Method for determining source of natural gas stratum by using gas chromatography-mass spectrometry

Abstract

The invention discloses a method for determining the source of a natural gas stratum by using a gas chromatography-mass spectrometry method, which comprises the following steps of: 1, sampling a natural gas sample with a known stratum source and a natural gas sample with an unknown source; detecting the natural gas standard gas, the natural gas sample with the known stratum source and the natural gas sample with the unknown source through a gas chromatograph-mass spectrometer; 3, constructing a control fingerprint spectrum of C6, C7 and C8 components of a natural gas sample with a known stratum source according to a detection result, and 4, comparing the control fingerprint spectrum of a natural gas sample with an unknown source with the control fingerprint spectrum of the natural gas sample with the known stratum source and a compound ratio to judge the natural gas sample with the unknown source. Whether is from the formation of the known source natural gas sample. C6, C7 and C8 components in the natural gas are taken as detection targets, and trace components in the natural gas are taken as a bridge for connecting'gas' and'source ', so that the stratum source of the natural gas can be quickly and accurately identified.

Description

Technical Field

[0001] This invention belongs to the field of natural gas exploration technology, specifically relating to a method for determining the source of natural gas formations using gas chromatography-mass spectrometry. Background Technology

[0002] Natural gas is a clean, low-carbon, and environmentally friendly green energy source, and its proportion in my country's energy structure is increasing. In the process of natural gas exploration and development, distinguishing the sources of natural gas from different formations to provide crucial information for exploration decisions has become a key challenge restricting natural gas exploration and development.

[0003] Chinese Patent CN 117216588 A discloses a method for identifying natural gas sources. Using existing natural gas data and source rock data, it calculates the natural gas maturity of the natural gas to be identified. The source of the natural gas is obtained by comparing the natural gas type with the organic matter type of the source rock, the ethane carbon isotope with the organic carbon isotope of the source rock, the natural gas composition with the components of the retained gas, and the natural gas isotope with the isotope of the retained gas. Chinese Patent CN 104749322 B provides a method for identifying over-mature natural gas sources. By testing and analyzing the geochemical characteristics of natural gas, reservoir bitumen, and source rocks, it establishes the genetic relationship between natural gas, reservoir bitumen, and source rocks, thereby identifying over-mature natural gas sources. Chinese patent CN114255828A provides a method and apparatus for identifying the alkane carbon isotope composition and origin of natural gas in complex, highly evolved, multi-source gas reservoirs. By acquiring alkane carbon isotope data of natural gas samples from different formations, the origin and origin of the natural gas sample to be tested are identified based on the ethane carbon isotope data and the difference between the ethane carbon isotope data and the methane carbon isotope data in the alkane carbon isotope data of the natural gas sample to be tested.

[0004] These methods primarily utilize biomarker compounds and carbon and hydrogen isotopes in natural gas. Biomarker compound analysis requires the extraction of saturated hydrocarbons, aromatics, asphaltenes, and non-hydrocarbon components. Biomarker compound analysis is then performed on a specific component to establish a correlation. This requires rock samples or crude oil as the basis for the study, is time-consuming, and is easily affected by maturity. Carbon and hydrogen isotope analysis, on the other hand, requires expensive isotope mass spectrometers. Furthermore, due to the complex origins of natural gas, carbon and hydrogen isotope reversals and other geochemical anomalies frequently occur. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the formation source of natural gas using gas chromatography-mass spectrometry, which can quickly and accurately identify the formation source of natural gas.

[0006] The objective of this invention is achieved through the following technical means: a method for determining the origin of natural gas formations using gas chromatography-mass spectrometry.

[0007] Step 1: Collect natural gas samples from known formations and natural gas samples from unknown formations. Collect multiple samples of natural gas from known formations.

[0008] Step 2: Analyze natural gas standard gas, natural gas samples from known formations, and natural gas samples from unknown sources using gas chromatography-mass spectrometry.

[0009] The detection parameters include the C6 component, specifically n-hexane, 2,2-dimethylbutane, 3-methylpentane, 2-methylpentane, benzene, and cyclohexane;

[0010] The C7 component specifically includes n-heptane, methylcyclohexane, and toluene;

[0011] The C8 component specifically includes n-octane, 2-methylheptane, 2,2-dimethylhexane, 1,2-dimethylcyclohexane, o-xylene, ethylbenzene, m-xylene, p-xylene, and ethylcyclohexane.

