Method for evaluating the degree of biodegradation of crude oil using oxygenates

Abstract

The application provides a method for evaluating the degree of biodegradation of crude oil by using oxygen-containing compounds, which comprises the following steps: S1, dissolving the crude oil in toluene, adding an ionization promoter after dilution, and preparing a sample solution; S2, ionizing the sample solution in a negative ion electrospray ionization source, analyzing the oxygen-containing compounds in the sample solution by using a Fourier transform ion cyclotron resonance mass spectrometer, and obtaining experimental data; S3, extracting the molecular formula of the oxygen-containing compounds in the experimental data: C x H y O z , and z is greater than or equal to 1, and calculating the equivalent double bond number; S4, calculating the ratio A / N of the relative abundance of monocyclic naphthenic acid (DBE2-O2) and di- to pentaloop naphthenic acid (DBE 3～6 -O2), and evaluating the degree of biodegradation of the crude oil sample. In the application, a new comprehensive evaluation index is provided by studying the oxygen-containing compounds in crude oil with different degrees of biodegradation, and the degree of biodegradation of the crude oil is accurately evaluated.

Description

Technical Field

[0001] This application relates to the field of petroleum sample analysis technology, and in particular to a method for evaluating the degree of biodegradation of crude oil using oxygen-containing compounds. Background Technology

[0002] Heavy oil, an important petroleum resource, has global reserves approximately three times the equivalent of conventional crude oil and natural gas. While crude oil typically contains fewer heteroatomic compounds such as oxygen, sulfur, and nitrogen, heavy oil contains a higher proportion of these compounds compared to conventional crude oil. With increased biodegradation, low-molecular-weight hydrocarbons in the reservoir are more easily destroyed, forming heteroatomic compounds that further increase the polarity, density, viscosity, and acidity of the crude oil. Severely biodegraded crude oil samples contain a large number of damaged hydrocarbon components, which, when detected by GC-MS, become difficult-to-identify complex mixtures (UCMs).

[0003] Biodegradation is one of the most common secondary regeneration methods in oil reservoirs, and determining the degree of biodegradation of crude oil is fundamental to oil and gas exploration research. Traditional methods for evaluating the degree of crude oil biodegradation primarily rely on GC-MS technology to identify specific compounds in the crude oil for qualitative assessment, followed by quantitative evaluation based on the personal experience of technical personnel. Due to the complexity of crude oil biodegradation, relying on personal experience to determine the degree of biodegradation may lead to inaccurate judgments due to subjective factors. Furthermore, GC-MS technology has low resolution and a small resolution range, making it unsuitable for effectively evaluating highly degraded heavy oil and bitumen.

[0004] Therefore, existing evaluation methods suffer from inaccuracies due to subjective human factors or low resolution, resulting in limited applicability. Consequently, there is an urgent need to develop a new method for evaluating the degree of crude oil biodegradation using oxygen-containing compounds to address these issues. Summary of the Invention

[0005] The main objective of this invention is to provide a method for evaluating the degree of biodegradation of crude oil using oxygen-containing compounds, in order to solve the technical problems of inaccurate judgments due to human subjectivity or low resolution of traditional technologies in existing evaluation methods, which result in inaccurate evaluation methods and narrow applicability.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for evaluating the degree of biodegradation of crude oil using oxygen-containing compounds is provided. The method includes: step S1, dissolving crude oil in toluene, diluting it, adding an ionization promoter, and preparing a sample solution; step S2, ionizing the sample solution in a negative ion electrospray ionization source, and analyzing the oxygen-containing compounds in the sample solution using Fourier transform ion cyclotron resonance mass spectrometry to obtain experimental data; and step S3, extracting the molecular formula of the oxygen-containing compounds from the experimental data: C x H y O z And z≥1, calculate its equivalent double bond number; Step S4, calculate the number of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2). 3～6 The ratio A / N, representing the relative abundance of O2, is used to evaluate the degree of biodegradation of crude oil samples: when A / N ≥ 1.8, the crude oil sample is not biodegraded, i.e., the degree of biodegradation is no degradation; when 1.5 ≤ A / N < 1.8, the degree of biodegradation of the crude oil sample is slight degradation; when 1.0 ≤ A / N < 1.5, the degree of biodegradation of the crude oil sample is moderate degradation; when 0.5 ≤ A / N < 1.0, the degree of biodegradation of the crude oil sample is severe degradation; when 0.1 ≤ A / N < 0.5, the degree of biodegradation of the crude oil sample is strong degradation; and when A / N < 0.1, the degree of biodegradation of the crude oil sample is extremely strong degradation.

