A method of restoring complex hydrocarbon accumulation processes

Abstract

The present application relates to the field of oil and gas exploration and development, and particularly relates to a method for restoring the process of oil and gas accumulation, which comprises the following steps: collecting core, crude oil and natural gas samples and preparing test samples, testing the components and carbon isotopes of the natural gas samples, analyzing the gas chromatogram and chromatograph-mass spectrometer of the crude oil samples, determining the source and origin of the oil and gas, observing the diagenesis of the core double-side polished thin section under a microscope and testing by scanning electron microscope, establishing the diagenetic evolution sequence, determining the oil and gas accumulation events and time according to the fluorescence observation and laser Raman test of fluid inclusions, combining the regional burial history and thermal history, and finally establishing the process of oil and gas accumulation by comprehensively considering the hydrocarbon source rock generation and expulsion history, oil and gas accumulation events and accumulation time. The method comprehensively considers the hydrocarbon source rock generation and expulsion history, diagenetic evolution history and oil and gas accumulation factors, fully and accurately restores the complex process of oil and gas accumulation, and provides accurate data basis for subsequent research and development.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development, and in particular to a method for restoring the oil and gas accumulation process, which can better guide oil and gas exploration and development. Background Technology

[0002] Establishing the hydrocarbon accumulation process is a crucial step in developing hydrocarbon accumulation models, analyzing key control factors, and evaluating favorable exploration zones. Complex hydrocarbon accumulation refers to reservoirs with high source rock maturity and where the accumulation process involves late-stage thermal cracking of crude oil and / or natural gas washing. For such reservoirs, due to the complexity of their hydrocarbon sources and the potential involvement of late-stage thermal cracking of crude oil and natural gas washing during accumulation, simply studying the natural gas accumulation process is insufficient and inaccurate. This leads to flawed hydrocarbon accumulation models, potentially resulting in reduced efficiency in subsequent oil and gas exploration and production, or even exploration / production failure.

[0003] During the formation of hydrocarbon reservoirs in continental tight sandstone, crude oil and natural gas usually undergo secondary changes. For example, late-stage natural gas can wash out early-stage crude oil. Furthermore, in areas with high-maturity source rocks, early-stage crude oil may undergo thermal cracking, forming bitumen and natural gas.

[0004] Therefore, a comprehensive analysis of the genesis of crude oil, natural gas, and bitumen should be conducted to identify complete hydrocarbon accumulation events. Then, by combining regional burial history, thermal history, and homogenization temperature of inclusions, the accumulation time should be determined, and finally, the hydrocarbon accumulation process should be reconstructed. Only by obtaining hydrocarbon accumulation process analysis results through this method can we accurately reflect hydrocarbon accumulation events and their timing, and precisely guide the efficient exploration and development of relevant oil and gas resources. Summary of the Invention

[0005] The purpose of this invention is to address the problem of insufficient and incomplete research on hydrocarbon accumulation processes in areas with complex hydrocarbon accumulation processes, by providing a method for reconstructing hydrocarbon accumulation processes. This method can comprehensively and effectively determine hydrocarbon accumulation events and their timing, providing valuable guidance for oil and gas exploration and development.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for reconstructing hydrocarbon accumulation processes includes the following steps:

[0008] S1. Sample collection and preparation: Select core samples, crude oil samples, natural gas samples, and source rock samples collected in the field from drilled wells in the study area. Prepare the core samples into double-sided polished thin sections and scanning electron microscope samples; preferably, the source rock samples collected in the field are outcrop source rock samples.

[0009] S2. Sample Testing: Component and carbon isotope testing of natural gas samples; gas chromatography and chromatography-mass spectrometry analysis of crude oil samples; microscopic observation of diagenesis, fluorescence microscopy, and laser Raman testing of double-sided polished thin sections; and scanning electron microscopy testing of scanning electron microscope samples.

[0010] S3. Establish the diagenetic evolution sequence: Based on the microscopic observation results of diagenesis and the scanning electron microscope test results, establish the diagenetic evolution sequence.

[0011] S4. Identify hydrocarbon accumulation events:

[0012] Determining the origin and source of natural gas by analyzing its composition and carbon isotope characteristics;

[0013] The origin and source of crude oil were determined by analyzing the components of crude oil samples and the results of gas chromatography and chromatography-mass spectrometry.