[0012] Step 3: Based on the detection results, construct a reference fingerprint spectrum for the C6, C7, and C8 components of natural gas samples from known formations, where the peak area of ​​each fingerprint peak in the reference fingerprint spectrum is greater than 3%.

[0013] Step 4: After performing gas chromatography-mass spectrometry on the natural gas sample of unknown origin, the total ion chromatogram of C6, C7, and C8 components of the sample is obtained. This chromatogram is then compared with the reference fingerprint spectrum of C6, C7, and C8 of the natural gas sample of known formation origin obtained in Step 3. If the similarity with the reference fingerprint spectrum is greater than a set value, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin.

[0014] Step 5: Calculate the total concentrations of C6, C7, and C8 components in multiple natural gas samples from known formation sources, calculate the C6 / C7 and C7 / C8 ratios, and obtain the mean values ​​of the C6 / C7 and C7 / C8 ratios, respectively.

[0015] Calculate the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source. If the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source are within ±10% of the mean C6 / C7 and C7 / C8 values ​​of the natural gas sample from a known formation, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not come from the formation of the natural gas sample from a known source.

[0016] Step 6: Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios in multiple natural gas samples from known formations, and obtain the mean values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios, respectively.

[0017] Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of the natural gas sample from an unknown source. If these ratios are within ±10% of the average values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of natural gas samples from known formations, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not originate from the formation of the natural gas sample from a known source.

[0018] Step 7: If the requirements of steps 4 to 6 are met simultaneously, it can be determined that the natural gas sample from the unknown source comes from the formation of the natural gas sample from the known source.

[0019] In step two, the chromatographic conditions are as follows: TG-5MS column, 60m×0.25mm×1.0μm; carrier gas: high-purity helium; flow rate: 1.0ml / min; injection port temperature: 200℃; split injection, split ratio 10:1.

[0020] Temperature program conditions: initial temperature 40℃, hold for 5 min, increase to 150℃ at 5℃ / min, hold for 4 min, EI ionization source, electron ionization at 70 eV, ion source temperature 250℃, transfer line temperature 220℃, solvent delay 4 min. Full scan mode (SCAN); scan range: 45–150 amu; injection volume: 100 μL.

[0021] In step four, if the similarity with the reference fingerprint spectrum is greater than 0.9, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin.

[0022] In step two, the quantitative ions and auxiliary ions for each detection parameter are respectively:

[0023]

[0024]

[0025] The beneficial effects of this invention are as follows: by using C6, C7, and C8 components in natural gas as detection targets, and by using trace components in natural gas as a bridge connecting "gas" and "source", the geological origin of natural gas can be quickly and accurately identified. Attached Figure Description

[0026] Figure 1 Total ion chromatogram of standard gases;

[0027] Figure 2 Overlapped chromatograms of natural gas samples from 10 Carboniferous strata;

[0028] Figure 3 A comparative fingerprint of natural gas samples from Carboniferous strata;

[0029] Figure 4 Evaluation of the similarity between the fingerprint spectra of unknown samples and Carboniferous natural gas;

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0031]

Example 1

[0032] A method for determining the formation origin of natural gas using gas chromatography-mass spectrometry.

[0033] Step 1: Collect natural gas samples from known formations and natural gas samples from unknown formations. Collect multiple samples of natural gas from known formations.

[0034] Specifically, fluoropolymer film gas bags were used for sampling, and there were more than 10 natural gas samples from known formations.

[0035] Step 2: Analyze natural gas standard gas, natural gas samples from known formations, and natural gas samples from unknown sources using gas chromatography-mass spectrometry.

[0036] The detection parameters include the C6 component, specifically n-hexane, 2,2-dimethylbutane, 3-methylpentane, 2-methylpentane, benzene, and cyclohexane;

[0037] The C7 component specifically includes n-heptane, methylcyclohexane, and toluene;

[0038] The C8 component specifically includes n-octane, 2-methylheptane, 2,2-dimethylhexane, 1,2-dimethylcyclohexane, o-xylene, ethylbenzene, m-xylene, p-xylene, and ethylcyclohexane.

[0039] Step 3: Based on the detection results, construct a reference fingerprint spectrum for the C6, C7, and C8 components of natural gas samples from known formations, where the peak area of ​​each fingerprint peak in the reference fingerprint spectrum is greater than 3%.

