Mixed source lithologic oil and gas reservoir oil and gas migration path description and favorable zone prediction method

Abstract

The invention discloses a mixed source lithologic oil and gas reservoir oil and gas migration path description and favorable zone prediction method. The method comprises the steps that hydrocarbon source rock evaluation is carried out according to depressions and strata; carrying out source rock sedimentary environment and parent source characteristic analysis; determining a multi-pit hydrocarbon supply range; performing oil and gas source analysis on the target lithologic oil and gas reservoir; depicting an oil-gas migration path; and predicting an oil and gas favorable zone and the like. According to the method, the oil and gas source and migration path of the multi-pit and multi-layer mixed source hydrocarbon supply oil reservoir can be finely and quantitatively represented, the migration path and capability of oil and gas along each well can be determined, and the favorable reservoir forming area on the hub zone is determined according to the oil and gas transportation range so as to predict the favorable oil and gas exploration zone.

Description

Technical Field

[0001] The invention belongs to the technical field of geochemical research in the field of petroleum exploration and development, and specifically relates to a method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs. Background Art

[0002] In recent years, with the continuous improvement of the exploration level of Bohai oilfield, favorable large-scale structural traps have become less and less, and the exploration of lithologic oil and gas reservoirs has gradually become an important successor to the Bohai oilfield to increase reserves and production. Large lithologic oilfields such as Kenli 10-2 and Kenli 6-1 have been discovered in the lower Ming section in the southern Bohai Sea, with reserves exceeding 1.0×10 8 t, revealing that the shallow layer has great potential for the formation of large lithologic oil and gas fields, and lithologic traps will be the main exploration type in the Bohai Sea in the future.

[0003] After more than 60 years of exploration and development, the Bohai Bay Basin still faces some problems in oil source comparison research. First, the Bohai Bay Basin has experienced multiple periods of fault block activities, and there are multiple sets of high-quality lacustrine source rocks in the same sag. Secondly, lacustrine source rocks in different periods have similar sedimentary backgrounds and organic matter sources, and therefore show similar geochemical characteristics, which are often difficult to distinguish during oil source comparison. In addition, lacustrine source rocks are highly heterogeneous laterally, and the geochemical characteristics of shallow lake and deep lake samples of the same set of source rocks will show great differences. The traditional oil source comparison method distinguishes different source rocks based on the spectral morphology of biomarker compounds or a few biomarker compound indicators, and its reliability and work efficiency are relatively low. Taking the Bozhong Sag in the Bohai Bay Basin as an example, the area developed the Paleogene Sha III Member (E S3 )、Sha Section 1(E S1 ) source rocks and Ed3 source rocks. The source rocks of both the Shah 3 and the East 3 sections were formed in a deep lake environment under a warm and humid climate. The sedimentary environments are similar and difficult to distinguish. When the Shah 1 section was deposited, a high-salinity salinized shallow lake appeared under a dry and hot climate, so it is characterized by high gammacerane content. However, the lacustrine source rocks have strong heterogeneity and the distribution range of salinized water bodies is relatively limited. Only the "typical" samples have the characteristics of high gammacerane, and the gammacerane abundance of some "typical" samples is low, even lower than that of the samples of Shah 3 and East 3 sections. Therefore, the "typical" samples cannot represent the overall characteristics of the source rocks.

[0004] The multiple interpretations and controversial nature of oil-source correlation results bring risks to the optimization of exploration targets. Oil source research is difficult. For complex shallow oil and gas reservoirs with multiple sources of hydrocarbons, multiple periods of filling, and biodegradation, a single method of oil and gas tracing (primary migration) cannot meet the needs of detailed exploration; there is a lack of quantitative means for the study of secondary migration and accumulation processes. At present, drilling data, seismic characterization, chemical analysis, and quantitative geological modeling are mostly used in combination with exploration practice to find the enrichment rules of large-scale lithologic oil reservoirs. There has been no systematic application of geochemical methods offshore to quantitatively, finely, and systematically characterize the oil and gas migration process, which has affected the exploration and development of lithologic oil and gas reservoirs.

[0005] Therefore, developing a method for characterizing oil and gas migration paths and predicting favorable zones in complex mixed-source lithologic oil and gas reservoirs remains one of the urgent issues to be solved in this field. Summary of the invention

[0006] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a method for characterizing the oil and gas migration path and predicting favorable zones in mixed-source lithologic oil and gas reservoirs.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs comprises the following steps:

[0009] A. Evaluate source rocks by depression and stratum;

[0010] B. Analyze the sedimentary environment and parent rock characteristics of source rocks;

[0011] C. Determination of hydrocarbon supply range in multiple depressions;

[0012] D. Conduct oil and gas source analysis on target lithologic oil and gas reservoirs;

[0013] E. Characterization of oil and gas migration pathways;

[0014] F. Prediction of favorable oil and gas zones.

