Method for identifying natural gas cause of high-sulfur-content gas reservoir and application

Abstract

The invention provides a method for identifying natural gas causes of a high-sulfur-content gas reservoir and application. The method comprises the following steps: S1, measuring carbon and hydrogen isotope and component data of high-sulfur-content natural gas of a research target layer and data of potential hydrocarbon source rock kerogen isotope and vitrinite reflectivity; s2, carrying out a natural gas sulfate thermochemical reduction reaction simulation experiment, and determining influence factors of the sulfate thermochemical reduction reaction on carbon and hydrogen isotopes and components of natural gas isotopes; s3, carrying out a potential hydrocarbon source rock hydrocarbon generation simulation experiment, and determining the influence of the hydrocarbon source rock thermal maturity on natural gas carbon and hydrogen isotopes and natural gas components; s4, selecting methane carbon and hydrogen isotopes of the natural gas as identification parameters according to the result, and establishing an identification chart of the gas source cause of the high-sulfur-content natural gas; and S5, substituting the measured carbon and hydrogen isotope values of the high-sulfur-content natural gas into the high-sulfur-content natural gas source cause judgment chart, and determining the cause and thermal evolution maturity of the high-sulfur-content natural gas sample.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas exploration, and in particular to a method for identifying the genesis of natural gas in a high-sulfur gas reservoir and its application. Background Art

[0002] Global oil and gas exploration practices have shown that carbonate-gypsum-salt rock symbiosis is an important oil and gas exploration area. Carbonate-gypsum-salt rock system gas reservoirs generally have the characteristics of high hydrogen sulfide gas content. Foreign gas fields such as the Ghawar gas field and the North gas field, as well as domestic industrial gas reservoirs with high hydrogen sulfide content in the Feixianguan Formation of the Lower Triassic in the Sichuan Basin, the Cambrian subsalt in the Tarim Basin, and the Ordovician subsalt in the Ordos Basin. Studies have shown that sulfate thermochemical reduction reactions are considered to be the main cause of hydrogen sulfide gas in high-sulfur gas reservoirs, and sulfate minerals and hydrocarbons are reduced to sulfides under thermal power. Most of the natural gas in high-sulfur gas reservoirs is mainly dry gas, and the natural gas component is mainly methane, with less heavy hydrocarbon components such as ethane and propane. At the same time, it was found that in the process of consuming hydrocarbons by the sulfate thermochemical reduction reaction, due to the low content of heavy hydrocarbons such as ethane and propane and their rapid consumption, the sulfate thermochemical reduction reaction has a greater impact on the isotopic composition and components of heavy hydrocarbons such as ethane and propane in natural gas, which in turn causes the natural gas drying coefficient to increase and the isotopes of heavy hydrocarbons such as ethane and propane to become heavier.

