Method for identifying algae bombardment type oil shale based on carbon isotope and biomarker

Abstract

The invention discloses a method for identifying algae bombardment type oil shale based on carbon isotopes and biomarkers, and belongs to the field of testing or analyzing materials by means of measuring chemical or physical properties of the materials.The method comprises the steps that firstly, Soxhlet extraction is conducted on a cleaned, dried and smashed sample, and soluble organic matter and residual rock powder are obtained; separating the soluble organic matter family components to obtain saturated hydrocarbon and aromatic hydrocarbon components; then extracting residual rock powder kerogen, and analyzing carbon isotope; the method comprises the following steps: according to gas chromatography-mass spectrometry biomarker data of saturated hydrocarbon and aromatic hydrocarbon components, obtaining a 4-methylstane index, a ratio of C30 tetracyclic polyisoprene to C27 rearrangement stane and a ratio of phenanthrene series to naphthalene series; and finally, analyzing a parameter correlation relationship, dividing parameter boundaries where different lithologic sample plumbing areas are located, and establishing an algae bomb type oil shale quantitative identification standard based on the carbon isotope and the biomarker. According to the method, scientific, accurate and reliable identification of the algae bombardment type oil shale is realized.

Description

Technical Field

[0001] The present invention belongs to the field of testing or analyzing materials by measuring the chemical or physical properties of materials, and particularly relates to a method for identifying algal bloom type oil shale based on carbon isotope and biomarker. Background Art

[0002] At present, in the crude oil exploration areas and production areas where algal bloom type oil shale is the main source rock, algal bloom type oil shale is mainly qualitatively discriminated by high total organic carbon content (TOC) and 4-methylsterane indicating algal biogenic input. However, no clear boundary has been proposed for the discrimination between algal bloom type oil shale and mudstone. In addition, with the large-scale use of oil-based drilling mud in recent years, rock samples are generally contaminated, and TOC is easily affected by oil-based drilling mud, resulting in distorted TOC data and making it impossible to accurately identify algal bloom type oil shale, further causing difficulties in the identification of oil shale. Therefore, it is urgent to establish a new index system to accurately identify algal bloom type oil shale. Summary of the Invention

[0003] The present invention is proposed to solve the problem that in the prior art, the total organic carbon content (TOC) and the molecular geochemical index 4-methylsterane index can qualitatively identify oil shale and mudstone, but due to the contamination of source rock samples by drilling mud, the TOC data is distorted, and it is difficult to accurately identify algal bloom type oil shale only relying on 4-methylsterane. The purpose is to provide a method for identifying algal bloom type oil shale based on carbon isotope and biomarker.

[0004] The present invention is achieved by the following technical solutions: A method for identifying algal bloom type oil shale based on carbon isotope and biomarker, comprising the following steps: (I) Sample pretreatment Take typical oil shale and mudstone core samples from the study area, wash off the mud on the surface of the samples, then dry them at 40 °C for 4 h, and then crush them to obtain powdered core samples with a particle size larger than 80 mesh; Process according to the Petroleum and Natural Gas Industry Standard SY / T 5118-2021 of the People's Republic of China; (II) Use a solvent to perform Soxhlet extraction on the powdered core samples obtained in step (I), and separate to obtain soluble organic matter and residual rock powder after extraction; (III) Perform group component separation on the soluble organic matter obtained in step (II), and analyze the separated saturated hydrocarbon and aromatic hydrocarbon components; (IV) Extract kerogen from the residual rock powder after extraction obtained in step (II), analyze the carbon isotope composition of the extracted kerogen, and obtain the carbon isotope content (δ 13 C 干酪根); (V) Obtain biomarker data based on the gas chromatography-mass spectrometry analysis of saturated hydrocarbon and aromatic hydrocarbon components in step (III). Call the mass chromatogram of m / z 217 of saturated hydrocarbons, integrate the C 29 steranes and C 30 4-methylsterane series compounds (integrate the peak areas of the corresponding compounds), and calculate the 4-methylsterane index; (VI) Obtain biomarker data based on the gas chromatography-mass spectrometry analysis of saturated hydrocarbon components in step (III). Call the mass chromatogram of m / z 259 of saturated hydrocarbons, integrate the C 30 tetracyclic polyisoprenoids and C 27 rearranged sterane series compounds (integrate the peak areas of the corresponding compounds), and calculate the ratio of C 30 tetracyclic polyisoprenoids to C 27 rearranged steranes; (VII) Obtain biomarker data based on the gas chromatography-mass spectrometry analysis of aromatic hydrocarbon components in step (III). Call the total ion current chromatogram of gas chromatography-mass spectrometry of aromatic hydrocarbons, integrate the naphthalene series compounds of C0-C3 and the phenanthrene series compounds of C0-C3 (integrate the peak areas of the corresponding compounds), and calculate the ratio of the phenanthrene series to the naphthalene series; (VIII) Fit the 13 C isotope, C 30 ratio of tetracyclic polyisoprenoids to C 27 rearranged steranes, the ratio of phenanthrene series / naphthalene series and the correlation relationship between the 4-methylsterane index, divide the parameter boundaries of the projection areas of different lithology samples, and establish a quantitative identification standard for algal-burst type oil shale based on carbon isotope and biomarkers.