[0015] In the above technical solution, the specific method of evaluating source rocks by depression and stratum in step A comprises the following steps:

[0016] a1. Clarify the abundance distribution of the main source rocks and parent sources;

[0017] a2. Clarify the hydrocarbon generation potential and charging period of the study area;

[0018] a3. Comprehensively evaluate the hydrocarbon expulsion and injection capabilities of the study area.

[0019] In the above technical solution, the specific method of step a1 to clarify the abundance distribution law of the main hydrocarbon source rock and the parent source is:

[0020] First, the pyrolysis analysis, micro-component analysis, vitrinite reflectance analysis and elemental analysis experiments of the source rocks in the study area were carried out;

[0021] Then, the thermal evolution degree, maceral type and organic matter abundance of source rocks in different depressions and strata in the study area are analyzed;

[0022] Finally, the abundance distribution patterns of the main source rocks and parent sources are clarified.

[0023] In the above technical solution, the specific method of step a2 for clarifying the hydrocarbon generation potential and charging period of the study area is:

[0024] First, conduct a gold tube thermal simulation experiment;

[0025] Then, according to the oil generation window of the main source rock and the law of gas generation transformation, the hydrocarbon generation evolution model is established;

[0026] Finally, the hydrocarbon generation potential and charging period of the study area were clarified by combining the burial history and inclusion temperature measurement;

[0027] In the above technical solution, the specific method of step a3 for comprehensively evaluating the hydrocarbon expulsion capacity and charging capacity of the oil and gas in the study area is:

[0028] First, we carried out thermal pressure simulation experiments on hydrocarbon generation and expulsion, quantitative fluorescence analysis of reservoirs, and inclusion abundance analysis experiments;

[0029] Then, the hydrocarbon expulsion capacity and injection capacity of oil and gas in the study area were comprehensively evaluated based on the hydrocarbon expulsion efficiency, QGF index, and GOI parameters.

[0030] In the above technical solution, the specific method of performing source rock sedimentary environment and parent source characteristic analysis in step B comprises the following steps:

[0031] b1. Use multiple biomarker compound parameters to draw a scatter intersection diagram, analyze the source rock sedimentary environment and parent source characteristics, and screen out biomarker compound parameters with good correlation and obvious characteristics;

[0032] b2. Analyze the sedimentary environment and source characteristics of different depressions and strata in the study area to determine the key biomarker compound parameters with high discrimination;

[0033] b3. Analyze the paleoclimate environment based on trace element data, analyze the maternal source type based on isotope data, and verify the accuracy and reliability of the biomarker compound parameters screened out in step b1 and the key biomarker compound parameters determined in step b2 in the study area.

[0034] In the above technical solution, the specific method of determining the hydrocarbon supply range of multiple depressions in step C comprises the following steps:

[0035] c1. Using the key biomarker compound parameters of different depressions and different strata with high discrimination screened out in step B, cluster analysis of reservoirs in the target oilfield surrounding area is carried out to divide multiple oil groups;

[0036] c2. Draw a scatter plot of the key biomarker compound parameters of each oil group divided using step B;

[0037] c3. Combine the key biomarker compound parameter configuration characteristics of each well in each oil group to conduct oil source analysis, and conduct detailed comparative analysis on oil reservoirs that are difficult to classify due to serious source mixing;

[0038] c4. Divide the hydrocarbon supply range of multiple depressions according to the oil and gas input of the reservoirs in the target oilfield surrounding area.

[0039] In the above technical solution, the specific method of performing oil and gas source analysis of the target lithologic oil and gas reservoir in step D comprises the following steps:

[0040] d1. According to the physical properties, group components and gas chromatography experimental data of the target oil reservoir, the degree of biodegradation of crude oil, the proportion of saturated hydrocarbons and the development of light components in each well are analyzed to clarify the differences in regional oil and gas biodegradation and charging capacity;

[0041] d2. Analyze the hydrocarbon supply characteristics of each well in the target reservoir from different depressions and different layers by using cluster analysis combined with the scatter plot distribution of biomarker compounds;

[0042] d3. Analyze the biomarker compounds and isotope data of the target oil field and its surrounding reservoirs to identify reservoirs with similar origins and characteristics to the target oil field.

[0043] In the above technical solution, the specific method of describing the oil and gas migration path in step E includes the following steps:

[0044] e1. Determine the sedimentary environment of the target lithologic oil and gas reservoir using the distribution of sporopollen, ostracod fossils and trace elements;

[0045] e2. Use the effective thickness, porosity and oil column height of the reservoir sand body to evaluate the degree of oil and gas migration and flooding;

[0046] e3. According to the distribution characteristics of ancient oil reservoirs in the QGF index well-connected map combined with the distribution characteristics of oil-bearing area and faults in the current oil reservoirs, determine the migration direction of oil and gas from each depression;

[0047] e4. Conduct migration studies on each well in the target lithologic oil and gas reservoir and each well in the surrounding area, and use the regular changes in parameters to clarify the migration path and capacity of oil and gas along each well; the parameters include nitrogen-containing compound parameters, methylphenanthrene index, sterane isomerization parameters, QGF index and dibenzothiophene series parameters.

