highly mature coal briquette gas in total coal briquette gas based on methane carbon isotopes: Let f be the proportion of in-situ coal briquette gas in the total coal briquette gas. i The proportion of highly mature coal-type gas is f h ,but: f i + f h =1 δ 13 C 1,coal-mix = f i ×δ 13 C 1,i + f h ×δ 13 C 1,h Where, δ 13 C 1,i The carbon isotope end-member value of methane in in-situ coal-type gas, δ 13 C 1,h The carbon isotope end-member value of methane in highly mature coal-type gas; The proportion of in-situ coal briquette gas f is thus calculated. i and the proportion of highly mature coal-type gas f h ; S7-4: Calculate the absolute contribution ratio of the three types of gases in the total mixture: F oil =f oil F i =f coal ×f i F h =f coal ×f h Among them, F oil F i F h These represent the absolute contribution ratios of oil-type gas, in-situ coal-type gas, and highly mature coal-type gas in the total mixed gas, respectively, and satisfy F... oil +F i +F h =1.

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