Method for correcting and judging parent material source
By using biomarker compound analysis and thermal maturity correction, the problem of outlier correction in shale parent material source identification was solved, enabling accurate identification of shale parent material source and improving the accuracy of shale oil and gas exploration.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-04-07
AI Technical Summary
In existing technologies, the classical source discrimination theory has failed to effectively solve the problem of outlier correction in shale source material, resulting in a lack of accuracy in shale oil and gas exploration.
Using biomarker compounds, extracts from shale reservoirs were collected, and saturated hydrocarbon components were analyzed using gas chromatography-mass spectrometry. The original relative percentage contents of C27, C28, and C29 steranes were calculated, and a thermal maturity correction coefficient was introduced to correct the C27/C29 ratio, eliminating the influence of thermal evolution, and thus determining the source of the parent material.
It enables more accurate and reliable identification of the source of the parent material, eliminates the interference of thermal evolution on sterane parameters, and provides a more reliable basis for shale oil and gas exploration.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of unconventional oil and gas exploration technology, and particularly to a method based on C 27 C 28 C 29 Methods for correcting and identifying the source of the parent material in the ratio. Background Technology
[0002] Shale oil and gas is an important unconventional oil and gas resource. In recent years, unconventional oil and gas exploration, represented by shale oil and gas, has been carried out on a large scale. Determining the parent material source of mudstone and shale helps to predict the oil and gas content of shale and provides technical support for shale oil and gas exploration.
[0003] In existing technologies, the classical source theory has provided an in-depth analysis of conventional source identification methods and guided conventional oil and gas exploration. However, for shale source identification methods, the classical source theory does not address the issue of outlier correction. Therefore, there is an urgent need for an effective source identification method for mudstone and shale to guide further exploration. Summary of the Invention
[0004] In order to solve the above-mentioned technical problems, the present invention provides a method for correction and identification of the source of maternal material.
[0005] The present invention is achieved by the following technical solution.
[0006] A method for correction and identification of maternal origin includes the following steps: S1. Collect reservoir extracts from the target shale to obtain saturated hydrocarbon data for the target formation; S2. Determine the values of the parent material source index for the target segmentation based on saturated hydrocarbon data; S3. Divide the correction coefficient and corresponding index values of the target layer according to the source of the parent material; S4. Determine the source of the parent material in the target layer based on the corrected index characteristic values.
[0007] Furthermore, the specific method of step S1 is as follows: collect core or rock fragment samples from the target mudstone and shale formation, extract soluble organic matter from the reservoir by organic solvent extraction, and then separate saturated hydrocarbon components by column chromatography; analyze the saturated hydrocarbon components using gas chromatography-mass spectrometry to obtain spectral data of biomarker compounds, including regular steranes.
[0008] Furthermore, the specific method for step S2 is as follows: Based on the saturated hydrocarbon gas chromatography-mass spectrometry data m / z 217, identify and integrate the peak areas of characteristic peaks of cholesterane, ergosterane, and stigmasterane compounds in regular steranes, and calculate the original relative percentage content and initial C of the three sterane components. 27 / C29 ratio.
[0009] Furthermore, the formula for calculating the original relative percentage content of cholesterol is: C 27 % = [C 27 / (C 27 + C 28 + C 29 The original relative percentage content of ergosterane is calculated as follows: C × 100%; 28 % = [C 28 / (C 27 + C 28 +C 29 The original relative percentage content of stigmasterane is calculated as follows: C × 100%; 29 % = [C 29 / (C 27 + C 28 +C 29 )] × 100%.
[0010] Furthermore, in step S3, in order to eliminate C during the thermal evolution process 29 The impact of sterane cracking on the source identification index was investigated using an empirical correction coefficient for the initial C2O .... 27 / C 29 The ratio is corrected and restored; the correction formula is: Corrected C 27 / C 29 Ratio = (Correction factor A × C) 27 Original relative percentage content) / (correction factor B × C) 29 (Original relative percentage content) Among them, correction coefficients A and B are empirical constants, used to compensate for C respectively. 27 Preservation of steranes and C 29 Steranes are broken down and lost.
[0011] Furthermore, the value of correction factor A is 1.28, and the value of correction factor B is 0.72.
[0012] Specifically, the identification index for biomarker compounds of parent material source is C. 27 / C 29 Correction ratio, C 27 / C 29 The correction ratio is calculated using the following formula: In the formula, C 27 / 29 The value is C 27 C 29 Content ratio, C 27 C27 The content in mass spectrometry, C 29 C 29 The concentrations in the mass spectrometer are 1.28 and 0.72, which are numerical correction constants.
