Coal measure strata abnormal weight delta13CCO2 cause analysis method

Abstract

The invention relates to the technical field of coal measure strata CO2 cause analysis, in particular to a coal measure strata abnormal heavy delta13CCO2 cause analysis method, which is characterized in that on the basis of judging CO2 causes by a geological background, a parameter method and a cross plot method, the lithology of parent rock of a target stratum is emphatically evaluated on the basis of main quantity, trace element data and organic element data, and the basis of determining the CO2 causes by the geological background, the parameter method and the cross plot method is provided. Whether abundance transition metal is distributed in a target layer is analyzed, whether inorganic natural gas caused by transition metal catalytic action exists in the target layer or not is determined, and the CO2 cause is comprehensively analyzed by combining natural gas and CO2 carbon isotope and component content data.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 origin analysis in coal-bearing strata, and particularly relates to a method for analyzing the origin of abnormal heavy δ 13 C CO2 in coal-bearing strata. Background Technique

[0002] CO2 is the main non-hydrocarbon gas in natural gas, and its origin mainly includes organic origin, inorganic origin and biogenic origin. Previous researchers usually used δ 13 C1 and C1 / C 2+3 , δ 13 C CO2 distribution, the cross plot of δ 13 C CO2 and the content of CO2 component, and 40 Ar / 36 Ar and 3 He / 4 He cross plot to judge the source of CO2. However, in the research, there are often different origins indicated by different methods. For example, in the natural gas in the Xihu Sag, part of the δ 13 C CO2 is abnormally heavy > -8‰, but 40 Ar / 36 Ar and 3 He / 4 He show that there is no mantle-derived inorganic gas. The geological background shows that there is no carbonate rock in the target layer, nor is there inorganic gas generated by thermal decomposition of carbonate rock. This brings difficulties to revealing the true origin of CO2. Therefore, the identification of the origin of abnormally heavy δ 13 C CO2 urgently needs to be solved.

[0003] The prior art usually judges the origin of CO2 by using the parameter method and the cross plot method on the basis of clarifying the geological background, that is, whether there are deep major faults leading to the mantle, whether there are carbonate rock strata, etc. Among them, the distribution range of δ 13 C CO2 can judge the origin. The organic thermal origin δ 13 C CO2 is usually between -10‰ and -25‰, the crust-mantle source inorganic origin δ 13 C CO2 is usually between -9‰ and -5‰, and the inorganic origin of carbonate rock heated δ13C CO2 is usually between -3‰ and +3‰; 40 Ar / 36 Ar and 3 He / 4 in the He cross plot 3 He / 4 He > 10 -6 and < 10-6 represent mantle-derived inorganic gas and crust-derived gas, respectively. 13 C CO2 The heavier ones are classified as crustal-mantle inorganic, while δ 13 C CO2 Less severe ones are classified as organic in origin.

[0004] However, the existing technology for δ 13 C CO2 The cause analysis of the abnormal 13 C CO2 The cause analysis is inaccurate, which virtually reduces the abnormal weight. 13 C CO2 The authenticity of the cause. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a method for 13 The CO2 genesis analysis method of the present invention focuses on evaluating the lithology of the target layer parent rock based on the major and trace element data and organic element data, based on the geological background, parameter method and intersection diagram method to determine the CO2 genesis, analyzes whether the target layer has high-abundance transition metals, clarifies whether the target layer has inorganic natural gas originated from the catalytic effect of transition metals, and comprehensively analyzes the CO2 genesis by combining the natural gas and CO2 carbon isotope and component content data.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: An abnormally heavy delta 13 The CO2 genesis analysis method comprises the following steps: Source rock samples were collected in the core library, and the sample depth and lithology information were recorded. Major and trace element determinations were performed to obtain Ni element concentrations and Al2O3 / TiO2 values. Organic elements were determined for source rock samples to obtain O / C ratios.

[0007] Collect natural gas samples at the natural gas well site and perform carbon isotope determination on the natural gas samples to obtain δ 13 C1 and δ 13 C CO2 .