[0014] By performing laser Raman spectroscopy on double-sided polished thin sections, the composition of natural gas and the origin of bitumen can be determined based on the laser Raman spectroscopy results.

[0015] By combining the diagenetic evolution sequence obtained from S3 with the observation results under a fluorescence microscope, the hydrocarbon accumulation events were determined.

[0016] S5. Establish the burial history, thermal history, and hydrocarbon source rock generation and expulsion history:

[0017] The regional burial and thermal histories were established using basin simulation software, and the hydrocarbon generation and expulsion histories of source rocks were established through thermal simulation experiments using source rock samples collected in the field.

[0018] S6. Determine the time of hydrocarbon accumulation: Based on the burial history and thermal history obtained in S5, combined with the results of fluid inclusion homogenization temperature test and salinity test, determine the time of hydrocarbon accumulation.

[0019] S7. Establish the hydrocarbon accumulation process: Based on the hydrocarbon accumulation events determined in S4, combined with the hydrocarbon generation and expulsion history of the source rocks obtained in S5 and the hydrocarbon accumulation time obtained in S6, establish the hydrocarbon accumulation process.

[0020] This invention provides a method for reconstructing hydrocarbon accumulation processes, applicable to the study of complex hydrocarbon accumulation processes. By analyzing and determining the source and genesis of hydrocarbons, establishing the diagenetic evolution sequence, and combining regional burial history and thermal history, it identifies hydrocarbon accumulation events and their timing. Finally, it integrates the hydrocarbon generation and expulsion history of source rocks, hydrocarbon accumulation events, and accumulation timing to establish the hydrocarbon accumulation process. This method integrates multiple factors, including the hydrocarbon generation and expulsion history of source rocks, diagenetic evolution, and hydrocarbon accumulation, facilitating a comprehensive and accurate reconstruction of complex hydrocarbon accumulation processes. It provides an accurate data foundation for subsequent evaluation of key regional hydrocarbon accumulation factors and favorable exploration zones.

[0021] The step numbers in the method of this invention are only for the convenience of describing the technical solution of this invention, and are not intended as a specific order of steps. Those skilled in the art can adjust the implementation order according to the interdependence between each step, as long as the corresponding detection and analysis purpose can be achieved.

[0022] Furthermore, in S1, the source rock sample collected from the field outcrop is an immature sample, and sample R... o Less than 0.5%. Vitreous reflectance (R o vitrinite reflectance (R0) is an important indicator characterizing the maturity of source rocks. The maturity of organic matter in source rocks of a basin directly relates to whether oil and gas can be generated, and is one of the key evaluation factors for oil and gas resources within the basin. o When the content is ≤0.5%, the organic matter is in an immature stage, and only immature source rocks can be used to conduct a complete study of the hydrocarbon generation and expulsion history of the source rocks. If the source rocks are in a mature stage, only the generation and expulsion history after the mature stage can be simulated. In particular, source rocks in the over-mature stage no longer generate oil and gas and cannot be used for hydrocarbon generation and expulsion history studies at all.

[0023] Furthermore, in S2, laser Raman testing refers to the testing of natural gas inclusions, bituminous inclusions, and bituminous veins in double-sided polished thin sections using a laser Raman spectrometer. Laser Raman testing can conveniently determine the types of ions and molecules and the structure of substances, enabling accurate identification and qualitative analysis of natural gas inclusions, bituminous inclusions, and bituminous veins in double-sided polished thin sections.

[0024] Furthermore, in S4, the origin and source of natural gas are determined by the composition and carbon isotope characteristics of the natural gas, using the identification chart proposed by Dai Jinxing in 1994. The identification chart proposed by Dai Jinxing in 1994 is the most widely used and recognized chart in the industry, and it can also be combined with other charts for comprehensive identification.

[0025] Furthermore, in S4, the analysis of asphalt formation using laser Raman spectroscopy results is performed by using the conversion formula proposed by Liu Dehan in 2009 to calculate the parameters of the laser Raman spectrum.

[0026] Furthermore, in S5, the basin simulation software is PetroMod. The regional burial history and thermal history are generated through simulation using PetroMod software, which is the most widely used advanced oil and gas system simulation software in the industry.

