A method for evaluating the relative contribution of non-hydrocarbon CO2 genesis based on the source of helium

Abstract

The present invention relates to an evaluation method for identifying the relative contribution of non-hydrocarbon gas CO2 to its genesis in combination with the source of helium, and belongs to the technical field of rare gas geochemistry research. 3 He ratio and δ 13 The CO2 value combination method is based on the CO2 / CO2 values ​​of three carbon sources: mantle source, carbonate mineral thermal decomposition and organic sediments. 3 The He ratio quantitatively analyzes the relative contributions of each end member of mantle origin, thermal decomposition of carbonate minerals and organic sediments to the formation process and content of CO2, supplements and improves the existing evaluation method that can only qualitatively analyze the origin of CO2 through isotopes, and to a certain extent can accurately characterize the source of high-abundance inorganic CO2, especially in areas where there is deep mantle fluid influence and deep and large faults are developed.

Description

Technical Field

[0001] The present invention relates to a method for combining CO2 / 3 The He test results are used to assist in the evaluation of the relative contributions of the mantle-derived inorganic, crust-derived inorganic and organic genesis of non-hydrocarbon gas CO2, and belong to the technical field of rare gas geochemistry research. Background Art

[0002] As an important component of non-hydrocarbon gas in natural gas, the origin and source (organic and / or inorganic) of CO2 and its enrichment process are of great significance for in-depth study of natural gas geochemical characteristics. Previous studies often used the CO2 content and carbon isotope composition δ 13 C CO2 For example, when the CO2 content is less than 20% or δ 13 C CO2 When the value is <-10‰, it is organic CO2; when δ 13 C CO2 When the value is > -9‰, the vast majority is inorganic CO2. When the CO2 content is > 60% or δ 13 C CO2 Values ​​between -8‰ and -3‰ indicate inorganic CO2. Previous identification methods have also made significant contributions to natural gas geology and geochemistry. Inorganic CO2 primarily originates from the thermal decomposition of mantle-derived and crust-derived carbonate minerals.

[0003] With further exploration deployment, high-abundance CO2 reservoirs (CO2 content >80%) have emerged in the deepwater layers of eastern my country's cratons and the South China Sea, with differential enrichment across different layers and blocks. Furthermore, a significant negative correlation exists between non-hydrocarbon gases and alkane gases. To mitigate exploration risks, precise characterization of the sources of high-abundance inorganic CO2 is crucial, particularly in areas affected by deep mantle-derived fluids and deep, large faults. However, the lack of deep mantle-derived analytical benchmarks has hindered quantitative analysis of the relative contributions of the mantle, carbonate mineral thermal decomposition, and organic sediments to the CO2 formation process and concentration, limiting our understanding of this phenomenon. Summary of the Invention

[0004] In view of the shortcomings of existing evaluation and analysis methods, in order to accurately identify the relative contributions of mantle-derived inorganic sources, carbonate mineral thermal decomposition inorganic sources and organic CO2, this paper proposes a novel CO2 / 3 He ratio and δ 13 The CO2 value combination method is based on the CO2 / CO2 values ​​of three carbon sources: mantle source, carbonate mineral thermal decomposition and organic sediments. 3 The He ratio further quantitatively characterizes the relative contribution of these three carbon sources to the formation of CO2.

[0005] The technical solutions of the present invention are as follows:

[0006] A CO2 / 3 The analytical method for evaluating the gas components derived from mantle, carbonate mineral thermal decomposition, and organic sediments based on He test results includes the following steps:

[0007] Step 1: Conduct geological background research and analyze the helium content in the study area. 3 He / 4 The He ratio and R / Ra ratio confirm the presence of mantle-derived influence. Preferably, R / Ra > 1 is considered to be a mantle-derived influence, which can be used as a criterion for early preparation. Mantle-derived influence can also be present when the geological setting includes deep faults, hot springs, volcanoes, and diapirs.