[0008] Establish the intersection diagram of transition metal elements and Al2O3 / TiO2, and make it clear that if the content of transition metal elements gradually increases as the parent rock lithology changes to intermediate-basic, then establish δ 13 C1, δ 13 C CO2 , transition metals and Al2O3 / TiO2 vs depth and δ 13 C1 and δ 13 C CO2 Intersection diagram.

[0009] Analyze δ 13 C1, δ 13 C CO2 , the variation trends of transition metals and Al2O3 / TiO2 with depth, clarify the variation of the distribution depth of intermediate-basic parent rocks. If the content of transition metal elements gradually increases with the increase of the depth of intermediate-basic parent rocks, δ 13 C1 gradually becomes lighter, while δ 13 C CO2 gradually becomes heavier, it indicates that there is δ 13 C1 and δ 13 C CO2 exchange resulting in abnormally heavy δ 13 C CO2 .

[0010] Establish a cross-plot of transition metal elements and O / C to clarify whether the enrichment of transition metal elements promotes the pyrolysis of coal-measure source rocks. When the enrichment of transition metals promotes the thermal decomposition of coal-measure source rocks, it indicates that there is abnormally heavy δ 13 C CO2 .

[0011] Based on the fact that the existing technology has an incomplete consideration of the origin analysis of δ 13 C CO2 , resulting in inaccurate origin analysis of abnormally heavy δ 13 C CO2 , this invention proposes a method for analyzing the origin of abnormally heavy δ 13 CO2 in coal-bearing strata. Based on the judgment of the origin of CO2 by geological background, parameter method and cross-plot method, and based on the major, trace element data and organic element data, it focuses on evaluating the lithology of the parent rock of the target layer, analyzes whether the target layer is distributed with high-abundance transition metals, clarifies whether there is inorganic natural gas caused by the catalytic action of transition metals in the target layer, combines the analysis of the lithological characteristics of the parent rock and whether the transition metals are enriched, as well as the vertical distribution characteristics of the transition metal content, δ 13 C1 and δ 13 C CO2 , clarifies the possibility of the occurrence of Fischer-Tropsch synthesis reaction and δ 13 C1 and δ 13 C CO2 exchange in the target layer, analyzes whether the real origin of abnormally heavy δ 13 C CO2 is organic origin, inorganic origin, abnormally heavy δ 13 C CO2 caused by Fischer-Tropsch synthesis reaction or abnormally heavy δ 13 C1 and δ 13 C CO2 exchange resulting in abnormally heavy δ 13 C CO2 , and then comprehensively analyzes abnormally heavy δ13 C CO2 True cause.

[0012] In a preferred embodiment of the present invention, the transition metal is Ni.

[0013] In a preferred embodiment of the present invention, a cross plot of Ni element and Al2O3 / TiO2 is established to clarify whether the Ni element content gradually increases as the parent rock lithology changes to neutral-basic, and to analyze whether the enrichment of Ni element is controlled by the lithology of the medium-basic parent rock.

[0014] In a preferred embodiment of the present invention, an Al2O3 / TiO2 value < 8 represents a basic parent rock, 8 - 21 represents a neutral parent rock, and > 21 represents an acidic parent rock.

[0015] In a preferred embodiment of the present invention, 40 Ar / 36 Ar and 3 He / 4 In the cross plot of He, 3 He / 4 He > 10 -6 Represents mantle-derived inorganic gas, 3 He / 4 He < 10 -6 Represents crust-derived inorganic gas.

[0016] In a preferred embodiment of the present invention, it also includes analyzing whether there is a source-connected fault and whether there is mantle-derived and crust-derived inorganic genetic gas in combination with the geological background, and then analyzing whether there may be an inorganic origin for the abnormal heavy δ 13 C CO2 Whether there may be an inorganic origin.

[0017] In a preferred embodiment of the present invention, δ 13 C CO2 < -10‰ is of organic origin, δ 13 C CO2 Between -10‰ and -8‰ is of organic-inorganic mixed origin, and δ13C CO2 > -8‰ is of inorganic origin.

