Method for identifying types of crude oil based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Abstract

The invention provides a method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, which comprises the following steps: dissolving a crude oil sample to be identified by using a diluent, and adding a 5alpha-androstane standard substance into the system to obtain a crude oil sample; the method comprises the following steps: carrying out chromatographic analysis on a crude oil sample by using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, and marking the ratio of the weight sum of n-alkane, isoparaffin, monocycloalkane, bicycloalkane, tricycloalkane, tetracycloalkane and pentacycloalkane in the crude oil sample to the weight of the crude oil sample to be identified as S; marking the ratio of the weight sum of monocycloalkane, bicycloalkane, tricycloalkane, tetracycloalkane and pentacycloalkane in the crude oil sample to the weight of the crude oil sample to be identified as N, and identifying the type of the crude oil sample according to the ratio of S to N. The identification method provided by the invention provides a new way for finely identifying the naphthenic crude oil and estimating the reserves of the naphthenic crude oil.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum geological exploration, and in particular to a method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. Background Art

[0002] Naphthenic crude oil is a scarce oil resource containing a large amount of cycloalkane components. The cycloalkane content in crude oil is directly related to the quality of cycloalkane crude oil. There are four main methods in the industry for quantitative identification of cycloalkane crude oil: key fraction method, characteristic factor K classification method, crude oil carbon content calculation method and gas chromatography / mass spectrometry quantification. Among them, the key fraction method is relatively complicated to operate, because impurities such as alkanes and aromatics are mixed in the distillation process, and it cannot truly reflect the content of cycloalkanes in crude oil; the characteristic factor K classification method is difficult to determine the average boiling point of crude oil, and cannot accurately characterize the composition of crude oil; the calculation process of the crude oil carbon type content calculation method is relatively cumbersome, and the calculated carbon type content is a theoretical value. Hydrocarbons are composed of carbon and hydrogen atoms. Only the carbon atom content is calculated, which cannot represent the cycloalkanes content and has a limited scope of application; gas chromatography / mass spectrometry is used to quantify different structural hydrocarbon compounds in crude oil. In one-dimensional chromatographic quantitative analysis, the chromatographic baseline often rises to form a "bulge", and the compounds in the "bulge" cannot be well separated and cannot be accurately characterized and quantified. When using mass spectrometry analysis, due to the different mass spectrometry signal response factors of hydrocarbon compounds with different structures, hydrocarbon compounds are only semi-quantitative, and the use of chromatography / mass spectrometry to quantify the cycloalkanes in crude oil has great limitations. Previous studies have believed that cycloalkanes are distributed in crude oil with a density greater than 0.93g / cm 3 In the heavy oil, but in fact, it is ignored that there is also a part of crude oil in the medium oil that belongs to the cycloparaffinic type crude oil. Since the proportion of cycloparaffinic crude oil in the medium oil is relatively small, it is more difficult to identify the cycloparaffinic crude oil in the medium oil. The existing technology cannot accurately quantify the cycloparaffins in crude oil, and it is even more difficult to quantitatively analyze the cycloparaffins from the medium oil with a small proportion. It is impossible to expand the identification range of cycloparaffinic crude oil, which makes the exploitation of cycloparaffinic crude oil limited.

[0003] In summary, the existing technology is difficult to accurately quantify the content of cycloalkanes in crude oil. There are problems such as complex operation, narrow application range, or poor separation effect, which lead to the inability to accurately quantify the content of cycloalkanes in crude oil. Based on this, it is necessary to provide a new analysis method to improve the above problems and expand the identification range of cycloalkanes in crude oil. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry to solve the problem in the prior art that cycloalkanes in crude oil are difficult to be accurately quantified.

[0005] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for identifying the type of crude oil based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry is provided, characterized in that the method comprises: preparing a crude oil sample: dissolving the crude oil sample to be identified by using a diluent, and then adding a 5α-androstane standard to the system to obtain a crude oil sample; testing: allowing the crude oil sample to enter the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry; qualitatively determining the peak positions of 5α-androstane, normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample according to the time-of-flight mass spectrometry. The method comprises the following steps: quantitatively analyzing the contents of normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes with a signal-to-noise ratio greater than 100 in the crude oil sample according to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatography; identifying: the ratio of the sum of the weights of the normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample to the weight of the crude oil sample to be identified is recorded as S; the ratio of the sum of the weights of the monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample to the weight of the crude oil sample to be identified is recorded as N;

[0006] When S≥50% and N≤30%, the crude oil sample to be identified is paraffin-type crude oil;

[0007] When S≥50%, 30%<N<40%, the crude oil sample to be identified is an intermediate crude oil;

[0008] When S≥50%, N≥40%, the crude oil sample to be identified is cycloparaffinic crude oil;

[0009] When S<50% and N<25%, the crude oil sample to be identified is aromatic-asphalt type crude oil;

[0010] When S is less than 50% and N is greater than or equal to 25%, the crude oil sample to be identified is an aromatic-cycloalkane type crude oil.

[0011] Furthermore, in the preparation of the crude oil sample, the weight of the crude oil sample to be identified is 5 to 15 mg per 1 ml of diluent.

[0012] Furthermore, in the preparation of the crude oil sample, the weight of the 5α-androstane standard is 0.001 to 0.01 mg per 1 ml of diluent.

[0013] Furthermore, the diluent is selected from n-hexane and / or dichloromethane, more preferably dichloromethane.

[0014] Furthermore, the comprehensive two-dimensional gas chromatograph has two chromatographic columns with different polarities, and the two chromatographic columns are independently selected from a DB-Petro column or a DB-17HT column.

[0015] Furthermore, the detector of the comprehensive two-dimensional gas chromatograph adopts a hydrogen flame ionization detector.