[0008] Secondly, because the rare gas content in geological samples is extremely low, while the rare gas content in the atmosphere is relatively high, samples such as natural gas are easily contaminated during the collection process, causing the experimental analysis data to deviate from the true value. To minimize the impact of air contamination and sampling on data measurement, strict handling measures are required for natural gas sampling for rare gas analysis: ① Use high-pressure steel cylinders with double valves for sampling; ② Before sampling, use vacuum equipment such as mechanical pumps and molecular pumps to pre-evacuate the sampling cylinder to a vacuum level of at least 10-3Pa; ③ During sampling, repeatedly flush the cylinder with natural gas 4-6 times, and finally sample the middle section of the continuous airflow; ④ After collecting the sample, insert the cylindrical cylinder into water for leak inspection.

[0009] In the third step, two getters with hot Ti foil (800°C) are used to separate the rare gases from other major components (such as hydrocarbons, carbon dioxide, and nitrogen). Preferably, the rare gases include He, Ne, Ar, Kr, and Xe. The temperature of the hot Ti foil is 800°C.

[0010] In the fourth step, after purification, the noble gas fraction was analyzed using a VG 5400 sector mass spectrometer (Fisons Instruments). Air standards were repeatedly measured between sample analyses to calibrate the mass discrimination of the mass spectrometer. Blanks prepared using the same procedure as the samples were measured before, after, and during sample analysis.

[0011] In the fifth step, due to the different boiling points of the noble gases, helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) were separated into their components using a cryogenic pump, an activated carbon furnace, and liquid nitrogen. Finally, these noble gases were sequentially fed into a static vacuum noble gas isotope mass spectrometer, where the abundance of He was determined using a Finnigan MAT-271 instrument and the mass spectrometry method according to national standards GB / T6041-2002 and GB / T10628-89. Isotope analysis was performed to obtain 3He, 4 He content and 3 He / 4 And ratio.

[0012] In the sixth step, after using a gas chromatograph GC-7860 to separate gases such as hydrocarbons, carbon dioxide, and nitrogen, a Finnigan MAT-271 instrument was used to determine the CO2 abundance according to the national standards GB / T 6041-2002 and GB / T10628-89 mass spectrometry.

[0013] The seventh step is to measure the stable carbon isotope composition of the gas using the Finnigan MAT-252 instrument to obtain δ 13 CO2 value; preferably, the analysis conditions are as follows: gas chromatography column: Porapak Q (30m), column ID: 19091P-Q04, film thickness: 20μm; oven temperature: 40 to 160 degrees Celsius, heating rate: 15℃ / min; pure helium carrier gas, flow rate: 1.2ml / min. δ 13 The analytical error of the CO2 value was <0.3‰. Each sample was measured three times, and the results of the three measurements were averaged.

[0014] In the eighth step, based on the above process, the CO2, δ 13 C CO2 、 3 He, 4 The He content is summarized and sorted out before proceeding to the next step.

[0015] Step 9: Combine CO2 / 3 He ratio and δ 13 C CO2 The contribution of the three main carbon sources, mantle source, thermal decomposition of carbonate minerals and organic sediments, is calculated using the following formula:

[0016] (δ 13 C CO2 / CO2) OBS =(δ 13 C CO2 / CO2) MORB A+(δ 13 C CO2 / CO2) LIM B+(δ 13 C CO2 / CO2) SED C (1)

[0017] 1 / (CO2 / 3 He) OBS =A / (CO2 / 3 He) MORB +B / (CO2 / 3 He) LIM +C / (CO2 / 3 He) SED (2)

[0018] Where, OBS is the observed value, i.e., the measured value of the sample; MORB, LIM, and SED refer to the thermal decomposition of mantle-derived, organic sediments, and carbonate minerals, respectively; A, B, and C are the corresponding relative contribution scores; where: (i) the CO2 / 3 The He ratio is 1.0×10 9 , CO2 / 3 The He ratio is 10 13 ; (ii) The isotope values ​​of each end member are δ 13 C MORB =-6.5‰, δ 13 C SED =-30‰ and δ 13 C LIM =0‰.

[0019] Step 10: Combine formula (1) and formula (2) with the CO2 and δ measured by the sample. 13 C CO2 、 3 The He concentration can be used to calculate the relative contribution scores of the three carbon sources A, B, and C, which are used to identify the relative contribution of non-hydrocarbon gas CO2.