[0007] Furthermore, the formula for calculating the double bond equivalence number is: DBE = xy / 2 + 1, where x is the number of carbon atoms and y is the number of hydrogen atoms.

[0008] Furthermore, in step S2, the analysis of oxygen-containing compounds in the sample solution includes one or more of the following: molecular formula, molecular composition, or component content.

[0009] Further, step S1 includes: dissolving the crude oil sample in toluene to prepare an initial solution with an initial concentration of 5-20 mg / mL; taking a portion of the initial solution and diluting it to 0.1-1.0 mg / mL with a toluene-methanol mixed solvent; adding an ionization promoter and mixing to obtain a sample solution.

[0010] Furthermore, the volume ratio of the toluene-methanol mixed solvent is 1:1.

[0011] Furthermore, the ionization promoter is ammonium hydroxide.

[0012] Furthermore, the operating parameters of the negative ion electrospray ionization source include: spray voltage of 3.5–4.5 kV and capillary temperature of 150–300 °C.

[0013] Furthermore, the operating parameters of the negative ion electrospray ionization source also include a flow rate of 50–200 μL / h.

[0014] Furthermore, in step S2, the operating parameters of the Fourier transform ion cyclotron resonance mass spectrometry include: a mass range of 200–1000 Da and a time-domain signal accumulation count of 64–512.

[0015] Furthermore, the sample solution is ionized in a negative ion electrospray ionization source, and the transition time of the ionized ions to the Fourier transform ion cyclotron resonance mass spectrometer after electrostatic focusing is 1.2 ms.

[0016] By applying the technical solution of this invention, the degree of biodegradation of a sample solution is evaluated by calculating the ratio of the abundance of monocyclic cycloalkanoic acids to the abundance of dicyclic to pentacyclic cycloalkanoic acids in oxygen-containing compounds. The evaluation method of this invention overcomes the problem of inaccurate judgments caused by subjective human factors, and further improves the accuracy of evaluation and broadens its applicability. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. In the drawings:

[0018] Figure 1 The total ion chromatogram and mass chromatogram of m / z = 217 for the saturated hydrocarbon components of the samples in Examples 1 to 16 of the present invention are shown.

[0019] Figure 2 Mass chromatograms of samples with m / z = 191 and m / z = 177 according to Examples 1 to 16 of the present invention are shown;

[0020] Figure 3 The bar charts showing the relative abundance of heteroatom compounds in the samples of Examples 1 to 16 according to the present invention are shown.

[0021] Figure 4 The correlation curves between the A / N value and sample density of the samples in Examples 1 to 16 of the present invention are shown; and

[0022] Figure 5 A correlation graph showing the A / N value of samples and the biodegradation level of samples according to Examples 1 to 16 of the present invention is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Definitions:

[0025] Double bond equivalence (DBE): also known as degree of unsaturation, it is a numerical value used to describe the degree of unsaturation in organic molecules. It represents the total number of rings and multiple bonds (such as double and triple bonds) in a molecule, and is used to infer the structural characteristics of the molecule.

[0026] Negative ion electrospray ionization source: A working mode of electrospray ionization (ESI) technology, suitable for analyzing negatively charged or easily deprotonated compounds in negative ion mode. By applying a negative high-voltage electric field, sample molecules lose protons (H+). + It can either capture electrons to form stable negative ions for mass spectrometry (MS) detection.