[0005] In the above technical solution, the solvent in step (II) is dichloromethane; the duration of Soxhlet extraction in step (II) is 72 h.

[0006] In the above technical solution, the separation of soluble organic matter group components in step (III) is carried out according to the industry standard SY / T5119-2016; The analysis of saturated hydrocarbon and aromatic hydrocarbon components in step (III) is carried out by Agilent 7890 / 5975 gas chromatography-mass spectrometry. The specific chromatographic conditions are as follows: the chromatographic column is HP-5MS capillary column (60 m × 0.25 mm × 0.25 μm); the inlet temperature is 300 °C, the carrier gas is 99.999% helium, and the flow rate is 1.0 mL / min; the initial temperature of the temperature programming is 40 °C, hold for 2 min, then increase the temperature at a rate of 10 °C / min to 100 °C, and then increase the temperature at a rate of 3 °C / min to 300 °C, and hold for 30 min; the detection method is full scan ion detection.

[0007] In the above technical solution, the extraction of kerogen in step (IV) is carried out according to the national standard GB / T 19144-2010; In step (IV), the carbon isotope analysis is performed using a Thermo Fisher MAT253 stable isotope mass spectrometer. The carbon isotope analysis is calibrated by the laboratory standard sample GBW4407 (-22.43‰), and the δ 13 C 干酪根 value is calculated relative to the United States Pee Dee belemnite standard (VPDB) standard. Based on repeated measurements, the analysis accuracy of δ 13 C 干酪根 is better than ±0.2‰.

[0008] In the above technical solution, the calculation formula for the 4-methylsterane index in step (V) is: 4-MSI = C 30 4-methylsterane / C 29 sterane where: 4-MSI is the 4-methylsterane index, C 30 4-methylsterane is the integrated area of C 30 4-methylsterane; C 29 sterane is the integrated area of C 29 sterane.

[0009] In the above technical solution, the quantitative identification criteria for algal-dominated oil shale based on carbon isotopes and biomarkers in step (VIII) are specifically as follows: When the kerogen carbon isotope (δ 13 C 干酪根 ) > -24.5‰, 4-methylsterane index (4-MSI) > 1.4, C 30 tetracyclic polyisoprenoids / C 27 rearranged sterane ratio > 1.5 and phenanthrene series / naphthalene series ratio > 3, the oil shale type is strongly algal-dominated oil shale; When the kerogen carbon isotope is between -26‰ and -24.5‰, the 4-methylsterane index is between 0.8 and 1.4, C 30 tetracyclic polyisoprenoids / C 27 rearranged sterane ratio is between 0.8 and 1.5 and phenanthrene series / naphthalene series ratio (Phs / Nas) is between 2 and 3, the oil shale type is weakly algal-dominated oil shale; When the kerogen carbon isotope < -26‰, 4-methylsterane index < 0.8, C 30 tetracyclic polyisoprenoids / C 27 rearranged sterane ratio < 0.8 and phenanthrene series / naphthalene series ratio < 2, the oil shale type is non-algal-dominated oil shale.

[0010] The beneficial effects of the present invention are as follows: The present invention provides a method for identifying algal bloom type oil shale based on carbon isotope and biomarker, which can scientifically, accurately and reliably identify algal bloom type oil shale; in addition to the 4-methylsterane index, the kerogen carbon isotope newly established in the present invention, C 30 tetracyclic polyisoprenoid / C 27 The ratio of rearranged sterane to phenanthrene series / naphthalene series is a good index for algal bloom, and can accurately and effectively distinguish algal bloom type oil shale from mudstone; moreover, regardless of the degree of oil-based mud pollution, the kerogen carbon isotope is hardly affected because the contaminated soluble organic matter has been completely removed before analysis and testing. Brief Description of the Drawings

[0011] Figure 1 It is a cross plot of the 4-methylsterane index and the kerogen carbon isotope values of the oil shale and mudstone samples in Example 1 of the present invention; Figure 2 It is a cross plot of the 4-methylsterane index and the C 30 tetracyclic polyisoprenoid / C 27 rearranged sterane values of the oil shale and mudstone samples in Example 1 of the present invention; Figure 3 It is a cross plot of the 4-methylsterane index and the phenanthrene series / naphthalene series values of the oil shale and mudstone samples in Example 1 of the present invention; Figure 4 It is the mass chromatogram of m / z 217 and m / z 259 of saturated hydrocarbons of the oil shale and mudstone samples in Example 1 of the present invention; Figure 5 It is the total ion current (TIC) chromatogram of gas chromatography-mass spectrometry of aromatic hydrocarbons of the oil shale and mudstone samples in Example 1 of the present invention.