[0027] Furthermore, in S6, double-sided polished thin sections are used to perform homogenization temperature and salinity tests on fluid inclusions, obtaining the results. The order of these tests can be adjusted. If they are performed after microscopic observation of diagenesis, microscopic fluorescence, and laser Raman spectroscopy, then the double-sided polished thin sections obtained after microscopic observation can be used. If the homogenization temperature and salinity tests are performed before or simultaneously with the microscopic observation tests, then double-sided polished thin sections need to be prepared separately.

[0028] Furthermore, in S6, the method for determining the hydrocarbon accumulation time is as follows: the homogenization temperature of fluid inclusions is combined with the diagenetic sequence to divide the hydrocarbon accumulation into stages, and the average homogenization temperature data of each stage is plotted on the burial history map to obtain the accumulation time. By combining the diagenetic sequence division into stages with the burial history study, the accumulation time corresponding to the hydrocarbon accumulation event can be accurately determined, which is beneficial for subsequent accurate analysis and research on hydrocarbon quality and exploitation potential.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. This invention targets regions with complex hydrocarbon accumulation processes, determining the genesis and timing of hydrocarbon accumulation, and comprehensively reconstructing the hydrocarbon accumulation process by combining the hydrocarbon generation and expulsion history and diagenetic evolution history of source rocks. By comprehensively utilizing multiple research factors, it can accurately analyze and determine the hydrocarbon accumulation process in complex areas, which is of great significance for analyzing, predicting, and identifying favorable exploration areas and guiding oil and gas development.

[0031] 2. Compared with previous research methods, the method of this invention fully integrates the entire process of hydrocarbon formation, including its genesis and source, accumulation process, crude oil thermal cracking, and natural gas washing, to conduct hydrocarbon accumulation research. This improves the accuracy of hydrocarbon accumulation process reconstruction and provides an accurate data foundation for the establishment of subsequent hydrocarbon accumulation models and the determination of the main controlling factors of hydrocarbon accumulation. It has good applicability. Attached Figure Description

[0032] Figure 1 The flowchart provided by this invention illustrates the process of restoring hydrocarbon accumulation.

[0033] Figure 2 It is the diagenetic evolution sequence of the Xusan Member in the CX Depression of the Sichuan Basin.

[0034] Figure 3This study compares the gas sources of natural gas and hydrocarbon source rock from the Xusan Formation in the CX Depression of the Sichuan Basin.

[0035] Figure 4 It is a diagram for identifying the genesis of natural gas proposed by Dai Jinxing in 1994.

[0036] Figure 5 This is a cross-plot of the carbon isotope composition of methane and the C1 / (C2+C3) ratio, used for binding. Figure 4 A comprehensive assessment of the origin of natural gas was conducted.

[0037] Figure 6 It refers to the laser Raman test object and test location containing asphaltene inclusions.

[0038] Figure 7 yes Figure 6 The laser Raman spectroscopy of the asphalt inclusions shown in the figure revealed that its composition was asphalt + CH4, exhibiting typical gas washing characteristics, indicating that the asphalt in this area was formed by crude oil undergoing gas washing.

[0039] Figure 8 The oil inclusions consist of a three-phase mixture of gas (CH4 + light hydrocarbons), liquid (liquid hydrocarbons), and solid (asphalt), indicating that the crude oil in this area underwent thermal cracking after being captured early on. (Where a and b are single-polarized micrographs, and c is a fluorescence micrograph.)

[0040] Figure 9 It is the burial history, thermal history, hydrocarbon generation and expulsion history, and hydrocarbon accumulation process of the Xusan Formation in the CX Depression of the Sichuan Basin. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0042]

Example 1

[0043] The source rocks of the Xujiahe Formation III (Xujiahe III) in the CX Depression of the Sichuan Basin are type III kerogen with high maturity. o The yield is 1.8% to 2.2%. The hydrocarbon accumulation process is complex, and whether the hydrocarbon accumulation process can be clearly defined is one of the main factors restricting the exploration progress.

[0044] A method for reconstructing complex hydrocarbon accumulation processes, with a flowchart of the reconstructed hydrocarbon accumulation process as shown below. Figure 1 As shown, the specific steps include:

[0045] Step 1: Sample Collection and Preparation: Five natural gas samples from the Xusan Formation of the CX Depression in the Sichuan Basin were collected for component and carbon isotope analysis, as well as light hydrocarbon component analysis. Crude oil samples were also collected for chromatographic and chromatographic-mass spectrometric analysis. Forty-two core samples were collected and prepared into double-sided polished thin sections and scanning electron microscope samples for diagenetic observation, scanning electron microscopy observation, and fluid inclusion system analysis.

