Method for dividing boundary of crude oil ethnic group by using similarity of bicyclic aromatic compounds

Abstract

The invention provides a method for dividing a crude oil group boundary by using the similarity of bicyclic aromatic hydrocarbon compounds. The method comprises the following steps: step 1, determining a main layer series of hydrocarbon source rock development; 2, determining typical biomarker characteristics of the main hydrocarbon source rock; 3, macroscopically performing crude oil group unit division on the main hydrocarbon source rock stratum system; 4, selecting two aromatic hydrocarbon compounds, and determining the indexes of the two aromatic hydrocarbon compounds in the crude oil sample; 5, comprehensively calculating the similarity of the indexes of the two aromatic hydrocarbon compounds selected from the crude oil sample; 6, determining the attribution of dispute well positions among the crude oil group units; and 7, carrying out final division on the crude oil group units. According to the method for dividing the boundary of the crude oil group by using the similarity of the bicyclic aromatic hydrocarbon compounds, the boundary of a crude oil group unit is divided by using the indexes of the aromatic hydrocarbon compounds, and an important basis is conveniently provided for fine oil source comparison and reservoir forming system research.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrocarbon accumulation research, and particularly to a method for dividing the boundaries of crude oil populations using the similarity of bicyclic aromatic hydrocarbon compounds. Background Art

[0002] After more than a decade of development, the concept of petroleum systems has become a powerful tool for evaluating hydrocarbon resource potential, understanding the distribution law of hydrocarbons, and guiding hydrocarbon exploration. However, each petroleum system has its own characteristics, so its classification is very important. Some foreign classification schemes have certain limitations when applied to China. The division of petroleum systems is an important part of petroleum system research. Its core is to follow the process of hydrocarbons from the source rock to the trap and trace and determine the maximum outer boundary of hydrocarbon activities in the three-dimensional geological unit. Among them, the study of hydrocarbon secondary migration is at the core. In the discussion of petroleum systems by Magoon et al., hydrocarbon secondary migration is simply defined as a process of expelling from the hydrocarbon kitchen and migrating through the carrier bed to the trap. This model is only applicable to simple petroleum systems with one-stage hydrocarbon accumulation. Many superimposed basins, such as the Jiyang Depression, have multiple source rocks, and the generation, migration, and accumulation of hydrocarbons are multi-periodic, forming the characteristics of a complex hydrocarbon accumulation zone with overlapping oil-bearing formations in the vertical direction and intersecting multiple oil and gas reservoir types on the plane. Therefore, the foreign classification schemes for petroleum systems have poor operability when applied to superimposed basins, and there are also scale effects in research.

[0003] Crude oils from the same source rock or the same oil source area are crude oils of one "population". Crude oils of the same "population" have differences in geochemical characteristics due to differences in migration, preservation, and late alteration, etc. Among them, a group of crude oils with the same or similar geochemical characteristics forms a "sub-population". The division of populations and sub-populations is the basic content of reservoir geochemistry research and is a genetic classification of crude oils from a geochemical perspective. The purpose of dividing crude oil populations and sub-populations is to conduct oil source correlation, study the heterogeneity and compartmentalization of crude oils. Through the division of crude oil populations, the relationship between each small layer within the oil reservoir group can be clarified, and the source of the oil produced from the same well and the production contribution of each single layer can also be further judged, providing a basis for the study of reservoir connectivity, hydrocarbon migration and accumulation, and multi-source injection history.

[0004] The methods for crude oil population division mainly include mathematical statistics methods (including cluster analysis method and factor analysis method) and conventional methods (including direct spectral comparison method, biomarker parameter correlation method, isotope comparison method, and crude oil property correlation comparison method). Currently, biomarker indicators and parameters are the most commonly used in crude oil population division at home and abroad. In the initial research of predecessors, a single indicator was often used for oil source comparison. However, with in-depth research, it was found that using a single indicator to divide crude oil populations often cannot draw correct conclusions. Therefore, at present, people use multiple indicators and parameters to conduct systematic research on oil reservoirs, and try to use as many indicators and parameters as possible for crude oil population division.