[0016] Furthermore, the modulator of the comprehensive two-dimensional gas chromatograph adopts a dual-nozzle thermal modulator; further preferably, the modulation period of the modulator is 8.0 to 10.0 s, and the heat blowing time is 2.0 to 3.0 s.

[0017] Furthermore, the column length of the DB-Petro column is 50 to 60 m, the outer diameter is 0.2 to 0.3 mm, the inner diameter is 0.1 to 0.2 mm, and the coating thickness is 0.1 to 0.5 μm; the column length of the DB-17HT column is 2.5 to 3.0 m, the outer diameter is 0.1 to 0.2 mm, the inner diameter is 0.1 to 0.2 mm, and the coating thickness is 0.1 to 0.5 μm.

[0018] Furthermore, the one-dimensional chromatographic column of the comprehensive two-dimensional gas chromatograph adopts a DB-Petro column, and the two-dimensional chromatographic column adopts a DB-17HT column; the temperature rising program of the one-dimensional chromatographic column is: keep the temperature at an initial temperature of 60-80°C for 0.1-0.2 min, heat it to 290-300°C at a rate of 2-3°C / min, keep it for 0.1-0.2 min, then heat it to 300-310°C at a rate of 0.1-0.2°C / min, and keep it for 8-10 min; the temperature rising program of the two-dimensional chromatographic column is: keep the temperature at an initial temperature of 70-90°C for 0.1-0.2 min, heat it to 290-300°C at a rate of 2-3°C / min, and keep it for 0.1-0.2 min. ℃ / min to 300-310℃, keep warm for 0.1-0.2min, then heat up to 310-320℃ at a rate of 0.1-0.2℃ / min, keep warm for 8-10min; the modulation temperature rising program is: keep at an initial temperature of 120-130℃ for 0.1-0.2min, increase to 330-350℃ at a rate of 2.0-3.0℃ / min, keep warm for 0.1-0.3min, then increase to 340-360℃ at a rate of 0.2℃ / min, keep warm for 10min, the modulator cycle is 7-9s, of which 1-3s is the hot blowing time.

[0019] Furthermore, the injection port temperature of the comprehensive two-dimensional gas chromatograph is 300-310°C.

[0020] Furthermore, the injection volume of the crude oil sample is 1.0 to 1.2 μL.

[0021] Furthermore, the carrier gas flow rate of the comprehensive two-dimensional gas chromatograph is 1.4 to 1.6 mL / min.

[0022] Furthermore, the carrier gas is helium.

[0023] Furthermore, the weight content of the components with a density greater than 0.87 g / cm3 in the crude oil sample to be identified is 45-55 wt%.

[0024] The technical scheme of the present invention is applied. The method of the present invention is based on the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry to identify the type of crude oil. The characteristics of the comprehensive two-dimensional gas chromatography analysis method, such as high resolution, large peak capacity, good sensitivity, group separation and tile effect, are utilized to separate normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes from other components to the maximum extent. At the same time, a suitable internal standard (5α-androstane) is added to accurately and quantitatively analyze each series of compounds in the crude oil. The quantitative precision and accuracy are much higher than those of one-dimensional gas chromatography, and the co-distillation phenomenon between different series of compounds is effectively eliminated. Almost all hydrocarbon compounds in the crude oil can be separated by one injection. The present invention can eliminate the influence of other impurities in crude oil or instrument noise on the accuracy of the content of normal alkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in crude oil by analyzing the content of normal alkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in crude oil with a signal-to-noise ratio greater than 100. At the same time, based on the determination of the content of the above substances in crude oil, the present invention can identify the type of crude oil sample according to the ratio of S and N, and provides a new way for finely identifying naphthenic crude oil and estimating the reserves of naphthenic crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 A three-dimensional stereogram of a comprehensive two-dimensional gas chromatograph of a crude oil sample according to Example 1 of the present invention is shown;

[0027] Figure 2 The dot plot of the comprehensive two-dimensional gas chromatograph of different components in the crude oil sample of Example 1 of the present invention is shown;

[0028] Figure 3 A three-dimensional stereogram of a comprehensive two-dimensional gas chromatograph of a crude oil sample according to Example 2 of the present invention is shown;

[0029] Figure 4 The dot plot of the comprehensive two-dimensional gas chromatograph of different components in the crude oil sample of Example 2 of the present invention is shown;

[0030] Figure 5 A three-dimensional stereogram of a comprehensive two-dimensional gas chromatograph of a crude oil sample according to Example 3 of the present invention is shown;

[0031] Figure 6 The dot plot of the comprehensive two-dimensional gas chromatograph of different components in the crude oil sample of Example 3 of the present invention is shown;

[0032] Figure 7 A three-dimensional stereogram of a comprehensive two-dimensional gas chromatograph of a crude oil sample according to Example 4 of the present invention is shown;

[0033] Figure 8 The dot plot of the comprehensive two-dimensional gas chromatograph of different components in the crude oil sample of Example 4 of the present invention is shown;

[0034] Fig. 9 This is a diagram for analyzing and identifying crude oil types according to an embodiment of the present invention.

[0035] The above figures include the following figure marks: Area 1 is paraffinic crude oil, Area 2 is intermediate crude oil, Area 3 is cycloparaffinic crude oil, Area 4 is aromatic-asphaltic crude oil, and Area 5 is aromatic-cycloparaffinic crude oil. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] The main components of crude oil include the following: saturated hydrocarbons, including normal and iso-alkanes (paraffins) and cycloalkanes; aromatic hydrocarbons, including pure aromatic hydrocarbons, cycloalkanes and cyclic sulfur-containing compounds; colloids and asphaltenes, which are composed of high molecular weight polycyclic compounds containing nitrogen, sulfur and oxygen in crude oil. This paper classifies crude oil according to the different proportions of each component:

[0038] Paraffin crude oil: Paraffin crude oil is crude oil mainly containing paraffin hydrocarbons. It has a low relative density, a high wax content, a high freezing point, and less sulfur and gum content.