[0003] The isotopic composition and components of natural gas are effective means to identify the genetic type of natural gas, trace the type of natural gas generation parent material, and estimate the maturity, migration path and accumulation mechanism of natural gas. The results of the study of natural gas isotope data of important oil and gas basins in the world show that the methane isotopic composition is mainly affected by the thermal evolution maturity of the source rock, and the isotopic composition of heavy hydrocarbons such as ethane and propane mainly depends on the carbon isotopic composition of the kerogen of the hydrocarbon-generating parent material, and has an obvious source relationship with the isotopic composition of the source rock parent material (see Appendix). Figure 1 ). Traditional gas source identification methods often use the isotopic composition of heavy hydrocarbons such as ethane and propane, and the natural gas dryness coefficient as key parameters for gas source identification. However, due to the alteration effect of sulfate thermochemical reactions on high-sulfur gas reservoirs, the heavy hydrocarbon components such as ethane and propane in high-sulfur gas reservoirs have changed, the natural gas dryness coefficient has increased, and the isotopes of heavy hydrocarbon components such as ethane and propane have become heavier. As a result, the carbon isotopic composition characteristics of heavy hydrocarbons such as ethane and propane in high-sulfur natural gas are similar to those of coal-generated gas, making it difficult to effectively distinguish between coal-generated gas and oil-type gas. How to construct an identification method suitable for the genesis of high-sulfur natural gas is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for identifying the genesis of natural gas in a high-sulfur gas reservoir and its application, so as to solve the problem that the existing methods cannot effectively identify and distinguish coal-generated gas and oil-type gas.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a method for identifying the origin of natural gas in a high-sulfur gas reservoir, which comprises: step S1, determining the carbon and hydrogen isotopes and component data of the high-sulfur natural gas in the target layer, and the carbon isotopes and vitrinite reflectance data of the kerogen of the potential hydrocarbon source rock; step S2, conducting a simulation experiment of the thermochemical reduction reaction of sulfate in natural gas to determine the influencing factors of the thermochemical reduction reaction of sulfate on the carbon and hydrogen isotopes and components of natural gas isotopes; step S3, conducting a simulation experiment of hydrocarbon generation in the potential hydrocarbon source rock to determine the hydrocarbon generation factors. Factors affecting the thermal maturity of source rocks on carbon and hydrogen isotopes of natural gas and natural gas components; Step S4, selecting natural gas methane carbon and hydrogen isotopes as identification parameters based on the results of Step 2 and Step 3, and establishing an identification chart for the origin of high-sulfur natural gas with the natural gas methane carbon isotope value as the horizontal coordinate and the natural gas methane hydrogen isotope value as the vertical coordinate; Step S5, substituting the measured high-sulfur natural gas carbon and hydrogen isotope values ​​into the chart for judging the origin of high-sulfur natural gas, so as to determine the origin and thermal evolution maturity of the high-sulfur natural gas sample.

[0006] Furthermore, step S1 includes: collecting samples of high-sulfur natural gas and source rocks in the research target layer, and the collection indicators include: natural gas composition, natural gas isotope composition, natural gas hydrogen sulfide content, source rock vitrinite reflectance, and source rock kerogen isotopes, wherein the natural gas isotope data are natural gas carbon isotope data and natural gas hydrogen isotope data; according to the carbon isotope distribution pattern diagram of the high-sulfur natural gas in the research target layer, the relationship between the carbon and hydrogen isotope composition of the natural gas and the kerogen isotope composition of the potential source rock isotope is established, if the carbon and hydrogen of the heavy hydrocarbons in the natural gas are close to the carbon isotopes of the kerogen of the source rock, it means that their relationship is strong, otherwise it is far, and the relationship between the hydrogen sulfide content of the natural gas and the isotope evolution is determined through the intersection chart between the hydrogen sulfide content of the natural gas and the natural gas isotopes.

[0007] Furthermore, the natural gas isotope composition includes natural gas carbon isotopes and natural gas hydrogen isotopes, and the natural gas composition, natural gas carbon isotopes and natural gas hydrogen isotopes are all determined based on the following natural gas components: CH4, C2H6, C3H8, i-C4H 10 、n-C4H 10 、i-C5H 12 、n-C5H 12 wait.

[0008] Furthermore, step S2 includes: conducting a sulfate thermochemical reduction reaction simulation experiment on high-sulfur natural gas in the form of an experimental group and a control group, wherein sulfate is not added to the control group, and determining the hydrogen sulfide content of the high-sulfur natural gas; analyzing the relationship between the hydrogen sulfide content of the high-sulfur natural gas and the isotopic composition of the natural gas and the content of the natural gas components, and finally determining the influencing factors of the sulfate thermochemical reduction reaction on the isotopic composition of the natural gas.

[0009] Furthermore, step S2 also includes: during the sulfate thermochemical reduction reaction simulation experiment, as the reaction proceeds, the natural gas isotope composition, component content and hydrogen sulfide content in the product are measured once every 24 hours, wherein the reaction temperature of the sulfate thermochemical reduction reaction simulation experiment is 360°C.