[0013] Furthermore, in step S4, based on the calculated corrected C... 27 / C 29 The ratio, combined with the causal significance represented by its numerical range, is used to determine the type of organic parent material input in the target layer. The criteria for judging the characteristics of the source of the maternal material are as follows: If C 27 / C 29 > 1: Indicative meaning: Aquatic lower organisms are dominant; Sedimentary environment: Usually represents lacustrine, marine, or deep lacustrine sedimentary environments; If C 27 / C 29 = 1: Indicative meaning: Mixed source, i.e., the input ratio of aquatic organisms and terrestrial plants is equal; Sedimentary environment: Commonly found in marine transitional facies or nearshore shallow lake environments; If C 27 / C 29 < 1: Indicative meaning: Terrestrial higher plants are dominant; Sedimentary environment: Usually represents swamp facies, coal-bearing strata, or large deltas near the source area.
[0014] This application has the following beneficial effects: This invention provides a method for correcting and identifying the source of parent material based on biomarker compounds. By introducing a thermal maturity correction coefficient, this method effectively eliminates the interference of organic matter thermal evolution on sterane parameters, thereby achieving a more accurate and reliable identification of the source of parent material. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of normal values for regular steranes unaffected by thermal maturity in an embodiment of the present invention; wherein, from top to bottom, they are: ① The mass chromatogram (m / z = 123) is a curve showing the change in ion current intensity with chromatographic retention time at a mass-to-charge ratio (m / z) of 123. Geological significance: m / z 123 is a characteristic fragment ion of steranes, a biomarker compound. By monitoring this ion, the distribution of sterane compounds in the sample can be highlighted, which can be used to preliminarily determine the source of organic matter (such as the relative contribution of aquatic algae and terrestrial higher plants). ② The mass chromatogram (m / z = 191) is a curve showing the change in ion current intensity with chromatographic retention time for a mass-to-charge ratio (m / z) of 191. Geological significance: m / z 191 is a characteristic fragment ion of terpanes, especially hopanes. This chromatogram is mainly used to reflect information on the microbial input of organic matter, redox conditions of the depositional environment, and the thermal maturity of organic matter. ③ Total Ion Chromatography (RIC): In GC-MS data analysis, RIC can sometimes be used as a background for calculating relative content or to assess the overall quality of chromatographic separation. The peak area of the target compound (such as C27, C28, and C29 steranes) on the characteristic mass chromatogram (m / z 217) is the direct basis for its quantification, while RIC provides the "panoramic" background in which it is located. The RIC chromatogram reflects the overall elution of all detectable compounds in the analyzed sample (i.e., the saturated hydrocarbon component in this patent) after separation in the chromatographic column. Each peak in the figure represents one or a group of co-eluted compounds. By comparing with the selected ion monitoring chromatogram above (such as m / z 123 and m / z 191), the peak position and relative abundance of the target biomarker (such as steranes and terpenes) in the total sample can be determined. Figure 2 This is a schematic diagram of the abnormal values of regular steranes after being affected by thermal maturity in an embodiment of the present invention; Figure 3 This is a triangular distribution diagram of sterane composition drawn based on the original data in an embodiment of the present invention; Figure 4 This is a triangular distribution diagram of sterane composition after thermal maturity correction in an embodiment of the present invention; Figure 5 This is a comparison diagram of the triangular distribution of sterane composition before and after thermal maturity correction in an embodiment of the present invention; Figure 6 This is a flowchart of the method of the present invention. Detailed Implementation
[0016] The present patent application will be further described below with reference to the embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials used in the preparation process in the following embodiments have not undergone further processing and have been commercially available.
[0017] A C-based 27 C 28 C 29 The method for correcting and determining the source of the parent material in the ratio includes the following steps: S1: Collect reservoir extracts from the target shale to obtain saturated hydrocarbon data for the target formation. Specifically, firstly, the target shale sample is pulverized to a predetermined particle size and subjected to Soxhlet extraction using an organic solvent to obtain the original extract. Then, the extract is treated with n-hexane to precipitate and deasphalt, yielding soluble organic matter. Next, the soluble organic matter is separated into components using alumina / silica gel column chromatography, with n-hexane used as the eluent to wash out saturated hydrocarbon components. Subsequently, the saturated hydrocarbon components are gently concentrated to a specific volume under inert gas protection and transferred to the injection port. Finally, the prepared saturated hydrocarbon sample is injected into a gas chromatography-mass spectrometry (GC-MS) system equipped with a capillary column and analyzed under a preset temperature program and ion monitoring mode (such as SIM mode) to obtain mass spectrometry data for the identification of biomarker compounds.
