Calculation method for gas mixing contribution ratio of coal rocks with different maturity degrees

Abstract

The invention discloses a method for calculating the gas mixing contribution ratio of coal rocks with different maturity degrees. The method comprises the following steps: S1, establishing a mixed source gas mixing ratio identification dynamic model; s2, taking a certain natural gas exploitation area as a research object, acquiring a plurality of coal rock gas and mudstone gas samples, and measuring methane carbon isotope, ethane carbon isotope and drying coefficient; s3, taking a plurality of unoxidized pure coal rock samples and pure mudstone samples, and measuring vitrinite reflectivity; s4, performing correlation analysis according to the data measured in the steps S2 and S3 to obtain a regression equation of each parameter; s5, substituting the regression equation into the model formula, and drawing a natural gas mixing ratio identification chart; and S6, substituting the data values of the methane carbon isotope, the ethane carbon isotope and the drying coefficient of the natural gas sample to be detected into the chart to obtain the coal-rock-gas mixing contribution ratio. According to the method disclosed by the invention, the contribution proportions of different types of hydrocarbon source rocks with different maturity degrees can be calculated through methane carbon isotope, ethane carbon isotope and a drying coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of oil extraction, and in particular to a method for calculating the mixed contribution ratio of coal-rock gas with different maturity levels. Background Art

[0002] Natural gas is a mixture of hydrocarbon and non-hydrocarbon gases naturally found in strata. The related coal rock gas, generated in the coal rock itself or transported into the coal rock from other sources, exists in both free and adsorbed states, with a high free gas content. Effective reservoir transformation can rapidly produce gas, enabling industrial production. Its essence is a hydrocarbon gas. In the complex geological structure of coal-bearing strata, coal is not the only source rock. In fact, mudstones developed in the upper and lower strata also have the ability to serve as source rocks and provide hydrocarbons. The carbon isotope composition of natural gas produced by the thermal cracking of organic matter is closely linked to the thermal evolution of the parent material. This correlation provides important clues to the nature of source rocks and can, to a certain extent, reflect their characteristics.

[0003] In the field of natural gas research, methane and ethane carbon isotopes play a key role and are often used to determine the maturity and genetic type of natural gas. Methane carbon isotopes are particularly affected by maturity and are therefore often used as a key indicator of natural gas maturity. While natural gas carbon isotopes are generally affected by thermal evolution, the carbon isotopes of heavier hydrocarbons such as ethane are relatively stable and less affected by thermal maturity. Instead, they primarily reflect differences in the type of gas parent material. Therefore, ethane carbon isotopes have become a key indicator for determining the genetic type of natural gas.

[0004] Coal-bearing source rocks and argillaceous source rocks, due to their distinct parent material types, produce natural gas with distinct characteristics. However, natural gas derived from both coal-bearing and argillaceous source rocks is humic, making conventional methods difficult to determine the mixing ratio between the two types of natural gas. While precise ethane carbon isotope analysis can distinguish these two types of natural gas to a certain extent, it is difficult to distinguish the contributions of different source rocks when identifying mixed-origin coal-rock gas, particularly when mixing humic coal-rock gas with humic mudstone gas. Currently, when determining the contribution ratio of different source rocks in mixed-origin coal-rock gas of varying maturity, the distinction between coal-rock gas and mudstone gas is often converted to that between humic and sapropelic natural gas, ignoring the influence of humic mudstone gas. Furthermore, the common phenomenon of mixed hydrocarbon sources in coal-rock gas makes it impossible to simultaneously determine the maturity and genetic type of coal-rock gas. Furthermore, the influence of thermal evolution on carbon isotopes is neglected, resulting in significant errors in conventional methods for determining the maturity and genetic type of mixed-origin coal-rock gas. In short, existing methods are unable to accurately determine the contribution ratios of different source rocks in mixed-origin coal-rock gas of varying maturity. Therefore, it is of great significance to establish a calculation method that can directly determine the contribution ratios of different source rocks in mixed-origin coal-rock gas and mudstone gas. Summary of the Invention

[0005] In view of the problem that existing technical methods cannot accurately determine the contribution ratio of different source rocks in mixed genetic coal-rock gas of different maturity, the present invention provides a method for calculating the mixed contribution ratio of coal-rock gas of different maturity.