[0012] For those of ordinary skill in the art, other relevant drawings can be obtained based on the above drawings without creative efforts. Detailed Embodiments

[0013] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the drawings in the specification and through specific embodiments.

[0014] Example 1 A method for identifying algal bloom type oil shale based on carbon isotope and biomarker includes the following steps: (I) Take typical oil shale and mudstone core samples in the study area, wash off the surface mud, dry and crush them for standby.

[0015] (II) Soxhlet extract the rock powder sample with dichloromethane for 72 hours to obtain soluble organic matter and the residual rock powder after extraction; (III) Separate the soluble organic matter into group components according to the industry standard SY / T 5119-2016, and analyze the separated saturated hydrocarbon and aromatic hydrocarbon components using an Agilent 7890 / 5975 gas chromatography-mass spectrometer; (IV) Extract kerogen from the residual powder after extraction according to the national standard GB / T 19144-2010, and analyze the carbon isotope composition of the extracted kerogen using a Thermo Fisher MAT253 stable isotope mass spectrometer.

[0016] (V) Obtain biomarker data based on gas chromatography-mass spectrometry analysis of saturated hydrocarbons and aromatic hydrocarbons, call the saturated hydrocarbon m / z217 mass chromatogram ( Figure 4 ), integrate the C 29 sterane and C 30 4-methylsterane series compounds, and calculate the 4-methylsterane index (4-MSI = C 30 4-methylsterane / C 29 sterane); (VI) Call the saturated hydrocarbon m / z 259 mass chromatogram ( Figure 4 ), integrate the C 30 tetracyclic polyisoprenoids and C 27 rearranged sterane series compounds, and calculate the C 30 tetracyclic polyisoprenoids / C 27 rearranged sterane ratio (C 30 TPP / D 27 St); (VII) Call the total ion current chromatogram of aromatic hydrocarbon gas chromatography-mass spectrometry ( Figure 5 ), integrate the naphthalene series compounds of C0-C3 and the phenanthrene series compounds of C0-C3, and calculate the phenanthrene series / naphthalene series ratio (Phs / Nas).

[0017] (VIII) Fit the correlation relationships between δ 13 C 干酪根 , C 30 TPP / D 27 St, Phs / Nas and 4-MSI, divide the parameter boundaries of the projection areas of different lithology samples, and establish a quantitative identification standard for algal bloom type oil shale based on carbon isotopes and biomarkers. The quantitative identification standard is shown in Table 1.

[0018] Table 1: Quantitative identification standard for algal bloom type oil shale based on kerogen carbon isotope and biomarkers

[0019] The 4-methyl sterane index (4-MSI) of the source rock core samples has a very good linear relationship with the kerogen carbon isotope (δ 13 C 干酪根 ), C 30 tetracyclic polyisoprenoids / C 27 rearranged steranes (C 30 TPP / D 27 St), and the ratio of phenanthrene series / naphthalene series (Phs / Nas) (see Appendix Figures 1 - 3 ), and can effectively distinguish source rocks of different lithologies.

[0020] As shown in Table 1, the present invention has established a quantitative identification standard for algal-dominated oil shales based on kerogen carbon isotope and biomarkers; among them, the δ 13 C 干酪根 , 4-MSI, C 30 TPP / D 27 St, and Phs / Nas values of oil shales are respectively greater than -26‰, 0.8, 0.8, and 2, while the indexes of mudstones are respectively less than the above values.

[0021] Oil shales can be further divided into strongly algal-dominated and weakly algal-dominated oil shales. The δ 13 C 干酪根 , 4-MSI, C 30 TPP / D 27 St, and Phs / Nas values of strongly algal-dominated oil shales are respectively greater than -24.5‰, 1.4, 1.5, and 3, while the indexes of weakly algal-dominated oil shales are respectively less than the above values.

[0022] The quantitative index system established by the present invention is based on the results obtained from corresponding analysis and tests on the cleaned core samples, excluding the influence of drilling mud pollution on the data; at the same time, combining carbon isotope and multi-indexes of saturated hydrocarbon and aromatic hydrocarbon biomarkers to quantitatively identify algal-dominated oil shales makes the identification result more accurate and more persuasive, providing an effective method for accurately identifying algal-dominated oil shales in the study area.