[0005] The division of crude oil populations involves many factors, and each has different applicable conditions. However, the definition of the boundary of crude oil population units is still relatively vague. At present, there is still no reliable method, and subjective and artificial factors are relatively large.

[0006] In the Chinese patent application with the application number: CN201910675959.8, it involves an oil source determination method under complex hydrocarbon accumulation conditions, belonging to the technical field of oil and gas geological exploration. The present invention first determines whether the crude oil has degraded, and then selects biomarker compound parameters to divide the crude oil populations according to whether it has degraded and the results of chromatographic-mass spectrometry analysis; then, the hydrocarbon group components of the source rock samples at each layer are separated, and the representative source rocks at each layer are determined through saturated hydrocarbon gas chromatogram and cluster analysis. Finally, the distribution map of oil source comparison parameter intervals is drawn, and the relevant parameters of different crude oil populations are plotted on the distribution map of oil source comparison parameter intervals to determine the oil source. Compared with the prior art, the present invention fully considers the influence of secondary changes such as biodegradation on the properties of crude oil and the heterogeneity characteristics of source rocks, and can improve the accuracy of oil source comparison under complex hydrocarbon accumulation backgrounds. At the same time, the comparison parameters of the present invention can be selected according to actual situations. Therefore, the oil source determination method of the present invention is applicable to all oil sources and has a high oil source comparison accuracy.

[0007] In the Chinese patent application with the application number: CN201410602524.8, it involves a method for identifying the oil and gas sources suitable for heterogeneous salt lake basins, belonging to the technical field of oil and gas exploration and development. The present invention divides the crude oil populations and source rock populations of heterogeneous salt lake basins through the acquisition of basic geological data. Based on the division results of the crude oil populations and source rock populations of heterogeneous salt lake basins, the oil and gas sources of heterogeneous salt lake basins are determined. The present invention fully applies the principle that the sedimentary environment and maturity of crude oil and source rocks are similar, and uses cluster analysis to divide the crude oil and source rocks into populations and establish the corresponding relationship between the two. According to the corresponding relationship, the oil and gas in single-rise single-sag heterogeneous salt lake basins can be effectively identified. For the single-rise multi-sag structural belt of heterogeneous salt lake basins, the mathematical model established by the gammacerane / C31 homohopane (22S) parameter can clearly distinguish the proportion of oil and gas sources in different sag zones and effectively guide the exploration of oil and gas in the sags.

[0008] In the book "Thoughts on Hierarchical Analysis of Hydrocarbon Accumulation Systems and Their Applications" by Dr. Ma Lixiang, the research status of the oil and gas system theory was reviewed. It was emphasized that the hierarchical division of the system is based on the oil source, and the study of the closed boundary of the system is the key. The Tarim Basin in the north and Bachu Uplift were taken as examples for elaboration and demonstration.

[0009] The above existing technologies are quite different from the present invention and cannot solve the technical problems we want to solve. Therefore, we have invented a new method to delimit the boundary of crude oil ethnic units using the index similarity of dimethylnaphthalene and methylbiphenyl, and use aromatic hydrocarbon compound indicators to delimit the boundary of crude oil ethnic units. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for delimiting the boundary of crude oil ethnic groups using the similarity of bicyclic aromatic hydrocarbon compounds, which is convenient for providing an important basis for fine oil source correlation and research on hydrocarbon accumulation systems.

[0011] The purpose of the present invention can be achieved by the following technical measures: A method for delimiting the boundary of crude oil ethnic groups using the similarity of bicyclic aromatic hydrocarbon compounds, which includes:

[0012] Step 1: Determine the main strata where source rocks develop;

[0013] Step 2: Determine the typical biomarker characteristics of the main source rocks;

[0014] Step 3: Macroscopically delimit the crude oil ethnic units for the main source rock strata;

[0015] Step 4: Select two aromatic hydrocarbon compounds and measure the indexes of these two aromatic hydrocarbon compounds for the crude oil samples;

[0016] Step 5: Comprehensively calculate the similarity of the indexes of the two aromatic hydrocarbon compounds selected for the crude oil samples;

[0017] Step 6: Determine the ownership of the disputed well positions among the crude oil ethnic units;

[0018] Step 7: Conduct the final delimitation of the crude oil ethnic units.