[0039] Naphthenic crude oil: Naphthenic crude oil is a type of crude oil that contains more cycloalkanes. The gasoline produced by naphthenic crude oil has a higher octane number and a lower cetane number of diesel. The lubricating oil fraction contains less or almost no wax, has a low freezing point, a low viscosity index, and the residual oil contains more asphalt.

[0040] Intermediate crude oil: Intermediate crude oil is a type of crude oil whose properties are between paraffinic crude oil and cycloparaffinic crude oil.

[0041] Aromatic-asphalt type crude oil: Aromatic-asphalt type crude oil is a type of crude oil that contains more aromatic hydrocarbons. The oil is heavy and viscous, and the content of colloid and asphalt can be as high as 25%.

[0042] Aromatic-cycloparaffinic crude oil: Aromatic-cycloparaffinic crude oil is a type of crude oil mainly containing aromatic hydrocarbons and cycloparaffins, and the oil is heavy and viscous.

[0043] As described in the background technology section of this application, it is difficult to accurately quantify cycloalkanes in crude oil in the prior art. In order to solve this problem, the present application provides a method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, which includes: crude oil sample preparation: using a diluent to dissolve the crude oil sample to be identified, and then adding a 5α-androstane standard to the system to obtain a crude oil sample; testing: allowing the crude oil sample to enter the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, and qualitatively determining the peak positions of 5α-androstane, normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample according to the time-of-flight mass spectrometry; quantitatively analyzing the content of normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes with a signal-to-noise ratio greater than 100 in the crude oil sample according to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatography; identification: the normal alkanes in the crude oil sample The ratio of the sum of the weights of isoalkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes to the weight of the crude oil sample to be identified is recorded as S (saturated hydrocarbon content); the ratio of the sum of the weights of monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample to the weight of the crude oil sample to be identified is recorded as N (cycloalkanes content); when S≥50% and N≤30%, the crude oil sample to be identified is a paraffin type crude oil; when S≥50% and 30%<N<40%, the crude oil sample to be identified is an intermediate type crude oil; when S≥50% and N≥40%, the crude oil sample to be identified is a cycloalkane type crude oil; when S<50% and N<25%, the crude oil sample to be identified is an aromatic-asphalt type crude oil; when S<50% and N≥25%, the crude oil sample to be identified is an aromatic-cycloalkane type crude oil.

[0044] The present invention proposes a method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, which solves the problem of difficulty in accurately quantifying cycloalkanes in crude oil in the prior art, mainly due to the following reasons:

[0045] First, the key fraction method, characteristic factor K classification method, and crude oil carbon type content calculation method in the prior art all establish relationships with cycloalkanes through crude oil density, boiling point, refractive index, boiling point, etc., and use cumbersome empirical calculation formulas to characterize the cycloalkanes content. However, the physical properties of crude oil are the result of the combined effects of saturated hydrocarbons, aromatic hydrocarbons, asphaltenes, and non-hydrocarbons. These methods cannot accurately reflect the cycloalkanes content in crude oil. The method of the present invention, by adding standard substances to crude oil, does not need to establish cumbersome empirical calculation formulas, and uses time-of-flight mass spectrometry in conjunction with comprehensive two-dimensional gas chromatography to qualitatively analyze 5α-androstane, normal alkanes, isoalkanes, and cycloalkanes in crude oil samples according to their molecular weights using time-of-flight mass spectrometry. At the same time, according to the ratio of the peak area of ​​normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the comprehensive two-dimensional gas chromatography to the peak area of ​​5α-androstane standard substance, the mass ratio of crude oil sample and 5α-androstane standard substance and the relative correction factor, the content of normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in crude oil can be accurately quantified. This method not only greatly improves the evaluation efficiency of cycloalkane crude oil, but also has higher accuracy.

[0046] Secondly, compared with the existing chromatography / mass spectrometry method for quantifying cycloalkanes in crude oil, the present invention uses fewer types of standard substances, and the crude oil does not need to undergo a complex pre-treatment process, which solves the qualitative and quantitative problems of indistinguishable complex mixtures (UCM). The inventors found that the molecular structure of the 5α-androstane standard is different from the molecular structure of normal alkanes, isoalkanes, and cycloalkanes in crude oil, and the position of the peak of 5α-androstane in the comprehensive two-dimensional gas chromatograph is different from that of normal alkanes, isoalkanes, and cycloalkanes in crude oil, and there is no interference with the separation of various substances in crude oil. At the same time, the response of the 5α-androstane standard in the comprehensive two-dimensional gas chromatograph is rapid and sensitive.

[0047] In summary, the method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry of the present invention utilizes the characteristics of high resolution, large peak capacity, good sensitivity, group separation and tile effect of comprehensive two-dimensional gas chromatography analysis to separate normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes from other components to the maximum extent. At the same time, a suitable internal standard (5α-androstane) is added to accurately quantitatively analyze each series of compounds in crude oil, and its quantitative precision and accuracy are much higher than those of one-dimensional gas chromatography, effectively eliminating the co-distillation phenomenon between different series of compounds, and almost all hydrocarbon compounds in crude oil can be separated by one injection. The present invention can eliminate the influence of other impurities in crude oil or instrument noise on the accuracy of the content of normal alkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in crude oil by analyzing the content of normal alkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in crude oil with a signal-to-noise ratio greater than 100. At the same time, based on the determination of the content of the above substances in crude oil, the present invention can identify the type of crude oil sample according to the ratio of S and N, and provides a new way for finely identifying naphthenic crude oil and estimating the reserves of naphthenic crude oil.