[0018] In a preferred embodiment of the present invention, it also includes measuring the component content of the natural gas sample to obtain the CO2 content, establishing a cross plot of δ 13 C CO2 And CO2, and analyzing whether the abnormal heavy δ 13 C CO2 Is of organic origin, inorganic origin or organic-inorganic mixed origin; in combination with the lithology distribution characteristics in the formation, analyze whether there is an inorganic origin caused by the thermal decomposition of carbonate rocks in the target layer of the source rock.

[0019] In a preferred embodiment of the present invention, it further includes determining the helium and argon isotopes of the natural gas sample to obtain 40 Ar / 36 Ar value and 3 He / 4 He value, establishing 40 Ar / 36 Ar and 3 He / 4 He cross plot, and analyzing whether there is an inorganic origin.

[0020] In a preferred embodiment of the present invention, 40 Ar / 36 Ar and 3 He / 4 He cross plot, 3 He / 4 He>10 -6 represents mantle-derived inorganic gas, 3 He / 4 He<10 -6 represents crust-derived inorganic gas.

[0021] In a preferred embodiment of the present invention, the source rock is crushed before testing.

[0022] In fact, the Fischer-Tropsch synthesis reaction and the δ 13 C1 and δ 13 C CO2 exchange will also cause δ 13 C CO2 to be abnormally heavy. In the prior art research process, these two factors are usually ignored because under laboratory simulation conditions, without the action of a catalyst, the above reactions cannot occur at a geothermal temperature of 200°C to 700°C, while the highest temperature in the sedimentary basin strata is usually 150°C to 200°C, and the sedimentary basin cannot provide the temperature conditions for these two reactions. Therefore, the causes of these two abnormal heavy δ 13 C CO2 are ignored. However, when there is a transition metal catalyst, the Fischer-Tropsch synthesis reaction occurs at 100°C to 350°C, and the δ13C1 and δ 13 C CO2 exchange can occur above 200°C. Therefore, the main disadvantage of the previous methods is that they do not analyze whether there is a catalytic effect of transition metal Ni in the geological conditions, which virtually reduces the authenticity of the cause of the abnormally heavy δ 13 C CO2 cause.

[0023] Compared with the prior art, the beneficial effects of the present invention are: Based on the fact that the prior art does not comprehensively consider the cause analysis of δ 13 C CO2 resulting in abnormally heavy δ13 C CO2 Regarding the problem of inaccurate cause analysis of 13 δ 13 C1 and δ 13 C CO2 vertical distribution characteristics, clarify the possibility of Fischer-Tropsch synthesis reaction and δ 13 C1 and δ 13 C CO2 exchange occurring in the target layer, and analyze whether the real cause of abnormal heavy δ 13 C CO2 is organic origin, inorganic origin, abnormal heavy δ 13 C CO2 caused by Fischer-Tropsch synthesis reaction or abnormal heavy δ 13 C1 and δ 13 C CO2 exchange. Furthermore, comprehensively analyze the real cause of abnormal heavy δ 13 C CO2 and propose a method for analyzing the origin of CO2 in coal measures strata. Based on the geological background, parameter method and cross-plot method for judging the origin of CO2, and based on the major, trace element data and organic element data, focus on evaluating the lithology of the source rock in the target layer, analyze whether there is a high abundance of transition metals in the target layer, clarify whether there is inorganic natural gas caused by the catalytic action of transition metals in the target layer, and combine the analysis of the lithology characteristics of the source rock and the enrichment of transition metals, as well as the content of transition metals, δ 13 C CO2 true origin. Description of the Drawings

[0024] Figure 1 It is the cross-plot of Al2O3 / TiO2 and Ti content of coal measures hydrocarbon source in the study area.

[0025] Figure 2 It is for the natural gas in the coal measures strata of the study area 40 Ar / 36 Ar and 3 He / 4 He cross-plot.

[0026] Figure 3 It is the statistical chart of the cumulative thickness of different lithologies of Pinghu Formation and Baoshi Formation in a single well in the study area.

[0027] Figure 4 It is the cross-plot of δ 13 C1 and C1 / C 2+3 for the natural gas in the coal measures strata of the study area.

[0028] Figure 5 It is the cross-plot of δ 13 C CO2 and CO2 in the coal measures strata of the study area.

[0029] Figure 6 Cross plot of δ 13 C1 and depth for the coal-bearing strata in the study area.

