Calculation method of cyanobacteria contribution evaluation index in hydrocarbon source rock

Abstract

The invention belongs to the technical field of oil-gas exploration and development, and relates to a method for calculating cyanobacteria contribution evaluation indexes in hydrocarbon source rocks, which comprises the following steps of: separating 2-methylhopane and hopane from saturated hydrocarbon of the hydrocarbon source rocks by a conventional single mass spectrum experimental test method and an improved single mass spectrum experimental test method respectively; calculating a new 2-methylhopane index 2MHI <-1 > and a C28 2-methylhopane relative content index according to data obtained by the improved single mass spectrum experimental test method; according to the new 2-methylhopane index 2MHI-1 and the C28 2-methylhopane relative content index, establishing a methylhopane index-relative content index model; and inputting data obtained by a conventional single mass spectrum experimental test method into the methylhopane index-relative content index model, and calculating a cyanobacteria contribution evaluation index 2-methylhopane index 2MHI <-1 >. The experimental test cost is reduced, the working efficiency is improved, the contribution of cyanobacteria in high-quality hydrocarbon source rocks is revealed, oil sources are compared, and the high-quality hydrocarbon source rocks are expected to be evaluated, and oil and gas sources are expected to be clarified.

Description

Technical Field

[0001] This invention relates to a method for calculating the contribution evaluation index of cyanobacteria in source rocks, belonging to the field of oil and gas exploration and development technology. Background Technology

[0002] Algae have long been considered a major source of organic matter in lacustrine and some marine source rocks; therefore, several molecular indicators of algal origin include the 4-methylsterane index (C). 30 4-Methylsterane / C 29 Regular sterane), C 27 / C 29 Steranes and other compounds are widely used to evaluate the contribution of algae to source rocks and the correlation between oil sources; that is, the greater the contribution of algae, the higher the molecular index of algal origin. With further research into source rocks, researchers have successively discovered that cyanobacteria and algae can both be important sources of organic matter in high-quality lacustrine and marine source rocks. Among them, lacustrine source rocks include the Eocene Sha-4 Member in the Bohai Bay Basin, the Permian Lucaogou / Fengcheng Formation in the Junggar-Santanghu Basin, the Permian Yanchang Formation in the Ordos Basin, and the Upper Triassic Towaco Formation in the Newark Supergroup in the United States; marine source rocks include the Miocene Monterey Formation in the Santa Maria Basin in the United States, and the dark mudstones of the Neoarchean Hamersley Province in Australia, where algae and / or cyanobacteria make significant contributions. 2-Methylhopane is a characteristic molecular compound from the cell membrane of cyanobacteria; however, under conventional saturated hydrocarbon gas chromatography-mass spectrometry (single-mass spectrometry) experimental conditions (60m capillary column + rapid heating), besides C... 28 In addition to 2-methylhopane, C 30- 35 2-Methylhopane and hopane series compounds commonly co-effervescence, making them difficult to separate. Therefore, the internationally accepted experimental method is to separate these two types of compounds using saturated hydrocarbon gas chromatography-tandem mass spectrometry (DMS) to establish the 2-methylhopane index (2-MHI) to evaluate the contribution of cyanobacteria in source rocks. However, the experimental cost of the mainstream international DMS method is high, with a single experiment costing three times or more than that of single-mass spectrometry, and the calculation of the 2-methylhopane index, which indicates the contribution of cyanobacteria, is quite cumbersome. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide a simple calculation method for evaluating the contribution of cyanobacteria to source rocks, thereby assessing the level of contribution of cyanobacteria to organic matter in source rocks. This method is simpler, faster, and more reliable than the internationally accepted 2-methylhope index calculation.

[0004] To achieve the above objectives, the present invention proposes the following technical solution: a method for calculating the contribution evaluation index of cyanobacteria in source rocks, comprising the following steps: separating 2-methylhopane and hopane from saturated hydrocarbons in source rocks using conventional single-mass spectrometry (MS / MS) experimental testing methods and an improved MS / MS experimental testing method, respectively; and calculating the new 2-methylhopane index 2MHI-1 and C based on the data obtained from the improved MS / MS experimental testing method. 28 2-Methylhope relative content index; based on the new 2-methylhope index 2MHI-1 and C 28 The relative content index of 2-methylhopane was established, and a methylhopane index-relative content index model was constructed. Data obtained by conventional single mass spectrometry experimental testing methods were input into the methylhopane index-relative content index model to calculate the 2-methylhopane index 2MHI-1, an evaluation index of cyanobacterial contribution.