[0048] In a preferred embodiment, in the preparation of the crude oil sample, the weight of the crude oil sample to be identified is 5 to 15 mg per 1 ml of diluent. The present invention can reduce the viscosity of the crude oil by diluting the crude oil sample with a diluent, and can make the crude oil sample have a good peak shape in the comprehensive two-dimensional gas chromatograph and have a high sensitivity by controlling the concentration of the crude oil sample in the diluent.

[0049] In a preferred embodiment, in the preparation of crude oil samples, the weight of the 5α-androstane standard is 0.001 to 0.01 mg per 1 ml of diluent. The present invention adds 5α-androstane to the crude oil sample to be identified. Since the molecular structure of the 5α-androstane standard is different from that of the normal alkanes, isoalkanes, and cycloalkanes in the crude oil, the peak position of 5α-androstane in the comprehensive two-dimensional gas chromatograph is different from that of the normal alkanes, isoalkanes, and cycloalkanes in the crude oil, there is no interference with the separation of various substances in the crude oil, and the content of normal alkanes, isoalkanes, monocycloalkanes, dicycloalkanes, tricycloalkanes, tetracycloalkanes, and pentacycloalkanes in the crude oil to be identified can be accurately and quantitatively analyzed according to the amount of 5α-androstane added and the peak area. At the same time, the present invention limits the concentration of the 5α-androstane standard in the crude oil sample, so that it has a better response value in the chromatograph, has an excellent peak shape, can not interfere with the peak shape of other substances, and more accurately quantitatively analyze the content of each component in the crude oil.

[0050] In a preferred embodiment, during the preparation of the crude oil sample, after adding the 5α-androstane standard, ultrasonic oscillation is used, and the crude oil sample is left to stand for a period of time after oscillation to obtain the crude oil sample. Preferably, the ultrasonic oscillation time is 5 to 20 minutes, and the standing time is 0.3 to 0.5 hours. The present invention adopts the above method to fully mix the standard substance with the crude oil, and the accuracy and reliability are higher when performing detection and analysis.

[0051] In order to further make the crude oil sample have excellent peak shape and better sensitivity in the comprehensive two-dimensional gas chromatograph, the diluent is preferably selected from n-hexane and / or dichloromethane, and more preferably dichloromethane. Since dichloromethane and crude oil have excellent similar solubility, it can dissolve crude oil more evenly. At the same time, dichloromethane and the components in crude oil will not interfere with each other in the chromatogram, so that the components in crude oil can have good separation, and the dichloromethane peak time is fast, which can greatly shorten the analysis time.

[0052] In a preferred embodiment, the comprehensive two-dimensional gas chromatograph has two chromatographic columns with different polarities, and the two chromatographic columns are independently selected from DB-Petro column or DB-17HT column. The present invention selects the above two chromatographic columns with different polarities, one adopts the non-polar DB-Petro column and the other adopts the strong polar DB-17HT column. Through the difference in polarity of the two columns, the saturated alkane components (such as normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes) in the crude oil sample are better separated from the aromatic hydrocarbon components in the crude oil sample. The DB-Petro column can effectively separate the components with different boiling points in the crude oil sample, while the DB-17HT column can effectively separate the co-distillation components with similar boiling points but different polarities in the crude oil sample.

[0053] In a preferred embodiment, the detector of the comprehensive two-dimensional gas chromatograph is a hydrogen flame ionization detector. The hydrogen flame ionization detector selected in the present invention has high sensitivity to alkane substances in crude oil, can more accurately quantify the cycloalkane content in the crude oil sample, and realizes the identification of crude oil types.

[0054] In order to achieve better separation of components in crude oil samples, the modulator of the comprehensive two-dimensional gas chromatograph adopts a dual-nozzle thermal modulator; further preferably, the modulation period of the modulator is 8.0 to 10.0 s, and the hot blowing time is 2.0 to 3.0 s.

[0055] In a preferred embodiment, the column length of the DB-petro column is 50 to 60 m, the outer diameter is 0.2 to 0.3 mm, the inner diameter is 0.1 to 0.2 mm, and the coating thickness is 0.1 to 0.5 μm; the column length of the DB-17HT column is 2.5 to 3.0 m, the outer diameter is 0.1 to 0.2 mm, the inner diameter is 0.1 to 0.2 mm, and the coating thickness is 0.1 to 0.5 μm. Among them, the coating of the DB-petro column is dimethyl polysiloxane, and the coating of the DB-17HT column is a high-temperature resistant polyimide coating. The present invention limits the column length, diameter, and coating thickness of the chromatographic column within the above range, and can separate normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes, pentacyclic alkanes and other components to the greatest extent, making the quantification of cycloalkanes in crude oil more accurate and reliable.

[0056] In a preferred embodiment, the one-dimensional chromatographic column of the comprehensive two-dimensional gas chromatograph adopts a DB-1 column, and the two-dimensional chromatographic column adopts a DB-17HT column; the heating program of the one-dimensional chromatographic column is: keep warm at an initial temperature of 60 to 80°C for 0.1 to 0.2 min, heat to 290 to 300°C at a rate of 2 to 3°C / min, keep warm for 0.1 to 0.2 min, then heat to 300 to 310°C at a rate of 0.1 to 0.2°C / min, and keep warm for 8 to 10 min; the heating program of the two-dimensional chromatographic column is: keep warm at an initial temperature of 70 to 90°C for 0.1 to 0.2 min, heat to 2 The temperature is raised to 300-310°C at a rate of ~3°C / min, kept warm for 0.1-0.2min, then raised to 310-320°C at a rate of 0.1-0.2°C / min, and kept warm for 8-10min; the modulation temperature rising program is as follows: at an initial temperature of 120-130°C, maintain for 0.1-0.2min, increase to 330-350°C at a rate of 2.0-3.0°C / min, maintain for 0.1-0.3min, then increase to 340-360°C at a rate of 0.2°C / min, and maintain for 10min. The modulator cycle is 7-9s, of which 1-3s is the hot blowing time.