[0019] The purpose of the present invention can also be achieved by the following technical measures:

[0020] In Step 1, according to the geochemical information such as organic carbon, pyrolysis, and vitrinite reflectance, combined with geological condition analysis, through the results of source rock evaluation, determine the main strata where source rocks develop.

[0021] In Step 2, by means of fine oil-source correlation, the sources of oil and gas in each reservoir within the sag or basin are determined, and the oil and gas distributions derived from source rocks in different main intervals are screened out.

[0022] In Step 3, based on the tectonic, pressure, and sedimentary distribution of the main source rock series in the entire sag or basin, the crude oil population units of the main source rock series are first divided macroscopically.

[0023] In Step 4, the two aromatic compounds selected are dimethylnaphthalene and methylbiphenyl. Crude oil samples from the source rocks of the same interval in the study area are selected, and on-line biomarker aromatic chromatography-mass spectrometry analysis is performed on the crude oil samples to calculate the dimethylnaphthalene index, which is used to reflect the characteristics of the biological assemblage in the sediment.

[0024] In Step 4, the calculation formula for the dimethylnaphthalene index is:

[0025] Dimethylnaphthalene index = 2,6-dimethylnaphthalene / (2,6-dimethylnaphthalene + 2,7-dimethylnaphthalene + 1,6-dimethylnaphthalene).

[0026] In Step 4, crude oil samples from the source rocks of the same interval in the study area are selected, and on-line biomarker aromatic chromatography-mass spectrometry analysis is performed on the crude oil samples to calculate the methylbiphenyl index, which is used to reflect the characteristics of the diagenetic environment and oxidation-reduction conditions in the sediment.

[0027] In Step 4, the calculation formula for the methylbiphenyl index is:

[0028] Methylbiphenyl index = 3-methylbiphenyl / (3-methylbiphenyl + 4-methylbiphenyl + dibenzofuran).

[0029] In Step 5, using the calculation formula, a comprehensive calculation of the similarity of the dimethylnaphthalene index and the methylbiphenyl index of the crude oil samples is performed; among them, the dimethylnaphthalene index is used to characterize the water environment and biological assemblage characteristics, and the methylbiphenyl index is used to characterize the rock fabric characteristics and oxidation-reduction environment.

[0030] In Step 5, assume that the dimethylnaphthalene index of Well 1 is A1, and the methylbiphenyl index is B1; the dimethylnaphthalene index of Well 2 is A2, and the methylbiphenyl index is B2; the dimethylnaphthalene index of Well 3 is A3, and the methylbiphenyl index is B3.

[0031] X1 = A1 / A3 * 100% or A3 / A1 * 100%, with the larger value of A1 and A3 as the denominator;

[0032] X2 = B1 / B3 * 100% or B3 / B1 * 100%, with the larger value of B1 and B3 as the denominator;

[0033]

[0034] Wherein: X1: The similarity index of dimethylnaphthalene between Well 1 and Well 3; X2: The similarity index of methylbiphenyl between Well 1 and Well 3; Sim(X1, X2): The comprehensive similarity index of dimethylnaphthalene and methylbiphenyl between Well 1 and Well 3;

[0035] X3 = A2 / A3 * 100% or A3 / A2 * 100%, where the larger value of A2 and A3 is the denominator;

[0036] X4 = B2 / B3 * 100% or B3 / B2 * 100%, where the larger value of B2 and B3 is the denominator;

[0037]

[0038] Wherein: X3: The similarity index of dimethylnaphthalene between Well 2 and Well 3; X4: The similarity index of methylbiphenyl between Well 2 and Well 3; Sim(X3, X4): The comprehensive similarity index of dimethylnaphthalene and methylbiphenyl between Well 2 and Well 3;

[0039] If Sim(X1, X2) > Sim(X3, X4), it indicates that the similarity between Well 1 and Well 3 is higher than that between Well 2 and Well 3; if Sim(X1, X2) < Sim(X3, X4), it indicates that the similarity between Well 1 and Well 3 is lower than that between Well 2 and Well 3.