[0018] S2: Determine the values of the parent material source index for the target segmentation based on the saturated hydrocarbon data, including C. 27 C 28 C 29 One of the following: peak area, peak height, or mass percentage Specifically, firstly, chromatographic data of saturated hydrocarbon components in the target shale sample were obtained on an m / z 217 mass chromatogram; subsequently, on the m / z 217 mass chromatogram, cholesterane (C) corresponding to regular steranes was accurately identified and confirmed. 27 ααα20R), ergosterane (C 28 ααα20R) and stigmasterane (C 29 The positions of the characteristic peaks (ααα20R) were determined; then, the peak areas of the three characteristic peaks were calculated by integrating the built-in integration function of the chromatography workstation; finally, the obtained C... 27 C 28 C 29 The peak areas of the three sterane components were normalized, and their relative percentage contents were calculated using the following formula: C 27 % = [C 27 / (C 27 + C 28 + C 29 )] × 100%, and calculate C in the same way. 28 % and C 29 %; ultimately, the output is C. 27 C 28 C 29 The relative percentage content of regular steranes is used as a characteristic indicator of the source of organic parent material, and the initial C is calculated. 27 / C 29 ratio.
[0019] S3: Based on the source of the parent material, adjust the correction coefficient to correct the index value corresponding to the target segment. Specifically, in obtaining the C of the target layer using the aforementioned method... 27 C 28 C 29 After determining the original peak area percentage of the regular sterane ααα20R configuration, a correction factor based on thermodynamic stability was introduced to process the original value; the correction is based on the fact that as the organic matter thermal maturity (Ro value) increases, the C from higher plants... 29 Steranes undergo carbon-carbon bond breaking, partially bridging to the carbon atom. 27 and C 28 Sterane conversion leads to an increase in measured C 29 The value is low and C 27 The value is relatively high, and this geochemical process causes a systematic bias in the source identification results. To restore the original source material input ratio, a verified thermal evolution correction coefficient is used to restore the data. The specific correction formula is: Corrected C 27 / C 29 Ratio = (1.28 × C) 27 (Original value) / (0.72 × C) 29 (Original values), where coefficients 1.28 and 0.72 correspond to C respectively. 27 With C 29 The empirical constant for the sterane thermal decomposition reaction rate; finally, the corrected C 27 / C 29 The ratio is used as an indicator for identifying the source of parent material after eliminating the interference of thermal maturity.
[0020] S4: Determine the source of the parent material for the target layer based on the corrected index characteristic values. Specifically, after obtaining C by using the thermal maturity correction formula to eliminate the influence of thermal evolution... 27 With C 29 After correcting the sterane ratio, C is taken into account. 27 C 28 C 29The corrected relative percentage content was used to qualitatively and semi-quantitatively classify the organic matter input type of the target layer according to the pre-established parent material source identification criteria (see Hunt, JM (1995). Petroleum Geochemistry and Geology (2nd ed.). WH Freeman and Company; Peters, KE, Walters, CC, & Moldowan, JM (2005). The Biomarker Guide: Volume 2, Biomarkers and Isotopes in Petroleum Exploration and Earth History (2nd ed.). Cambridge University Press; Huang, WY, & Meinschein, WG (1979). Sterols as ecological indicators. Geochimica et Cosmochimica Acta, 43(5), 739-745). Specifically, the corrected C 27 / C 29 The ratio is used as a core discriminant indicator: When C 27 / C 29 When > 1, the following meanings are indicated: the parent material was mainly composed of aquatic lower organisms (algae); the sedimentary environment typically represents lacustrine (especially algae-rich lacustrine), marine, or deep lacustrine sedimentary environments. These environments are far from terrestrial inputs, and productivity is mainly derived from aquatic organisms such as algae.
[0021] When C 27 / C 29 =1 indicates a mixed source. The input ratio of aquatic organisms and terrestrial plants is roughly equal. Sedimentary environment: Commonly found in marine-terrestrial transitional facies (such as deltas and lagoons) or nearshore shallow lacustrine environments, with both marine or lacustrine productivity and significant terrestrial organic matter brought by rivers.