[0030] Figure 7 Cross plot of δ 13 C CO2 and depth for the coal-bearing strata in the study area.

[0031] Figure 8 In the figure, A is the cross plot of Al2O3 / TiO2 and depth for the coal-bearing hydrocarbon source rocks in the study area, and B is the cross plot of Ni and depth.

[0032] Figure 9 Cross plot of Ni and O / C for the coal-bearing hydrocarbon source rocks in the study area.

[0033] Figure 10 Cross plot of δ 13 C1 and δ 13 C CO2 for the coal-bearing strata in the study area. Specific implementation manners

[0034] The following combines the embodiments of the present invention, and uses preferred embodiments and accompanying drawings for detailed description. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] It should be noted that all the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through the market or prepared by existing methods.

[0036] Embodiment 1 Taking the analysis of the abnormal heavy δ 13 C CO2 formation reason of the Pinghu Formation in the Pinghu Slope Belt of the Xihu Sag as an example, it includes the following steps: (1) Select the coal-bearing hydrocarbon source rocks of the Pinghu Formation and Baoshi Formation in the Pinghu Slope Belt of the Xihu Sag for sampling, record the depth and lithology information of the hydrocarbon source rock samples, and conduct major element and trace element tests on these hydrocarbon source rock samples to obtain the Ni element concentration and Al2O3 / TiO2 value. Conduct organic element determination on the hydrocarbon source rock samples to obtain the O / C ratio.

[0037] (2) Select natural gas samples from the industrial gas flow gas reservoirs of the Pinghu Formation and Baoshi Formation in the Pinghu Slope Belt of the Xihu Sag, and conduct helium and argon isotope determination on these natural gas samples to obtain40 Ar / 36 Ar and 3 He / 4 He, carbon isotope determination gives δ 13 C1 and δ 13 C CO2 , for the determination of the component content of natural gas, C1 / C 2+3 , the component content of CO2.

[0038] (3) Establish the intersection diagram of Ni and Al2O3 / TiO2. The values of Al2O3 / TiO2 less than 8, 8 - 21, and greater than 21 represent basic parent rock, intermediate parent rock, and acidic parent rock respectively. The distribution of the Al2O3 / TiO2 values in the source rocks in the study area shows that 46% of the source rock parent rocks in the study area are intermediate - basic rocks, and as the parent rock lithology changes from acidic to intermediate and basic, the Ni element content in the source rocks increases significantly, as Figure 1 shown. This is because intermediate and basic parent rocks are rich in transition metals themselves. Therefore, for source rocks with intermediate - basic parent rocks, their transition metal content will also increase.

[0039] (4) Based on previous studies, although there are source - connected faults in the study area, 40 Ar / 36 Ar and 3 He / 4 He intersection diagram shows that there is no mantle - sourced inorganic - origin gas in the study area, mainly crust - sourced gas, as Figure 2 shown.

[0040] (5) The lithologic logging of the wells drilling through the Baoshi Formation in the study area shows that there is no development of carbonate rocks in the Pinghu Formation and Baoshi Formation in the study area. Therefore, there is no gas formed by carbonate rock thermal decomposition in the study area, as Figure 3 shown.

[0041] (6) The intersection diagram of δ 13 C1 and C1 / C 2+3 is as Figure 4 shown. The natural gas in the study area is all thermogenic from type III kerogen, but this is inconsistent with the intersection diagram of δ Figure 5 shown, which shows that for the intersection diagram of δ 13 C CO2 and CO2 content, some δ 13 C CO2 > - 8‰ is for inorganic - origin gas. It can be seen that the traditional discrimination chart is inaccurate for judging the origin of abnormal heavy δ 13 C CO2 origin.