[0048] In the above technical solution, the specific method of predicting favorable oil and gas zones in step F is: according to the oil and gas migration path, the favorable areas for reservoir formation on the hub belt are identified, and prediction of favorable oil and gas zones is carried out.

[0049] The beneficial effects of the present invention are:

[0050] The present invention provides a method for characterizing the oil and gas migration path and predicting favorable zones in mixed-source lithologic oil and gas reservoirs, which can perform precise quantitative characterization of the oil and gas sources and migration paths of multi-depression and multi-layer mixed-source hydrocarbon reservoirs, clarify the oil and gas migration paths and capacities along each well, and predict favorable zones for oil and gas exploration by clarifying favorable areas for reservoir formation in hub belts based on the oil and gas transportation range. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a single depression source rock evaluation diagram in Example 1 of the present invention;

[0052] Figure 2 is a diagram showing the distribution regularity of maternal abundance in Example 1 of the present invention;

[0053] Figure 3 It is a cluster analysis diagram of oil reservoirs in the target oil field area in Example 1 of the present invention;

[0054] Figure 4 is a diagram of the lithologic oil and gas reservoir formation model in Example 1 of the present invention;

[0055] Figure 5 is C in Example 1 of the present invention 23 tricyclic terpane / hopane-sterane / hopane (S / H) intersection diagram;

[0056] Figure 6 It is the gammacerane / αβ-hopane-C in Example 1 of the present invention. 27 Dia / C 27 St intersection diagram.

[0057] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0059] A method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs comprises the following steps:

[0060] A. Evaluate source rocks by depression and stratum. The specific process is as follows:

[0061] a1. Clarify the abundance distribution of the main source rocks and parent sources. The specific process is as follows:

[0062] First, the pyrolysis analysis, micro-component analysis, vitrinite reflectance analysis and elemental analysis experiments of the source rocks in the study area were carried out;

[0063] Then, based on the above-mentioned rock pyrolysis analysis, micro-component analysis, vitrinite reflectance analysis and element analysis experimental results, the thermal evolution degree, micro-component type and organic matter abundance of source rocks in different depressions and strata in the study area were analyzed;

[0064] Finally, the abundance distribution patterns of the main source rocks and parent sources are clarified.

[0065] Among them, the above experimental methods can refer to "SY / T 5117-1996 Rock Pyrolysis Analysis Method", "SY / T5125-2014 Transmitted Light-Fluorescence Kerogen Microscopic Component Identification and Type Classification Method", "SY / T5124-95 Vitrinite Reflectance Determination Method in Sedimentary Rocks", and "GB / T 19143-2017 Analysis Method for Carbon, Hydrogen, Oxygen and Nitrogen Elements in Rock Organic Matter".

[0066] a2. Clarify the hydrocarbon generation potential and charging period of the study area. The specific process is as follows:

[0067] First, conduct a gold tube thermal simulation experiment;

[0068] Then, according to the oil generation window of the main source rock and the law of gas generation transformation, the hydrocarbon generation evolution model is established;

[0069] Finally, the hydrocarbon generation potential and charging period of the study area were clarified by combining the burial history and inclusion temperature measurement;

[0070] Among them, the gold tube experimental method is based on "SY / T 7035-2016 Gold tube hydrocarbon generation thermal simulation experimental method"; the hydrocarbon generation evolution model is based on the literature "Li Kuo, Cheng Yan, Su Long, et al. Experimental study on hydrocarbon generation characteristics of lacustrine mudstone in the third section of the East Section of Bohai Oilfield, Bohai Bay Basin [J]. Natural Gas Geoscience, 2023, 34(12): 2210-2221.";

[0071] The method for determining hydrocarbon generation potential is based on the literature "Wang Bo, Zhang Tongyao, Shi Changlin, et al. Analysis of factors affecting activation energy of different types of source rocks in Laizhou Bay Sag, Bohai Sea[J]. Chinese Journal of Geomechanics, 2022, 28(03): 492-500."

[0072] a3. Comprehensively evaluate the hydrocarbon expulsion and injection capacity of the study area. The specific process is as follows:

[0073] First, we carried out thermal pressure simulation experiments on hydrocarbon generation and expulsion, quantitative fluorescence analysis of reservoirs, and inclusion abundance analysis experiments;

[0074] Then, based on the hydrocarbon expulsion efficiency, QGF index, and GOI parameters obtained from the aforementioned experiments, the hydrocarbon expulsion and charging capacities of the oil and gas in the study area were comprehensively evaluated;

[0075] Among them, the above experimental methods can refer to "SY / T 7616-2021 Thermal Pressure Hydrocarbon Generation and Expulsion Simulation Procedure", "SY / T 7309-2016 Reservoir Quantitative Fluorescence Analysis Method", and "SY / T 6010-2010 Sedimentary Rock Inclusion Homogenization Temperature and Salinity Determination Method";

[0076] B. Analyze the source rock sedimentary environment and parent source characteristics. The specific process is as follows:

[0077] First, more than 20 biomarker compound parameters were used to draw a scatter plot, analyze the source rock sedimentary environment and parent source characteristics, and screen out biomarker parameters with good correlation and obvious characteristics;

[0078] Then, the sedimentary environment and parent source characteristics of different depressions and different strata in the study area were further analyzed, and key biomarker parameters with high discrimination were determined;

[0079] Finally, the paleoclimate environment was analyzed based on trace element data, and the origin of the maternal source type was analyzed based on isotope data to verify the accuracy and reliability of the above results;

[0080] C. Determination of hydrocarbon supply range in multiple depressions. The specific process is as follows:

[0081] First, using the key biomarker compound parameters with high discrimination in different depressions and different formations screened out in step B, cluster analysis of reservoirs in the target oilfield surrounding area was carried out to divide multiple oil groups;

[0082] Then, a scatter plot is drawn for each divided oil group using the key biomarker compound parameters in step B;

[0083] Then, we conduct oil source analysis based on the configuration characteristics of key biomarker compound parameters in each oil group, and conduct detailed comparative analysis on reservoirs that are difficult to classify due to severe source mixing.

[0084] Finally, the hydrocarbon supply ranges of multiple depressions are divided according to the oil and gas input of reservoirs in the target oilfield surrounding area;

[0085] Among them, the oil source analysis can refer to "Hao Peng, Zang Chunyan, Wang Bo, et al. Geochemical characteristics of source rocks and oil source correlation in the western sub-basin of Bozhong Sag [J]. Fault Block Oil and Gas Field, 2019, 26(06): 681-686."

[0086] D. Analyze the oil and gas sources of the target lithologic oil and gas reservoirs. The specific process is as follows:

[0087] First, based on the physical properties, group composition and gas chromatography experimental data of the target reservoir crude oil, the degree of crude oil biodegradation, the proportion of saturated hydrocarbons and the development of light components in each well were analyzed to clarify the regional differences in oil and gas biodegradation and charging capacity.

[0088] Then, cluster analysis combined with biomarker scatter plot distribution was used to analyze the hydrocarbon supply characteristics of each well in the target reservoir from different depressions and different layers;

[0089] Finally, the biomarker compounds and isotope data of the target oil field and its surrounding reservoirs are analyzed to identify reservoirs with similar sources and characteristics to the target reservoirs;

[0090] Among them, the oil source analysis can refer to "Qi Yumin, Hao Peng, Wang Yu, et al. Detailed oil source comparison in the steep slope zone of the western sub-sag of Bozhong Sag [J]. Fault Block Oil and Gas Field, 2018, 25(02): 151-156."

[0091] E. Characterization of oil and gas migration path. The specific process is as follows:

[0092] e1. Determine the sedimentary environment of the target lithologic oil and gas reservoir. The specific process is as follows:

[0093] Determine the sedimentary environment of the target lithologic oil and gas reservoir using the distribution of sporopollen, ostracod fossils and trace elements;

[0094] e2. Evaluate the degree of oil and gas migration and flooding. The specific process is as follows:

[0095] The effective thickness, porosity and oil column height of the reservoir sand body are used to evaluate the degree of oil and gas migration and flooding;

[0096] e3. Determine the migration direction of oil and gas from each depression. The specific process is as follows:

[0097] According to the distribution characteristics of ancient oil reservoirs in the QGF index well-connected map combined with the distribution characteristics of oil-bearing areas and faults in current oil reservoirs, the migration direction of oil and gas from each depression is determined;

[0098] e4. Clarify the migration path and capacity of oil and gas along each well. The specific process is as follows:

[0099] The migration of target lithologic reservoir wells and surrounding wells was studied by using nitrogen compound parameters, methylphenanthrene index (1-methylphenanthrene, 9-methylphenanthrene), sterane isomerization parameter (C 29 ααS / (S+R), C 29 The regular changes of parameters such as ββ / (αα+ββ)), QGFindex, and dibenzothiophene series (1-methyldibenzothiophene, 1,4-dimethyldibenzothiophene) can clarify the migration path and capacity of oil and gas along each well;

[0100] F. Prediction of favorable oil and gas zones. The specific process is as follows:

[0101] Based on the oil and gas migration paths, favorable areas for oil and gas accumulation in the hub belt are identified, and prediction of favorable oil and gas zones is carried out.