[0006] The method for calculating the mixed contribution ratio of coal-rock gas with different maturities provided by the present invention comprises the following steps:

[0007] S1. Establish a dynamic model for identifying the mixing ratio of mixed source gas. The model includes the following two formulas:

[0008]

[0009] Where, δ 13 C 1(混合) is the carbon isotope of methane in mixed natural gas, δ 13 C 2(混合) is the carbon isotope of ethane in mixed natural gas, α is the mixing ratio of coal gas and natural gas, To calculate the methane gas content using coal gas maturity; To calculate the ethane gas content using coal gas maturity, R o煤 is the maturity of coal gas, To calculate methane carbon isotopes using coal gas maturity, To calculate ethane carbon isotopes using coal gas maturity, δ 13 C 1(β煤)To calculate methane carbon isotopes using the coal gas drying coefficient, δ 13 C 2(β煤) To calculate ethane carbon isotopes using the coal gas drying coefficient; To calculate the methane gas content using mud gas maturity, To calculate ethane gas content using mud gas maturity, R o泥 is the maturity of mudstone gas, To calculate methane carbon isotopes using mud gas maturity, To calculate ethane carbon isotopes using mud gas maturity, δ 13 C 1(β泥) To calculate the methane carbon isotope using the shale gas drying coefficient, δ 13 C 2(β泥) To calculate ethane carbon isotopes using the shale gas drying coefficient, β 煤 is the coal gas drying coefficient, β 泥 is the shale gas drying coefficient;

[0010] S2. Within a natural gas production area, several coal-rock gas and mud-rock gas samples were obtained to determine their methane and ethane carbon isotopes, as well as their drying coefficients. The coal-rock gas and mud-rock gas samples were obtained from pure mudstone and coal samples through hydrocarbon generation thermal simulation experiments.

[0011] S3. Take several unoxidized pure coal rock samples and pure mudstone samples to measure the vitrinite reflectance.

[0012] S4, perform correlation analysis based on the data measured in steps S2 and S3, and obtain the correlation between the parameters involved in step S1 and R o煤 , β 煤 , or R o泥 The relationship between , that is, the regression equation of each parameter is obtained.

[0013] S5. Substitute the regression equation obtained in step S4 into formulas (1) and (2) and draw a natural gas mixture ratio identification chart. The specific method is as follows:

[0014] S51, respectively, 13 C1, δ 13 C and drying coefficient are used as coordinates to establish a three-dimensional coordinate system;

[0015] S52, through the hypothesis method, the regression equation of each parameter is used to o煤 or R o泥 Indicates that the default R o煤 and R o泥 The value is equal to the natural gas maturity R o , using R o Replace R o煤 and R o泥, then substitute the regression equations of each parameter into formula (1) and (2), and R o The value range is set to 0.4~4.4%, and different R o煤 Value, δ in the three-dimensional coordinate system 13 C1-δ 13 Draw on the C2 plane to get δ 13 C1 and δ 13 C2 intersection diagram;

[0016] S53, through the hypothesis method, first R o煤 and R o泥 The drying coefficient β 煤 and β 煤 Then the regression equation of each parameter is transformed into the drying coefficient β 煤 and β 煤 Indicates that the default β 煤 and β 煤 The value of is equal to the natural gas drying coefficient β, and β is replaced by β 煤 and β 煤 , then substitute the regression equations of each parameter into formula (1) and (2), set the β value range to 1.6~90.6, and take different β values ​​at equal intervals. 13 C1-drying coefficient plane drawing to obtain δ 13 C1 and drying coefficient intersection diagram; δ in the three-dimensional coordinate system 13 C2-drying coefficient plane drawing to obtain δ 13 The intersection diagram of C2 and dryness coefficient; ultimately forming a natural gas mixing ratio identification chart.