[0023] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for identifying algal bloom type oil shale based on carbon isotopes and biomarkers, characterized in that: It includes the following steps: (Ⅰ) Take typical oil shale and mudstone core samples from the study area, wash the mud on the surface of the samples, and then obtain powdered core samples through drying and crushing; (Ⅱ) Use a solvent to perform Soxhlet extraction on the powdered core samples obtained in step (Ⅰ), and separate soluble organic matter and residual rock powder after extraction; (Ⅲ) Perform separation of group components on the soluble organic matter obtained in step (Ⅱ), and analyze the separated saturated hydrocarbon and aromatic hydrocarbon components; (Ⅳ) Extract kerogen from the residual rock powder after extraction obtained in step (Ⅱ), analyze the carbon isotope composition of the extracted kerogen, and obtain the carbon isotope content of kerogen; (V) Obtain biomarker data based on the gas chromatography-mass spectrometry analysis of saturated hydrocarbon and aromatic hydrocarbon components in step (III), call the mass chromatogram of saturated hydrocarbon m / z 217, integrate the C 29 sterane and C 30 4-methylsterane series compounds, and calculate the 4-methylsterane index; (VI) Obtain biomarker data based on the gas chromatography-mass spectrometry analysis of the saturated hydrocarbon fraction in step (III), call the mass chromatogram of m / z 259 for the saturated hydrocarbons, and integrate the tetracyclic polyisoprenoids and C 30 tetracyclic polyisoprenoids and C 27 rearranged sterane series compounds, and calculate the ratio of C 30 tetracyclic polyisoprenoids and C 27 rearranged steranes; (Ⅶ) Obtain biomarker data based on gas chromatography-mass spectrometry analysis of aromatic hydrocarbon components in step (Ⅲ), call the total ion current chromatogram of aromatic hydrocarbon gas chromatography-mass spectrometry, integrate naphthalene series compounds from C0-C3 and phenanthrene series compounds from C0-C3, and calculate the ratio of the phenanthrene series to the naphthalene series; (VIII) fitting kerogen 13 C isotope, C 30 ratio of tetracyclic polyisoprenoids to C 27 correlation relationship between the ratio of rearranged steranes, phenanthrene series / naphthalene series ratio and 4-methylsterane index, divide the parameter boundaries of the projection areas of different lithologic samples, and establish a quantitative identification standard for algal bloom type oil shale based on carbon isotope and biomarkers.

2. The method for identifying algal bloom type oil shale based on carbon isotope and biomarker according to claim 1, wherein: The solvent in step (Ⅱ) is dichloromethane; the Soxhlet extraction duration in step (Ⅱ) is 72 h.

3. The method for identifying algal bloom type oil shale based on carbon isotope and biomarker according to claim 1, wherein: The separation of group components of soluble organic matter in step (Ⅲ) is carried out according to industry standard SY / T 5119-2016; The analysis of saturated hydrocarbon and aromatic hydrocarbon components in step (Ⅲ) is performed using an Agilent 7890 / 5975 gas chromatography-mass spectrometry.

4. The method for identifying algal bloom type oil shale based on carbon isotope and biomarker according to claim 1, wherein: The extraction of kerogen in step (Ⅳ) is carried out according to national standard GB / T 19144-2010; The analysis of carbon isotope in step (Ⅳ) is performed using a Thermo Fisher MAT253 stable isotope mass spectrometer.

5. The method for identifying algal bloom type oil shale based on carbon isotope and biomarker according to claim 1, wherein: The calculation formula for the 4-methylsterane index in step (Ⅴ) is: 4-MSI=C 30 4-Methylsterane / C 29 Sterane In the formula: 4-MSI is the 4-methyl sterane index, C 30 4-methyl sterane is C 30 the integrated area of 4-methyl sterane; C 29 sterane is C 29 the integrated area of sterane.

6. The method for identifying algal bloom-type oil shale based on carbon isotopes and biomarkers according to claim 1, wherein: The quantitative identification standard for algal-burst type oil shale based on carbon isotope and biomarker in step (Ⅷ) is specifically: When the kerogen carbon isotope > -24.5‰, the 4-methylsterane index > 1.4, C 30 tetracyclic polyisoprenoids / C 27 rearranged sterane ratio > 1.5 and phenanthrene series / naphthalene series ratio > 3, the oil shale type is strongly algal-burst type oil shale; When the kerogen carbon isotope is between -26‰ and -24.5‰, the 4-methylsterane index is between 0.8 and 1.4, and C 30 tetracyclic polyisoprenoids / C 27 the ratio of rearranged steranes is between 0.8 and 1.5 and the ratio of phenanthrene series / naphthalene series is between 2 and 3, the oil shale type is weakly algal explosive oil shale; When the kerogen carbon isotope < -26‰, the 4-methylsterane index < 0.8, C 30 tetracyclic polyisoprenoids / C 27 the ratio of rearranged steranes < 0.8 and the ratio of phenanthrene series / naphthalene series < 2, the oil shale type is algal-free explosive oil shale.

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