[0010] Furthermore, step S3 includes: conducting a simulation experiment of hydrocarbon generation in source rocks to obtain isotopic composition and component data of natural gas generated at different evolutionary stages; combining the isotopic composition of natural gas in high-sulfur gas reservoirs, the intersection chart of the dry-wet ratio C1 / (C2+C3) of natural gas components and carbon and hydrogen isotopes, the carbon and hydrogen isotopes of natural gas are proportional to the dry-wet ratio C1 / (C2+C3) of natural gas components, as the dry-wet ratio C1 / (C2+C3) of natural gas components increases, the carbon and hydrogen isotopes of natural gas components become heavier, the dry-wet ratio C1 / (C2+C3) of natural gas components is also proportional to the vitrinite reflectance of the source rock, as the vitrinite reflectance increases, the dryness coefficient of natural gas increases, and the positive relationship between the thermal maturity of the source rock and the isotopic composition and components of natural gas is determined.

[0011] Furthermore, during the hydrocarbon generation simulation experiment of source rocks, the raw materials were selected from the following: (1) low-maturity humic coal - kerogen type III, with an organic carbon content greater than 50%; (2) marine shale - kerogen type I, with an organic carbon content greater than 2%; the test temperature was selected from 120°C, 240°C, 360°C, and 480°C, and as the experiment progressed, the natural gas isotope composition, component content, and hydrogen sulfide content in the product were measured every 48 hours.

[0012] Further, step S4 includes: based on the experimental data obtained from the hydrocarbon generation simulation experiment of the source rock, as the temperature increases, the thermal maturity of the source rock - the vitrinite reflectance increases, and the carbon and hydrogen isotopes of the natural gas gradually become heavier, and a recognition chart of the carbon and hydrogen isotopes of the high-sulfur natural gas in the low-maturity-high-maturity stage is constructed, wherein the ordinate is the natural gas methane hydrogen isotope δ 2 H CH4 / ‰, the horizontal axis is the carbon isotope δ of natural gas methane 13 C CH4 / ‰, the arrow indicates the evolution direction of natural gas thermal maturity from high to low, and the thermal maturity of natural gas is 0.8% to 2.0%, which represents the thermal maturity of natural gas predicted by the point data.

[0013] Furthermore, the origin of natural gas in high-sulfur gas reservoirs is determined by the following standards: when the carbon isotope of natural gas methane is between -42‰ and -28‰, and the hydrogen isotope of natural gas methane is between -240 and -160‰, the natural gas in high-sulfur gas reservoirs is coal-derived gas; when the carbon isotope of natural gas methane is between -52‰ and -38‰, and the hydrogen isotope of natural gas methane is between -240 and -160‰, the natural gas in high-sulfur gas reservoirs is oil-type gas; when the carbon and hydrogen isotopes of natural gas methane are between the two, it is a mixture of high-sulfur coal-derived gas and oil-type gas.

[0014] According to another aspect of the present invention, there is also provided an application of the above-mentioned method for identifying the genesis of natural gas in high-sulfur gas reservoirs in the field of oil and gas exploration.

[0015] The technical scheme of the present invention is applied, based on the carbon and hydrogen isotope composition and components of high-sulfur natural gas, hydrogen sulfide content, and source rock kerogen isotope data analysis, to systematically evaluate the influence of source rock parent material type, source rock thermal maturity, and sulfate thermochemical reduction reaction on natural gas isotopes. According to the natural gas distribution model, the relationship between source rock parent material type and natural gas isotopes is established, and sulfate thermochemical reduction reaction experiments are carried out to quantitatively evaluate the influencing factors of sulfate thermochemical reduction reaction on natural gas isotope composition and components. At the same time, hydrocarbon generation simulation experiments of source rocks are carried out to further clarify the relationship between thermal maturity and natural gas isotope composition and components. Based on the above research results, key parameters are optimized and a high-sulfur natural gas genesis identification chart is constructed. This method fills the defect that the genesis of high-sulfur natural gas is difficult to identify, provides a basis for the identification of the genesis of natural gas in high-sulfur gas reservoirs, and lays a solid foundation for the study of natural gas migration, accumulation, and accumulation mechanism in high-sulfur gas reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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:

[0017] Figure 1 It is a diagram of the natural gas distribution pattern;

[0018] Figure 2 This is a comparative table of carbon isotopes of global natural gas source rocks;

[0019] Figure 3 This is the cross plot of ethane carbon isotope and hydrogen sulfide content;

[0020] Figure 4 It is the cross-plot of natural gas dry-wet ratio and methane;

[0021] Figure 5 is the relationship between methane isotope and reaction time;

[0022] Figure 6 This is a chart for identifying high-sulfur natural gas. DETAILED DESCRIPTION

[0023] 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 in conjunction with the embodiments.