[0022] When C 27 / C 29 When < 1, it indicates that terrestrial higher plant input is dominant. Sedimentary environment: usually represents environments close to the source area, such as swamp facies, coal-bearing strata, or large deltas, with a large input of higher plant debris (such as leaves, trunks, pollen, etc.).
[0023] At the same time, C 27 C 28 C29 The corrected relative percentages of the three factors are plotted on the sterane ternary configuration diagram. The specific distribution location of these factors in the diagram is used to further verify and accurately determine the source of the parent material, and finally, a comprehensive geological interpretation conclusion on the source of the organic matter parent material of the target layer is output.
[0024] Example Taking the mudstone and shale of WC-19-1M-1 and WC19-1-3 as examples, the method for classifying the parent material source of these mudstones and shale includes the following steps: (1) Data acquisition and processing Acquire saturated hydrocarbon gas chromatography-mass spectrometry (GC-MS) analysis data for the target layer (taking samples from wells WC-19-1M-1 and WC19-1-3 as examples).
[0025] ① Sample pretreatment Fresh core samples of 500g each from the target formations of wells WC-19-1M-1 (depth: 3520-3535m) and WC19-1-3 (depth: 3488-3502m) were selected. The core surfaces were wiped with dichloromethane to remove drilling mud contamination, and then dried in a 60°C oven for 24 hours. The samples were initially crushed using a clean jaw crusher, then ground in an agate mortar, and passed through a 100-mesh (0.15 mm) standard sieve to obtain uniform rock powder for extraction. After processing, 480g and 490g of analytical powder were obtained from the two samples, respectively.
[0026] ② Organic matter extraction Weigh 100.0 g (accurate to 0.1 g) of each of the above-mentioned rock powders and place them in the fiber paper tube of a Soxhlet extractor. Use a mixed solvent of dichloromethane and methanol (volume ratio 93:7) as the extractant and extract for 72 hours. After extraction, concentrate the extract to 5 mL using a rotary evaporator in a 40°C water bath. Then add excess n-hexane (40 mL) to precipitate and remove asphaltenes. Centrifuge and collect the supernatant. Concentrate the supernatant again by rotary evaporation to near dryness to obtain a brownish-yellow viscous total organic extract. Weighing, the extract from the WC-19-1M-1 well sample was 85.6 mg, and the extract from the WC19-1-3 well sample was 78.3 mg.
[0027] ③ Separation of saturated hydrocarbon components Saturated hydrocarbons were separated by column chromatography. The chromatographic column (1 cm inner diameter) was packed from bottom to top with activated silica gel (2 g, 100-200 mesh) and activated alumina (1 g, 100-200 mesh). The total organic extract was dissolved in a small amount of n-hexane and loaded onto the column. A gradient elution was performed sequentially with 15 mL of n-hexane, 15 mL of a hexane / dichloromethane mixture (1:1 v / v), and 15 mL of a dichloromethane / methanol mixture (1:1 v / v), collecting saturated hydrocarbons, aromatic hydrocarbons, and non-hydrocarbon fractions, respectively. The n-hexane eluent (saturated hydrocarbon fraction) was collected in a concentration flask, purged with mild nitrogen to a volume of 100 µL, and transferred to a 2 mL chromatographic sample vial for GC-MS analysis.
[0028] ④ GC-MS analysis The prepared saturated hydrocarbon samples were analyzed using an Agilent 7890B / 5977B GC-MS system. The chromatographic column was an HP-5MS quartz capillary column (30 m × 0.25 mm × 0.25 µm). Gas chromatography conditions: injector temperature 300°C, splitless injection, injection volume 1 µL; carrier gas was high-purity helium, constant flow rate 1.0 mL / min; temperature program: initial 80°C, hold for 2 min, ramp at 4°C / min to 290°C and hold for 30 min. Mass spectrometry conditions: electron impact (EI) ion source, electron energy 70 eV, ion source temperature 230°C, interface temperature 280°C. Data acquisition was performed simultaneously in full scan mode (Scan, m / z 50-550) and selected ion monitoring mode (SIM). For regular steranes, the characteristic ion monitored was m / z 217. After the analysis was completed, total ion current chromatograms (RIC) and characteristic mass chromatograms were obtained for each sample.