[0057] The present invention performs a staged heating program on the one-dimensional chromatographic column, the two-dimensional chromatographic column, and the modulator, prolongs the analysis time of different components in crude oil, and makes all components in crude oil flow out as much as possible, thereby improving the accuracy of the cycloalkane content in crude oil. In addition, two different heating rates are used in the heating program of the present invention, firstly, a higher heating rate of 2 to 3°C / min is used for heating, and then a lower heating rate of 0.1 to 0.2°C is used for heating. Compared with the one-stage heating, it has the advantages of high separation, easy qualitative analysis, and accurate integration.

[0058] In order to further improve the determination accuracy of cycloalkanes in crude oil samples, preferably the injection port temperature of the comprehensive two-dimensional gas chromatograph is 300-310°C, and preferably the injection volume of the crude oil sample is 1.0-1.2 μL; preferably, the comprehensive two-dimensional gas chromatograph adopts a splitless injection mode.

[0059] In a preferred embodiment, the carrier gas flow rate of the comprehensive two-dimensional gas chromatograph is 1.4 to 1.6 mL / min. The present invention controls the carrier gas flow rate of the comprehensive two-dimensional gas chromatograph within the above range, which can more accurately quantitatively analyze the cycloalkane content in the crude oil sample to be identified. When the carrier gas flow rate is too high, it will cause large baseline noise; when the carrier gas flow rate is too low, it will cause the chromatographic peak to tail or extend.

[0060] In a preferred embodiment, the carrier is helium. Helium has good chemical inertness, and its ionization energy is 24.6 eV, which is the highest among all gases. It is difficult to ionize, and will not affect the chromatogram baseline due to unstable airflow. In addition, helium has a relative molecular mass of 4, a large flow conductivity, is easy to separate from other components, has an enrichment effect on the sample, and has simple ion fragmentation without interference.

[0061] In order to more accurately qualitatively analyze the retention time of each component in the crude oil sample, in some preferred embodiments, the mass spectrometry conditions of the time-of-flight mass spectrometer are as follows: the mass spectrometry source temperature is 230-250°C; the detection voltage is 1.8-1.85 kV, the mass scanning range is 40-520 amu, and the desolvation gas flow rate is 500-700 L / Hr.

[0062] In a preferred embodiment, the density of the crude oil sample to be identified is greater than 0.87 g / cm 3 The weight content of the component is 45-55wt%. The present invention can further simulate the analysis of the cycloalkane content of medium oil by controlling the density of the crude oil sample to be identified, verifying that the analysis method of the present invention can identify cycloalkane crude oil from medium oil, solving the problem that it is difficult to accurately and quantitatively analyze the cycloalkane content of medium oil in the prior art.

[0063] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0064] Example

[0065] The sampling points of the crude oil samples to be identified in the embodiment of the present invention are crude oil from different regions of the Junggar Basin, and the physical property data of the crude oil are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] Example 1

[0070] Preparation of crude oil sample: 2 mL of dichloromethane (chromatographic grade, CAS No. 75-09-2) was used to dissolve 16 mg of light crude oil from the Triassic Baikouquan Formation in the Mahu area of ​​the Junggar Basin, and then 20 μL of 5α-androstane standard (CAS No. 438-22-2) was added to the system, wherein the mass concentration of 5α-androstane was 0.2670 mg / mL, and ultrasonic vibration was used for 10 minutes to fully mix the 5α-androstane standard with the crude oil to be identified, and the mixture was allowed to stand for 0.5 hour to obtain a crude oil sample.

[0071] The crude oil sample is subjected to a comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer to obtain a three-dimensional stereogram of the comprehensive two-dimensional gas chromatography of the crude oil sample (such as Figure 1 ), and the dot plot of the comprehensive two-dimensional gas chromatograph (as shown Figure 2 shown).

[0072] The mass spectrometry conditions of time-of-flight mass spectrometry are:

[0073] The mass spectrometer source temperature was 240°C; the detection voltage was 1.83 kV, the mass scanning range was 40-520 amu, and the desolvation gas flow rate was 600 L / Hr.

[0074] The chromatographic conditions of the comprehensive two-dimensional gas chromatograph are:

[0075] One-dimensional chromatographic column: DB-petrol column (manufacturer: Agilent), column length 60m, diameter 0.2mm, coating (100% dimethylpolysiloxane) thickness 0.25μm; heating program: initial temperature 80°C, hold for 0.2min, increase to 290°C at a rate of 2.5°C / min, hold for 0.2min, then increase to 300°C at a rate of 0.2°C / min, hold for 10min.

[0076] Two-dimensional chromatographic column: DB-1701 column (manufacturer: Agilent), column length 4.0m, diameter 0.1mm, coating (high temperature resistant polyimide coating) thickness 0.1μm; heating program: initial temperature 90℃, hold for 0.2min, increase to 300℃ at a rate of 2.5℃ / min, hold for 0.2min, then increase to 310℃ at a rate of 0.2℃ / min, hold for 10min.

[0077] The modulator is a double-nozzle thermal modulator; the heating program is: the initial temperature is 130°C, maintained for 0.2 min, increased to 340°C at a rate of 2.5°C / min, maintained for 0.2 min, and then increased to 350°C at a rate of 0.2°C / min, maintained for 10 min. The modulator cycle is 8s, of which 2s is the hot blowing time.

[0078] The injection port temperature was 300 °C, the crude oil sample injection volume was 1 μL, helium was used as the carrier gas, and the carrier flow rate was set to 1.5 mL / min.

[0079] The retention time of different components in crude oil on comprehensive two-dimensional gas chromatography (e.g. Figure 2 As shown), according to the three-dimensional stereogram of the comprehensive two-dimensional gas chromatograph (as shown Figure 1 The contents of normal alkanes, isoalkanes, monocyclic alkanes, dicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes with a signal-to-noise ratio greater than 100 in crude oil samples were quantitatively analyzed. The analysis results are shown in Table 2.