[0017] S6, bring the data values ​​of methane carbon isotope, ethane carbon isotope and drying coefficient of the natural gas sample to be tested into the chart of step S5 and 13 C1-δ 13 C2 plane, δ 13 C1-drying coefficient plane and δ 13 Project the C2-dryness coefficient plane and read the corresponding value on the intersection diagram. The average of the read values ​​is the coal-rock gas mixing contribution ratio; the mudstone gas mixing contribution ratio is equal to 100% minus the coal-rock gas mixing contribution ratio.

[0018] In step S6, if the projection point on a certain plane does not fall within the intersection diagram, the value cannot be read, and the average of the read values ​​of the other two planes is used as the coal-rock gas mixing contribution ratio; if the projection point on two planes does not fall within the intersection diagram, the value cannot be read, and the read value of another plane is directly used as the coal-rock gas mixing contribution ratio; if the projection point on none of the three planes falls within the intersection diagram, it means that the plate is not suitable for the test of the sample, and it is necessary to re-sample and make a new plate according to the method of steps S2-S5.

[0019] Compared with the prior art, the present invention is beneficial in that:

[0020] (1) The calculation method of the present invention is applicable to coal-rock gas of mixed origin with various maturity levels, and the accuracy of calculating the contribution ratio of different source rocks of coal-rock gas of mixed origin of coal-measure source rocks and muddy source rocks is high.

[0021] (2) For different natural gas production areas, the method of the present invention can be used to draw a natural gas mixing ratio identification chart suitable for the area, which can then be used to determine the coal-rock gas mixing contribution ratio of all samples to be tested in the area.

[0022] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the δ obtained by analysis in the embodiment 13 C 1(β煤) and β 煤 The relationship curve between .

[0024] Figure 2 This is a natural gas mixing ratio identification chart drawn in the embodiment. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] The present invention provides a method for calculating the mixed contribution ratio of coal-rock gas at different maturities based on methane carbon isotopes, ethane carbon isotopes, and dryness coefficient. Methane carbon isotopes become heavier as the degree of thermal evolution increases. There are obvious differences in the parent material sources of coal and mudstone. In the process of gas generation from source rocks, the carbon isotopes of kerogen have an inherited effect. Therefore, under the same or similar degree of thermal evolution, coal-rock gas from coal-bearing source rocks has a heavier carbon isotope composition than mudstone gas from muddy source rocks. According to the analysis of geochemical data of coal-rock gas samples, coal-rock gas is generally dominated by methane, with most of the methane content exceeding 80%, and the methane carbon isotope values ​​are mainly distributed in the range of -45‰ to -25‰. Ethane carbon isotopes are divided into two categories: coal-bearing source rocks and muddy source rocks. The ethane carbon isotopes of natural gas generated from coal-bearing source rocks are relatively heavy, mainly distributed in the range of -22‰ to -16‰; the ethane carbon isotopes of natural gas generated from muddy source rocks are relatively light, mainly distributed in the range of -29‰ to -22‰.

[0027] The study found that there is a significant difference between the identification of the mixing ratio of coal gas and mud gas and the traditional identification of humic natural gas and sapropelic natural gas. The traditional method uses methane carbon isotopes and ethane carbon isotopes as the basis for identification. There are obvious deficiencies in the identification of coal gas and mud gas. Both coal gas and mud gas have humic kerogen gas supply, and the error of relying solely on methane carbon isotopes and ethane carbon isotopes for judgment is large. Therefore, in addition to methane carbon isotopes and ethane carbon isotopes, the present invention also analyzed a large amount of hydrocarbon generation thermal simulation experimental data and found that there is a certain difference in the dryness coefficient of coal gas and mud gas. Under the same maturity conditions, the dryness coefficient of mud gas is significantly lower than that of coal gas. The dryness coefficient can be used to assist in judging the mixing ratio of mud gas and coal gas.

[0028] Based on this, the method of the present invention calculates the mixed contribution ratio of coal gas with different maturity levels through methane carbon isotope, ethane carbon isotope and dryness coefficient.