[0005] Furthermore, the saturated hydrocarbons in the source rock are components separated from the organic matter of the source rock or condensate oil. The separation method is as follows: the source rock is crushed and chloroform bitumen A is obtained by Soxhlet extraction. The extracted chloroform bitumen A and crude oil are separated by group component chromatography. The asphaltenes of the chloroform bitumen A are precipitated with n-hexane. The soluble matter is passed through an activated alumina chromatography column and eluted with n-hexane to obtain saturated hydrocarbons.

[0006] Furthermore, the conventional single mass spectrometry experimental testing method is as follows: a quartz fused capillary column with a length of 60 m is used, the furnace temperature is set to 20℃ and held for 1 minute, then increased to 100℃ at a rate of 20℃ / min, and then increased from 100℃ to 310℃ at a rate of 4℃ / min, and finally held for 18 minutes, with helium as the carrier gas at a flow rate of 1.0 mL / min; the injection method is non-separation injection.

[0007] Furthermore, the improved single mass spectrometry experimental test method is as follows: a quartz fused capillary column with a length of 30 m is used, the furnace temperature is set to 50℃, and increased to 120℃ at a rate of 8℃ / min, then increased to 200℃ at a rate of 4℃ / min, and then increased to 300℃ at a rate of 1.5℃ / min, and held for 5 minutes. Helium is used as the carrier gas at a flow rate of 1.0 mL / min; the injection method is non-separation injection.

[0008] Furthermore, the single-mass spectrometry experimental testing method is implemented using an Agilent chromatography-mass spectrometry system.

[0009] Furthermore, the calculation method for the new 2-methylhope index 2MHI-1 is as follows: New 2MHI-1=C 31 2-Methylhope relative content / C 30 Relative content of αβ-hopane C31 2-Methylhope and C 30 The relative content of αβ-hopane is calculated by: m / z C was identified on the 205 mass chromatogram. 31 2-Methylhope and C 30 The peak position corresponding to αβ hopane is determined by calculating the peak area at that position, thereby determining C. 31 2-Methylhope and C 30 The relative content of αβ hopane.

[0010] Furthermore, the C 28 The method for calculating the relative content index of 2-methylhopane is as follows: C 28 2-Methylhopane relative content index = C 28 2-Methylhope relative content / C 27 Relative content of conventional hopane × 100; C 28 2-Methylhope and C 27 The conventional method for calculating the relative content of hopane is as follows: by... m / z C was identified on the 205 mass chromatogram. 28 The peak position of 2-methylhopeane is determined, and the peak area at the corresponding peak position is calculated to determine C. 28 The relative content of 2-methylhopane; by m / z C was identified on the mass chromatogram of 191. 27 The peak positions of conventional hopanes are determined, and the peak areas at the corresponding positions are calculated to determine C. 27 Relative content of conventional hopane.

[0011] Furthermore, the calculation formula for the methylhope index-relative content index model is as follows: New 2MHI-1=C 28 2-Methylhopane relative content index × 0.1289 - 0.053.

[0012] Furthermore, the internationally recognized 2-methylhope index 2-MHI was used to compare the new 2-methylhope index 2MHI-1 and C. 28 The reliability of the relative content index of 2-methylhopane was verified. The technical solution of the present invention has at least the following technical effects or advantages: The solution of the present invention reduces the cost of experimental testing, improves work efficiency, reveals the contribution of cyanobacteria in high-quality source rocks and conducts oil source comparison, in order to evaluate high-quality source rocks, clarify the source of oil and gas, further reveal the development law of high-quality source rocks, serve the decision-making of oil and gas exploration and development, and has great application value. Attached Figure Description