[0024] As described in the background technology, the existing methods cannot effectively identify and distinguish between coal-generated gas and oil-generated gas. In order to solve the above technical problems, this application provides a method for identifying the origin of natural gas in high-sulfur gas reservoirs, including:

[0025] Step S1, determining the carbon and hydrogen isotope and component data of the high-sulfur natural gas in the target layer, and the carbon isotope and vitrinite reflectance data of the kerogen of the potential source rock;

[0026] Step S2, conducting a simulation experiment of the thermochemical reduction reaction of sulfate in natural gas to determine the influencing factors of the thermochemical reduction reaction of sulfate on the isotopes and components of natural gas;

[0027] Step S3, conducting a hydrocarbon generation simulation experiment of source rocks to determine the factors affecting thermal maturity on natural gas composition and natural gas isotopes;

[0028] Step S4, selecting the carbon and hydrogen isotopes of natural gas methane as identification parameters according to the results of step 2 and step 3, and establishing an identification chart of the origin of the high-sulfur natural gas source with the carbon isotope value of natural gas methane as the horizontal coordinate and the hydrogen isotope value of natural gas methane as the vertical coordinate;

[0029] Step S5, substituting the measured methane carbon and hydrogen isotope values ​​of the high-sulfur natural gas into a plate for determining the origin of the high-sulfur natural gas source, so as to determine the origin and thermal evolution maturity of the high-sulfur natural gas sample.

[0030] Aiming at the difficulty in identifying the genesis of high-sulfur natural gas in carbonate-gypsum rock symbiosis system, based on the carbon and hydrogen isotope composition and components of high-sulfur natural gas, hydrogen sulfide content, and source rock kerogen isotope data analysis, the influence of source rock parent material type, source rock thermal maturity, and sulfate thermochemical reduction reaction on natural gas isotopes is systematically evaluated. According to the natural gas distribution model, the relationship between source rock parent material type and natural gas isotopes is established. Sulfate thermochemical reduction reaction experiments are carried out to quantitatively evaluate the influence of sulfate thermochemical reduction reaction on natural gas isotope composition and components. At the same time, source rock hydrocarbon generation simulation experiments are carried out to further clarify the relationship between thermal maturity and natural gas isotope composition and components. Based on the above research results, key parameters are optimized and a high-sulfur natural gas genesis identification chart is constructed. This method fills the defect that the genesis of high-sulfur natural gas is difficult to identify, provides a basis for the identification of the genesis of natural gas in high-sulfur gas reservoirs, and lays a solid foundation for the study of natural gas migration, accumulation, and accumulation mechanism in high-sulfur gas reservoirs. In particular, it provides additional evidence to prove whether low-abundance source rocks in the carbonate-gypsum salt system can generate hydrocarbons on a large scale.

[0031] Step S1: Develop the natural gas components and isotopic composition of high-sulfur gas reservoirs in carbonate rock-gypsum salt rock system.

[0032] Samples of high-sulfur natural gas and source rocks in the target layer are collected. The collection indicators include: natural gas composition, natural gas isotope composition, natural gas hydrogen sulfide content, source rock maturity, and source rock kerogen isotope. The natural gas isotope data include natural gas carbon isotope data and natural gas hydrogen isotope data.