[0102] Example 1

[0103] In this example, the lithologic oil and gas reservoirs in Bohai Central Depression have been the main force for increasing reserves and production in the Bohai Sea in recent years, and their oil and gas sources and accumulation rules are the focus of exploration. Previous researchers analyzed the formation conditions of lithologic oil reservoirs in Bohai Oilfield and summarized the source-sink system and its control on lithologic oil and gas reservoirs. According to the research on the distribution characteristics and enrichment rules of Neogene oil and gas in Bohai Sea, it is proposed that "convergent ridge" is the key to favorable closure accumulation in Neogene. The main controlling factors and accumulation patterns of oil and gas accumulation in the Bohai Central area are summarized, and the four elements of "ridge-fault-sand-belt" are proposed as the basis for oil and gas enrichment. The "convergent ridge-fault-trap (ridge-fault-circle)" ternary control accumulation model is established. It is recognized that the convergence ability of deep oil and gas is a prerequisite for shallow oil and gas enrichment, which enriches the late accumulation theory of Bohai Oilfield. In recent years, based on the Neogene "convergent ridge control accumulation theory and technology", typical lithologic oil and gas reservoirs in Bohai Central Depression have been discovered, which have the characteristics of few vertical oil layers, large single sand body area, and high test production capacity.

[0104] At present, the oil and gas enrichment control mode, shallow sand body sedimentary characteristics, and deep oil and gas accumulation capacity of the lithologic oil and gas reservoirs in the Bozhong Sag have been studied, and regional research understanding has been achieved, but there is a lack of quantitative indicative characterization methods for the oil and gas accumulation and migration process. In order to solve the problem of oil source comparison and quantitative characterization of oil and gas migration caused by mixed source hydrocarbon supply in multiple depressions and multiple layers, this embodiment provides a method for characterizing the oil and gas migration path and predicting favorable zones in complex mixed source lithologic oil and gas reservoirs, which includes the following steps:

[0105] Step A: Evaluate source rocks by depression and layer

[0106] a1. Carry out experiments such as pyrolysis analysis, micro-component analysis, vitrinite reflectance analysis and element analysis of source rocks in the study area, analyze the thermal evolution degree, micro-component type and organic matter abundance of source rocks in different depressions and strata in the study area, and clarify that the East Third Section of the study area is a Ⅱ1-Ⅱ2 type source rock with medium to good abundance and medium hydrocarbon generation potential.

[0107] The evaluation diagram of source rocks in a single sag is shown in Figure 2. Figure 1 As shown in the figure, the distribution law of maternal abundance is as follows Figure 2 As shown in the figure, the first member of the Shahe Formation is a good-excellent source rock of type II1 with high abundance and large hydrocarbon generation potential. The third member of the Shahe Formation is a good-excellent source rock of type I and II1 with high thermal evolution. It is clear that the main source rocks are the third member of the Donghe Formation, the first member of the Shahe Formation, and the third member of the Shahe Formation. From the perspective of organic matter abundance, the provenance is good, and the organic matter abundance decreases from northeast to southwest.

[0108] a2. Conducting gold tube thermal simulation experiments, establishing hydrocarbon generation evolution model according to the oil generation window of the main source rock and the law of gas conversion, combining burial history and inclusion temperature measurement, etc., it is clear that the source rock in the study area has a wide oil generation window, strong gas generation in the later period, and the hydrocarbon generation process lasts for a long time until Ro=3.8. Combined with the right figure of the oil and gas filling process, it can be clearly seen that the period from 12 to 5.1 Ma was the stage of large-scale crude oil generation. At this time, the generated oil and gas were discharged and accumulated in large quantities. Since 5.1 Ma, it has rapidly settled in the late period to form an overpressure mudstone caprock, which effectively seals the oil and gas and accelerates the generation of hydrocarbon gas.

[0109] a3. Carry out experiments such as thermal pressure simulation of hydrocarbon generation and expulsion, quantitative fluorescence analysis of reservoirs, and inclusion abundance analysis, and comprehensively evaluate the hydrocarbon expulsion capacity and injection capacity of the study area based on parameters such as hydrocarbon expulsion efficiency, QGF index, and GOI.

[0110] The hydrocarbon expulsion efficiency in the main oil generation stage in the study area is 0.38-0.73; the hydrocarbon expulsion efficiency in oil cracking gas generation is 0.81-0.98. It can be seen that the abnormally high pressure brings strong fluid pressure and provides sufficient power for hydrocarbon expulsion.

[0111] The average QGF index of each well is much greater than 3.5, indicating that the shallow oil and gas migration capacity is strong. At the same time, combined with the inclusion abundance parameters, it shows that the deep oil and gas filling degree is high and the oil and gas charging intensity is strong. Overall, the Bozhong Sag has a good source foundation, strong hydrocarbon generation capacity, high hydrocarbon expulsion efficiency, strong shallow oil and gas migration capacity, and strong deep buried hill oil and gas charging intensity.