[0013] Figure 1 This is a graph showing the effect of conventional single-mass spectrometry method in separating 2-methylhopane and conventional hopane in one embodiment of the present invention; Figure 2 This is a graph showing the effect of the improved dual mass spectrometry experimental test method in one embodiment of the present invention on the separation of 2-methylhopane and conventional hopane; Figure 3 This is a diagram showing the effect of separating 2-methylhopane and conventional hopane using an internationally accepted dual mass spectrometry experimental testing method in one embodiment of the present invention; Figure 4 This is a correlation diagram between the novel 2-methylhope index 2MHI-1 and the internationally recognized 2-methylhope index 2-MHI in one embodiment of the present invention; Figure 5 C is an embodiment of the present invention 28 Correlation diagram between the relative content index of 2-methylhope and the internationally recognized 2-methylhope index 2-MHI; Figure 6 This is a schematic diagram of the methylhopane index-relative content index model in one embodiment of the present invention; Figure 7 This is a profile of 2MHI-1, TOC, and 4-methylsterane index in source rock samples of the Liushagang Formation from six representative wells in the Beibu Gulf Basin, tested using an improved and conventional single-mass spectrometry experimental method in one embodiment of the present invention. Figure (a) is a distribution map of the six representative wells in the Beibu Gulf Basin; Figure (b) is the representative well numbered W6; Figure (c) is the representative well numbered W12; Figure (d) is the representative well numbered W12-1; Figure (e) is the representative well numbered S16; Figure (f) is the representative well numbered W1; and Figure (g) is the representative well numbered S16-1. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for a better understanding of the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] To address the high experimental costs of the internationally mainstream dual mass spectrometry method and the cumbersome calculation of the 2-methylhopane index, a key indicator of cyanobacterial contribution, in existing technologies, this invention proposes a method for calculating the cyanobacterial contribution evaluation index in source rocks. The method includes the following steps: separating 2-methylhopane and hopane from saturated hydrocarbons in source rocks using both conventional and improved single mass spectrometry methods; and calculating the new 2-methylhopane index 2MHI-1 and C based on data obtained from the improved single mass spectrometry method. 28 2-Methylhope relative content index; based on the new 2-methylhope index 2MHI-1 and C 28 The relative abundance index of 2-methylhopane was used to establish a methylhopane index-relative abundance index model. Data obtained from conventional single-mass spectrometry experiments were input into the methylhopane index-relative abundance index model to calculate the 2-methylhopane index (2MHI), an evaluation index for cyanobacterial contribution. This invention reduces experimental testing costs, improves work efficiency, reveals the contribution of cyanobacteria in high-quality source rocks, and facilitates oil source comparison, aiming to evaluate high-quality source rocks and clarify oil and gas origins. The following detailed description of the invention, with reference to the accompanying drawings, uses examples to illustrate the invention.

[0016] Example 1 This embodiment discloses a method for calculating the contribution evaluation index of cyanobacteria in source rocks, including the following steps: S1 separated 2-methylhopane and hopane from saturated hydrocarbons in source rocks using both conventional and improved single-mass spectrometry methods.

[0017] This embodiment uses 76 Eocene lacustrine source rock samples from the Beibu Gulf Basin as examples. Saturated hydrocarbons from source rocks are components separated from the organic matter of source rocks or condensate oil. The separation method is as follows: the source rock is crushed, and chloroform bitumen A is obtained through Soxhlet extraction for 72 hours. The extracted chloroform bitumen A and crude oil are separated using group fraction chromatography. The asphaltenes of chloroform bitumen A are precipitated with n-hexane. The soluble matter is passed through an alumina chromatography column activated at 400℃ for 4 hours, followed by elution with n-hexane to obtain saturated hydrocarbons. The saturated hydrocarbon component is concentrated to 2 ml and not dried.

[0018] The standard single-mass spectrometry (MS / MS) experimental method was as follows: A 60m HP-5MS or DB-5MS quartz fused capillary column with an inner diameter of 0.25mm and a thickness of 0.25μm was used. The quartz fused capillary column was placed in an Agilent chromatography-mass spectrometry (GC-MS) system. The oven temperature was set to 20℃ and held for 1 minute. The temperature was then increased to 100℃ at a rate of 20℃ / min, and then increased to 310℃ at a rate of 4℃ / min, finally held for 18 minutes. Helium was used as the carrier gas at a flow rate of 1.0 mL / min. Non-separation injection was used. The separation of 2-methylhopane and hopane using the standard MS / MS experimental method is shown in the figure below. Figure 1 As shown.

[0019] The improved single-mass spectrometry (MS / MS) experimental method is as follows: A 30m HP-5MS quartz fused capillary column with an inner diameter of 0.25mm and a thickness of 0.25μm is used. The quartz fused capillary column is placed in an Agilent chromatography-mass spectrometry (GC-MS) system. The oven temperature is set to 50℃, increased to 120℃ at a rate of 8℃ / min, then increased to 200℃ at a rate of 4℃ / min, and finally increased to 300℃ at a rate of 1.5℃ / min, held for 5 minutes. Helium is used as the carrier gas at a flow rate of 1.0 mL / min; non-separation injection is used. The improved MS / MS experimental method for separating 2-methylhopane and hopane is shown in the figure below. Figure 2 As shown.