[0046] Step 2, Sample Testing: Natural gas samples are subjected to component and carbon isotope testing; crude oil samples are subjected to gas chromatography and chromatography-mass spectrometry analysis; double-sided polished thin sections are subjected to diagenesis observation, fluorescence observation, and laser Raman testing under a microscope; and scanning electron microscopy samples are subjected to scanning electron microscopy testing.

[0047] Step 3: Establishing the diagenetic evolution sequence: Based on the microscopic observations of diagenesis and the results of scanning electron microscopy, a diagenetic evolution sequence is established. The results are as follows: Figure 2 As shown.

[0048] Step 4: Determine the hydrocarbon accumulation event: Determine the origin and source of natural gas by analyzing its composition and carbon isotope characteristics; determine the origin and source of crude oil by analyzing its composition and gas chromatography and chromatography-mass spectrometry results; determine the composition of natural gas and the origin of bitumen by laser Raman spectroscopy results; and finally determine the hydrocarbon accumulation event by combining the diagenetic evolution sequence and the results of microscopic fluorescence observation.

[0049] The results indicate that the three phases of natural gas and oil injection in the Xusan Member of the CX Depression in the Sichuan Basin all originated from the hydrocarbon source rocks within the Xusan Member, such as... Figure 3 As shown. The natural gas is formed from kerogen cracking gas, such as... Figure 4 , Figure 5 As shown. Furthermore, crude oil undergoes early gas washing to form asphalt, such as... Figure 6 , Figure 7 As shown, the peak positions of the laser Raman spectrum are 1344, 1581, 2694, 2944, and 3247 cm⁻¹. -1 The peak is characteristic of asphalt, with a spectral peak position of 2913 cm⁻¹. -1 The characteristic peak of CH4; Raman reflectance calculation formula: R o % = 0.0537d(GD) - 11.21, Figure 7 The D and G peaks have been marked.

[0050] Laser Raman spectral analysis results

[0051]

[0052] Microscopic fluorescence observation of double-sided polished thin sections indicates that late-stage thermal cracking of the source rock produced bitumen and natural gas. Specific sample photographs are shown below. Figure 8 As shown.

[0053] The final determination of the hydrocarbon accumulation events in the Xusan Member of the CX Depression in the basin includes: the early stage was the first phase of crude oil and the first phase of natural gas charging, with some crude oil undergoing gas washing; the middle stage was the second phase of natural gas charging; and the late stage was the third phase of natural gas charging, with the early crude oil beginning to thermally crack to form bitumen and natural gas.

[0054] Step 5: Establish the burial history, thermal history, and hydrocarbon generation and expulsion history of source rocks: Low-maturity oil and natural gas were generated in the Early Jurassic to Early Cretaceous, and a large amount of high-maturity gas was generated in the Early Cretaceous to Late Cretaceous.

[0055] Step 6: Determine the hydrocarbon accumulation time and reconstruct the hydrocarbon accumulation process: Combine the hydrocarbon generation and expulsion history of the study area, hydrocarbon accumulation events, and hydrocarbon charging time and phases to comprehensively analyze the dynamic hydrocarbon accumulation process.

[0056] The process of hydrocarbon accumulation can be divided into three stages:

[0057] ① Early to Middle Jurassic-Early Cretaceous: Source rocks were in a low-maturity stage, R o The range is 0.5% to 1.5%, generating low-maturity crude oil and natural gas. The oil and gas are driven by the self-sourced high pressure generated by hydrocarbon generation in the source rock to inject into the adjacent reservoir, and the crude oil injected in the early stage undergoes gas washing.

[0058] ② Early Cretaceous to Late Cretaceous: Source rocks were in a medium to high maturity stage, R o The range is 1.5% to 2.0%, the reservoir begins to tighten, and only a small amount of high-maturity gas generated in the medium to high maturity stage is injected.

[0059] ③ Late Cretaceous-Late Paleogene: Source rocks were in an over-mature stage, R o The reservoir has a density of 2.0-2.2%, and is already compacted. During this stage, a very small amount of highly matured gas is injected, and the crude oil injected in the early stage is thermally cracked to form cracked gas and bitumen.