[0033] According to the distribution pattern of carbon and hydrogen isotopes of high-sulfur natural gas in the target layer (such as Figure 1 ), establish the relationship between the carbon and hydrogen isotope composition of the natural gas and the isotope composition of the potential source rock kerogen (as shown in Figure 2 If the carbon and hydrogen isotopes of the natural gas heavy hydrocarbons are close to those of the source rock kerogen, it means that their relationship is strong, otherwise it is far, and the intersection chart between the natural gas hydrogen sulfide content and the natural gas isotopes (such as Figure 3 (as shown), determine the relationship between the hydrogen sulfide content in natural gas and its isotopes.

[0034] Furthermore, the natural gas isotope composition includes natural gas carbon isotopes and natural gas hydrogen isotopes, and the natural gas composition, natural gas carbon isotopes and natural gas hydrogen isotopes are all determined based on the following components: CH4, C2H6, C3H8, i-C4H 10 、n-C4H 10 、i-C5H 12 、n-C5H 12 wait.

[0035] The natural gas components were analyzed using a CP3800Ⅱ three-channel gas chromatograph produced by Varian, USA.

[0036] The carbon isotope analysis instrument is the DeltaPlusXP gas isotope mass spectrometer produced by Thermo Fisher Scientific.

[0037] Step S2: Conduct a simulation experiment of sulfate thermochemical reduction reaction to clarify the factors affecting the composition and properties of natural gas by sulfate reduction reaction.

[0038] A simulation experiment of sulfate thermochemical reduction reaction was carried out on high-sulfur natural gas in the form of an experimental group and a control group, wherein sulfate was not added to the control group, and the hydrogen sulfide content of the high-sulfur natural gas was determined;

[0039] The relationship between the hydrogen sulfide content of high-sulfur natural gas and the isotopic composition and components of natural gas is analyzed, and finally the influencing factors of sulfate thermochemical reduction reaction on the isotopic composition of natural gas are determined.

[0040] In a preferred embodiment, during the first test, the experimental group is composed of light oil (10 mg), magnesium sulfate (600 mg) and pure water (100 mg), and the control group is composed of crude oil (10 mg) and pure water (100 mg); during the second test, the experimental group is composed of standard gas sample (13.5 ml), magnesium sulfate (600 mg) and pure water (10 mg); the control group is composed of standard gas sample (13.5 ml) and pure water (10 mg); experimental temperature: 360°C; as the reaction proceeds, the natural gas isotope composition, component content and hydrogen sulfide content in the product are determined every 24 hours, for example, the reaction time is: 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours.

[0041] Reference for the simulation experiment of the thermochemical reduction reaction of sulfate: Zhang Yonghan, Simulation experiment and kinetic study of the thermochemical sulfate reduction reaction of crude oil and sulfate, Journal of Sedimentary Research, Vol. 29, No. 5: 994-999.

[0042] Step S3: Conduct source rock hydrocarbon generation simulation experiments to clarify the factors affecting thermal maturity on natural gas composition and isotopes.

[0043] Including: conducting hydrocarbon generation simulation experiments on source rocks to obtain isotopic composition and component data of natural gas generated at different evolutionary stages; combining the isotopic composition of natural gas in high-sulfur gas reservoirs, the intersection chart of the dry-wet ratio C1 / (C2+C3) of natural gas components and carbon and hydrogen isotopes ( Figure 4), the carbon and hydrogen isotopes of natural gas are proportional to the dry-wet ratio C1 / (C2+C3) of natural gas components. As the dry-wet ratio C1 / (C2+C3) of natural gas components increases, the carbon and hydrogen isotopes of natural gas become heavier. The dry-wet ratio C1 / (C2+C3) of natural gas components is also proportional to the vitrinite reflectance of source rock. As the vitrinite reflectance increases, the dryness coefficient of natural gas increases, which determines the positive relationship between the thermal maturity of source rock and the isotopic composition and components of natural gas.

[0044] References for hydrocarbon generation simulation experiment of source rocks: Yang Hua, Zhang Wenzheng, Zan Chuanli, et al., Geochemical characteristics of Ordovician subsalt natural gas in the eastern Ordos Basin and its re-understanding of the gas source of Jingbian gas field, Natural Gas Geoscience, Vol. 20, No. 1: 9-14.