[0020] Based on MATLAB software, link the database and input the three end-member isotope values ​​of mantle source, organic sediments and carbonate mineral thermal decomposition in step 9 as well as the CO2 / 3 He ratio, based on CO2 / 3 He ratio and δ 13 The CO2 value combination method is used to solve the contribution of the three main carbon sources: mantle source, carbonate mineral thermal decomposition, and organic sediments. The execution steps are as follows:

[0021] (1) for i 1:n&(n is the number of samples)&edit the loop statement

[0022] (2) Y1=A(i) Y2=B(i)& link database, input CO2 / 3 He ratio and δ 13 CO2 value, Y1 represents the observable isotope value δ 13 C CO2 , Y2 represents the observable CO2 / 3 He ratio, the observed value is the sample measurement value;

[0023] (3) Eq1 = c = 1 – a – b& (a, b, c represent the relative contributions from mantle sources, thermal decomposition of carbonate minerals, and organic sediments, in %, i.e. And, a+b+c=1);

[0024] Eq1 is in MATLAB language, that is, equation 1 is set, which is c=1-ab. The equation means that there are three end members in the genesis of non-hydrocarbon gas CO2, so the sum of the contributions of the three is 1.

[0025] (4) Eq2 = Y1 = Q*a + W*b + E*c & Edit the MATLAB language of formula (1) (Q, W, E represent the isotope values ​​of each end member δ 13 C MORB =-6.5, δ 13 C SED =-30 and δ 13 C LIM = 0, unit ‰, MORB, LIM and SED refer to mantle origin, thermal decomposition of carbonate minerals and organic sediments, respectively);

[0026] (5) Eq3 = 1 / Y2 = A / R + B / T + C / T & Edit the formula (2) in MATLAB language (R, T represent the mantle-derived CO2 / 3 The He ratio is 1.0×10 9 , the ratio of thermal decomposition end members of organic sediments and carbonate minerals is 10 13 );

[0027] (6) [sola,solb,solc] = solve([Eq1,Eq2,Eq3],[a,b,c]); Calculate Eq1, Eq2, Eq3 and solve for a, b, and c;

[0028] Each end member value obtained will fall between 0 and 1. The larger the value, the higher the relative contribution. If a certain end member value is negative, it means that the end member value has no relative contribution to CO2, which means that CO2 is not affected by this source and no geological activities related to this source have occurred in the area.

[0029] The present invention uses the contribution fractions (A, B, C) of mantle source, carbonate mineral thermal decomposition and organic sediment source to analyze the relationship between CO2 / 3 He ratio and carbon isotope δ of non-hydrocarbon gas CO2 13 C CO2Using the MATLAB language, we can quickly calculate the relative contributions of the three major end-members: mantle-derived inorganic sources, inorganic sources from thermal decomposition of carbonate minerals, and organic CO2. This goes beyond simply distinguishing between organic and inorganic origins, achieving a more detailed breakdown. The output is a fixed value rather than a defined region, providing a more accurate description of the impact of each source, employing quantitative rather than qualitative characterization.

[0030] The beneficial effects of the present invention are:

[0031] The present invention is based on CO2 / 3 He test results were obtained by combining δ 13 C CO2 The numerical value can assist in the evaluation of the relative contribution of CO2 from mantle sources, thermal decomposition of carbonate minerals and organic sediments, and quantitatively analyze the relative contribution of each end member of mantle sources, thermal decomposition of carbonate minerals and organic sediments to the formation process and content of CO2. It supplements and improves the existing evaluation method that can only use isotope qualitative analysis to analyze the origin of CO2, and to a certain extent, it can accurately characterize the source of high-abundance inorganic CO2, especially in areas where there is deep mantle fluid influence and deep and large faults are developed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The relative contributions of mantle source, thermal decomposition of carbonate minerals and organic sediments to the CO2 source from typical wells in gas field A;

[0033] Figure 2 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to embodiments and accompanying drawings, but is not limited thereto.