[0040] Using the 2004A edition of the "Similarity Evaluation System for Chromatographic Fingerprints of Traditional Chinese Medicine" published by the National Pharmacopoeia Commission, reference fingerprint spectra for the C6, C7, and C8 components of natural gas samples from known geological formations were constructed. The peak area of ​​each fingerprint peak in the reference fingerprint spectra was greater than 3%.

[0041] Step 4: After performing gas chromatography-mass spectrometry on the natural gas sample of unknown origin, the total ion chromatogram of C6, C7, and C8 components of the sample is obtained. This chromatogram is then compared with the reference fingerprint spectrum of C6, C7, and C8 of the natural gas sample of known formation origin obtained in Step 3. If the similarity with the reference fingerprint spectrum is greater than a set value, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin.

[0042] Step 5: Calculate the total concentrations of C6, C7, and C8 components in multiple natural gas samples from known formation sources, calculate the C6 / C7 and C7 / C8 ratios, and obtain the mean values ​​of the C6 / C7 and C7 / C8 ratios, respectively.

[0043] Calculate the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source. If the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source are within ±10% of the mean C6 / C7 and C7 / C8 values ​​of the natural gas sample from a known formation, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not come from the formation of the natural gas sample from a known source.

[0044] Step 6: Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios in multiple natural gas samples from known formations, and obtain the mean values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios, respectively.

[0045] Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of the natural gas sample from an unknown source. If these ratios are within ±10% of the average values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of natural gas samples from known formations, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not originate from the formation of the natural gas sample from a known source.

[0046] Step 7: If the requirements of steps 4 to 6 are met simultaneously, it can be determined that the natural gas sample from the unknown source comes from the formation of the natural gas sample from the known source.

[0047] In step two, the chromatographic conditions are as follows: TG-5MS column, 60m×0.25mm×1.0μm; carrier gas: high-purity helium; flow rate: 1.0ml / min; injection port temperature: 200℃; split injection, split ratio 10:1.

[0048] Temperature program conditions: initial temperature 40℃, hold for 5 min, increase to 150℃ at 5℃ / min, hold for 4 min, EI ionization source, electron ionization at 70 eV, ion source temperature 250℃, transfer line temperature 220℃, solvent delay 4 min. Full scan mode (SCAN); scan range: 45–150 amu; injection volume: 100 μL.

[0049] In step four, if the similarity with the reference fingerprint spectrum is greater than 0.9, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin.

[0050] In step two, the quantitative ions and auxiliary ions for each detection parameter are respectively:

[0051]

[0052]

[0053] Taking a specific experiment as an example,

[0054] Step 1: Using fluoropolymer film gas bags, natural gas samples were collected from 11 Carboniferous strata and 1 natural gas sample from an unknown source.

[0055] Step 2: Method validation of gas chromatography-mass spectrometry for the detection of C6, C7, and C8 components in natural gas.

[0056] Chromatographic conditions: TG-5MS column, 60m × 0.25mm × 1.0μm; carrier gas: high-purity helium; flow rate: 1.0ml / min; injection port temperature: 200℃; split injection, split ratio 10:1. Temperature program: initial temperature 40℃, hold for 5 min, increase to 150℃ at 5℃ / min, hold for 4 min; EI ionization source, electron ionization at 70eV, ion source temperature 250℃, transfer line temperature 220℃, solvent delay 4 min. Full scan mode (SCAN), scan range: 45–150 amu. Injection volume: 100μL.

[0057] ① Standard gas: No. 156230082107, with the following components and their mole fractions: 2,2-dimethylbutane (0.0312%), 2-methylpentane (0.03152%), 3-methylpentane (0.03153%), n-hexane (0.0538%), cyclohexane (0.03001%), benzene (0.05241%), n-heptane (0.0315%), toluene (0.03178%), methylcyclohexane (0.0099%). 51%), 2,2-dimethylhexane (0.001043%), n-octane (0.005192%), 2-methylheptane (0.001093%), ethylcyclohexane (0.001077%), ethylbenzene (0.005287%), o-xylene (0.005265%), dimethylcyclohexane (0.001062%), m-xylene (0.005274%), p-xylene (0.005213%), methane (99.63%).

[0058] The final standard gas total ion chromatogram is as follows: Figure 1 As shown.

[0059] Retention time, quantitative ions, and auxiliary qualitative ions of the target compound

[0060]

[0061] ② Standard curve plotting: Using high-purity methane as the equilibrium gas, the standard gas was successively diluted from 100% to 80%, 60%, 50%, 40%, and 20% using an S4000 gas dilution instrument to form six groups of standard samples with different concentrations from high to low for testing.