[0045] In a preferred embodiment, in the first experiment, a source rock hydrocarbon generation simulation experiment was carried out using low-mature humic coal-kerogen type III, with an organic carbon content greater than 50% as coal rock, and a control group used low-mature coal (100 mg) + magnesium sulfate (600 mg) as raw materials; in the second experiment, a source rock hydrocarbon generation simulation experiment was carried out using marine mud shale-kerogen type I, with an organic carbon content greater than 2% as mud shale, and a control group used marine mud shale (100 mg) + magnesium sulfate (600 mg) as raw materials; the test temperature was selected from 120°C, 240°C, 360°C, and 480°C, and as the experiment progressed, the natural gas isotope composition, component content and hydrogen sulfide content in the product were determined every 48 hours.

[0046] Step S4: Optimize the carbon and hydrogen isotopes of natural gas methane as key parameters and establish a high-sulfur natural gas source comparison chart.

[0047] Based on the above experimental analysis results, combined with the fitting relationship between the isotopic composition, components and hydrogen sulfide content of high-sulfur natural gas, it is confirmed that the sulfate thermochemical reduction reaction has a greater impact on the natural gas dryness coefficient, ethane and other heavy hydrocarbon isotopes, while the methane isotope has a smaller impact. The natural gas isotopes with a positive carbon sequence are proportional to the maturity. With the increase of the maturity of the source rock, the methane isotopes gradually become heavier.

[0048] Step S4 includes: According to the experimental data obtained from the hydrocarbon generation simulation experiment of the source rock, as the temperature increases, the thermal maturity of the source rock - the vitrinite reflectance increases, and the carbon and hydrogen isotopes of the natural gas gradually become heavier (such as Figure 5 As shown in the figure), a recognition chart of carbon and hydrogen isotopes of high-sulfur natural gas in the low-maturity to high-maturity stage was constructed (as shown in the figure). Figure 6 As shown), the ordinate is the natural gas methane hydrogen isotope δ 2 H CH4 / ‰, the horizontal axis is the carbon isotope δ of natural gas methane 13 CCH4 / ‰, the arrow indicates the evolution direction of natural gas thermal maturity from high to low, and the thermal maturity of natural gas is 0.8% to 2.0%, which represents the thermal maturity of natural gas predicted by the point data.

[0049] Specifically, ① the gas source identification parameters of high-sulfur natural gas are preferred: the source rock has a positive carbon sequence carbon isotope (C1<C2<C3) in the low-maturity-mature stage. Under the same thermal evolution maturity, the methane carbon isotope of coal-derived gas is -10% lighter than that of coal-derived gas, and the methane carbon isotope of coal-derived gas is mainly between -42‰ and -28‰. The methane carbon isotope of oil-type gas is mainly between -52‰ and -38‰. The methane hydrogen isotope of coal-derived gas is heavier than that of oil-type gas, and the methane hydrogen isotope of coal-derived gas is between -240‰ and -160‰, and the methane hydrogen isotope of oil-type gas is between -180‰ and -100‰. Therefore, the carbon and hydrogen isotopes of natural gas methane are used as the main identification parameters.

[0050] ②Construction of a genetic identification chart for high-sulfur natural gas: Based on the natural gas isotope evolution law of source rock hydrocarbon generation simulation experiments and the evolution relationship between natural gas isotopes and thermal maturity in typical oil and gas basins, a genetic identification chart for high-sulfur natural gas with carbon and hydrogen isotopes in the low-maturity to high-maturity stage was constructed. The vertical axis is the natural gas methane hydrogen isotope (δ 2 H CH4 / ‰), the horizontal axis is the carbon isotope of natural gas methane (δ 13 C CH4 / ‰), the arrow indicates the evolution direction of natural gas thermal maturity from high to low, and the thermal maturity of natural gas is 0.8% to 2.0%, which represents the thermal maturity of natural gas predicted by the injection point data.