[0080] Table 2

[0081] Component Type Component content / % Normal alkanes 23.35 Isoalkanes 25.17 Monocycloalkanes 15.51 Bicycloalkanes 4.81 Tricycloalkanes 0.48 Tetracycloalkanes 1.16 Pentacyclic Alkanes 0.15 S(Saturated hydrocarbons) 70.63 N(cycloalkanes) 22.11

[0082] The crude oil sample of Example 1 has an S of 70.63 and a N of 22.11, wherein S ≥ 50% and N ≤ 30%. Fig. 9 According to the crude oil type identification diagram, the light crude oil from the Triassic Baikouquan Formation in the Mahu area of ​​the Junggar Basin to be identified in Example 1 is a paraffin-type crude oil.

[0083] The present invention applies the light crude oil of the Triassic Baikouquan Formation in the Mahu area of ​​the Junggar Basin to the fields of gasoline, kerosene, light diesel, etc., which is in line with the expectation of applying paraffin-type crude oil to these fields and meets the index of high saturated hydrocarbon content, indicating that the light crude oil of the Triassic Baikouquan Formation in the Mahu area of ​​the Junggar Basin identified by the present invention as paraffin-type crude oil is reliable.

[0084] Example 2

[0085] Preparation of crude oil samples: 25 mg of medium crude oil from the Permian Lucaogou Formation in the Jimusar area of ​​the Junggar Basin was dissolved in 2 mL of dichloromethane (chromatographic grade, CAS No. 75-09-2), and 20 μL of 5α-androstane standard (CAS No. 438-22-2) was added to the system, wherein the mass concentration of 5α-androstane was 0.2670 mg / mL. Ultrasonic vibration was used for 10 minutes to fully mix the 5α-androstane standard with the crude oil to be identified, and the mixture was allowed to stand for 0.5 hour to obtain a crude oil sample.

[0086] The crude oil sample is subjected to a comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer to obtain a three-dimensional stereogram of the comprehensive two-dimensional gas chromatography of the crude oil sample (such as Figure 3 ), and the dot plot of the comprehensive two-dimensional gas chromatograph (as shown Figure 4 The chromatographic conditions of the comprehensive two-dimensional gas chromatograph and the mass spectrometry conditions of the time-of-flight mass spectrometer are the same as those of Example 1.

[0087] The retention time of different components in crude oil on comprehensive two-dimensional gas chromatography (e.g. Figure 3 As shown), according to the three-dimensional stereogram of the comprehensive two-dimensional gas chromatograph (as shown Figure 4 According to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatogram, the contents of normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes with a signal-to-noise ratio greater than 100 in the crude oil sample were quantitatively analyzed. The analysis results are shown in Table 3.

[0088] Table 3

[0089] Component Type Component content / % Normal alkanes 18.28 Isoalkanes 14.20 Monocycloalkanes 16.38 Bicycloalkanes 9.30 Tricycloalkanes 3.64 Tetracycloalkanes 1.49 Pentacyclic Alkanes 1.38 S(Saturated hydrocarbons) 64.67 N(cycloalkanes) 32.19

[0090] The crude oil sample of Example 2 has an S of 64.67 and a N of 32.19, wherein S≥50%, 30%<N<40%. Fig. 9 The crude oil type identification diagram shows that the medium-quality crude oil from the Permian Lucaogou Formation in the Jimusar area of ​​the Junggar Basin in Example 2 is an intermediate crude oil.

[0091] The present invention applies the medium crude oil of the Permian Lucaogou Formation in the Jimusar area of ​​the Junggar Basin to the field of lubricating oil, which meets the expectation of applying intermediate crude oil to this field and satisfies the general composition of alkanes (straight chain, branched chain, multi-branched chain), cycloalkanes (monocyclic, bicyclic, multicyclic), aromatics (monocyclic aromatics, polycyclic aromatics), cycloalkyl aromatics, and oxygen-containing, nitrogen-containing, sulfur-containing organic compounds and non-hydrocarbon compounds such as colloids and asphaltenes, indicating that the medium crude oil of the Permian Lucaogou Formation in the Jimusar area of ​​the Junggar Basin identified by the present invention as medium crude oil is reliable.

[0092] Example 3

[0093] Preparation of crude oil samples: 25 mg of Carboniferous medium crude oil from the Chepaizi area of ​​the Junggar Basin was dissolved in 2 mL of dichloromethane (chromatographic grade, CAS No. 75-09-2), and then 20 μL of 5α-androstane standard (CAS No. 438-22-2) was added to the system, wherein the mass concentration of 5α-androstane was 0.2670 mg / mL. Ultrasonic vibration was used for 10 minutes to fully mix the 5α-androstane standard with the crude oil to be identified, and the mixture was allowed to stand for 0.5 hour to obtain a crude oil sample.

[0094] The crude oil sample is subjected to a comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer to obtain a three-dimensional stereogram of the comprehensive two-dimensional gas chromatography of the crude oil sample (such as Figure 5 ), and the dot plot of the comprehensive two-dimensional gas chromatograph (as shown Figure 6 The chromatographic conditions of the comprehensive two-dimensional gas chromatograph and the mass spectrometry conditions of the time-of-flight mass spectrometer are the same as those of Example 1.

[0095] According to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatogram, the contents of normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes with a signal-to-noise ratio greater than 100 in the crude oil sample were quantitatively analyzed. The analysis results are shown in Table 4.