[0062] Standard curve of C6 to C8 components in natural gas

[0063]

[0064]

[0065] ③ Method detection limit: Prepare samples with a standard gas concentration of 10% using an S4000 gas dilution instrument, perform parallel determinations on 7 samples, determine the minimum detection limit based on 3 times the signal-to-noise ratio of the quantitative ion peak area, and calculate the detection limit for each compound.

[0066]

[0067]

[0068] Step 3: Gas chromatography-mass spectrometry was used to detect natural gas samples from 10 Carboniferous formations in an oilfield. The total ion chromatograms of the natural gas samples from the 10 Carboniferous formations were processed using the "Similarity Evaluation System for Chromatographic Fingerprints of Traditional Chinese Medicine" (2004A edition) published by the National Pharmacopoeia Commission to generate reference fingerprint spectra.

[0069] Overlapped chromatograms of natural gas samples from 10 Carboniferous strata are shown below. Figure 2 As shown,

[0070] Fingerprint of natural gas samples from Carboniferous formations as shown in the figure. Figure 3 As shown,

[0071] The similarity between the natural gas samples from the 10 Carboniferous strata and the control fingerprints was 0.986, 0.992, 0.988, 0.975, 0.987, 0.996, 0.993, 0.973, 0.990, and 0.989, respectively.

[0072] Step 4: Similarity calculation. The total ion chromatogram of the natural gas sample from the unknown source was obtained. The similarity was evaluated by comparing the fingerprint chromatogram of the sample with that of the natural gas sample from the Carboniferous strata using the "Similarity Evaluation System of Chromatographic Fingerprint of Traditional Chinese Medicine" (2004A edition) published by the National Pharmacopoeia Commission. The similarity was 0.991.

[0073] The comparison chart is as follows Figure 4 As shown.

[0074] Step 5: Based on the detection results of natural gas samples from 10 Carboniferous strata, calculate the total concentration of C6 component (n-hexane, 2,2-dimethylbutane, 3-methylpentane, 2-methylpentane, benzene, cyclohexane), C7 component (n-heptane, methylcyclohexane, toluene), and C8 component (n-octane, 2-methylheptane, 2,2-dimethylhexane, 1,2-dimethylcyclohexane, o-xylene, ethylbenzene, m-xylene, p-xylene, ethylcyclohexane). Calculate the "C6 / C7" ratio, which has an average value of 1.040. Therefore, the range of the "C6 / C7" ratio for natural gas samples in the Carboniferous strata is determined to be 0.936–1.144.

[0075] The C7 / C8 ratio was calculated and found to have an average value of 1.165. Therefore, the range of the C7 / C8 ratio for natural gas samples in the Carboniferous strata is determined to be 1.049 to 1.249.

[0076] <![CDATA[C6 / C7]]> <![CDATA[C7 / C8]]> 1 1.004 1.221 2 1.018 1.132 3 1.113 1.155 4 1.075 1.148 5 1.043 1.189 6 0.998 1.142 7 1.094 1.213 8 1.025 1.147 9 1.008 1.167 10 1.025 1.135 mean 1.040 1.165

[0077] The calculated C6 / C7 ratio in the natural gas sample from an unknown source is 1.073, and the C7 / C8 ratio is 1.184.

[0078] Step 6: Based on the detection results of natural gas samples from 10 Carboniferous strata, the "n-hexane / methylcyclohexane" ratio was calculated, and the average value was 1.325. Therefore, the range of the "n-hexane / methylcyclohexane" ratio for natural gas samples in the Carboniferous strata can be determined to be 1.193 to 1.458.

[0079] The methylcyclohexane / n-octane ratio was calculated and found to be 0.634. Therefore, the methylcyclohexane / n-octane ratio range of natural gas samples in the Carboniferous strata can be determined to be 0.571 to 0.697.

[0080]

[0081] The calculated ratio of "n-hexane / methylcyclohexane" in the natural gas sample from an unknown source is 1.385, and the ratio of "methylcyclohexane / n-octane" is 0.611.