[0040] In Step 6, according to the calculation results of the similarity, perform spatially correlated connections on each well location, compare the similarity data of the samples within each crude oil ethnic group unit and at the critical positions of the crude oil ethnic group units. The similarity within the crude oil ethnic group unit is high, and the similarity between different crude oil ethnic group units is low.

[0041] In Step 7, according to the magnitude of the correlation, determine the crude oil ethnic groups. The reservoirs represented by the well locations with relatively large correlations are determined to be in the same ethnic group, and the reservoirs represented by the well locations with relatively small correlations are determined to be in other ethnic groups.

[0042] The object of the present invention can also be achieved by the following technical measures: A system for dividing the boundary of crude oil ethnic groups using the similarity of bicyclic aromatic hydrocarbon compounds, characterized in that the system for dividing the boundary of crude oil ethnic groups using the similarity of bicyclic aromatic hydrocarbon compounds analyzes the similarity of crude oil components by using the method for dividing the boundary of crude oil ethnic groups described in any one of Claims 1 - 12.

[0043] The method for dividing the boundary of crude oil groups by the similarity of bicyclic aromatic hydrocarbon compounds in the present invention uses aromatic hydrocarbon compound indicators to divide the boundary of crude oil group units, which is convenient for providing an important basis for fine oil source correlation and reservoir formation system research. The two indicators used in this invention patent can fully reflect many factors such as biological assemblages, diagenetic environments, and oxidation-reduction conditions in sediments, and are relatively comprehensive. The original similarity formula created by these two indicators is novel and can well divide the boundary of crude oil groups in oil and gas reservoirs. Moreover, the operation process is relatively simple and fast, with good prospects for popularization and application. It can be effectively applied to the rapid and accurate division of the boundary of crude oil groups in oil and gas reservoirs, and can play an important role in tracing the migration of oil and gas in conventional reservoirs and defining the boundary of oil and gas reservoir formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 FIG. is a flowchart of a specific embodiment of the method for dividing the boundary of crude oil groups by the similarity of bicyclic aromatic hydrocarbon compounds in the present invention;

[0045] Figure 2 FIG. is a diagram for identifying and citing an embodiment of dividing the boundary of crude oil group units by using the dimethylnaphthalene and methylbiphenyl indices in the present invention;

[0046] Figure 3 FIG. is a diagram for identifying and citing an embodiment of dividing the boundary of crude oil group units by using the similarity of dibenzofuran and methylbiphenyl indices in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0047] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0048] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0049] The present invention analyzes the similarity of crude oil components by using dimethylnaphthalene and methylbiphenyl indices in aromatic hydrocarbon compounds. The method for dividing the boundary of crude oil groups by using dimethylnaphthalene and methylbiphenyl indices in aromatic hydrocarbon compounds includes:

[0050] Step 1, determine the main strata in which source rocks develop through the evaluation results of source rocks;

[0051] Step 2, determine the typical biomarker characteristics of the main source rocks;

[0052] Step 3: Based on the structure, pressure, and sedimentary distribution of the main hydrocarbon source rock series in the entire depression or basin, the crude oil population units of the main hydrocarbon source rock series were first macroscopically divided.

[0053] Step 4: Select crude oil samples from the hydrocarbon source rocks of the same interval to determine the dimethylnaphthalene index in the aromatic compounds.

[0054] Step 5: Select crude oil samples from the hydrocarbon source rocks of the same interval to determine the methylbiphenyl index in the aromatic compounds.

[0055] Step 6: Use the calculation formula to comprehensively calculate the similarity of the dimethylnaphthalene index and the methylbiphenyl index of the crude oil samples.

[0056] Step 7: Use the calculated similarity to connect the well positions spatially.

[0057] Step 8: Determine the crude oil populations according to the magnitude of the correlation. The reservoirs represented by the well positions with a larger correlation are determined to be in the same population, and the reservoirs represented by the well positions with a smaller correlation are determined to be in other populations.

[0058] In Step 1, according to the geochemical information such as organic carbon, pyrolysis, and vitrinite reflectance, combined with the analysis of geological conditions, the main layer series in which the hydrocarbon source rocks developed was determined.