[0029] ⑤ Data processing: In the MSD ChemStation workstation, mass chromatograms of each sample at m / z 217 were extracted. On these chromatograms, cholesteranes (C14) in the regular sterane series were identified and integrated. 27 ααα20R), ergosterane (C 28 ααα20R) and stigmasterane (C 29 The characteristic peak area of ααα20R). The integral peak areas of the WC-19-1M-1 well sample are as follows: C 27 : 1254500, C 28 :856200, C 29 : 987300. The integral peak areas of the WC19-1-3 well sample are as follows: C 27 : 1678900, C 28 765400, C 29: 2156300. This original peak area data is the basis for subsequent calculations.
[0030] (2) Calculation of relative content The C obtained above 27 C 28 C 29 The peak areas of the sterane components were normalized, and their relative percentage contents were calculated. The calculation formula is as follows: C 27 % = [C 27 Peak area / (C 27 Peak area + C 28 Peak area + C 29 Peak area) × 100% C 28 % = [C 28 Peak area / (C 27 Peak area + C 28 Peak area + C 29 Peak area) × 100% C 29 % = [C 29 Peak area / (C 27 Peak area + C 28 Peak area + C 29 Peak area) × 100% At the same time, calculate the uncorrected C 27 / C 29 Original relative percentage content ratio (i.e., C) 27 % / C 29 %).
[0031] For the sample from well WC-19-1M-1: C 27 % = 1254500 / (1254500 + 856200 + 987300) × 100% = 40.5% C 28 % = 856200 / (1254500 + 856200 + 987300) × 100% = 27.6% C 29 % = 987300 / (1254500 + 856200 + 987300) × 100% = 31.9% Initial C 27 / C 29 The ratio = 40.5% / 31.9% = 1.27 For samples from well WC19-1-3: C 27 % = 1678900 / (1678900 + 765400 + 2156300) × 100% = 36.5% C 28 % = 765400 / (1678900 + 765400 + 2156300) × 100% = 16.6% C 29 % = 2156300 / (1678900 + 765400 + 2156300) × 100% = 46.9% Initial C 27 / C 29 The initial relative percentage content ratio = 36.5% / 46.9% = 0.78 (3) Correction of thermal maturity To eliminate C during the thermal evolution of organic matter 29 The systematic bias in source identification caused by the cracking of steranes into lighter components is corrected using an empirical correction factor for C. 27 With C 29 The measured values are then restored and corrected. The correction formula is as follows: Corrected C 27 / C 29 Ratio = (1.28 × C) 27 Original percentage content) / (0.72 × C) 29 Original percentage content) Wherein, coefficients 1.28 and 0.72 are respectively the C based on the thermodynamic model. 27 Sterane preservation coefficient and C 29 Sterane cracking correction factor.
[0032] For the sample from well WC-19-1M-1: Corrected C 27 / C 29 The ratio = (1.28 × 40.5%) / (0.72 × 31.9%) = (51.84) / (22.97) = 2.26 For samples from well WC19-1-3: Corrected C 27 / C 29 The ratio = (1.28 × 36.5%) / (0.72 × 46.9%) = (46.72) / (33.77) = 1.38 (4) Determination of the source of the parent material Based on the calculated corrected C 27 / C29 The ratio is used to qualitatively determine the source of organic parent material based on the following preset standards: If the corrected C 27 / C 29 A ratio > 1 indicates that the organic parent material is mainly supplied by aquatic lower organisms (such as algae).
[0033] If the corrected C 27 / C 29 A ratio of 1 indicates that the organic parent material is of mixed origin (the proportion of aquatic organisms and terrestrial plant inputs is roughly equal).
[0034] If the corrected C 27 / C 29 A ratio of <1 indicates that the organic parent material is mainly supplied by terrestrial higher plants.
[0035] According to the corrected C 27 / C 29 The ratio is determined based on a preset standard: The corrected ratio of the WC-19-1M-1 well sample is 2.26, indicating that its organic parent material is dominated by aquatic lower organisms (algae), and the sedimentary environment may be marine or deep lacustrine far from terrestrial input.
[0036] The corrected ratio of the WC19-1-3 well sample was 1.38, which also indicates that the input was mainly aquatic lower organisms. However, the ratio was lower than that of the WC-19-1M-1 well, which may reflect that its parent material contained a small amount of terrestrial organic matter, or that it was in a transitional environment with relatively shallow water and certain terrestrial influence.
[0037] (5) Comprehensive analysis and result output The corrected C 27 / C 29 The ratio discrimination result, combined with C 27 C 28 C 29 The distribution of the corrected relative percentage content on the sterane ternary diagram was cross-validated, and the final geological interpretation conclusion on the source type of organic matter in the target layer (WC-19-1M-1 and WC19-1-3) was output.