[0112] Step B: Analysis of source rock sedimentary environment and parent rock characteristics

[0113] b1. Use more than 20 biomarker parameters to draw a scatter plot ( Figure 5 , 6 ), including: Ts / (Ts+Tm), gammacerane / αβ-hopane, ETR, C 35 / C 34 22S-Hippophane, C 27 Dia / C 27 St, C 29 ααS / (S+R), C 29 ββ / (αα+ββ), 4-methylsterane / C 29 Steranes, C 24 Four-ring post / C 26 Tricyclic terpenes, C 19 / C 23 Tricyclic terpane, C 20 / C 23 Tricyclic terpane, C 23 Tricyclic terpane / hopane, sterane / hopane (S / H), Pr / Ph, Pr / nC 17 、Ph / nC 18 , C24 Tetracyclic tert-butyl / ∑hopane, C 30 βα-Molane / C 30 βα-hopane, 25-norhopane / 17α(H), 21β(H), (Pr+Ph) / C 30 Hop), and analyzed the source rocks. The third segment of the Shahejie Formation in the Qinnan Sag is a deep-water strongly reducing environment, and the first segment of the Shahejie Formation is a saltwater strongly reducing environment. The terrigenous input of the source rocks in Qinnan and Bozhong is weak, while the terrigenous input of the Dongying Formation is relatively strong. The third segment of the Shahejie Formation in Qinnan and the first and second segments of the Shahejie Formation in Bozhong have obvious contributions.

[0114] Screen out biomarker parameters with good correlation and obvious characteristics, including: ETR, C 35 / C 34 22S-Hippophane, C 27 Dia / C 27 St, gammacerane / αβ-hopane, C 19 / C 23 Tricyclic terpane, 4-methylsterane / C 29 Steranes were used to further analyze the sedimentary environment and parent source characteristics of different depressions and strata in the study area, and key biomarker parameters with high discrimination were determined.

[0115] b2. According to the analysis of the paleoclimate environment based on the trace element data, the Paleogene V / (V+Ni) value is 0.37~0.82, and the Sr / Ba value is 0.23~0.93, indicating a freshwater-slightly brackish terrestrial sedimentary environment. According to the isotope data of Dongsan Section -29.09‰~-25.60‰, Shayi Section -28.21‰~-25.90‰, and Shasan Section -27.85‰~-25.24‰, the source of the parent source type is mainly mixed source.

[0116] Step C: Determine the hydrocarbon supply range of multiple depressions

[0117] c1. Using the key biomarker parameters of different depressions and different strata with high discrimination selected in step B, cluster analysis of reservoirs in the target oilfield surrounding area was carried out. The Ward method (average Euclidean distance) was used and all raw data were standardized between 0 and 1.0.

[0118] c2. Draw a scatter plot of the key biomarker parameters of each well in step B for each well group, and conduct oil source analysis based on the key biomarker parameters and configuration characteristics of each well group. Perform detailed comparative analysis on reservoirs that are difficult to divide into oil groups due to serious mixed sources;

[0119] It shows that the oil from Qinnan source of type I provides hydrocarbons with low C 27 Dia / C 27 St characteristics; Class II oil: high C 27 Dia / C 27 S, high C 35 / C34 22S hopane, high γ-cerane abnormal index; high C 23 Tricyclic terpanes / hopanes, high C 19 / C 23 Tricyclic terpenes, originated from Bozhong Sag, mixed with input from Qinnan Sag. (Shanxi 1 source rock biomarkers are obvious); Class III oil: high C 27 Dia / C 27 S, medium-high γ-cerane abnormal index, medium C 35 / C 34 22S Hopane; high 4MSI, low C 23 Tricyclic terpanes / hopanes, medium C 19 / C 23 The tricyclic terpanes are originated from the third section of the Shahejie Formation in the Bozhong Sag and mixed with the first section of the Shahejie Formation.

[0120] c3. Divide the hydrocarbon supply range of multiple depressions according to the oil and gas input of the reservoirs in the target oilfield surrounding area;

[0121] Step D: Analysis of oil and gas sources in target lithologic reservoirs

[0122] d1. According to the physical properties, group composition and gas chromatography experimental data of crude oil in the target reservoir, the degree of biodegradation of crude oil in each well, the proportion of saturated hydrocarbons and the development degree of light components were analyzed to clarify the regional differences in oil and gas biodegradation and charging capacity, which showed that the crude oil in the study area was biodegraded as a whole, and the secondary charging of oil and gas was strong in the northeast.

[0123] d2. Use cluster analysis combined with the scatter plot distribution of biological markers ( Figure 3 ), analyze the hydrocarbon supply characteristics of each well in the target reservoir from different depressions and different layers. Type I crude oil has high C 19 / C 23 Tricyclic terpanes, high C 20 / C 23 Tricyclic terpanes, high C 35 / C 34 22S hopane, high gamma cerane / αβ-hopane, low C 27 Dia / C 27 St, Qinnan Sag source oil. Type II crude oil with low C 19 / C 23 Tricyclic terpanes, low C 20 / C 23 Tricyclic terpanes, low-medium C 35 / C 34 22S hopane, low-medium gamma cerane / αβ-hopane, high C 27 Dia / C 27 St, high 4MSI, source oil from Bozhong Sag. Type III crude oil, medium C 19 / C 23 Tricyclic terpanes, medium-high C 27Dia / C 27 St, High C 35 / C 34 22S ascending hopane, high gamma cerane / αβ-hopane, Bohai and Qinnan mixed source oil. Type IV crude oil with high C 19 / C 23 Tricyclic terpanes, low C 27 Dia / C 27 St, low gamma cerane / αβ-hopane, low 4MSI, Qinnan and Bozhong mixed source oil. It is clear that the source oil of Qinnan Sag has a greater contribution from the first section of the near-source Shahejie Formation; the third section of the far-source Shahejie Formation has a greater contribution. The source oil of Bozhong Sag has a similar contribution from the first section of the near-source Shahejie Formation and the third section of the far-source Shahejie Formation, and has a strong filling capacity; the third section of the far-source Shahejie Formation has a weaker contribution to the upper part (0, Ⅰ oil group) due to the influence of filling capacity. The mixed source oil of well 7 has a greater contribution to Bozhong Sag; well 10 has a greater contribution to Qinnan Sag.