[0027] Fourier transform ion cyclotron resonance mass spectrometry (FTMS) is an ultra-high resolution mass spectrometry technique based on the cyclotron resonance phenomenon of ions in a strong magnetic field. It uses the Fourier transform (FT) to convert the time-domain signal of ion motion into a frequency-domain signal, thereby obtaining mass spectrometry data with ultra-high precision (resolution up to 1,000,000 or higher) and high quality accuracy (error <1 ppm).

[0028] As described in the background section of this invention, existing evaluation methods suffer from inaccurate judgments due to human subjectivity or low resolution of traditional techniques, resulting in inaccurate evaluation methods and narrow applicability. Therefore, this invention provides a method for evaluating the degree of biodegradation of crude oil using oxygen-containing compounds. The method includes: Step S1, dissolving crude oil in toluene, diluting it, adding an ionization promoter, and preparing a sample solution; Step S2, ionizing the sample solution in a negative ion electrospray ionization source, and analyzing the oxygen-containing compounds in the sample solution using Fourier transform ion cyclotron resonance mass spectrometry to obtain experimental data; Step S3, extracting the molecular formula of the oxygen-containing compounds from the experimental data: C x H y O z And z≥1, calculate its double bond equivalence number; Step S4, calculate the equivalence of monocyclic cycloalkanoic acid (DBE2-O2) and di- to pentacyclic cycloalkanoic acid (DBE2-O2). 3～6The ratio A / N, representing the relative abundance of O2, is used to evaluate the degree of biodegradation of crude oil samples: when A / N ≥ 1.8, the crude oil sample is not biodegraded, i.e., the degree of biodegradation is no degradation; when 1.5 ≤ A / N < 1.8, the degree of biodegradation of the crude oil sample is slight degradation; when 1.0 ≤ A / N < 1.5, the degree of biodegradation of the crude oil sample is moderate degradation; when 0.5 ≤ A / N < 1.0, the degree of biodegradation of the crude oil sample is severe degradation; when 0.1 ≤ A / N < 0.5, the degree of biodegradation of the crude oil sample is strong degradation; and when A / N < 0.1, the degree of biodegradation of the crude oil sample is extremely strong degradation.

[0029] The current method of evaluating the degree of biodegradation of crude oil using gas chromatography-mass spectrometry (GC-MS) combined with human experience involves: firstly, qualitatively identifying specific compounds in saturated and aromatic hydrocarbons in the crude oil; and then, based on their relative abundance and presence, further qualitatively evaluating the degree of biodegradation using personal experience. However, this method is highly susceptible to human influence. Secondly, in severely degraded crude oil or asphalt samples, saturated and aromatic hydrocarbons are severely damaged or even disappear. Therefore, current evaluation methods cannot effectively and accurately assess the degree of biodegradation.

[0030] The evaluation method provided by this invention utilizes negative ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to calculate the relative abundance of different types of oxygen-containing compounds by summarizing and analyzing the oxygen-containing compounds in crude oil samples. Generally, the oxygen-containing compounds in undegraded crude oil are mainly acyclic fatty acids (DBE1-O2). As the degree of biodegradation of crude oil increases, the content of acyclic fatty acids gradually decreases, and even almost disappears in the severe degradation stage. Subsequently, the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) shows a slight increasing trend in the mild and moderate degradation stages, but decreases significantly in the severe degradation stage. Dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2)... 3～6 The relative abundance of (-O2) gradually increases with the degree of biodegradation of crude oil samples, thus surpassing acyclic fatty acids to become the most abundant acid. The abundance of monocyclic cycloalkanoic acids and dicyclic to pentacyclic cycloalkanoic acids in oxygen-containing compounds is calculated, and the ratio of these two is used to evaluate the degree of biodegradation of the sample solution. Therefore, this invention provides a new comprehensive evaluation index for accurately and efficiently quantitatively evaluating the degree of biodegradation of crude oil through the study of oxygen-containing compounds in crude oil with different degrees of biodegradation.