[0042] (7) The intersection diagram of δ 13 C1, δ 13 C CO2 and depth is as Figure 6and Figure 7 As shown, with the increase of depth, δ 13 C1 has the characteristic of first becoming heavier and then lighter, and δ 13 C CO2 shows a gradually increasing trend of becoming heavier with the increase of depth, and with the increase of depth, the abnormal heavy δ > -8‰ 13 C CO2 increases. In addition, the intersection diagrams of Al2O3 / TiO2 vs. depth and Ni vs. depth are as shown in Figure 8 A and B. With the increase of depth, Al2O3 / TiO2 shows a gradually decreasing trend, indicating that with the increase of burial depth, the neutral-basic parent rocks in the source rocks increase, and the Ni content increases; during the thermal evolution stage, the coal-measure source rocks in the study area can produce a large amount of CO2 and H2 by themselves. With the increase of burial depth, the content of neutral-basic parent rocks increases, and the Ni content increases. Catalyzed by Ni element, a large amount of H2 and CO2 produced by the coal-measure source rocks undergo the Fischer-Tropsch synthesis reaction, ultimately resulting in δ 13 C1 becoming lighter and δ 13 C CO2 becoming abnormally heavy; at the same time, the coal-measure source rocks themselves will also produce a large amount of CH4 with the enhancement of the degree of thermal evolution. The thermogenic CH4 undergoes carbon isotope exchange with CO2, resulting in δ 13 C CO2 becoming abnormally heavy.

[0043] (8)The intersection diagram of Ni element and O / C is as shown in Figure 9 As shown, with the increase of the Ni element content, O / C shows a gradually decreasing trend, indicating that the enrichment of Ni element promotes the thermal decomposition of the coal-measure source rocks, and then leads to δ 13 C CO2 becoming abnormally heavy.

[0044] (9)The intersection diagram of δ 13 C1 and δ 13 C CO2 is as shown in Figure 10 As shown, with the decrease of δ 13 C1 and the abnormal increase of δ 13 C CO2 is due to the Fischer-Tropsch synthesis reaction catalyzed by Ni element and the exchange between δ 13 C1 and δ 13 C CO2 ; while the trend of δ 13 C1 and δ 13 C CO2 becoming heavier simultaneously is due to the thermal decomposition of the coal-measure source rocks catalyzed by Ni element.

[0045] (10)The intersection diagram of δ 13 C CO2 and CO2 is as shown in Figure 5 showing the abnormally heavy inorganic origin δ13 C CO2 , and its true cause is that under the conditions of neutral-basic parent rocks, transition metals are enriched. During the thermal maturation process of coal-measure source rocks, a large amount of CH4, CO2, and H2 can be generated by themselves. Under the catalytic action of Ni, the Fischer-Tropsch synthesis reaction, δ 13 C1 and δ 13 C CO2 exchange lead to the abnormal increase in δ 13 C CO2 ; in addition, Ni element can also catalyze the thermal decomposition of coal-measure source rocks, and the generated δ 13 C CO2 also shows the characteristic of abnormal increase in weight. Therefore, the analysis of the lithology of the parent rock and the enrichment of transition metals, as well as the matching relationship between the Ni element content distribution and δ 13 C1, δ 13 C CO2 is the core of the present invention.

[0046] In summary, based on the fact that the prior art does not comprehensively consider the cause analysis of δ 13 C CO2 , resulting in inaccurate cause analysis of abnormal heavy δ 13 C CO2 , the present invention proposes a method for analyzing the cause of abnormal heavy δ 13 CO2 in coal-bearing strata. Based on the judgment of CO2 origin by geological background, parameter method and crossplot method, and based on the major, trace element data and organic element data, the lithology of the target layer parent rock is mainly evaluated, whether the target layer is distributed with high-abundance transition metals is analyzed, and whether there is inorganic natural gas caused by the catalytic action of transition metals in the target layer is clarified. Combining the carbon isotope and component content data of natural gas and CO2, the true cause of abnormal heavy δ 13 C CO2 is analyzed as whether it is caused by organic origin, inorganic origin, Fischer-Tropsch synthesis reaction resulting in abnormal heavy δ 13 C CO2 or abnormal heavy δ 13 C1 and δ 13 C CO2 exchange, and then the cause of abnormal heavy δ 13 C CO2 is comprehensively analyzed. 13 C CO2 Cause.