[0059] In Step 2, through the method of fine oil-source correlation, the oil and gas sources of each reservoir in the depression or basin were determined, and the oil and gas distributions from the hydrocarbon source rocks of different main intervals were screened out.

[0060] In Step 3, based on the structure, pressure, erosion line, and sedimentary distribution of the main hydrocarbon source rock intervals in the entire depression or basin, the crude oil population units of the main hydrocarbon source rock intervals were first macroscopically divided.

[0061] In Step 4, select crude oil samples from the hydrocarbon source rocks of the same series in the study area, conduct on-line biomarker aromatic chromatography-mass spectrometry analysis on the crude oil samples, and calculate the dimethylnaphthalene index to reflect the characteristics of the biological assemblage in the sediment.

[0062] Dimethylnaphthalene index = 2,6-dimethylnaphthalene / (2,6-dimethylnaphthalene + 2,7-dimethylnaphthalene + 1,6-dimethylnaphthalene)

[0063] In Step 5, select crude oil samples from the hydrocarbon source rocks of the same interval in the study area, conduct on-line biomarker aromatic chromatography-mass spectrometry analysis on the crude oil samples, and calculate the methylbiphenyl index to reflect the characteristics of the diagenetic environment and oxidation-reduction conditions in the sediment.

[0064] Methylbiphenyl index = 3 - methylbiphenyl / (3 - methylbiphenyl + 4 - methylbiphenyl + dibenzofuran)

[0065] In step 6, using the calculation formula, the comprehensive similarity of the dimethylnaphthalene index and the methylbiphenyl index of the crude oil sample is calculated; among them, the dimethylnaphthalene index is used to characterize the water environment and biological combination characteristics, and the methylbiphenyl index is used to characterize the rock fabric characteristics and redox environment.

[0066] Assume that the dimethylnaphthalene index of Well 1 is A1, and the methylbiphenyl index is B1; the dimethylnaphthalene index of Well 2 is A2, and the methylbiphenyl index is B2; the dimethylnaphthalene index of Well 3 is A3, and the methylbiphenyl index is B3.

[0067] X1 = A1 / A3 * 100% or A3 / A1 * 100% (the larger value of A1 and A3 is the denominator)

[0068] X2 = B1 / B3 * 100% or B3 / B1 * 100% (the larger value of B1 and B3 is the denominator)

[0069]

[0070] Where: X1: The similarity of the dimethylnaphthalene index between Well 1 and Well 3; X2: The similarity of the methylbiphenyl index between Well 1 and Well 3; Sim(X1, X2): The comprehensive similarity of the dimethylnaphthalene index and the methylbiphenyl index between Well 1 and Well 3

[0071] X3 = A2 / A3 * 100% or A3 / A2 * 100% (the larger value of A2 and A3 is the denominator)

[0072] X4 = B2 / B3 * 100% or B3 / B2 * 100% (the larger value of B2 and B3 is the denominator)

[0073]

[0074] Where: X3: The similarity of the dimethylnaphthalene index between Well 2 and Well 3; X4: The similarity of the methylbiphenyl index between Well 2 and Well 3; Sim(X3, X4): The comprehensive similarity of the dimethylnaphthalene index and the methylbiphenyl index between Well 2 and Well 3

[0075] If Sim(X1, X2) > Sim(X3, X4), it means that the similarity between Well 1 and Well 3 is higher than that between Well 2 and Well 3; if Sim(X1, X2) < Sim(X3, X4), it means that the similarity between Well 1 and Well 3 is lower than that between Well 2 and Well 3

[0076] In step 7, according to the calculation results of the similarity, the similarity data of the samples inside each crude oil ethnic unit and at the critical positions of the crude oil ethnic units are compared. The similarity inside the crude oil ethnic unit is high, and the similarity between different crude oil ethnic units is low.

[0077] In step 8, according to the above comparison results, determine the final ownership of the disputed boundaries between crude oil population units, and divide the final crude oil population units.