[0060] By comprehensively establishing the hydrocarbon accumulation process based on the burial history, thermal history, source rock generation and expulsion history, hydrocarbon accumulation events, and hydrocarbon accumulation time determined in the above studies, a hydrocarbon accumulation process was constructed, and the source rock generation and expulsion history, diagenetic sequence, and hydrocarbon accumulation process of the Xusan Member in the CX Depression were plotted. The results are as follows: Figure 9 As shown.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reconstructing complex hydrocarbon accumulation processes, wherein the complex hydrocarbon accumulation refers to a gas reservoir with high source rock maturity and where the hydrocarbon accumulation process involves late-stage thermal cracking of crude oil and / or natural gas washing, characterized in that, Includes the following steps: S1. Sample collection and preparation: Core samples, crude oil samples, natural gas samples, and source rock samples collected in the field from drilled wells in the study area were selected. The source rock samples collected in the field were immature samples. Core samples were prepared into double-sided polished thin sections and scanning electron microscope samples. S2. Sample testing: Perform composition and carbon isotope testing on natural gas samples; Gas chromatography and chromatography-mass spectrometry were used to analyze crude oil samples; Diagenesis was observed under a microscope, observed under a fluorescence microscope, and tested with laser Raman spectroscopy on double-sided polished thin sections. And to perform scanning electron microscopy tests on the samples; S3. Establish the diagenetic evolution sequence: Based on the microscopic observation results of diagenesis and the scanning electron microscope test results, establish the diagenetic evolution sequence; S4. Identify hydrocarbon accumulation events: The genesis and origin of natural gas were determined by analyzing its composition and carbon isotope characteristics, using the identification chart proposed by Dai Jinxing in 1994. The origin and source of crude oil were determined by analyzing the components of crude oil samples and the results of gas chromatography and chromatography-mass spectrometry. By performing laser Raman testing on double-sided polished thin slices, the parameters of the laser Raman spectrum were calculated using the conversion formula proposed by Liu Dehan in 2009. The composition of natural gas and the origin of asphalt were determined based on the laser Raman test results. Based on the diagenetic evolution sequence obtained from S3 and the observation results under a fluorescence microscope, hydrocarbon accumulation events were determined, including whether thermal cracking and / or gas washing occurred in each accumulation event. S5. Establish burial history, thermal history and hydrocarbon generation and expulsion history of source rocks: Establish regional burial history and thermal history through basin simulation software PetroMod, and establish hydrocarbon generation and expulsion history of source rocks by conducting thermal simulation experiments through field collection of source rock samples. S6. Determine the time of hydrocarbon accumulation: Use double-sided polished thin sections to perform fluid inclusion homogenization temperature and salinity tests. Combine the results with the burial history and thermal history obtained in S5 to determine the time of hydrocarbon accumulation. The method for determining the hydrocarbon accumulation time is as follows: the homogenization temperature of fluid inclusions is combined with the diagenetic sequence to divide the process into stages, and the average homogenization temperature data of each stage is plotted on the burial history map to obtain the accumulation time. S7. Establish the hydrocarbon accumulation process: Based on the hydrocarbon accumulation events determined in S4, combined with the hydrocarbon generation and expulsion history of the source rocks obtained in S5 and the hydrocarbon accumulation time obtained in S6, establish the hydrocarbon accumulation process.

2. The method for reconstructing complex hydrocarbon accumulation processes according to claim 1, characterized in that, In S1, the source rock samples collected in the field are outcrop source rock samples.

3. The method for reconstructing complex hydrocarbon accumulation processes according to claim 1, characterized in that, In S1, the source rock samples collected in the field are immature samples with a Ro value of less than 0.5%. When the vitrinite reflectance Ro is less than or equal to 0.5%, the organic matter is in an immature stage. Only immature source rocks can be selected to conduct a complete study on the hydrocarbon generation and expulsion history of the source rocks.

4. The method for reconstructing complex hydrocarbon accumulation processes according to claim 1, characterized in that, In S2, the laser Raman test refers to the testing of natural gas inclusions, bituminous inclusions, and bituminous veins in a double-sided polished thin film under a laser Raman spectrometer.

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