A method for analyzing the origin of abnormal heavy δ in coal measures strata 13 C CO2 Origin analysis method

Abstract

The present invention relates to coal-bearing stratum CO <subgt;2< / subgt;成因分析技术领域,具体涉及一种煤系地层异常重δ<supgt;13< / supgt;C<subgt;CO2< / subgt;成因分析方法,本发明在地质背景、参数法和交汇图法判断CO<subgt;2< / subgt;成因的基础上,基于主量、微量元素资料和有机元素资料,重点评价目的层母岩岩性,分析目的层是否分布高丰度过渡金属,明确目的层是否存在过渡金属催化作用成因的无机天然气,结合天然气和CO<subgt;2< / subgt;碳同位素和组分含量资料,综合分析CO<subgt;2< / subgt;成因。

Description

Technical Field

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

[0002] CO2 is the main non-hydrocarbon gas in natural gas, and its origin mainly includes organic origin, inorganic origin and biogenic origin. Previous studies usually used δ 13 C1 and C1 / C 2+3 、δ 13 C CO2 distribution, the cross plot of δ 13 C CO2 and CO2 component content, and 40 Ar / 36 Ar and 3 He / 4 He cross plot to judge the source of CO2. However, in the research, it often occurs that the origins indicated by different methods are different. For example, in the natural gas of the Xihu Sag, some 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 inorganic gas from carbonate rock thermal decomposition. This brings difficulties to revealing the true origin of CO2. Therefore, the identification of the origin of abnormal heavy δ 13 C CO2 needs to be solved urgently.

[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 Milder 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 is based on the geological background, parameter method and intersection diagram method to judge the CO2 genesis, and based on the major and trace element data and organic element data, focuses on evaluating the lithology of the target layer parent rock, analyzes whether the target layer has high-abundance transition metals, clarifies whether the target layer has inorganic natural gas caused by transition metal catalysis, and combines the natural gas and CO2 carbon isotope and component content data to comprehensively analyze the CO2 genesis.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] An abnormally heavy delta 13 The CO2 genesis analysis method includes the following steps:

[0008] 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 element determinations were performed on the source rock samples to obtain O / C ratios.

[0009] 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 .

[0010] Establish the intersection diagram of transition metal elements and Al2O3 / TiO2, and make it clear that if the transition metal content 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 δ13 C CO2 Convergence diagram.

[0011] Analyze δ 13 C1, δ 13 C CO2 , the variation trends of transition metals and Al2O3 / TiO2 with depth, clarify the distribution depth change 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, which indicates the existence of δ 13 C1 and δ 13 C CO2 exchange resulting in abnormally heavy δ 13 C CO2 abnormally heavy.

[0012] Establish a convergence diagram 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 the existence of abnormally heavy δ 13 C CO2 abnormally heavy.

[0013] Based on the fact that the existing technology has an incomplete consideration of the genesis analysis of δ 13 C CO2 , resulting in inaccurate genesis analysis of abnormally heavy δ 13 C CO2 , this invention proposes a method for analyzing the genesis of abnormally heavy δ 13 CO2 in coal-bearing strata. Based on the judgment of CO2 genesis by geological background, parameter method and convergence diagram method, and based on 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 lithology characteristics of the parent rock and whether the transition metals are enriched, as well as the vertical distribution characteristics of transition metal content, δ 13 C1 and δ 13 C CO2 , 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 true genesis 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 δ 13 C1 and δ 13 C CO2 exchange resulting in δ 13C CO2 Exceptionally heavy, and then comprehensively analyze the exceptionally heavy δ 13 C CO2 True cause.

[0014] In a preferred embodiment of the present invention, the transition metal is Ni.

[0015] In a preferred embodiment of the present invention, establish a Ni element and Al2O3 / TiO2 intersection diagram to clarify whether the Ni element content gradually increases as the parent rock lithology changes to neutral-basic, and analyze whether the enrichment of the Ni element is controlled by the neutral-basic parent rock lithology.

[0016] 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.

[0017] In a preferred embodiment of the present invention, 40 Ar / 36 Ar and 3 He / 4 In the He intersection diagram, 3 He / 4 He > 10 -6 Represents mantle-derived inorganic gas, 3 He / 4 He < 10 -6 Represents crust-derived inorganic gas.