[0124] d3. Analyze the biomarker compounds and isotope data of the target oil field and its surrounding reservoirs to identify reservoirs with similar origins and characteristics to the target oil field.

[0125] Step E: Characterization of oil and gas migration pathways ( Figure 4 )

[0126] e1. The sedimentary environment of the target lithologic oil and gas reservoirs is determined using the distribution of pollen, ostracod fossils and trace elements. The typical fossil genera in the study area are Trichoderma and Schizosphaeria, indicating a humid and hot climate and a freshwater sedimentary environment, mainly river-delta plain deposits, with swamp deposits visible in some areas.

[0127] e2. The effective thickness of the reservoir sand body, porosity and oil column height were used to evaluate the degree of oil and gas migration and flooding. The results showed that the average oil column height was 18.9m, the average effective thickness of the sand body was 4.37m (Oil Group 0: 4.49m, Oil Group I: 4.51m, Oil Group II: 4.08m), and the average porosity was 34.8%, indicating that the reservoir properties were good and the conditions for oil and gas migration were good.

[0128] e3. According to the distribution characteristics of ancient oil reservoirs in the QGF index well-connected map combined with the distribution characteristics of the oil-bearing area of ​​the current oil reservoirs and the fault distribution characteristics, there are large sets of ancient oil reservoirs in the southeast, ancient oil reservoirs in the II and III oil groups in the northwest, and the oil column is high in the east; multiple faults are developed in the southeast, the conditions for oil and gas migration are good, the ancient oil reservoirs correspond to the current oil reservoirs, the migration of the oil-water interface is small, and the shallow oil and gas accumulation is stable.

[0129] The migration of target lithologic reservoir wells and surrounding wells was studied by using nitrogen compound parameters, methylphenanthrene index (1-methylphenanthrene, 9-methylphenanthrene), sterane isomerization parameter (C 29 ααS / (S+R), C 29The regular changes in parameters such as ββ / (αα+ββ)), QGFindex, and dibenzothiophene series (1-methyldibenzothiophene, 1,4-dimethyldibenzothiophene) clarify the migration path and capacity of oil and gas along each well. According to the nitrogen-containing compounds "TNC" (decreased), "1,8DM-Ca / 2,7DM-Ca" (increased), and "Ben[a]-Ca / Ben[c]-Ca" (increased), it is clear that the existence of oil and gas is adjusted from south to north. With the increase of maturity, the methyl rearrangement reduces the content of 1-methylphenanthrene and 9-methylphenanthrene; the biological configuration of sterane (R configuration) changes to the geological configuration (S configuration), C 14 and C 17 The α-H at the position will also transform to β-H to reach equilibrium. As migration proceeds, the lone pair of electrons of the dibenzothiophene molecule forms hydrogen bonds with the hydrogen atoms of the medium, causing the dibenzothiophene molecule to be easily adsorbed and cause a fractionation effect. However, 1-methyldibenzothiophene and 1,4-dimethyldibenzothiophene are not easy to form hydrogen bonds, so the thiophene analog value can be used to indicate the migration path. The QGF index of each well is not effective in indicating the migration path. From a regional perspective, the stepped distribution shows the characteristics of oil and gas graded filling ( Figure 4 ).

[0130] Step F: Prediction of favorable oil and gas zones

[0131] Based on the oil and gas migration paths, favorable areas for oil and gas accumulation in the hub belt are identified, and prediction of favorable oil and gas zones is carried out.

[0132] The present invention can carry out precise quantitative characterization of the oil and gas sources and migration paths of multi-depression and multi-layer mixed-source hydrocarbon reservoirs. The present invention can clarify the migration paths and capacities of oil and gas along each well, and predict favorable zones for oil and gas exploration based on the favorable areas for reservoir formation in the hub belt according to the oil and gas transportation range.

[0133] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs, characterized by: The following steps are involved: A. Evaluate source rocks by depression and stratum; B. Analyze the sedimentary environment and parent rock characteristics of source rocks; C. Determination of hydrocarbon supply range in multiple depressions; D. Conduct oil and gas source analysis on target lithologic oil and gas reservoirs; E. Characterization of oil and gas migration pathways; F. Prediction of favorable oil and gas zones.

2. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method of evaluating source rocks by depression and stratum in step A comprises the following steps: a1. Clarify the abundance distribution of the main source rocks and parent sources; a2. Clarify the hydrocarbon generation potential and charging period of the study area; a3. Comprehensively evaluate the hydrocarbon expulsion and injection capabilities of the study area.

3. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 2, characterized in that: The specific method of the step a1 to clarify the abundance distribution law of the main hydrocarbon source rock and the parent source is: First, the pyrolysis analysis, micro-component analysis, vitrinite reflectance analysis and elemental analysis experiments of the source rocks in the study area were carried out; Then, the thermal evolution degree, maceral type and organic matter abundance of source rocks in different depressions and strata in the study area are analyzed; Finally, the abundance distribution patterns of the main source rocks and parent sources are clarified.

4. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 2, characterized in that: The specific method of determining the hydrocarbon generation potential and charging period of the study area in step a2 is: First, conduct a gold tube thermal simulation experiment; Then, according to the oil generation window of the main source rock and the law of gas generation transformation, the hydrocarbon generation evolution model is established; Finally, the hydrocarbon generation potential and charging period of the study area were clarified by combining the burial history and inclusion temperature measurement.

5. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 2, characterized in that: The specific method of step a3 for comprehensively evaluating the hydrocarbon expulsion capacity and charging capacity of the study area is: First, we carried out thermal pressure simulation experiments on hydrocarbon generation and expulsion, quantitative fluorescence analysis of reservoirs, and inclusion abundance analysis experiments; Then, the hydrocarbon expulsion capacity and injection capacity of oil and gas in the study area were comprehensively evaluated based on the hydrocarbon expulsion efficiency, QGF index, and GOI parameters.

6. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method of performing source rock sedimentary environment and parent source characteristic analysis in step B comprises the following steps: b1. Use multiple biomarker compound parameters to draw a scatter intersection diagram, analyze the source rock sedimentary environment and parent source characteristics, and screen out biomarker compound parameters with good correlation and obvious characteristics; b2. Analyze the sedimentary environment and source characteristics of different depressions and strata in the study area to determine the key biomarker compound parameters with high discrimination; b3. Analyze the paleoclimate environment based on trace element data, analyze the maternal source type based on isotope data, and verify the accuracy and reliability of the biomarker compound parameters screened out in step b1 and the key biomarker compound parameters determined in step b2 in the study area.

7. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method for determining the hydrocarbon supply range of the multiple depressions in step C comprises the following steps: c1. Using the key biomarker compound parameters of different depressions and different strata with high discrimination screened out in step B, cluster analysis of reservoirs in the target oilfield surrounding area is carried out to divide multiple oil groups; c2. Draw a scatter plot of the key biomarker compound parameters of each oil group divided using step B; c3. Combine the key biomarker compound parameter configuration characteristics of each well in each oil group to conduct oil source analysis, and conduct detailed comparative analysis on oil reservoirs that are difficult to classify due to serious source mixing; c4. Divide the hydrocarbon supply range of multiple depressions according to the oil and gas input of the reservoirs in the target oilfield surrounding area.

8. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method of performing oil and gas source analysis on the target lithologic oil and gas reservoir in step D comprises the following steps: d1. According to the physical properties, group components and gas chromatography experimental data of the target oil reservoir, the degree of biodegradation of crude oil, the proportion of saturated hydrocarbons and the development of light components in each well are analyzed to clarify the differences in regional oil and gas biodegradation and charging capacity; d2. Analyze the hydrocarbon supply characteristics of each well in the target reservoir from different depressions and different layers by using cluster analysis combined with the scatter plot distribution of biomarker compounds; d3. Analyze the biomarker compounds and isotope data of the target oil field and its surrounding reservoirs to identify reservoirs with similar origins and characteristics to the target oil field.

9. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method of describing the oil and gas migration path in step E comprises the following steps: e1. Determine the sedimentary environment of the target lithologic oil and gas reservoir using the distribution of sporopollen, ostracod fossils and trace elements; e2. Use the effective thickness, porosity and oil column height of the reservoir sand body to evaluate the degree of oil and gas migration and flooding; e3. According to the distribution characteristics of ancient oil reservoirs in the QGF index well-connected map combined with the distribution characteristics of oil-bearing area and faults in the current oil reservoirs, determine the migration direction of oil and gas from each depression; e4. Conduct migration studies on each well in the target lithologic oil and gas reservoir and each well in the surrounding area, and use the regular changes in parameters to clarify the migration path and capacity of oil and gas along each well; the parameters include nitrogen-containing compound parameters, methylphenanthrene index, sterane isomerization parameters, QGF index and dibenzothiophene series parameters.

10. The method for characterizing oil and gas migration paths and predicting favorable zones in mixed-source lithologic oil and gas reservoirs according to claim 1, characterized in that: The specific method of predicting favorable oil and gas zones in step F is: according to the oil and gas migration path, the favorable areas for reservoir formation on the hub belt are identified, and the prediction of favorable oil and gas zones is carried out.

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