[0029] The following describes the calculation method of the mixed contribution ratio of coal and rock gas with different maturity levels provided by the present invention, taking a natural gas mining area in a basin as an example. The specific steps are as follows:

[0030] S1. Establish a dynamic model for identifying the mixing ratio of mixed source gases.

[0031] δ 13 C1 can reflect the maturity of natural gas, δ 13 C2 can reflect the type of natural gas parent material. In actual operation, it is difficult to identify it only by these two parameters. 13 C1 and δ 13 In addition to C2, a parameter needs to be selected to establish a mixed equation. 13 C1 and δ13 C2 is fitted and it is found that the drying coefficient is related to δ 13 C1 and δ 13 C2 has a good correlation (see Table 1), so the drying coefficient is selected as the third parameter.

[0032] Table 1 Correlation coefficient between carbon isotope and drying coefficient

[0033]

[0034]

[0035] Based on the definition of isotopes and the principle of mass balance, precise formulas for the carbon isotope ratios of mixed-source gases, the carbon isotope ratios of end-member gases, and the mixing ratio can be derived. These formulas can be approximated as weighted averages of the end-member gases. Using the geochemical model of end-member gases instead of static parameters, a dynamic model for determining the mixing ratio of mixed-source gases is derived. The model includes the following two formulas:

[0036]

[0037] In the formula, the meaning of each parameter is explained in Table 2.

[0038] Table 2 Explanation of the meaning of relevant parameters

[0039]

[0040]

[0041] S2. Obtain several coal-rock gas and mud-rock gas samples from the study area and determine their methane and ethane carbon isotopes, as well as their drying coefficients. Coal-rock gas and mud-rock gas samples were obtained from pure mudstone and coal samples through hydrocarbon generation thermal simulation experiments.

[0042] The determination method of methane carbon isotopes and ethane carbon isotopes is as follows:

[0043] (1) Take 3 ml of coal gas or mud gas sample and inject it into an Agilent 6890N gas chromatograph equipped with a flame ionization detector. Then pass it through a capillary column (filled with alumina, 50 m × 0.53 mm) for gas separation.

[0044] (2) The temperature program of the gas chromatograph was set as follows: initial temperature was 40°C, constant temperature was maintained for 7 min, then the temperature was increased at 10°C / min to 180°C, constant temperature was maintained for 15 min, and the carrier gas was helium at a flow rate of 13 ml / min;

[0045] (3) collecting separated hydrocarbon compounds, including methane gas and ethane gas, by chromatographic separation;

[0046] (4) The separated methane gas reacts with oxygen in a high-temperature reaction tube at a reaction temperature of 1000°C. The resulting reaction gas passes through a liquid nitrogen cold trap and an alcohol cold trap in sequence to separate the carbon dioxide gas from water and helium;

[0047] (5) The obtained carbon dioxide gas is detected in a Thermo Delta V mass spectrometer equipped with an Agilent 6890N gas chromatograph to obtain the value of the methane carbon isotope in the natural gas;

[0048] (6) The separated ethane gas reacts with oxygen in a high-temperature reaction tube at a reaction temperature of 900°C. The resulting reaction gas passes through a liquid nitrogen cold trap and an alcohol cold trap in sequence to separate the carbon dioxide gas from water and nitrogen;

[0049] (7) The obtained carbon dioxide gas is detected in a Thermo Delta V mass spectrometer equipped with an Agilent 6890N gas chromatograph to obtain the value of the ethane carbon isotope in the natural gas.

[0050] The drying coefficient is determined as follows:

[0051] (1) Use a stainless steel high-pressure sampling bottle with a double-valve design and passivation treatment; maintain the pipeline pressure (≥5MPa) to prevent the volatilization of light components; keep the temperature consistent with the ambient temperature to avoid condensation; flush the pipeline with the gas to be tested at least three times before sampling to reduce air contamination. Analyze within 24 hours after sampling, or store the sample at a low temperature (-20℃) to inhibit composition changes.