[0018] 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 the exceptionally heavy δ 13 C CO2 Whether there may be an inorganic origin.

[0019] 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, δ13C CO2 > -8‰ is of inorganic origin.

[0020] 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 δ 13 C CO2 And CO2 intersection diagram, analyzing whether the exceptionally heavy δ 13 C CO2 Is of organic origin, inorganic origin or organic-inorganic mixed origin; combining the lithology distribution characteristics in the formation, analyzing whether there is an inorganic origin caused by the thermal decomposition of carbonate rocks in the target layer of the hydrocarbon source rock.

[0021] In a preferred embodiment of the present invention, the natural gas sample is subjected to helium and argon isotope determination to obtain 40 Ar / 36 Ar value and 3 He / 4 He value, establish 40 Ar / 36 Ar and 3 He / 4 Use the intersection diagram to analyze whether there is an inorganic cause.

[0022] In a preferred embodiment of the present invention, 40 Ar / 36 Ar and 3 He / 4 In the He intersection diagram, 3 He / 4 He>10 -6 Represents mantle-derived inorganic gas, 3 He / 4 He<10 -6 Represents shell-derived inorganic gas.

[0023] In a preferred embodiment of the present invention, the source rock is crushed before testing.

[0024] In fact, the Fischer-Tropsch synthesis reaction and δ 13 C1 and δ 13 C CO2 The exchange also results in δ 13 C CO2 Abnormally heavy. Existing technologies usually ignore these two factors in the research process. This is because under laboratory simulation conditions, without the action of catalysts, the above reactions cannot occur at ground temperatures between 200℃ and 700℃. However, the highest formation temperature in sedimentary basins is usually between 150℃ and 200℃. Sedimentary basins cannot provide the temperature conditions for these two reactions. Therefore, these two δ 13 C CO2 However, when transition metal catalyzed, the Fischer-Tropsch synthesis reaction is at 100℃~350℃, and the δ13C1 and δ 13 C CO2 The exchange can occur above 200 ° C. Therefore, the main disadvantage of the previous method is that it does not analyze whether there is transition metal Ni catalysis in the geological conditions, which invisibly increases the abnormal δ 13 C CO2 The authenticity of the cause is reduced.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention is based on the prior art 13 CCO2 The cause analysis is not comprehensive enough, resulting in abnormal heavy δ 13 C CO2 Regarding the problem of inaccurate cause analysis of C 13 A method for analyzing the origin of CO2 in coal measures strata is proposed. 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, the lithology of the source rock of the target layer is mainly evaluated, whether the target layer is distributed with high-abundance transition metals is analyzed, and whether there is inorganic natural gas with the origin of transition metal catalysis in the target layer is clarified. Combining the analysis of the lithology characteristics of the source rock and whether the transition metal is enriched, as well as the content of transition metal, δ 13 C1, and δ 13 C CO2 Vertical distribution characteristics, clarify the Fischer-Tropsch synthesis reaction and δ 13 C1 and δ 13 C CO2 The possibility of exchange occurring in the target layer is analyzed, and the true cause of abnormal heavy δ 13 C CO2 The true cause is organic origin, inorganic origin, abnormal heavy δ caused by Fischer-Tropsch synthesis reaction 13 C CO2 Abnormal heavy or δ 13 C1 and δ 13 C CO2 Exchange-caused δ 13 C CO2 Abnormal heavy, and then comprehensively analyze the true cause of abnormal heavy δ 13 C CO2 True cause. Brief Description of the Drawings

[0027] Figure 1 Cross-plot of Al2O3 / TiO2 and Ti content of coal measures hydrocarbon source in the study area.

[0028] Figure 2 For the natural gas in the coal measures strata of the study area 40 Ar / 36 Ar and 3 He / 4 He cross-plot.

[0029] Figure 3 Statistical chart of cumulative thickness of different lithologies of Pinghu Formation and Baoshi Formation of single wells in the study area.

[0030] Figure 4 For the natural gas δ 13 C1 and C1 / C 2+3 Cross-plot.

[0031] Figure 5 For the δ 13 C CO2Intersection diagram with CO2.

[0032] Figure 6 For the natural gas δ 13 C1 intersection diagram with depth in the study area coal measure strata.

[0033] Figure 7 For the natural gas δ 13 C CO2 Intersection diagram with depth.