[0051] Preferably, the origin of the natural gas in the high-sulfur gas reservoir is determined by the following standards: when the carbon isotope of the natural gas methane is between -42‰ and -28‰, and the hydrogen isotope of the natural gas methane is between -240 and -160‰, the natural gas in the high-sulfur gas reservoir is coal-generated gas; when the carbon isotope of the natural gas methane is between -52‰ and -38‰, and the hydrogen isotope of the natural gas methane is between -240 and -160‰, the natural gas in the high-sulfur gas reservoir is oil-type gas.

[0052] The second aspect of the present application also provides an application of the above-mentioned method for identifying the origin of natural gas in high-sulfur gas reservoirs in the field of oil and gas exploration.

[0053] The method for identifying the origin of high-sulfur natural gas provided in the present application adopts a simple, effective and rapid identification plate for the origin of natural gas, with the methane carbon and hydrogen isotopes of natural gas as the main identification parameters. The method of mutual reference of the methane carbon and hydrogen isotopes of natural gas is used to determine the origin of natural gas. According to the location of the injection point, it can be determined whether the origin type of natural gas is coal-generated gas or oil-generated gas. Secondly, the thermal evolution maturity of the natural gas can be determined, thereby clarifying the thermal evolution stage experienced by the oil and gas reservoir.

[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0055] The above description is only a preferred embodiment of the present invention and is 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 the origin of natural gas in a high-sulfur gas reservoir, characterized in that: The method for identifying the genesis of the natural gas in the high-sulfur gas reservoir comprises: Step S1, determining the carbon and hydrogen isotope and component data of the high-sulfur natural gas in the target layer, and the kerogen isotope and vitrinite reflectance data of the potential source rock; Step S2, conducting a simulation experiment of the thermochemical reduction reaction of sulfate in natural gas to determine the influencing factors of the thermochemical reduction reaction of sulfate on the carbon and hydrogen isotopes and components of the natural gas; Step S3, conducting a simulation experiment of hydrocarbon generation of potential source rocks to determine the factors affecting the thermal maturity of source rocks on the carbon and hydrogen isotopes of natural gas and the composition of natural gas; Step S4, selecting the carbon and hydrogen isotopes of natural gas methane as identification parameters according to the results of step 2 and step 3, and establishing an identification chart of the origin of the high-sulfur natural gas source with the carbon isotope value of natural gas methane as the horizontal coordinate and the hydrogen isotope value of natural gas methane as the vertical coordinate; Step S5, substituting the measured methane carbon and hydrogen isotope values ​​of the high-sulfur natural gas into the identification plate of the gas source genesis of the high-sulfur natural gas to determine the genesis and thermal evolution maturity of the high-sulfur natural gas sample.

2. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 1, characterized in that: Step S1 includes: Samples of high-sulfur natural gas and source rock in the target layer are collected, and the collection indicators include: natural gas composition, natural gas isotope composition, natural gas hydrogen sulfide content, source rock vitrinite reflectance, source rock kerogen isotope, wherein the natural gas isotope data are natural gas carbon isotope data and natural gas hydrogen isotope data; According to the carbon isotope distribution pattern of the high-sulfur natural gas in the research target layer, the relationship between the carbon and hydrogen isotope composition of the natural gas and the isotope composition of the potential source rock kerogen isotope is established. If the carbon isotope of the heavy hydrocarbon carbon in the natural gas is close to that of the source rock kerogen, it means that their relationship is strong, otherwise it is distant. The relationship between the hydrogen sulfide content of the natural gas and the isotope evolution is determined by the intersection chart between the hydrogen sulfide content of the natural gas and the natural gas isotopes.

3. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 2, characterized in that: The natural gas isotope composition includes natural gas carbon isotopes and natural gas hydrogen isotopes, and the natural gas composition, the natural gas carbon isotopes and the natural gas hydrogen isotopes are all determined based on the following natural gas components: CH4, C2H6, C3H8, i-C4H 10 、n-C4H 10 、i-C5H 12 、n-C5H 12 wait.

4. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 1, characterized in that: The step S2 comprises: Conducting a sulfate thermochemical reduction reaction simulation experiment on the high-sulfur natural gas in the form of an experimental group and a control group, wherein sulfate is not added to the control group, and determining the hydrogen sulfide content of the high-sulfur natural gas; The relationship between the hydrogen sulfide content of the high-sulfur natural gas and the isotopic composition and component content of the natural gas is analyzed, and finally the influencing factors of the sulfate thermochemical reduction reaction on the isotopic composition of the natural gas are determined.

5. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 4, characterized in that: The step S2 also includes: during the sulfate thermochemical reduction reaction simulation experiment, as the reaction proceeds, the natural gas isotope composition, component content and hydrogen sulfide content in the product are measured once every 24 hours, wherein the reaction temperature of the sulfate thermochemical reduction reaction simulation experiment is 360°C.

6. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to any one of claims 1 to 5, characterized in that: The step S3 comprises: Carry out the hydrocarbon generation simulation experiment of the source rock to obtain the isotopic composition and component data of the natural gas generated at different evolution stages; Combined with the intersection chart of natural gas isotope composition, dry-wet ratio C1 / (C2+C3) of natural gas components and carbon and hydrogen isotopes of high-sulfur gas reservoirs, the carbon and hydrogen isotopes of natural gas are proportional to the dry-wet ratio C1 / (C2+C3) of natural gas components. As the dry-wet ratio C1 / (C2+C3) of natural gas components increases and the carbon and hydrogen isotopes of natural gas become heavier, the dry-wet ratio C1 / (C2+C3) of natural gas components is also proportional to the vitrinite reflectance of source rocks. As the vitrinite reflectance increases, the dryness coefficient of natural gas increases, and the positive relationship between the thermal maturity of source rocks and the isotopic composition and components of natural gas is determined.

7. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 6, characterized in that: During the hydrocarbon generation simulation experiment of source rocks, the raw materials are selected from the following: (1) Low-maturity humic coal—kerogen type III, with an organic carbon content greater than 50%; (2) Marine shale—kerogen type I, with an organic carbon content greater than 2%; The test temperature is selected from 120°C, 240°C, 360°C, and 480°C, and as the experiment proceeds, the natural gas isotopic composition, component content, and hydrogen sulfide content in the product are measured every 48 hours.

8. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 1, characterized in that: The step S4 comprises: according to the experimental data obtained from the hydrocarbon generation simulation experiment of the source rock, as the temperature rises, the thermal maturity of the source rock - the vitrinite reflectance increases, and the carbon and hydrogen isotopes of the natural gas gradually become heavier, and a recognition plate of the mutual reference of the carbon and hydrogen isotopes of methane in the high-sulfur natural gas in the low-maturity-high-maturity stage is constructed, wherein the ordinate is the hydrogen isotope δ 2 H CH4 / ‰, the horizontal axis is the carbon isotope δ of natural gas methane 13 C CH4 / ‰, the arrow indicates the evolution direction of natural gas thermal maturity from high to low, and the thermal maturity of natural gas is 0.8% to 2.0%, which represents the thermal maturity of natural gas predicted by the point data.

9. The method for identifying the origin of natural gas in a high-sulfur gas reservoir according to claim 8, characterized in that: The origin of the natural gas in the high-sulfur gas reservoir is determined by the following criteria: When the carbon isotope of natural gas methane is between -42‰ and -28‰, and the hydrogen isotope of natural gas methane is between -240‰ and -160‰, the natural gas in the high-sulfur gas reservoir is coal-derived gas; When the carbon isotope of natural gas methane is between -52‰ and -38‰, and the hydrogen isotope of natural gas methane is between -240‰ and -160‰, the natural gas in the high-sulfur gas reservoir is oil-type gas; When the carbon and hydrogen isotopes of natural gas methane are between the two, it is a mixture of high-sulfur coal-derived gas and oil-type gas.

10. Application of the method for identifying the origin of natural gas in high-sulfur gas reservoirs according to any one of claims 1 to 9 in the field of oil and gas exploration.

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