[0035] Example 1:

[0036] A CO2 / 3 The analytical method for evaluating the gas components derived from mantle, carbonate mineral thermal decomposition, and organic sediments based on He test results includes the following steps:

[0037] Step 1: Conduct geological background research and analyze the helium content in the study area. 3 He / 4 The He ratio and R / Ra ratio confirm the presence of mantle-derived influence. A mantle-derived influence is considered when R / Ra is greater than 1 and can be used as a criterion for early preparation. Mantle-derived influence can also be present when the geological setting includes deep faults, hot springs, volcanoes, and diapirs.

[0038] Secondly, because the rare gas content in geological samples is extremely low, while the rare gas content in the atmosphere is relatively high, samples such as natural gas are easily contaminated during the collection process, causing the experimental analysis data to deviate from the true value. To minimize the impact of air contamination and sampling on data measurement, strict handling measures are required for natural gas sampling for rare gas analysis: ① Use high-pressure steel cylinders with double valves for sampling; ② Before sampling, use vacuum equipment such as mechanical pumps and molecular pumps to pre-evacuate the sampling cylinder to a vacuum level of at least 10-3Pa; ③ During sampling, repeatedly flush the cylinder with natural gas 4-6 times, and finally sample the middle section of the continuous airflow; ④ After collecting the sample, insert the cylindrical cylinder into water for leak inspection.

[0039] In the third step, two getters with hot Ti foil (800°C) are used to separate the rare gases (He, Ne, Ar, Kr, Xe) from other major components such as hydrocarbons, carbon dioxide, and nitrogen.

[0040] In the fourth step, after purification, the noble gas fraction was analyzed using a VG 5400 sector mass spectrometer (Fisons Instruments). Air standards were repeatedly measured between sample analyses to calibrate the mass discrimination of the mass spectrometer. Blanks prepared using the same procedure as the samples were measured before, after, and during sample analysis.

[0041] In the fifth step, due to the different boiling points of the noble gases, helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) were separated into their components using a cryogenic pump, an activated carbon furnace, and liquid nitrogen. Finally, these noble gases were sequentially fed into a static vacuum noble gas isotope mass spectrometer, where the abundance of He was determined using a Finnigan MAT-271 instrument and the mass spectrometry method according to national standards GB / T6041-2002 and GB / T10628-89. Isotope analysis was performed to obtain 3 He, 4 He content and 3 He / 4 And ratio.

[0042] In the sixth step, after using a gas chromatograph GC-7860 to separate gases such as hydrocarbons, carbon dioxide, and nitrogen, a Finnigan MAT-271 instrument was used to determine the CO2 abundance according to the national standards GB / T 6041-2002 and GB / T10628-89 mass spectrometry.

[0043] The seventh step is to measure the stable carbon isotope composition of the gas using the Finnigan MAT-252 instrument to obtain δ 13CO2 value; preferably, the analysis conditions are as follows: gas chromatography column: Porapak Q (30m), column ID: 19091P-Q04, film thickness: 20μm; oven temperature: 40 to 160 degrees Celsius, heating rate: 15℃ / min; pure helium carrier gas, flow rate: 1.2ml / min. δ 13 The analytical error of the CO2 value was <0.3‰. Each sample was measured three times, and the results of the three measurements were averaged.

[0044] In the eighth step, based on the above process, the CO2, δ 13 C CO2 、 3 He, 4 The He content is summarized and sorted out before proceeding to the next step.

[0045] Step 9: Combine CO2 / 3 He ratio and δ 13 C CO2 The contribution of the three main carbon sources, mantle source, thermal decomposition of carbonate minerals and organic sediments, is calculated using the following formula:

[0046] (δ 13 C CO2 / CO2) OBS =(δ 13 C CO2 / CO2) MORB A+(δ 13 C CO2 / CO2) LIM B+(δ 13 C CO2 / CO2) SED C (1)

[0047] 1 / (CO2 / 3 He) OBS =A / (CO2 / 3 He) MORB +B / (CO2 / 3 He) LIM +C / (CO2 / 3 He) SED (2)

[0049] Where, OBS is the observed value, i.e., the measured value of the sample; MORB, LIM, and SED refer to the thermal decomposition of mantle-derived, organic sediments, and carbonate minerals, respectively; A, B, and C are the corresponding relative contribution scores; where: (i) the CO2 / 3 The He ratio is 1.0×10 9 , CO2 / 3The He ratio is 10 13 ; (ii) The isotope values ​​of each end member are δ 13 C MORB =-6.5‰, δ 13 C SED =-30‰ and δ 13 C LIM =0‰.