[0078] The following are several specific embodiments of applying the present invention

[0079] Embodiment 1

[0080] In a specific embodiment 1 of applying the present invention, as Figure 1 shown, Figure 1 is a flowchart of a specific embodiment of the method for dividing the boundaries of crude oil population units by using the dimethylnaphthalene and methylbiphenyl indices of the present invention. The method for dividing the boundaries of crude oil populations by using the similarity of bicyclic aromatic hydrocarbon compounds includes the following steps:

[0081] In step 101, according to geochemical information such as organic carbon, pyrolysis, and vitrinite reflectance, and combined with geological condition analysis, determine the main layer segments where source rocks develop. The process proceeds to step 102.

[0082] In step 102, through a method of fine oil-source correlation, determine the oil and gas sources of each oil reservoir in the sag or basin, and screen out the oil and gas distributions from source rocks in different main layer segments. The process proceeds to step 103.

[0083] In step 103, based on the structure, pressure, erosion line, and sedimentary distribution of the main source rock layer segments in the entire sag or basin, first macroscopically divide the crude oil population units of the main source rock layer segments. The process proceeds to step 104.

[0084] In step 104, select single-source oil samples from the source rocks of the same layer segment in the study area. To ensure data accuracy, generally select crude oil sample points evenly in the study area, and conduct on-line biomarker aromatic chromatography-mass spectrometry analysis on the crude oil samples to calculate the dimethylnaphthalene and methylbiphenyl indices. Dimethylnaphthalene index = 2,6-dimethylnaphthalene / (2,6-dimethylnaphthalene + 2,7-dimethylnaphthalene + 1,6-dimethylnaphthalene);

[0085] Methylbiphenyl index = 3-methylbiphenyl / (3-methylbiphenyl + 4-methylbiphenyl + dibenzofuran).

[0086] The process proceeds to step 105.

[0087] In step 105, use a calculation formula to comprehensively calculate the similarity of the dimethylnaphthalene index and methylbiphenyl index of the crude oil samples; among them, the dimethylnaphthalene index is used to characterize the water environment and biological assemblage characteristics, and the methylbiphenyl index is used to characterize the rock fabric characteristics and redox environment. The process proceeds to step 106.

[0088] In step 106, according to the calculation results of the similarity, the similarity data of the samples within each crude oil ethnic group unit and at the critical positions are compared. The similarity within the crude oil ethnic group unit is high, while the similarity between different crude oil ethnic group units is low. The process proceeds to step 107.

[0089] In step 107, based on the above comparison results, the final ownership of the disputed boundary between the crude oil ethnic group units is determined, and the final crude oil ethnic group units are divided.

[0090] Example 2

[0091] Figure 2 Taking a certain sag in a certain basin as an example, the figure for identifying the boundary of crude oil ethnic group units by using the dimethylnaphthalene and methylbiphenyl indices is cited.

[0092] Taking a certain sag in the Jiyang Depression of the Bohai Bay Basin as an example, in the division of the current crude oil ethnic group units, the geological units from hydrocarbon generation to hydrocarbon accumulation formed with the structural ridge, hydrocarbon drainage trough, and pressure coefficient as the boundaries are primarily considered. Within the sag, 6 crude oil ethnic groups are divided. Among them, units 1-3 roughly correspond to the range of the western sub-sag, while units 4-6 roughly correspond to the range of the eastern sub-sag ( Figure 2 ). On the basis of the division by the basic geological characteristics, through the fine oil source correlation of the key well areas ( Figure 2 the part enclosed by the dotted line in the figure), and by selecting homologous samples for the similarity analysis of the dimethylnaphthalene and methylbiphenyl indices of aromatic hydrocarbons, the boundaries between the units are defined.

[0093] Taking units 1-3 and unit 4 of the crude oil ethnic groups as examples, there is an obvious separating structural ridge between the two units, which becomes the dividing line of the two migration systems, and there are relatively obvious differences between the two crude oil ethnic group units. The source of the key well positions near the structural ridge determines which hydrocarbon accumulation system it belongs to. According to the comprehensive similarity calculation results of the dimethylnaphthalene and methylbiphenyl indices of aromatic hydrocarbons, the similarity of the key well positions with unit 4 of the crude oil ethnic group reaches 85%, while the similarity with units 1-3 of the crude oil ethnic group is only 67%. Therefore, it is classified into the hydrocarbon accumulation system of unit 4 of the crude oil ethnic group, and thus the boundaries of the two crude oil ethnic group units are accurately divided. Similarly, the boundaries of the remaining crude oil ethnic group units in the sag are also defined by this method.