[0020] 2-Methylhope and hopane were separated from saturated hydrocarbons in source rocks using an internationally accepted dual-mass spectrometry (DMS) method. The separation efficiency of 2-methylhope and conventional hopane was compared using this internationally accepted DMS method.

[0021] The internationally accepted experimental method for the detection of 2-methylhope is based on saturated hydrocarbon dual mass spectrometry (gas chromatography-tandem mass spectrometry). This method involves selecting the molecular ion M+ and the base peak ion of 2-methylhope. m / z 205 was subjected to an ion field to accurately detect the abundance of 2-methylhope. After the 2-methylhope detection was completed, the internationally accepted method for calculating the 2-methylhope index is as follows: 2-Methylhopane index = (C 28 -C 34 2-Methylhopane / (C 28 -C 34 2-Methylhopane + C 30 αβ-hopane)*100 Among them, C 28 -C 34 2-Methylhopane in m / z The sum of peak areas obtained by integrating the M+ (molecular ion) → 205 chromatogram; C 30 αβ-hopane is in m / z The peak area obtained by integrating the chromatogram of 412 (molecular ion) → 191.

[0022] The results of the separation effect comparison show that, Figure 1 In China, single-mass spectrometry experimental testing methods cannot separate C. 30 -C 34 2-Methylhopane and conventional hopane only have C 28 2-Methylhope was completely separated; Figure 2 In China, internationally accepted dual mass spectrometry experimental testing methods and Figure 3 The improved single-mass spectrometry experimental test method can completely separate C 28 -C 34 2-Methylhopane and conventional hopane.

[0023] S2 calculated the new 2-methylhopane index 2MHI-1 and C based on data obtained from the improved single-mass spectrometry experimental testing method. 28 2-Methylhopane relative content index.

[0024] The calculation method for the new 2-methylhope index 2MHI-1 is as follows: New 2MHI-1=C 31 2-Methylhope relative content / C 30 Relative content of αβ-hopane C 31 2-Methylhope and C 30 The relative content of αβ-hopane is calculated by: m / z C was identified on the 205 mass chromatogram. 31 2-Methylhope and C 30 The peak position corresponding to αβ hopane is determined by calculating the peak area at that position, thereby determining C. 31 2-Methylhope and C 30 The relative content of αβ hopane.

[0025] The correlation between the new 2-methylhope index 2MHI-1 and the internationally accepted 2-MHI was analyzed to verify the reliability of the new 2-methylhope index 2MHI-1. Using an improved single-mass spectrometry experimental method, data from 76 Eocene lacustrine source rocks were obtained to establish the correlation between the new 2-methylhope index 2MHI-1 and the internationally accepted 2-MHI, and correlation analysis was performed. The results are as follows: Figure 4As shown, the results indicate that the new 2-methylhope index 2MHI-1 is linearly correlated with the internationally accepted 2-MHI, with the linear correlation formula being 2MHI = 0.5405 × 2MHI-1 + 0.3922, and the correlation coefficient R0. 2 = 0.98; This indicates that the new 2-methylhope index 2MHI-1 can replace the internationally used 2-MHI and has good reliability.

[0026] C 28 The method for calculating the relative content index of 2-methylhopane is as follows: C 28 2-Methylhopane relative content index = C 28 2-Methylhope relative content / C 27 Relative content of conventional hopane × 100; C 28 2-Methylhope and C 27 The conventional method for calculating the relative content of hopane is as follows: by... m / z C was identified on the 205 mass chromatogram. 28 The peak position of 2-methylhopeane is determined, and the peak area at the corresponding peak position is calculated to determine C. 28 The relative content of 2-methylhopane; by m / z C was identified on the mass chromatogram of 191. 27 The peak positions of conventional hopanes are determined, and the peak areas at the corresponding positions are calculated to determine C. 27 Relative content of conventional hopane.

[0027] Analysis C 28 The correlation between the relative content index of 2-methylhopane and the internationally accepted 2-MHI verifies C 28 The reliability of the relative content index of 2-methylhopane. For example... Figure 5 As shown, C 28 The correlation between the relative content index of 2-methylhopane and the internationally accepted 2-MHI is as follows: 2-MHI = 0.7057 × C 28 The relative content index of 2-methylhopane is -0.1417. The results show that C 28 The linear correlation coefficient R between the relative content index of 2-methylhope and the internationally accepted 2-MHI 2 =0.958, indicating that C 28 The relative content index of 2-methylhopane is reliable.