[0050] Step 10: Combine formula (1) and formula (2) with the CO2 and δ measured by the sample. 13 C CO2 、 3 The He concentration can be used to calculate the relative contribution scores of the three carbon sources A, B, and C, which are used to identify the relative contribution of non-hydrocarbon gas CO2.

[0051] Based on MATLAB software, link the database and input the three end-member isotope values ​​of mantle source, organic sediments and carbonate mineral thermal decomposition in step 9 as well as the CO2 / 3 He ratio, based on CO2 / 3 He ratio and δ 13 The CO2 value combination method is used to solve the contribution of the three main carbon sources: mantle source, carbonate mineral thermal decomposition, and organic sediments. The execution steps are as follows:

[0052] (1) for i 1:n&(n is the number of samples)&edit the loop statement

[0053] (2) Y1=A(i)Y2=B(i)&Link database, input CO2 / 3 He ratio and δ 13 CO2 value, Y1 represents the observable isotope value δ 13 C CO2 , Y2 represents the observable CO2 / 3 He ratio, the observed value is the sample measurement value;

[0054] (3) Eq1 = c = 1 – a – b& (a, b, c represent the relative contributions from mantle sources, thermal decomposition of carbonate minerals, and organic sediments, in %, i.e. And, a+b+c=1);

[0055] Eq1 is in MATLAB language, that is, equation 1 is set, which is c=1-ab. The equation means that there are three end members in the genesis of non-hydrocarbon gas CO2, so the sum of the contributions of the three is 1.

[0056] (4) Eq2 = Y1 = Q*a + W*b + E*c & Edit the MATLAB language of formula (1) (Q, W, E represent the isotope values ​​of each end member δ 13 CMORB =-6.5, δ 13 C SED =-30 and δ 13 C LIM = 0, unit ‰, MORB, LIM and SED refer to mantle origin, thermal decomposition of carbonate minerals and organic sediments, respectively);

[0057] (5) Eq3 = 1 / Y2 = A / R + B / T + C / T & Edit the formula (2) in MATLAB language (R, T represent the mantle-derived CO2 / 3 The He ratio is 1.0×10 9 , the ratio of thermal decomposition end members of organic sediments and carbonate minerals is 10 13 );

[0058] (6) [sola,solb,solc] = solve([Eq1,Eq2,Eq3],[a,b,c]); Calculate Eq1, Eq2, Eq3 and solve for a, b, and c;

[0059] Each end member value obtained will fall between 0 and 1. The larger the value, the higher the relative contribution. If a certain end member value is negative, it means that the end member value has no relative contribution to CO2, which means that CO2 is not affected by this source and no geological activities related to this source have occurred in the area.

[0060] Experimental example

[0061] Using the method described in Example 1, typical wells in gas field A, where deep mantle-derived fluids and deep faults are present, were selected for verification. The R / Ra of the natural gas produced from these wells was greater than 1, indicating the presence of mantle-derived contributions. Through steps 2 to 10, gas samples were collected from the wells and tested to obtain the main components CO2, 3 He, 4 He, δ 13 C CO2 Use the Matlab language program edited in step 10 to calculate the corresponding a, b, and c end member contribution values.