[0052] (2) A chromatograph equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD) was used. A Porapak Q precolumn was used to separate interfering compounds such as CO2 and H2S. A HP-PLOT Al2O3 (50 m × 0.53 mm × 15 μm) main column was used to separate C1-C6 hydrocarbons. High-purity helium was used as the carrier gas at a flow rate of 1.5 mL / min. The inlet temperature was set to 200°C with a split ratio of 50:1. The column temperature was initially set at 40°C for 5 min, then increased to 180°C at a rate of 10°C / min and held for 10 min. The detector temperatures were set to 250°C for the FID and 200°C for the TCD. The injection volume was 1 μL (via a six-port valve loop).

[0053] (3) Use GC-MS for qualitative analysis of complex components (such as sulfur-containing compounds) to avoid interference from overlapping chromatographic peaks.

[0054] (4) Data processing

[0055] Normalize the peak areas, integrate the peak areas of each component, and combine them with a correction factor. The correction factor must be pre-calibrated using standard gases, i.e., a multi-point calibration using NIST SRM standard gases (e.g., SRM 2614a).

[0056] Drying coefficient calculation:

[0057]

[0058] A is the peak area, and f is the correction factor for each component.

[0059] (5) Error control and quality control

[0060] Repeatability: three parallel determinations, relative standard deviation (RSD) ≤ 1%;

[0061] Standard addition method: add C2H6 standard gas of known concentration to the sample, and the recovery rate needs to be between 90% and 102%;

[0062] Blank experiment: Use high-purity helium to verify the system background.

[0063] (6) Auxiliary analysis method (cross validation)

[0064] Dew point measurement: A chilled mirror dew point meter (Michelson interferometer type) is used to measure the water dew point and hydrocarbon dew point of the gas. The drying coefficient is negatively correlated with the hydrocarbon dew point and is used to verify GC results.

[0065] Infrared spectroscopy (FTIR): Detection of CH4 and C2H6 characteristic absorption peaks (CH4: 3018cm -1 、C2H6:2975cm -1 ), supplemented with quantitative analysis.

[0066] S3. measuring the vitrinite reflectance;

[0067] Take several unoxidized pure coal rock samples and pure mudstone samples to measure the vitrinite reflectance respectively. The measurement method is as follows:

[0068] (1) Select unoxidized pure coal rock samples or pure coal rock samples, seal and store them in an argon environment to avoid photothermal decomposition; vacuum impregnate the samples with epoxy resin (cured at 40℃ for 24h) to avoid high temperature-induced changes in the organic matter structure; grind them with silicon carbide sandpaper from 400 to 1200 mesh, and then polish them with diamond suspension (3μm to 0.25μm) until the surface is rough R a ≤0.02μm, ensuring no scratches interfere with reflectivity measurement.

[0069] (2) A halogen lamp (546 nm monochromatic light, color temperature 3200 K) combined with a polarized light system was used, the objective lens was a 50× oil immersion objective lens (NA = 0.85), the refractive index of the immersion oil was n = 1.518 (calibrated at 23 °C), and the detector was a photomultiplier tube (PMT) or a high dynamic range CCD (signal-to-noise ratio ≥ 10 6 :1) microphotometer system; and using synthetic sapphire (R o =0.58%) or YAG crystal (R o =0.89%) for calibration, and the daily calibration deviation is ≤0.02%.

[0070] (3) Identify homogeneous vitrinite under transmitted light and exclude fragmentary vitrinite or oxidized areas (oxidized areas show blue light in fluorescence mode); measure each particle 10 times under rotated polarized light to eliminate the influence of anisotropy, and randomly select no less than 50 particles (particle size ≥ 5 μm) and record the maximum reflectance (R o,max ) and random reflectivity (R o,ran ).

[0071] (4) Eliminate outliers through Grubbs test to make the confidence level 95%; calculate the mean R o,mean and standard error (SE), and a histogram was drawn to analyze the maturity distribution pattern.