[0028] S2.4: Establishing a new 2-methylhope index 2MHI-1 and C 28 The correlation between the relative content indices of 2-methylhopane was investigated, and an empirical model between the two was established.

[0029] Using an improved single-mass spectrometry experimental method, data from 76 Eocene lacustrine source rocks were obtained. A methylhope index-relative content index model was established, and the calculation formula for the methylhope index-relative content index model is as follows: 2MHI-1=C 28 2-Methylhope relative content index × 0.1289 - 0.053 like Figure 6 As shown, the methylhopane index-relative content index model exhibits good correlation, with a linear correlation coefficient R0. 2 =0.96, indicating high accuracy of the methylhopane index-relative content index model.

[0030] S3 is based on the new 2-methylhope index 2MHI-1 and C. 28 The relative content index of 2-methylhopane was determined, and a methylhopane index-relative content index model was established.

[0031] Using an improved single-mass spectrometry experimental testing method, a large amount of Eocene lacustrine source rock data was obtained, and a C1S2S3S4S5S6 ...6S6S6< / 28 The relative content index of 2-methylhopane and the methylhopane index-relative content index model of the new 2-methylhopane index 2MHI-1.

[0032] The formula for calculating the methylhopane index-relative content index model is as follows: New 2MHI-1=C 28 2-Methylhopane relative content index × 0.1289 - 0.053.

[0033] S4 inputs the data obtained by conventional single mass spectrometry experimental testing methods into the methylhope index-relative content index model to calculate the 2-methylhope index 2MHI, an evaluation index of cyanobacterial contribution.

[0034] Conventional single-mass spectrometry methods can typically only separate C 28 2-Methylhopane, C 29 -C 34 2-Methylhopane typically co-effervesces with conventional hopane and cannot be separated. Therefore, C2 can only be calculated from source rock data analyzed using conventional single-mass spectrometry methods. 28 2-Methylhope Relative Content Index. Using the established methylhope index-relative content index model, the 2-methylhope index 2MHI was calculated. Based on data from 43 source rocks in the Liushagang Formation of the Beibu Gulf Basin, the new 2-methylhope index 2MHI-1 was calculated as follows: 2-MHI = 0.7057 × C 28 The relative content index of 2-methylhopane is -0.1417.

[0035] 2-MHI-1 profiles of typical source rocks in the Beibu Gulf Basin were established based on conventional single-mass spectrometry (SMS) experimental data and improved conventional SMS experimental data, such as... Figure 7 As shown. Conventional single-mass spectrometry experimental data from 43 source rock samples from three wells (W12 / S16-1 / W1) in the Beibu Gulf Basin were analyzed using C... 28 2-MHI-1 is calculated using a correlation model between the relative content index of 2-methylhopane and 2MHI-1. The 2-MHI-1 profile was obtained directly from modified conventional single-mass spectrometry experimental data of 21 source rock samples from three wells (W6 / W12- / S16) in the Beibu Gulf Basin.

[0036] 4-Methylsterane, also known as 4α-methyl, 23,24-trimethylsterane, is a class of tetracyclic terpenoids with ≥28 carbon atoms. Studies have shown that 4-methylsterane mainly originates from cell membrane sterols in algae, primarily dinoflagellates. 4-Methylsterane and C... 29 Identification of regular sterane series compounds using conventional and improved single-mass spectrometry experimental data m / z 217. The relative content is identified on the mass chromatogram and determined by the peak area. 4-Methylsterane index = C 30 4-Methylsterane / C 29 Regular steranes. The higher the 4-methylsterane index, the greater the contribution of phytoplankton, mainly dinoflagellates, in the source rock.

[0037] TOC, or Total Organic Carbon, is the content of organic carbon in source rocks, obtained through experiments using a carbon-sulfur analyzer. A higher TOC indicates better quality source rocks.