[0062] By converting the mantle-derived CO2 / 3 The He ratio is 1.0±0.5×10 9 , the ratio of thermal decomposition end members of organic sediments and carbonate minerals to 10 13 ; The isotope values ​​of each end member are δ 13 C MORB =-6.5±2.5‰, δ 13 C SED =-30±10‰ and δ 13 C LIM =0±2‰ and δ obtained from sample testing and analysis13 C CO2 With CO2 / 3 The observed value of He is substituted into formulas (1) and (2):

[0063] Y1=-6.5a-30b+0c (1)

[0064] 1 / Y2=a / 1×10 9 +b / 10 13 +c / 10 13 (2)

[0065] Qualifications: And, a+b+c=1); (3)

[0066] In formulas (1)-(3), Y1 is the δ of the sample test 13 C CO2 Value; Y2 is the CO2 / 3 He value; a, b, and c are the relative contributions of mantle origin, thermal decomposition of carbonate minerals, and organic sediments.

[0067] The sample information, test results and calculation results involved are shown in Table 1.

[0068] Table 1. A gas field sample information, test data and Mtalab calculation results statistics

[0069]

[0070]

[0071] The atmospheric standard for data calculation is 4 He / 20 Ne=0.3185, 4 He / 40 Ar=0.00056328,Ra= 3 He / 4 He=1.400E-6, 40 Ar / 36 Ar=295.5;M,L,S in the table represent the noble gas and δ 13 C CO2 (‰) Ratios are the mass fractions (%) of components derived from mantle, thermal decomposition of carbonate minerals, and organic sediments calculated by Matlab.

[0072] The evaluation results of the three end members are as follows: Figure 1As shown, the results show that in the natural gas of typical well gas samples in gas field A with R / Ra>1, the contribution rate of mantle-derived CO2 is between 40.8% and 49.7%. When R / Ra≈1, there is still 18.4% to 20.8% of mantle-derived CO2. The inorganic CO2 with R / Ra<<1 shows that the contribution rate of CO2 from thermal decomposition of carbonate minerals (such as calcareous mudstone) is higher. For example, when R / Ra=0.08, the CO2 from thermal decomposition of carbonates is between 70.8% and 75.0%.