[0031] Specifically, the ratio A / N, representing the relative abundance of monocyclic cycloalkanoic acids and dicyclic to pentacyclic cycloalkanoic acids in the oxygen-containing compounds, is calculated to determine the degree of degradation of the crude oil sample. This includes: when A / N ≥ 1.8, the crude oil sample is not biodegraded, i.e., the degree of biodegradation is no degradation; when 1.5 ≤ A / N < 1.8, the degree of biodegradation is slight degradation; when 1.0 ≤ A / N < 1.5, the degree of biodegradation is moderate degradation; when 0.5 ≤ A / N < 1.0, the degree of biodegradation is severe degradation; when 0.1 ≤ A / N < 0.5, the degree of biodegradation is intense degradation; and when A / N < 0.1, the degree of biodegradation is extremely intense degradation. Therefore, under normal circumstances, the oxygen-containing compounds in undegraded crude oil are mainly acyclic fatty acids (DBE1-O2). As the degree of biodegradation of crude oil increases, the content of acyclic fatty acids gradually decreases, and even almost disappears in the severe degradation stage. Subsequently, the relative abundance of monocycloalkanoic acids (DBE2-O2) showed a slight increasing trend during the mild and moderate degradation stages, but decreased significantly during the severe degradation stages. Di- to pentacycloalkanoic acids (DBE2-O2) 3～6 The relative abundance of cycloalkanoic acids (-O2) gradually increases with the degree of biodegradation of crude oil samples, thus surpassing acyclic fatty acids to become the most abundant acid. The degree of biodegradation of samples is evaluated by calculating the ratio of the relative abundance of monocyclic cycloalkanoic acids and di- to pentacyclic cycloalkanoic acids in the oxygen-containing compound data.

[0032] In a preferred embodiment, the formula for calculating the double bond equivalence number is: DBE = xy / 2 + 1, where x is the number of carbon atoms and y is the number of hydrogen atoms. The DBE value represents the total number of rings and double bonds in the molecule, reflecting the degree of unsaturation of the molecules in crude oil.

[0033] In a preferred embodiment, in step S2, the sample solution is ionized in a negative ion electrospray ionization source, and Fourier transform ion cyclotron resonance mass spectrometry is used to analyze the oxygen-containing compounds in the sample solution. The analysis of oxygen-containing compounds includes: molecular formula, molecular composition and component content, thereby providing a basis for the evaluation method.

[0034] To further ensure the complete dissolution of nonpolar components (such as saturated hydrocarbons and aromatic hydrocarbons) in crude oil, a crude oil sample was dissolved in toluene to prepare an initial solution with an initial concentration of 5–20 mg / mL. A portion of this initial solution was diluted with a toluene-methanol mixed solvent to 0.1–1.0 mg / mL to further enhance the solubility of oxygen-containing compounds (such as carboxylic acids) and improve the ESI response of negative ions. An ionization promoter was then added and mixed to promote the deprotonation of carboxylic acids, resulting in the sample solution.

[0035] In a preferred embodiment, the volume ratio of the toluene-methanol mixed solvent is 1:1 to balance the dissolution of both polar and nonpolar components in the sample solution. More preferably, ammonium hydroxide is used as the ionization promoter to further promote the deprotonation of oxygen-containing compounds, thereby preventing excessive salting out.

[0036] In a preferred embodiment, the operating parameters of the negative ion electrospray ionization source include: a spray voltage of 3.5–4.5 kV, a capillary temperature of 150–300 °C, and a flow rate of 50–200 μL / h. By limiting the above operating parameters, the ionization efficiency of the sample can be further improved, the signal stability can be enhanced, the response of negative ion ESI to oxygenated compounds in crude oil can be maximized, and matrix interference can be avoided.

[0037] In Fourier transform ion cyclotron resonance mass spectrometry analysis, in order to further cover the typical molecular weight range of oxygen-containing compounds in crude oil and eliminate low-mass solvent interference and high-molecular-weight insoluble components, the preferred operating parameters include: a mass range of 200–1000 Da and a time-domain signal accumulation of 64–512 times, thereby further improving the signal-to-noise ratio and balancing detection sensitivity and time cost.

[0038] In a preferred embodiment, the sample solution is ionized in a negative ion electrospray ionization source, and the transition time of the ionized ions into the Fourier transform ion cyclotron resonance mass spectrometer after electrostatic focusing is 1.2 ms, to ensure efficient ion transport without significant fragmentation or diffusion.