[0034] Figure 8 In it, A is the intersection diagram of Al2O3 / TiO2 with depth of the coal measure source rocks in the study area, and B is the intersection diagram of Ni with depth.

[0035] Figure 9 For the intersection diagram of Ni and O / C of the coal measure source rocks in the study area.

[0036] Figure 10 For the natural gas δ 13 C1 and δ 13 C CO2 Intersection diagram. Specific implementation manner

[0037] 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 fall within the scope of protection of the present invention.

[0038] 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.

[0039] Example 1

[0040] Taking the analysis of the origin of the abnormal heavy δ 13 C CO2 in the Pinghu Formation of the Pinghu Slope Belt in the Xihu Sag as an example, it includes the following steps:

[0041] (1) Select the coal measure source rocks of the Pinghu Formation and the Baoshi Formation in the Pinghu Slope Belt of the Xihu Sag for sampling, record the depth and lithology information of the source rock samples, and conduct major element and trace element tests on these source rock samples to obtain the Ni element concentration and the Al2O3 / TiO2 value. Conduct organic element determination on the source rock samples to obtain the O / C ratio.

[0042] (2) Natural gas samples were collected from industrial gas flow gas reservoirs in the Pinghu Formation and Baoshi Formation in the Pinghu Slope Zone of the Xihu Sag, and helium and argon isotope determinations were carried out on these natural gas samples to obtain 40 Ar / 36 Ar and 3 He / 4 He, carbon isotope determination to obtain δ 13 C1 and δ 13 C CO2 , determination of the content of natural gas components, C1 / C 2+3 , the content of the CO2 component.

[0043] (3) A cross plot of Ni and Al2O3 / TiO2 was established. 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 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 shown in Figure 1 , 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.

[0044] (4) Combining the previous research foundation, although there are source - connected faults in the study area, 40 Ar / 36 Ar and 3 He / 4 He cross plot shows that there is no mantle - derived inorganic - origin gas in the study area, and it is mainly crust - derived gas, as shown in Figure 2 .

[0045] (5) Lithologic logging of wells drilled 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 generated by carbonate rock thermal decomposition in the study area, as shown in Figure 3 .

[0046] (6) The cross plot of δ 13 C1 and C1 / C 2+3 is as shown in Figure 4 . Natural gas in the study area is all thermogenic from type III kerogen, but this is inconsistent with the cross plot of δ Figure 5 shown in 13 C CO2 and the CO2 content, which shows that some δ 13 C CO2 > - 8‰ is for inorganic - origin gas. It can be seen that the traditional discrimination chart is inaccurate in judging the origin of abnormal heavy δ 13 C CO2 origin.

[0047] (7)δ 13 C1, δ 13 C CO2 The cross-plot with depth is as shown in Figure 6 and Figure 7 As the depth increases, δ 13 C1 first becomes heavier and then lighter, and δ 13 C CO2 shows a trend of gradually becoming heavier as the depth increases. Also, as the depth increases, the abnormal heavy δ 13 C CO2 increases. In addition, the cross-plots of Al2O3 / TiO2 with depth and Ni with depth are as shown in Figure 8 A and B in. As the depth increases, Al2O3 / TiO2 shows a trend of gradually decreasing, indicating that as the burial depth increases, the neutral-basic parent rocks in the source rocks increase and the Ni content increases. In the study area, the coal-measure source rocks can generate a large amount of CO2 and H2 during the thermal evolution stage. As the burial depth increases, the content of neutral-basic parent rocks increases and the Ni content increases. Catalyzed by Ni, the large amount of H2 and CO2 generated 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 generate a large amount of CH4 as the degree of thermal evolution increases. The thermogenic CH4 undergoes carbon isotope exchange with CO2, resulting in δ 13 C CO2 being abnormally heavy.

[0048] (8)The cross-plot of Ni element and O / C is as shown in Figure 9 As the Ni element content increases, O / C shows a trend of gradually decreasing, indicating that the enrichment of Ni promotes the thermal decomposition of the coal-measure source rocks, and thus leads to δ 13 C CO2 becoming abnormally heavy.

[0049] (9)The cross-plot of δ 13 C1 and δ 13 C CO2 is as shown in Figure 10 As δ 13 C1 becomes lighter, the trend of δ 13 C CO2 becoming abnormally heavy is due to the Fischer-Tropsch synthesis reaction catalyzed by Ni 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.