Claims

1. A method for evaluating the relative contribution of non-hydrocarbon gas CO2 to its origin in combination with the source of helium, characterized in that: The steps are as follows: Step 1: Conduct geological background research and analyze the helium content in the study area. 3 He / 4 The He ratio and R / Ra ratio confirm the existence of mantle source influence; The second step is to implement strict handling measures for natural gas sampling for rare gas analysis: ① Use high-pressure steel cylinders with double valves for sampling; ② Use mechanical pumps or molecular pumps to pre-evacuate the sampling cylinders before sampling, with a vacuum level of at least 10-3Pa; ③ During sampling, flush the cylinders with natural gas 4-6 times, and finally sample the middle section of the continuous gas flow; ④ After collecting the sample, immerse the cylinder in water for a leak check; In the third step, two getters with hot Ti foil are used to separate the noble gases, which include He, Ne, Ar, Kr, and Xe, from other components, including hydrocarbons, carbon dioxide, and nitrogen. In the fourth step, after purification, the noble gas fraction is analyzed by mass spectrometry; air standards are repeatedly measured between sample analyses, and blanks prepared using the same procedure as the samples are measured before, after, and during sample analysis; The fifth step is to separate the components of the noble gases using a cryogenic pump, activated carbon furnace, and liquid nitrogen due to their different boiling points. Finally, these noble gases are sequentially fed into a static vacuum noble gas isotope mass spectrometer to determine the abundance of He using mass spectrometry and perform isotope analysis to obtain 3 He, 4 He content and 3 He / 4 He ratio; In the sixth step, after separating hydrocarbons, carbon dioxide and nitrogen gases using a gas chromatograph, the CO2 abundance is determined by mass spectrometry; The seventh step is to measure the stable carbon isotope composition of the gas and obtain δ 13 CO2 value; In the eighth step, based on the above process, the CO2, δ 13 C CO2 、 3 He, 4 He content is summarized and sorted out, and then the next step is carried out; Step 9: Combine CO2 / 3 He ratio and δ 13 C CO2 The contribution of the three main carbon sources, mantle source, thermal decomposition of carbonate minerals and organic sediments, is calculated using the following formula: (δ 13 C CO2 / CO2) OBS =(δ 13 C CO2 / CO2) MORB A+(δ 13 C CO2 / CO2) LIM B+(δ 13 C CO2 / CO2) SED C (1) 1 / (CO2 / 3 He) OBS =A / (CO2 / 3 He) MORB +B / (CO2 / 3 He) LIM +C / (CO2 / 3 He) SED (2) Where, OBS is the observed value, i.e., the measured value of the sample; MORB, LIM, and SED refer to the thermal decomposition of mantle-derived, organic sediments, and carbonate minerals, respectively; A, B, and C are the corresponding relative contribution scores; where: (i) the CO2 / 3 The He ratio is 1.0×10 9 , CO2 / 3 The He ratio is 10 13 ; (ii) The isotope values ​​of each end member are δ 13 C MORB =-6.5‰, δ 13 C SED =-30‰ and δ 13 C LIM =0‰; Step 10: Combine formula (1) and formula (2) with the CO2 and δ measured by the sample. 13 C CO2 、 3 The relative contribution scores A, B, and C of the three carbon sources are calculated from the He concentration and used to identify the relative contribution of non-hydrocarbon CO2. Based on MATLAB software, link the database and input the three end-member isotope values ​​of mantle source, organic sediments and carbonate mineral thermal decomposition in step 9 as well as the CO2 / 3 He ratio, based on CO2 / 3 He ratio and δ 13 The CO2 value combination method is used to solve the contribution of the three main carbon sources: mantle source, carbonate mineral thermal decomposition, and organic sediments. The execution steps are as follows: (1) for i 1:n & n is the number of samples & edit the loop statement (2) Y1=A(i)Y2=B(i)&Link database, input CO2 / 3 He ratio and δ 13 CO2 value, Y1 represents the observable isotope value δ 13 C CO2 , Y2 represents the observable CO2 / 3 He ratio, the observed value is the sample measurement value; (3) Eq1 = c = 1 – a – b & a, b, c represent the relative contributions from mantle sources, thermal decomposition of carbonate minerals, and organic sediments, in %, i.e. Moreover, a+b+c=1; (4) Eq2 = Y1 = Q*a + W*b + E*c Edit the MATLAB language of formula (1), where Q, W, and E represent the isotope values ​​of each end member δ 13 C MORB =-6.5, δ 13 C SED =-30 and δ 13 C LIM = 0, unit ‰, MORB, LIM and SED refer to mantle origin, thermal decomposition of carbonate minerals and organic sediments, respectively; (5) Eq3 = 1 / Y2 = A / R + B / T + C / T Edit the formula (2) in MATLAB language, where R and T represent the mantle-derived CO2 / 3 The He ratio is 1.0×10 9 , the ratio of thermal decomposition end members of organic sediments and carbonate minerals is 10 13 ; (6) [sola,solb,solc] = solve([Eq1,Eq2,Eq3],[a,b,c]); Calculate equations Eq1, Eq2, Eq3 and solve for a, b, and c; each end-member value obtained will fall between 0 and 1. The larger the value, the higher the relative contribution. If a certain end-member value is negative, it means that the end-member value has no relative contribution to CO2, which means that CO2 is not affected by this source and no geological action related to this source has occurred in the area.

2. The method for evaluating the relative contribution of non-hydrocarbon gas CO2 to the formation of helium according to claim 1, characterized in that: In the first step, when R / Ra>1, it is determined that there is mantle influence.

3. The method for evaluating the relative contribution of non-hydrocarbon gas CO2 to the formation of CO2 in combination with the source of helium according to claim 1, characterized in that: In the third step, the temperature of the hot Ti foil is 800°C.

4. The method for evaluating the relative contribution of non-hydrocarbon gas CO2 to the formation of helium according to claim 1, wherein: In the seventh step, the analysis conditions were as follows: GC column: Porapak Q, 30 m; column ID: 19091P-Q04, film thickness: 20 μm; oven temperature: 40 to 160 °C, heating rate: 15 °C / min; pure helium carrier gas, flow rate: 1.2 ml / min; δ 13 The analytical error of the CO2 value was <0.3‰; each sample was measured three times, and the results of the three measurements were averaged.

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