[0072] (5) Error control and quality control

[0073] Repeat the experiment to ensure that the deviation between different operators of the same sample is ≤0.05%. A standard sample (SARM 20, Ro = 0.58%) is inserted into each batch, and the measured value must be within ±0.03%. The laboratory temperature is controlled at 23 ± 1 ° C and the humidity is less than 40% to avoid thermal drift and sample moisture absorption.

[0074] S4, perform correlation analysis between parameters based on the large amount of data measured in steps S2 and S3, and obtain the correlation between the parameters involved in step S1 and R o煤 , β 煤 , or R o泥 The relationship between , that is, the regression equation of each parameter is obtained.

[0075] To analyze δ 13 C 1(β煤) and β 煤 The relationship between Figure 1 As shown, according to the methane carbon isotope and drying coefficient data of several coal gas measured in step S2, β 煤 is the horizontal axis, δ 13 C 1(煤) As the ordinate, draw a graph in the plane coordinate system, and fit the fitting curve and the corresponding fitting formula, which is δ 13C 1(β煤) and β 煤 The relationship between δ and δ is as follows: 13 C 1(β煤) =16.763β 煤 -47.702.

[0076] According to the same method, other parameters and R o煤 , β 煤 , or R o泥 The regression equations of the parameters obtained in this embodiment are shown in equations (4)-(16), and the correlation coefficients of the regression equations are shown in Table 3.

[0077] β 煤 =0.3758lnR o煤 +0.2824 (4)

[0078] C 1(煤) =0.3758lnR o煤 +0.2824 (5)

[0079] C 2(煤) =-0.117lnR o煤 +0.1567 (6)

[0080] δ 13 C 1(煤) =10.409lnR o煤 +40.974 (7)

[0081] δ 13 C 2(煤) =12.897lnR o煤 -25.595 (8)

[0082] δ 13 C 1(β煤) =16.763β 煤 -47.702 (9)

[0083] δ 13 C 2(β煤) =29.003β 煤 -44.82 (10)

[0084] β 泥 =0.3689lnR o泥 +0.2563 (11)

[0085] C 1(泥) =0.3689lnR o泥 +0.2563 (12)

[0086] C 2(泥)=-0.115lnR o泥 +0.1496 (13)

[0087] δ 13 C 1(泥) =10.906lnR o泥 +41.318 (14)

[0088] δ 13 C 2(泥) =8.7242R o泥 +38.469 (15)

[0089] δ 13 C 1(β泥) =24.483β 煤 -54.159 (16)

[0090] Table 3 Correlation coefficients of regression equations

[0091] Parameter 1 Parameter 2 Correlation coefficient <![CDATA[β 煤 ]]> <![CDATA[R o煤 ]]> 0.9665 <![CDATA[C 1(煤) ]]> <![CDATA[R o煤 ]]> 0.9751 <![CDATA[C 2(煤) ]]> <![CDATA[R o煤 ]]> 0.9683 <![CDATA[δ 13 C 1(煤) ]]> <![CDATA[R o煤 ]]> 0.9909 <![CDATA[δ 13 C 2(煤) ]]> <![CDATA[R o煤 ]]> 0.9645 <![CDATA[β 泥 ]]> <![CDATA[R o泥 ]]> 0.9714 <![CDATA[C 1(泥) ]]> <![CDATA[R o泥 ]]> 0.9834 <![CDATA[C 2(泥) ]]> <![CDATA[R o泥 ]]> 0.9635 <![CDATA[δ 13 C 1(泥) ]]> <![CDATA[R o泥 ]]> 0.9621 <![CDATA[δ 13 C 2(泥) ]]> <![CDATA[R o泥 ]]> 0.9477 <![CDATA[δ 13 C 1(β煤) ]]> <![CDATA[β 煤 ]]> 0.7691 <![CDATA[δ 13 C 2(β煤) ]]> <![CDATA[β 煤 ]]> 0.704 <![CDATA[δ 13 C 1(β泥) ]]> <![CDATA[β 泥 ]]> 0.8436 <![CDATA[δ 13 C 2(β泥) ]]> <![CDATA[β 泥 ]]> 0.6114