[0082] Step 7: The similarity of the fingerprint spectrum between the natural gas sample from the unknown source and the Carboniferous natural gas sample from a certain oilfield is 0.991, which is greater than 0.9; the "C6 / C7" ratio is 1.073, which is within the range of Carboniferous natural gas sample ratios (0.936~1.144); the "C7 / C8" ratio is 1.184, which is within the range of Carboniferous natural gas sample ratios (1.049~1.249); the "n-hexane / methylcyclohexane" ratio is 1.385, which is within the range of Carboniferous natural gas sample ratios (1.193~1.458); and the "methylcyclohexane / n-octane" ratio is 0.611, which is within the range of Carboniferous natural gas sample ratios (0.571~0.697).

[0083] If all of the above conditions are met, it can be determined that the natural gas sample of unknown origin comes from the Carboniferous strata of the oilfield.

Claims

1. A method for determining the source of natural gas formations using gas chromatography-mass spectrometry, characterized in that: Step 1: Collect natural gas samples from known formations and natural gas samples from unknown formations. Collect multiple samples of natural gas from known formations. Step 2: Analyze natural gas standard gas, natural gas samples from known formations, and natural gas samples from unknown sources using gas chromatography-mass spectrometry. Step 3: Based on the detection results, construct a reference fingerprint spectrum for the C6, C7, and C8 components of natural gas samples from known formations, where the peak area of ​​each fingerprint peak in the reference fingerprint spectrum is greater than 3%. Step 4: After performing gas chromatography-mass spectrometry on the natural gas sample of unknown origin, the total ion chromatogram of C6, C7, and C8 components of the sample is obtained. This chromatogram is then compared with the reference fingerprint spectrum of C6, C7, and C8 of the natural gas sample of known formation origin obtained in Step 3. If the similarity with the reference fingerprint spectrum is greater than a set value, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin. Step 5: Calculate the total concentrations of C6, C7, and C8 components in multiple natural gas samples from known formation sources, calculate the C6 / C7 and C7 / C8 ratios, and obtain the mean values ​​of the C6 / C7 and C7 / C8 ratios, respectively. Calculate the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source. If the C6 / C7 and C7 / C8 values ​​of the natural gas sample from an unknown source are within ±10% of the mean C6 / C7 and C7 / C8 values ​​of the natural gas sample from a known formation, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not come from the formation of the natural gas sample from a known source. Step 6: Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios in multiple natural gas samples from known formations, and obtain the mean values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios, respectively. Calculate the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of the natural gas sample from an unknown source. If these ratios are within ±10% of the average values ​​of the hexane / methylcyclohexane and methylcyclohexane / n-octane ratios of natural gas samples from known formations, proceed to the next step. Otherwise, it can be determined that the natural gas sample from an unknown source does not originate from the formation of the natural gas sample from a known source. Step 7: If the requirements of steps 4 to 6 are met simultaneously, it can be determined that the natural gas sample from the unknown source comes from the formation of the natural gas sample from the known source.

2. The method for determining the source of natural gas formations using gas chromatography-mass spectrometry according to claim 1, characterized in that: In step two, the chromatographic conditions are: TG-5MS column, 60m × 0.25mm × 1.0μm; Carrier gas: high-purity helium; flow rate: 1.0 ml / min; injection port temperature: 200℃; split injection, split ratio 10:1; Temperature program conditions: initial temperature 40℃, hold for 5 min, increase to 150℃ at 5℃ / min, hold for 4 min, EI ionization source, electron ionization at 70 eV, ion source temperature 250℃, transfer line temperature 220℃, solvent delay 4 min, full scan mode (SCAN); scan range: 45~150 amu; injection volume: 100 μL.

3. The method for determining the source of natural gas formations using gas chromatography-mass spectrometry according to claim 1, characterized in that: In step four, if the similarity with the reference fingerprint spectrum is greater than 0.9, proceed to the next step; otherwise, it can be determined that the natural gas sample of unknown origin does not come from the formation of the natural gas sample of known origin.

4. The method for determining the source of natural gas formations using gas chromatography-mass spectrometry according to claim 1, characterized in that: The detection parameters include the C6 component, specifically including n-hexane, 2,2-dimethylbutane, 3-methylpentane, 2-methylpentane, benzene, and cyclohexane; The C7 component specifically includes n-heptane, methylcyclohexane, and toluene; The C8 component specifically includes n-octane, 2-methylheptane, 2,2-dimethylhexane, 1,2-dimethylcyclohexane, o-xylene, ethylbenzene, m-xylene, p-xylene, and ethylcyclohexane.

5. The method for determining the source of natural gas formations using gas chromatography-mass spectrometry according to claim 4, characterized in that: In step two, the quantitative ions and auxiliary ions for each detection parameter are respectively:

Images