[0038] C before and after correction of the two samples 27 C 28 C 29 The relative percentage content was plotted on the sterane composition triangle diagram (see...). Figure 3 , Figure 4 Before calibration, the sample point of well WC-19-1M-1 fell on C. 27 The dominant area, while the sample point from well WC19-1-3 falls in C. 29In the dominant region, the two differ significantly, and the latter is misjudged as primarily terrestrial input. After correction, both sample points point towards C in the triangular diagram. 27 The endmembers moved directionally and all fell within a clearly defined "aquatic organism dominance" region, consistent with the conclusions drawn from the corrected ratios. Ultimately, it was concluded that the organic matter parent material of the mudstone and shale in both wells of the studied section was primarily derived from aquatic lower organisms. The method of this invention effectively corrected the Co ratio under high maturity. 29 The deviation caused by sterane cracking reveals the true source material, providing a more reliable organic geochemical basis for shale oil and gas exploration in the area.
[0039] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for correcting and identifying the origin of parent material, characterized in that: Includes the following steps: S1. Collect reservoir extracts from the target shale to obtain saturated hydrocarbon data for the target formation; S2. Determine the values of the parent material source index for the target segmentation based on saturated hydrocarbon data; S3. Divide the correction coefficient and corresponding index values of the target layer according to the source of the parent material; S4. Determine the source of the parent material in the target layer based on the corrected index characteristic values.
2. The method for correcting and identifying the source of maternal material according to claim 1, characterized in that: The specific method of step S1 is as follows: collect core or rock fragment samples of the target mudstone and shale section, extract soluble organic matter from the reservoir by organic solvent extraction, and then obtain saturated hydrocarbon components by column chromatography; use gas chromatography-mass spectrometry to analyze the saturated hydrocarbon components and obtain spectral data of biomarker compounds, including regular steranes.
3. The method for correcting and identifying the source of maternal material according to claim 1, characterized in that: The specific method for step S2 is as follows: Based on the saturated hydrocarbon gas chromatography-mass spectrometry data m / z 217, identify and integrate the peak areas of characteristic peaks of cholesterane, ergosterane, and stigmasterane compounds in regular steranes, and calculate the original relative percentage content and initial C of the three sterane components. 27 / C 29 ratio.
4. The method for correcting and identifying the source of parent material according to claim 3, characterized in that: The formula for calculating the original relative percentage content of cholesterol is: C 27 % = [C 27 / (C 27 + C 28 + C 29 The original relative percentage content of ergosterane is calculated as follows: C × 100%; 28 % = [C 28 / (C 27 + C 28 + C 29 The original relative percentage content of stigmasterane is calculated as follows: C × 100%; 29 % = [C 29 / (C 27 + C 28 + C 29 )] × 100%.
5. The method for correcting and identifying the source of maternal material according to claim 1, characterized in that: In step S3, in order to eliminate C during the thermal evolution process 29 The impact of sterane cracking on the source identification index was investigated using an empirical correction coefficient for the initial C2O .... 27 / C 29 The ratio is corrected and restored; the correction formula is: Corrected C 27 / C 29 Ratio = (Correction factor A × C) 27 (Original relative percentage content) / (Correction factor B × C) 29 (Original relative percentage content) Among them, correction coefficients A and B are empirical constants, used to compensate for C respectively. 27 Preservation of steranes and C 29 Steranes are broken down and lost.
6. The method for correcting and identifying the source of maternal material according to claim 5, characterized in that: The value of correction factor A is 1.28, and the value of correction factor B is 0.
72.
7. The method for correcting and identifying the source of maternal material according to claim 1, characterized in that: In step S4, based on the calculated corrected C 27 / C 29 The ratio, combined with the causal significance represented by its numerical range, is used to determine the type of organic parent material input in the target layer. The criteria for judging the characteristics of the source of the maternal material are as follows: If C 27 / C 29 > 1: Indicative meaning: Aquatic lower organisms are dominant; Sedimentary environment: Usually represents lacustrine, marine, or deep lacustrine sedimentary environments; If C 27 / C 29 = 1: Indicative meaning: Mixed source, i.e., the input ratio of aquatic organisms and terrestrial plants is equal; Sedimentary environment: Commonly found in marine transitional facies or nearshore shallow lake environments; If C 27 / C 29 < 1: Indicative meaning: Terrestrial higher plants are dominant; Sedimentary environment: Usually represents swamp facies, coal-bearing strata, or large deltas near the source area.