[0039] To ensure the crude oil sample solution enters the negative ion electrospray ionization source in an ionized state, a flow rate of 150 μL / h is preferred. This flow rate affects ionization efficiency; too high a flow rate leads to insufficient atomization, while too low a flow rate may reduce sensitivity. Further, a voltage of 4 kV is preferred applied to the electrospray needle tip, i.e., the polarization voltage of the negative ions, to charge the liquid and form tiny droplets. More preferably, a capillary column inlet voltage of 4.5 kV ensures smooth droplet entry into the capillary and the initiation of desolvation. A voltage of -320 V is preferred applied to the capillary outlet for further focusing and acceleration of ions, ensuring effective negative ion transport.

[0040] In a preferred embodiment, the operating parameters of the negative ion electrospray ionization source further include: the accumulation time of negative ions in the hexapole ion source is 0.1 s, thereby ensuring a sufficient number of ions to enter the next stage while avoiding excessive accumulation leading to space charge effects. Preferably, the accumulation time of negative ions through a quadrupole in an argon-filled hexapole collision cell is 1 s. This time for the ions to collide and fragment with argon in the collision cell ensures sufficient fragment ion generation for subsequent analysis.

[0041] To further improve the accuracy and efficiency of the evaluation method, the working parameters of the Fourier transform ion cyclotron resonance mass spectrometer in the optimization step S2 also include: excitation decay of 10 dB, data volume of 2 M, and time domain signal superposition of 256 times; thereby further improving the high-quality, high-resolution data acquisition and analysis of the mass spectrometer.

[0042] To further prepare the crude oil sample solution, in step S1, the mass fraction of the solute in the ammonium hydroxide solution is preferably 28%. More preferably, 25 μL of toluene solution containing the crude oil sample is diluted to 1 mL in a toluene-methanol mixture, and then 15 μL of ammonium hydroxide solution is added and mixed to prepare the sample solution.

[0043] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0044]

Example 1

[0045] Take crude oil sample 1, which is a freshwater lacustrine crude oil. Dissolve 10 mg of crude oil sample 1 in 1 mL of toluene to prepare a 10 mg / mL solution. Take 25 μL and dilute it to 1 mL with a toluene-methanol (volume ratio 1:1) mixture. Add 15 μL of a 28% ammonium hydroxide solution and gently shake to mix thoroughly. (Among the instruments used, except for the 10 μL Hamilton syringe with a stainless steel piston, all other instruments used glassware for solvent conversion.) to obtain sample solution 1.

[0046] The prepared sample solution 1 was input into a negative ion electrospray ionization (ESI) source via a syringe pump at a flow rate of 150 μL / h. The negative ion polarization voltage, capillary column inlet voltage, and outlet voltage were 4.0 kV, 4.5 kV, and -320 V, respectively. The accumulation time of ions in the hexapole ion source and the accumulation time of ions in the argon-filled hexapole collision cell via a quadrupole were 0.1 s and 1 s, respectively. The transition time of ions entering the ICR after electrostatic focusing was 1.2 ms. The operating conditions for Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were: excitation decay of 10 dB, mass range of 200–1000 Da, data volume of 2 M, and time-domain signal superposition of 256 times; the molecular formula of the oxygen-containing compound in sample solution 1 was obtained as C. x H y O z Calculate the double bond equivalence number.

[0047] Finally, the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in the oxygen-containing compound data were calculated. 3～6 The relative abundance ratio of O2) is A / N is 1.8, indicating that the sample is not biodegraded.

[0048]

Example 2

[0049] Crude oil sample 2 was taken, which is a freshwater lacustrine crude oil, and the evaluation method was the same as in Example 1.

[0050] The oxygen-containing compound in sample solution 2 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0051] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) was 1.75, indicating that the sample was not biodegraded.

[0052]

Example 3

[0053] Crude oil sample 3 was taken, which is a freshwater lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0054] The oxygen-containing compound in sample solution 3 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0055] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2) is A / N is 0.4, indicating that the sample is severely degraded.