[0050] (10)δ13 C CO2 The intersection diagram with CO2 is as Figure 5 shown, showing the abnormal heavy inorganic origin δ 13 C CO2 , and its true origin is: under the conditions of neutral-basic parent rocks, transition metals are enriched. During the thermal maturation process of coal-bearing hydrocarbon source rocks, a large amount of CH4, CO2 and H2 can be produced by themselves. The Fischer-Tropsch synthesis reaction occurs under the catalytic action of Ni, and the exchange between δ 13 C1 and δ 13 C CO2 results in the abnormal increase in δ 13 C CO2 ; in addition, the Ni element will also catalyze the thermal decomposition of coal-bearing hydrocarbon source rocks, and the produced 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.

[0051] In summary, due to the incomplete consideration of the origin analysis of δ 13 C CO2 in the prior art, which leads to the inaccurate origin analysis of abnormal heavy δ 13 C CO2 , the present invention proposes a method for analyzing the origin of abnormal heavy δ 13 CO2 in coal-bearing strata. On the basis of judging the origin of CO2 by geological background, parameter method and intersection diagram method, 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, analyze whether the true origin of abnormal heavy δ 13 C CO2 is caused by organic origin, inorganic origin, Fischer-Tropsch synthesis reaction resulting in abnormal heavy δ 13 C CO2 or the exchange between δ 13 C1 and δ 13 C CO2 results in abnormal heavy δ 13 C CO2 , and then comprehensively analyze the origin of abnormal heavy δ 13 C CO2 .

[0052] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and the two endpoints can be selected. Since the adopted step method is the same as that of the embodiment, in order to prevent repetition, 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 attached is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0053] 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 its 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 it includes: Including the following steps: Collect source rock samples, record the sample depth and lithology information, conduct major element and trace element determinations to obtain the content of transition metal elements and the 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 ; Construct the intersection diagrams 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 construct the intersection diagrams of δ 13 C1, δ 13 C CO2 , transition metals, Al2O3 / TiO2 and depth, as well as the intersection diagram of δ 13 C1 and δ 13 C CO2 ; Analysis of δ 13 C1, δ 13 C CO2 , the variation trends of transition metals and Al2O3 / TiO2 with depth. If the distribution of intermediate-basic parent rocks increases with increasing depth, the content of transition metal elements gradually increases, δ 13 C1 gradually becomes lighter, while δ 13 C CO2 gradually becomes heavier, indicating that there is δ 13 C1 and δ 13 C CO2 exchange resulting in abnormally heavy δ 13 C CO2 ; 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 abnormal heavy δ 13 C CO2 resulting from the Fischer-Tropsch synthesis reaction.

2. The abnormal heavy δ of coal measures strata according to claim 1 13 C CO2 Analysis method of genetic cause, characterized in that The transition metal is Ni.

3. The abnormal heavy δ in coal measures strata according to claim 1 13 C CO2 Cause analysis method, 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 coal measures 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 inorganic origin gases in combination with the geological background, and then analyzing the abnormal heavy δ 13 C CO2 whether there may be an inorganic origin.

5. The abnormal heavy δ of coal measures 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 measure strata according to claim 1 13 C CO2 The genetic analysis method is characterized in that It also includes determining the component content of the natural gas sample to obtain the CO2 content, and establishing a cross plot of δ 13 C CO2 and CO2 to analyze whether the abnormal heavy δ 13 C CO2 is of organic origin, inorganic origin or a mixture of organic and inorganic origins; combined with the lithological distribution characteristics in the formation, analyze whether there is an inorganic origin caused by the thermal decomposition of carbonate rocks in the target source rock layer.

7. The method for analyzing the origin of abnormal heavy δ in coal measures strata according to claim 1, characterized in that, 13 C CO2 It also includes measuring the helium and argon isotopes of the natural gas sample to obtain 40 Ar / 36 Ar value and 3 He / 4 He value, and establishing 40 Ar / 36 Ar and 3 He / 4 He crossplot to analyze whether there is an inorganic origin. ​ 8. The abnormal heavy δ of the coal measure 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 the coal measure strata according to claim 1 13 C CO2 The genetic analysis method is characterized in that Crush the source rock before testing.

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