[0096] Table 4

[0097] Component Type Component content / % Normal alkanes 2.06 Isoalkanes 4.03 Monocycloalkanes 32.80 Bicycloalkanes 18.45 Tricycloalkanes 3.47 Tetracycloalkanes 5.71 Pentacyclic Alkanes 1.29 S(Saturated hydrocarbons) 67.81 N(cycloalkanes) 61.72

[0098] The crude oil sample of Example 3 has an S of 67.81 and a N of 61.72, wherein S≥50% and N≥40%. Fig. 9 According to the crude oil type identification diagram, the Carboniferous medium crude oil in Chepaizi area of ​​Junggar Basin in Example 3 is a cycloparaffinic crude oil.

[0099] The present invention applies the Carboniferous medium crude oil from the Chepaizi area of ​​the Junggar Basin to the fields of aviation and rocket oil, which meets the expectation of applying cyclopentane-type crude oil to this field and satisfies the characteristic indicators such as low freezing point, good solubility, strong thermal stability, and good rubber compatibility. This shows that the Carboniferous medium crude oil from the Chepaizi area of ​​the Junggar Basin identified by the present invention as cyclopentane-type crude oil is reliable.

[0100] Example 4

[0101] Preparation of crude oil samples: 28 mg of extra-heavy crude oil from the Qigu Formation of the Jurassic System in Fengcheng area of ​​Junggar Basin was dissolved in 2 mL of carbon disulfide (chromatographically pure, CAS No. 75-09-2), and then 20 μL of 5α-androstane standard (CAS No. 438-22-2) was added to the system, wherein the mass concentration of 5α-androstane was 0.2670 mg / mL. Ultrasonic vibration was used for 10 minutes to fully mix the 5α-androstane standard with the crude oil to be identified, and the mixture was allowed to stand for 0.5 hour to obtain a crude oil sample.

[0102] The crude oil sample is subjected to a comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer to obtain a three-dimensional stereogram of the comprehensive two-dimensional gas chromatography of the crude oil sample (such as Figure 7 ), and the dot plot of the comprehensive two-dimensional gas chromatograph (as shown Figure 8 The chromatographic conditions of the comprehensive two-dimensional gas chromatograph and the mass spectrometry conditions of the time-of-flight mass spectrometer are the same as those of Example 1.

[0103] According to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatogram, the contents of normal alkanes, isoalkanes, monocyclic alkanes, bicyclic alkanes, tricyclic alkanes, tetracyclic alkanes and pentacyclic alkanes with a signal-to-noise ratio greater than 100 in the crude oil sample were quantitatively analyzed. The analysis results are shown in Table 5.

[0104] Table 5

[0105]

[0106]

[0107] The crude oil sample of Example 4 has an S of 35.93 and a N of 34.89, wherein S is less than 50% and N is greater than or equal to 25%. Fig. 9 According to the crude oil type identification diagram, the extra heavy crude oil of the Qigu Formation of the Jurassic in the Fengcheng area of ​​the Junggar Basin in Example 4 is an aromatic-cycloparaffinic crude oil.

[0108] The present invention applies the extra-heavy crude oil of the Qigu Formation of the Jurassic in the Fengcheng area of ​​the Junggar Basin to the fields of power generation and new material processing, which meets the expectation of applying aromatic-cycloalkane type crude oil to this field and satisfies the indicators of high density, high viscosity, high gum content, low wax content and low freezing point, indicating that the extra-heavy crude oil of the Qigu Formation of the Jurassic in the Fengcheng area of ​​the Junggar Basin identified by the present invention as aromatic-cycloalkane type crude oil is reliable.

[0109] Comparative Example 1

[0110] The key fraction method is adopted to analyze the medium-quality crude oil of the Permian Lucaogouquan Formation in the Jimusar area of ​​the Gar Basin and the medium-quality crude oil of the Carboniferous in the Chepaizi area of ​​the Junggar Basin. The process is as follows: weigh crude oil samples of the same weight as those of Example 2 and Example 3, respectively, add 30ppm of demulsifier (polyether demulsifier) ​​and softened water to the crude oil samples of Example 2 and Example 3, and then pass a high-voltage electric field (electric field strength 1.5kV / cm, power on for 10 minutes) to make the salt-containing water droplets gather and settle, thereby removing salt, water and other impurities in the crude oil; the crude oil of Example 2 and Example 3 after pretreatment is heated and sent to the primary distillation tower of the atmospheric distillation device to distill out most of the light gasoline, and the crude oil at the bottom of the primary distillation tower is heated to 370°C, and the density of the first key fraction is tested, and then the temperature is raised to 500°C under an absolute pressure of about 6kPa, and the density of the second key fraction is tested.

[0111] The first key fraction density and the second key fraction density of the crude oil sample of Example 2 were tested to be 0.792 g / cm 3 and 0.857 g / cm 3 The first key fraction density and the second key fraction density of the crude oil sample in Example 3 are 0.799 g / cm 3 and 0.851 g / cm 3 . It can be found that the density of the first key fraction and the second key fraction of the two are similar, judging that they are the same type of crude oil, which is intermediate crude oil. However, from the freezing point (such as 12, -22.4 / ℃) and wax content (9.9, 2.14) of the above two crude oils, it can be concluded that the two crude oils are obviously different and are not the same type of crude oil. It can be seen that when using the key fraction method to measure medium-quality crude oils of the same density, it is difficult to accurately distinguish the type of crude oil and cannot reflect the true quality of the crude oil.

[0112] Comparative Example 2

[0113] The key fraction method was used to analyze the extra heavy crude oil of the Qigu Formation of the Jurassic in the Fengcheng area of ​​the Junggar Basin, and the process was the same as that of Comparative Example 1.

[0114] According to the key fraction method, the density of the first key fraction and the second key fraction of the Jurassic Qigu Formation super-heavy crude oil in Fengcheng area of ​​Junggar Basin are 0.898 g / cm 3 and 0.958 g / cm 3 , identified as naphthenic crude oil. However, from the physical properties of the Jurassic Qigu Formation extra-heavy crude oil in Fengcheng area of ​​Junggar Basin, its freezing point is relatively high, at 38°C, it does not contain wax, and its viscosity is high, at 175800mPa·s (50°C). This type of crude oil is of poor quality and does not meet the requirements of naphthenic crude oil type. It can be seen that the key fraction method has a limited scope of application and cannot reflect the true quality of crude oil under certain circumstances.