[0092] S5. Draw a natural gas mixture ratio identification chart. The specific method is as follows:

[0093] S51, respectively, 13 C1, δ 13 C and drying coefficient are used as coordinates to establish a three-dimensional coordinate system;

[0094] S52, through the hypothesis method, the regression equations (4)-(16) of each parameter are transformed into R o煤 or R o泥 Indicates that the default R o煤 and R o泥 The value is the same and equal to the natural gas maturity R o , using R o Replace R in the regression equation formula o煤 and R o泥 , and then substitute the regression equations of each parameter into formula (1) and (2); o The value range of is set to 0.4~4.4%, and different R o煤 Value, δ in the three-dimensional coordinate system 13 C1-δ 13 Draw on the C2 plane to get δ 13 C1 and δ 13 C2 intersection diagram, see Figure 2 Medium black plate.

[0095] S53, through the hypothesis method, first R o煤 and R o泥 The drying coefficient β 煤 and β煤 Then the regression equation of each parameter is transformed into the drying coefficient β 煤 and β 煤 Indicates that the default β 煤 and β 煤 The value is the same and equal to the natural gas drying coefficient β, and β is used to replace β in the regression equation. 煤 and β 煤 , and then substitute the regression equations of each parameter into formula (1) and (2); set the β value range to 1.6~90.6, and take different β values ​​at equal intervals (interval 1), and in the δ 13 C1-drying coefficient plane drawing to obtain δ 13 C1 and drying coefficient intersection diagram, see Figure 2 Middle red plate. δ in the three-dimensional coordinate system 13 C2-drying coefficient plane drawing to obtain δ 13 C2 and drying coefficient intersection diagram, see Figure 2 Medium blue plate. The final form Figure 2 The natural gas mixture ratio identification chart shown.

[0096] S6. For the natural gas sample to be tested, first measure the specific values ​​of the methane carbon isotope, ethane carbon isotope and drying coefficient of the natural gas sample. The test method is the same as that described in step S2, but replace the test sample with the natural gas sample here. Then, substitute the specific values ​​of the methane carbon isotope, ethane carbon isotope and drying coefficient of the natural gas sample measured into Figure 2 In the plate and in δ 13 C1-δ 13 C2 plane, δ 13 C1-drying coefficient plane and δ 13 Project the C2-dryness coefficient plane and read the corresponding value on the intersection diagram. The average of the read values ​​is the coal-rock gas mixing contribution ratio. The mud gas mixing contribution ratio is equal to 100% minus the coal-rock gas mixing contribution ratio.

[0097] In order to verify the accuracy of the calculation method of the present invention, the geochemical parameters of the artificially mixed gas mixture were substituted into the identification chart for comparative analysis with the actual mixing ratio. The results are shown in Tables 4 and 5.

[0098] Table 4 Comparison of calculated ratio and actual ratio

[0099]

[0100] Table 5 Prediction effect table

[0101]

[0102]

[0103] The data in the table show that the calculation method of the present invention for the mixed contribution ratio of coal-rock gas with different maturities produces results with high accuracy.