[0047] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods adopted are the same as those in the embodiments, in order to avoid redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0048] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and the scope of equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for analyzing the origin of abnormal heavy δ in coal measures strata, characterized in that, 13 C CO2 the method comprises: It includes the following steps: Collect source rock samples, record the sample depth and lithology information, conduct major element and trace element determinations to obtain the transition metal element concentration and Al2O3 / TiO2 value, conduct organic element determination on the source rock samples to obtain the O / C ratio; Collect a natural gas sample, conduct carbon isotope determination on the natural gas sample, and obtain δ 13 C1 and δ 13 C CO2 ; Establish a cross-plot of transition metal elements and Al2O3 / TiO2. If the content of transition metal elements gradually increases as the lithology of the parent rock changes to intermediate-basic, then establish δ 13 C1, δ 13 C CO2 , a cross-plot of transition metals, Al2O3 / TiO2 and depth, and a cross-plot of δ 13 C1 and δ 13 C CO2 cross-plot; Analysis of δ 13 C1, δ 13 C CO2 , the variation trends of transition metals and Al2O3 / TiO2 with depth, clarify the distribution depth variation of intermediate-basic parent rocks. If the content of transition metal elements gradually increases with the increase of the distribution depth of intermediate-basic parent rocks, δ 13 C1 gradually becomes lighter, while δ 13 C CO2 gradually becomes heavier, indicating that there is an abnormally heavy δ 13 C1 caused by the exchange with δ 13 C CO2 ; 13 C CO2 Abnormally heavy; Construct a transition metal element vs. O / C cross plot to clarify whether the enrichment of transition metal elements promotes the pyrolysis of coal measure source rocks. When the enrichment of transition metals promotes the thermal decomposition of coal measure source rocks, it indicates the presence of a significant δ caused by Fischer-Tropsch synthesis reaction. 13 C CO2 anomaly.

2. The abnormal heavy δ of the coal measure strata according to claim 1 13 C CO2 Cause analysis method, characterized in that The transition metal is Ni.

3. The abnormal heavy δ of the coal measure strata according to claim 1 13 C CO2 The genetic analysis method is characterized in that An Al2O3 / TiO2 value < 8 represents a basic parent rock, 8 - 21 represents an intermediate parent rock, and > 21 represents an acidic parent rock.

4. The abnormal heavy δ of the coal measure strata according to claim 1 13 C CO2 Cause analysis method, characterized in that It also includes analyzing whether there are source-connected faults and whether there are mantle-derived and crust-derived abiogenic gases in combination with the geological background, and then analyzing the abnormal heavy δ 13 C CO2 whether abiogenic origin is possible.

5. The abnormal heavy δ of the coal-bearing strata according to claim 4 13 C CO2 The genetic analysis method is characterized in that δ 13 C CO2 < -10‰ is of organic origin, δ 13 C CO2 between -10‰ and -8‰ is of organic-inorganic mixed origin, δ 13 C CO2 > -8‰ is of inorganic origin.

6. The abnormal heavy δ of the coal-bearing strata according to claim 1 13 C CO2 Cause analysis method, characterized in that It also includes determining the component content of the natural gas sample to obtain the CO2 content, and establishing a δ 13 C CO2 intersection diagram with CO2 to analyze the abnormal heavy δ 13 C CO2 whether it is of organic origin, inorganic origin or a mixture of organic and inorganic origins; combining the lithological distribution characteristics in the formation, analyze whether there is inorganic origin caused by thermal decomposition of carbonate rocks in the target source rock layer.

7. The abnormal heavy δ of the coal-bearing strata according to claim 1 13 C CO2 Cause analysis method, characterized in that It also includes determining the helium and argon isotopes of the natural gas sample to obtain 40 Ar / 36 Ar value and 3 He / 4 He value, establishing 40 Ar / 36 Ar and 3 He / 4 He cross plot to analyze whether there is an inorganic origin.

8. The abnormal heavy δ of the coal-bearing strata according to claim 7 13 C CO2 The genetic analysis method is characterized in that 40 Ar / 36 Ar and 3 He / 4 In the intersection diagram of He, 3 He / 4 He > 10 -6 represents mantle-derived inorganic gas, 3 He / 4 He < 10 -6 represents crust-derived inorganic gas.

9. The abnormal heavy δ of coal measures strata according to claim 1 13 C CO2 The genetic analysis method is characterized in that The source rock is crushed before testing.

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