[0056]

Example 4

[0057] Crude oil sample 4 was taken, which is a freshwater lacustrine crude oil. The evaluation method was the same as in Example 1.

[0058] The oxygen-containing compound in sample solution 4 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0059] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.04, indicating that the sample is extremely strongly biodegraded.

[0060]

Example 5

[0061] Five crude oil samples were taken, which were freshwater lacustrine crude oils. The evaluation method was the same as in Example 1.

[0062] The oxygen-containing compound in sample solution 5 has the molecular formula Cx H y O z Calculate the double bond equivalence number.

[0063] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.04, indicating that the sample is extremely strongly biodegraded.

[0064]

Example 6

[0065] Crude oil sample 6 was taken, which is a freshwater lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0066] The oxygen-containing compound in sample solution 5 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0067] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2) is A / N is 0.05, indicating that the biodegradation of this sample is extremely severe.

[0068]

Example 7

[0069] Crude oil sample 7 was taken, which is a freshwater lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0070] The oxygen-containing compound in sample solution 7 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0071] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.03, indicating that the sample is extremely strongly biodegraded.

[0072]

Example 8

[0073] Eight crude oil samples were taken, which belong to the saline lacustrine facies crude oil. The evaluation method was the same as that in Example 1.

[0074] The oxygen-containing compound in sample solution 7 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0075] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) was 1.82, indicating that the sample was not biodegraded.

[0076]

Example 9

[0077] Crude oil sample 9 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0078] The oxygen-containing compound in sample solution 9 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0079] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 1.1, indicating that the sample is moderately degraded.

[0080]

Example 10

[0081] Take 10 crude oil samples, which are saline lacustrine crude oils, and evaluate them using the same method as in Example 1.

[0082] The oxygen-containing compound in sample solution 10 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0083] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 1.3, indicating that the sample is moderately degraded.

[0084]

Example 11

[0085] Crude oil sample 11 was taken, which is a saline lacustrine crude oil, and the evaluation method was the same as in Example 1.

[0086] The oxygen-containing compound in sample solution 11 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0087] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.52, indicating that the sample is severely degraded.

[0088]

Example 12

[0089] Crude oil sample 12 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0090] The oxygen-containing compound in sample solution 12 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0091] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) was 0.57, indicating that the sample was severely degraded.

[0092]

Example 13

[0093] Crude oil sample 13 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0094] The oxygen-containing compound in sample solution 13 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0095] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.25, indicating that the sample is severely degraded.

[0096]

Example 14

[0097] Crude oil sample 14 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0098] The oxygen-containing compound in sample solution 14 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0099] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) was 0.49, indicating that the sample was severely degraded.

[0100]

Example 15

[0101] Crude oil sample 15 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0102] The oxygen-containing compound in sample solution 15 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0103] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2) was A / N was 0.07, indicating that the sample was extremely strongly biodegraded.

[0104]

Example 16

[0105] Crude oil sample 16 was taken, which is a saline lacustrine crude oil. The evaluation method is the same as that in Example 1.

[0106] The oxygen-containing compound in sample solution 16 has the molecular formula C x H y O z Calculate the double bond equivalence number.

[0107] Calculate the relative abundance of monocyclic cycloalkanoic acids (DBE2-O2) and dicyclic to pentacyclic cycloalkanoic acids (DBE2-O2) in oxygen-containing compound data. 3～6 The relative abundance ratio of O2 (A / N) is 0.03, indicating that the sample is extremely strongly biodegraded.

[0108] The biodegradation degree of the sample solutions prepared in the above examples was evaluated, and the results are shown in Table 1.