[0038] The results show that the 2MHI-1 content in the mudstone (Lower Eocene) of the upper part of the Liu-3 Member and the lower part of the Liu-2 Member in the Beibu Gulf Basin is higher than that in the lower oil shale of the Liu-2 Member, the middle and upper parts of the Liu-2 Member, and the source rocks of the Liu-2 Member (Middle-Upper Eocene). Therefore, this index can be used to compare the crude oil sources of the Lower Eocene and Middle-Upper Eocene source rocks in the Beibu Gulf Basin. In addition, there is an inverse relationship between 2MHI-1 and 4-methylsterane, revealing the ecological competition between algae, mainly cyanobacteria and dinoflagellates, for the enrichment of organic matter in source rocks.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims

1. A method for calculating the contribution evaluation index of cyanobacteria in source rocks, characterized in that, Includes the following steps: 2-Methylhopane and hopane were separated from saturated hydrocarbons in source rocks using conventional single-mass spectrometry (MS / MS) and an improved MS / MS method, respectively. Based on data obtained from the improved single-mass spectrometry experimental testing method, the new 2-methylhopane index 2MHI-1 and C were calculated. 28 2-Methylhope relative content index; According to the new 2-methylhopane index 2MHI-1 and C 28 The relative content index of 2-methylhopane was determined, and a methylhopane index-relative content index model was established. Data obtained from conventional single-mass spectrometry experiments were input into the methylhope index-relative content index model to calculate the 2-methylhope index 2MHI-1, an evaluation index of cyanobacterial contribution.

2. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 1, characterized in that, The saturated hydrocarbons in the source rock are components separated from the organic matter of the source rock or condensate oil. The separation method is as follows: the source rock is crushed and chloroform bitumen A is obtained by Soxhlet extraction. The extracted chloroform bitumen A and crude oil are separated by group component chromatography. The asphaltenes of the chloroform bitumen A are precipitated with n-hexane. The soluble matter is passed through an activated alumina chromatography column and eluted with n-hexane to obtain saturated hydrocarbons.

3. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 2, characterized in that, The conventional single mass spectrometry experimental test method is as follows: a quartz fused capillary column with a length of 60 m is used, the furnace temperature is set to 20℃ and held for 1 minute, then increased to 100℃ at a rate of 20℃ / min, and then increased from 100℃ to 310℃ at a rate of 4℃ / min, and finally held for 18 minutes. Helium is used as the carrier gas at a flow rate of 1.0 mL / min; non-separation injection is used.

4. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 2, characterized in that, The improved single mass spectrometry experimental test method is as follows: a quartz fused capillary column with a length of 30 m is used, the furnace temperature is set to 50℃, and increased to 120℃ at a rate of 8℃ / min, then increased to 200℃ at a rate of 4℃ / min, and then increased to 300℃ at a rate of 1.5℃ / min, and held for 5 minutes. Helium is used as the carrier gas at a flow rate of 1.0 mL / min; non-separation injection is used for the sample injection method.

5. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 3 or 4, characterized in that, The single-mass spectrometry experimental testing method was implemented using an Agilent chromatography-mass spectrometry system.

6. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in any one of claims 1-5, characterized in that, The method for calculating the new 2-methylhope index 2MHI-1 is as follows: New 2MHI-1=C 31 2-Methylhope relative content / C 30 Relative content of αβ-hopane C 31 2-Methylhope and C 30 The relative content of αβ-hopane is calculated by: m / z C was identified on the 205 mass chromatogram. 31 2-Methylhope and C 30 The peak position corresponding to αβ hopane is determined by calculating the peak area at that position, thereby determining C. 31 2-Methylhope and C 30 The relative content of αβ hopane.

7. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 6, characterized in that, The C 28 The method for calculating the relative content index of 2-methylhopane is as follows: C 28 2-Methylhopane relative content index = C 28 2-Methylhope relative content / C 27 Relative content of conventional hopane × 100; C 28 2-Methylhope and C 27 The conventional method for calculating the relative content of hopane is as follows: by... m / z C was identified on the 205 mass chromatogram. 28 The peak position of 2-methylhopeane is determined, and the peak area at the corresponding peak position is calculated to determine C. 28 The relative content of 2-methylhopane; by m / z C was identified on the mass chromatogram of 191. 27 The peak positions of conventional hopanes are determined, and the peak areas at the corresponding positions are calculated to determine C. 27 Relative content of conventional hopane.

8. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 7, characterized in that, The calculation formula for the methylhopane index-relative content index model is as follows: New 2MHI-1=C 28 2-Methylhopane relative content index × 0.1289 - 0.

053.

9. The method for calculating the contribution evaluation index of cyanobacteria in source rocks as described in claim 8, characterized in that, The internationally recognized 2-methylhope index 2-MHI was used to compare the new 2-methylhope index 2MHI-1 and C. 28 The reliability of the relative content index of 2-methylhopane was verified.

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