[0115] Through the identification results of Comparative Examples 1 and 2, it can be found that there are errors in the identification and analysis of crude oil in the prior art, and the scope of application is relatively narrow. However, when the present invention identifies the type of crude oil based on comprehensive two-dimensional gas chromatography, the content of cycloalkanes in crude oil can be accurately quantified, and the scope of application is wide, and it can identify light crude oil, as well as medium crude oil and extra heavy crude oil.

[0116] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, characterized in that: The method comprises: Preparation of crude oil samples: using a diluent to dissolve the crude oil sample to be identified, and then adding 5α-androstane standard to the system to obtain a crude oil sample; Test: subjecting the crude oil sample to comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry; qualitatively determining the peak positions of 5α-androstane, normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes in the crude oil sample according to the time-of-flight mass spectrometry; and quantitatively analyzing the contents of normal alkanes, isoalkanes, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes and pentacycloalkanes with a signal-to-noise ratio greater than 100 in the crude oil sample according to the peak area of ​​5α-androstane in the comprehensive two-dimensional gas chromatography; Identification: the ratio of the sum of the weights of the normal alkanes, the isoalkanes, the monocycloalkanes, the bicycloalkanes, the tricycloalkanes, the tetracycloalkanes and the pentacycloalkanes in the crude oil sample to the weight of the crude oil sample to be identified is recorded as S; the ratio of the sum of the weights of the monocycloalkanes, the bicycloalkanes, the tricycloalkanes, the tetracycloalkanes and the pentacycloalkanes in the crude oil sample to the weight of the crude oil sample to be identified is recorded as N; When S≥50% and N≤30%, the crude oil sample to be identified is paraffin-type crude oil; When S≥50%, 30%<N<40%, the crude oil sample to be identified is an intermediate crude oil; When S≥50%, N≥40%, the crude oil sample to be identified is a cycloparaffinic crude oil; When S<50% and N<25%, the crude oil sample to be identified is an aromatic-asphalt type crude oil; When S<50% and N≥25%, the crude oil sample to be identified is an aromatic-cycloalkane type crude oil.

2. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to claim 1, characterized in that: In the preparation of the crude oil sample, the weight of the crude oil sample to be identified is 5 to 15 mg per 1 ml of the diluent.

3. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to claim 1 or 2, characterized in that: In the preparation of the crude oil sample, the weight of the 5α-androstane standard is 0.001-0.01 mg per 1 ml of the diluent.

4. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to any one of claims 1 to 3, characterized in that: The diluent is selected from n-hexane and / or dichloromethane, more preferably dichloromethane.

5. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to any one of claims 1 to 4, characterized in that: The comprehensive two-dimensional gas chromatograph has two chromatographic columns with different polarities, and the two chromatographic columns are independently selected from a DB-Petro column or a DB-17HT column; Preferably, the detector of the comprehensive two-dimensional gas chromatograph adopts a hydrogen flame ionization detector; Preferably, the modulator of the comprehensive two-dimensional gas chromatograph adopts a dual-nozzle thermal modulator; further preferably, the modulation period of the modulator is 8.0 to 10.0 s, and the heat blowing time is 2.0 to 3.0 s.

6. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to claim 5, characterized in that: The DB-Petro column has a column length of 50 to 60 m, an outer diameter of 0.2 to 0.3 mm, an inner diameter of 0.1 to 0.2 mm, and a coating thickness of 0.1 to 0.5 μm; the DB-17HT column has a column length of 2.5 to 3.0 m, an outer diameter of 0.1 to 0.2 mm, an inner diameter of 0.1 to 0.2 mm, and a coating thickness of 0.1 to 0.5 μm.

7. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to claim 5 or 6, wherein the one-dimensional chromatographic column of the comprehensive two-dimensional gas chromatograph adopts the DB-Petro column, and the two-dimensional chromatographic column adopts the DB-17HT column; the heating program of the one-dimensional chromatographic column is: keep the temperature at an initial temperature of 60-80°C for 0.1-0.2 min, heat it to 290-300°C at a rate of 2-3°C / min, keep it for 0.1-0.2 min, then heat it to 300-310°C at a rate of 0.1-0.2°C / min, and keep it for 8-10 min; The temperature program of the two-dimensional chromatographic column is as follows: at an initial temperature of 70-90°C, keep the temperature for 0.1-0.2 min, heat to 300-310°C at a rate of 2-3°C / min, keep the temperature for 0.1-0.2 min, then heat to 310-320°C at a rate of 0.1-0.2°C / min, keep the temperature for 8-10 min; The modulation temperature rising procedure is: maintain the initial temperature at 120-130°C for 0.1-0.2min, increase to 330-350°C at a rate of 2.0-3.0°C / min, maintain for 0.1-0.3min, then increase to 340-360°C at a rate of 0.2°C / min, maintain for 10min, and the modulator cycle is 7-9s, of which 1-3s is the hot blowing time.

8. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to any one of claims 1 to 7, characterized in that: The injection port temperature of the comprehensive two-dimensional gas chromatograph is 300-310°C; Preferably, the injection volume of the crude oil sample is 1.0-1.2 μL.

9. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to any one of claims 1 to 8, characterized in that: The carrier gas flow rate of the comprehensive two-dimensional gas chromatograph is 1.4 to 1.6 mL / min; Preferably, the carrier gas is helium.

10. The method for identifying crude oil types based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry according to any one of claims 1 to 9, characterized in that: The density of the crude oil sample to be identified is greater than 0.87 g / cm 3 The weight content of the component is 45 to 55 wt%.

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