[0109] Table 1

[0110]

[0111] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0112] Depend on Figure 1 and Figure 2 Based on the total ion chromatograms and chromatographic-mass spectra of the saturated hydrocarbon components of the samples from the above examples, the following results can be obtained: Examples 1 and 8 showed no biodegradation; Example 2 showed slight biodegradation; Examples 9 and 10 showed moderate degradation; Examples 11 and 12 showed severe degradation; Examples 3, 13, and 14 showed strong degradation; and Examples 4, 5, 6, 7, 15, and 16 showed extremely strong degradation. Figure 3 It can be seen that the relative abundance of O2 compounds in different types of crude oil increases with the degree of biodegradation. Further calculation of the A / N ratio, such as... Figure 4 As shown, a correlation analysis of the A / N ratio and density of crude oil revealed a strong negative correlation between the two. Figure 5 As shown, a correlation analysis of the A / N value of crude oil and its biodegradability grade (PM) revealed a strong negative correlation between the two. This demonstrates that the novel evaluation standard provided in this invention, which uses the A / N value to determine the degree of biodegradability of crude oil, exhibits extremely high accuracy and universality.

[0113] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of a particular invention. Certain features described in the various embodiments herein may also be implemented in combination in a single embodiment. Conversely, various features described in a single embodiment may also be implemented separately in various embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation thereof.

[0114] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0115] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings are not necessarily shown in a specific order or sequence to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0116] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0117] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for evaluating the degree of biodegradation of crude oil using oxygenated compounds, characterized in that, The above methods include: Step S1: Dissolve crude oil in toluene, dilute it, add an ionization promoter, and prepare a sample solution; Step S2: The sample solution is ionized in a negative ion electrospray ionization source, and the oxygen-containing compounds in the sample solution are analyzed by Fourier transform ion cyclotron resonance mass spectrometry to obtain experimental data. Step S3, extract the molecular formula of oxygen-containing compounds from the experimental data: C x H y O z Given that z≥1, calculate its double bond equivalence number; Step S4, calculate the concentrations of monocyclic cycloalkanoic acids (DBE2-O2) and di- to pentacyclic cycloalkanoic acids (DBE2-O2). 3～6 The ratio A / N, representing the relative abundance of O2, is used to evaluate the degree of biodegradation in crude oil samples. When A / N≥1.8, the crude oil sample is not biodegraded, that is, the degree of biodegradation is no degradation; When 1.5 ≤ A / N < 1.8, the degree of biodegradation of the crude oil sample is slight degradation; When 1.0 ≤ A / N < 1.5, the degree of biodegradation of the crude oil sample is moderate. When 0.5 ≤ A / N < 1.0, the degree of biodegradation of the crude oil sample is severe degradation; When 0.1 ≤ A / N < 0.5, the degree of biodegradation of the crude oil sample is severe degradation; When A / N < 0.1, the degree of biodegradation of the crude oil sample is extremely strong.

2. The method according to claim 1, characterized in that, The formula for calculating the double bond equivalence number is: DBE = xy / 2 + 1, where x is the number of carbon atoms and y is the number of hydrogen atoms.

3. The method according to claim 1, characterized in that, In step S2, the analysis of oxygen-containing compounds in the sample solution includes molecular formula, molecular composition, and component content.

4. The method according to claim 1, characterized in that, Step S1 includes: dissolving a crude oil sample in toluene to prepare an initial solution with an initial concentration of 5-20 mg / mL; taking a portion of the initial solution and diluting it to 0.1-1.0 mg / mL with a toluene-methanol mixed solvent; adding an ionization promoter and mixing to obtain the sample solution.

5. The method according to claim 4, characterized in that, The volume ratio of the toluene-methanol mixed solvent is 1:

1.

6. The method according to claim 1 or 4, characterized in that, The ionization promoter is ammonium hydroxide.

7. The method according to claim 1, characterized in that, The operating parameters of the negative ion electrospray ionization source include: spray voltage of 3.5–4.5 kV and capillary temperature of 150–300 °C.

8. The method according to claim 1, characterized in that, The operating parameters of the negative ion electrospray ionization source also include: a flow rate of 50–200 μL / h.

9. The method according to claim 1, characterized in that, In step S2, the operating parameters of the Fourier transform ion cyclotron resonance mass spectrometer include: a mass range of 200–1000 Da and a time-domain signal accumulation count of 64–512.

10. The method according to claim 1, characterized in that, The sample solution is ionized in a negative ion electrospray ionization source, and the transition time of the ionized ions into the Fourier transform ion cyclotron resonance mass spectrometer after electrostatic focusing is 1.2 ms.

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