[0104] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for calculating the mixed contribution ratio of coal-rock gas with different maturity levels, characterized in that: The following steps are involved: S1. Establish a dynamic model for identifying the mixing ratio of mixed source gas. The model includes the following two formulas: Where, δ 13 C 1(混合) is the carbon isotope of methane in mixed natural gas, δ 13 C 2(混合) is the carbon isotope of ethane in mixed natural gas, α is the mixing ratio of coal gas and natural gas, To calculate the methane gas content using coal gas maturity; To calculate the ethane gas content using coal gas maturity, R o煤 is the maturity of coal gas, To calculate methane carbon isotopes using coal gas maturity, To calculate ethane carbon isotopes using coal gas maturity, δ 13 C 1(β煤) To calculate methane carbon isotopes using the coal gas drying coefficient, δ 13 C 2(β煤) To calculate ethane carbon isotopes using the coal gas drying coefficient; To calculate the methane gas content using mud gas maturity, To calculate ethane gas content using mud gas maturity, R o泥 is the maturity of mudstone gas, To calculate methane carbon isotopes using mud gas maturity, To calculate ethane carbon isotopes using mud gas maturity, δ 13 C 1(β泥) To calculate the methane carbon isotope using the shale gas drying coefficient, δ 13 C 2(β泥) To calculate ethane carbon isotopes using the shale gas drying coefficient, β 煤 is the coal gas drying coefficient, β 泥 is the mud gas drying coefficient; S2. Taking a natural gas production area as the research object, obtain several coal gas and mud gas samples to measure the methane carbon isotope and ethane carbon isotope, as well as the drying coefficient; S3. Take a number of unoxidized pure coal rock samples and pure mudstone samples to measure the vitrinite reflectance; S4, perform correlation analysis based on the data measured in steps S2 and S3, and obtain the correlation between the parameters involved in step S1 and R o煤 , β 煤 , or R o泥 The relationship between , that is, the regression equation of each parameter is obtained; S5, substituting the regression equation obtained in step S4 into formulas (1) and (2) and drawing a natural gas mixing ratio identification chart; S6, bring the data values ​​of methane carbon isotope, ethane carbon isotope and drying coefficient of the natural gas sample to be tested into the chart of step S5 and 13 C1-δ 13 C2 plane, δ 13 C1-drying coefficient plane and δ 13 Project the C2-dryness coefficient plane and read the corresponding value on the intersection diagram. The average of the read values ​​is the coal-rock gas mixing contribution ratio.

2. The method for calculating the mixed contribution ratio of coal-rock gas with different maturity levels according to claim 1, characterized in that: The specific method of step S5 is as follows: S51, respectively, 13 C1, δ 13 C and drying coefficient are used as coordinates to establish a three-dimensional coordinate system; S52, through the hypothesis method, the regression equation of each parameter is used to o煤 or R o泥 Indicates that the default R o煤 and R o泥 The value is equal to the natural gas maturity R o , using R o Replace R o煤 and R o泥 , then substitute the regression equations of each parameter into formula (1) and (2), and R o The value range is set to 0.4~4.4%, and different R o煤 Value, δ in the three-dimensional coordinate system 13 C1-δ 13 Draw on the C2 plane to get δ 13 C1 and δ 13 C2 intersection diagram; S53, through the hypothesis method, first R o煤 and R o泥 The drying coefficient β 煤 and β 煤 Then the regression equation of each parameter is transformed into the drying coefficient β 煤 and β 煤 Indicates that the default β 煤 and β 煤 The value of is equal to the natural gas drying coefficient β, and β is replaced by β 煤 and β 煤 , then substitute the regression equations of each parameter into formula (1) and (2), set the β value range to 1.6~90.6, and take different β values ​​at equal intervals. 13 C1-drying coefficient plane drawing to obtain δ 13 C1 and drying coefficient intersection diagram; δ in the three-dimensional coordinate system 13 C2-drying coefficient plane drawing to obtain δ 13 The intersection diagram of C2 and dryness coefficient; ultimately forming a natural gas mixing ratio identification chart.

3. The method for calculating the mixed contribution ratio of coal-rock gas with different maturity levels according to claim 1, characterized in that: In step S6, if the projection point on a certain plane does not fall within the intersection diagram, the value cannot be read, and the average of the read values ​​of the other two planes is used as the coal-rock gas mixing contribution ratio; if the projection point on two planes does not fall within the intersection diagram, the value cannot be read, and the read value of another plane is directly used as the coal-rock gas mixing contribution ratio; if the projection point on none of the three planes falls within the intersection diagram, it means that the plate is not suitable for the test of the sample, and it is necessary to re-sample and make a new plate according to the method of steps S2-S5.

4. The method for calculating the mixed contribution ratio of coal-rock gas with different maturity levels according to claim 1, wherein: In step S2, coal rock gas and mudstone gas samples are obtained from pure mudstone and pure coal rock samples through hydrocarbon generation thermal simulation experiments.

Images