[0094] Finally, the similarities of the dimethylnaphthalene and methylbiphenyl indices in all 6 crude oil ethnic group units in the entire sag are compared. It is obvious that the similarity within the crude oil ethnic group units is high, while the similarity between different units is low, which perfectly verifies the feasibility of this method.

[0095] Example 3

[0096] Figure 3Taking a certain depression in a certain area as an example, it is a reference example figure for identifying the boundary of crude oil population units by using the similarity of dibenzofuran and methylbiphenyl indices.

[0097] For the division of the crude oil population units this time, the geological units from hydrocarbon generation to hydrocarbon accumulation formed with the structural ridge, hydrocarbon drainage trough, and pressure coefficient as the boundaries are primarily considered. Within the depression, 8 crude oil populations are divided. Among them, units 1-3 roughly correspond to the range of the western sub-depression, while units 4-5 roughly correspond to the range of the eastern sub-depression, and units 6-8 roughly correspond to the range of the eastern sub-depression ( Figure 3 ). On the basis of the division by basic geological characteristics, through the fine oil source correlation of the key well areas ( Figure 3 the part enclosed by the dotted line in the figure), and by selecting homologous samples for the similarity analysis of the dibenzofuran and methylbiphenyl indices of aromatic hydrocarbons, the boundaries between each unit are defined.

[0098] Taking the crude oil population units 1-2 and 4 as an example, there is an obvious separating structural ridge between the two units, which becomes the dividing line of the two migration systems, and there are relatively obvious differences between the two crude oil population units. According to the comprehensive similarity calculation results of the dibenzofuran and methylbiphenyl indices of aromatic hydrocarbons, the similarity between the key well position and the crude oil population unit 4 reaches 89%, while the similarity with the crude oil population units 1-2 is only 65%. Therefore, it is classified into the hydrocarbon accumulation system of the crude oil population unit 4, and thus the boundaries of the two crude oil population units are accurately divided. Similarly, the boundaries of the remaining crude oil population units in the depression are also defined by this method.

[0099] Finally, the similarities of the dibenzofuran and methylbiphenyl indices in all 8 crude oil population units in the entire depression are compared. It is obvious that the similarity within the crude oil population units is high, and the similarity between different units is low, which once again perfectly verifies the feasibility of this method.

[0100] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0101] Except for the technical features described in the specification, they are all known technologies to those skilled in the art.

Claims

1. A method for dividing the boundary of crude oil groups by the similarity of bicyclic aromatic hydrocarbon compounds, characterized in that The method for dividing the boundary of crude oil groups by the similarity of bicyclic aromatic hydrocarbon compounds includes: Step 1: Determine the main series of source rock development. Step 2: Determine the typical biomarker characteristics of the main source rocks. Step 3: Macroscopically divide the crude oil group units of the main source rock series. Step 4: Select two aromatic hydrocarbon compounds and measure the indices of these two aromatic hydrocarbon compounds for the crude oil samples. Step 5: Conduct a comprehensive calculation of the similarity of the indices of the two selected aromatic hydrocarbon compounds for the crude oil samples. Step 6: Determine the ownership of the disputed well positions among the crude oil group units. Step 7: Conduct the final division of the crude oil group units.

2. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 1, wherein In Step 1, based on the geochemical information such as organic carbon, pyrolysis, and vitrinite reflectance, combined with the analysis of geological conditions, determine the main series of source rock development through the results of source rock evaluation.

3. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 1, characterized in that In Step 2, through the method of fine oil-source correlation, determine the oil and gas sources of each oil reservoir in the sag or basin, and screen out the oil and gas distributions from the source rocks of different main intervals.

4. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 1, characterized in that In Step 3, based on the structure, pressure, and sedimentary distribution of the main source rock series in the entire sag or basin, first macroscopically divide the crude oil group units of the main source rock series.

5. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 1, characterized in that, In Step 4, the two selected aromatic hydrocarbon compounds are dimethylnaphthalene and methylbiphenyl. Select the crude oil samples from the source rocks of the same interval in the study area, conduct on-line aromatic hydrocarbon chromatography-mass spectrometry analysis of biomarkers on the crude oil samples, and calculate the dimethylnaphthalene index to reflect the characteristics of the biological assemblage in the sediment.

6. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 5, wherein In Step 4, the calculation formula for the dimethylnaphthalene index is: Dimethylnaphthalene index = 2,6-dimethylnaphthalene / (2,6-dimethylnaphthalene + 2,7-dimethylnaphthalene + 1,6-dimethylnaphthalene).

7. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 6, characterized in that In Step 4, select the crude oil samples from the source rocks of the same interval in the study area, conduct on-line aromatic hydrocarbon chromatography-mass spectrometry analysis of biomarkers on the crude oil samples, and calculate the methylbiphenyl index to reflect the characteristics of the diagenetic environment and oxidation-reduction conditions in the sediment.

8. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 7, characterized in that In Step 4, the calculation formula for the methylbiphenyl index is: Methylbiphenyl index = 3-methylbiphenyl / (3-methylbiphenyl + 4-methylbiphenyl + dibenzofuran).

9. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 8, characterized in that, In Step 5, use the calculation formula to conduct a comprehensive calculation of the similarity of the dimethylnaphthalene index and the methylbiphenyl index of the crude oil samples; among them, the dimethylnaphthalene index is used to characterize the water environment and biological assemblage characteristics, and the methylbiphenyl index is used to characterize the rock fabric characteristics and oxidation-reduction environment.

10. The method for dividing the crude oil population boundary by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 9, characterized in that, In Step 5, assume that the dimethylnaphthalene index of Well 1 is A1, the methylbiphenyl index is B1; the dimethylnaphthalene index of Well 2 is A2, the methylbiphenyl index is B2; the dimethylnaphthalene index of Well 3 is A3, the methylbiphenyl index is B3. X1 = A1 / A3 * 100% or A3 / A1 * 100%, the larger value of A1 and A3 is the denominator. X2 = B1 / B3 * 100% or B3 / B1 * 100%, the larger value of B1 and B3 is the denominator. Where: X1: Similarity of dimethylnaphthalene index between Well 1 and Well 3; X2: Similarity of methylbiphenyl index between Well 1 and Well 3; Sim(X1,X2): Comprehensive similarity of dimethylnaphthalene index and methylbiphenyl index between Well 1 and Well 3. X3 = A2 / A3 * 100% or A3 / A2 * 100%, where the larger value of A2 and A3 is the denominator; X4 = B2 / B3 * 100% or B3 / B2 * 100%, where the larger value of B2 and B3 is the denominator; Where: X3: the similarity index of dimethylnaphthalene between Well 2 and Well 3; X4: the similarity index of methylbiphenyl between Well 2 and Well 3; Sim(X3, X4): the comprehensive similarity index of dimethylnaphthalene index and methylbiphenyl index between Well 2 and Well 3; If Sim(X1, X2) > Sim(X3, X4), it means that the similarity between Well 1 and Well 3 is higher than that between Well 2 and Well 3; if Sim(X1, X2) < Sim(X3, X4), it means that the similarity between Well 1 and Well 3 is lower than that between Well 2 and Well 3.

11. The method for dividing the boundary of crude oil groups by the similarity of dicyclic aromatic hydrocarbon compounds according to claim 1, wherein In Step 6, according to the calculation results of the similarity, perform spatially correlated connections on each well position, compare the similarity data of samples within each crude oil group unit and at the critical positions of crude oil group units. The similarity within the crude oil group unit is high, and the similarity between different crude oil group units is low.

12. The method for dividing the crude oil population boundary using the similarity of dicyclic aromatic hydrocarbon compounds according to claim 11, wherein, In Step 7, determine the crude oil groups according to the degree of correlation. The reservoirs represented by the well positions with a larger correlation are determined to be in the same group, and the reservoirs represented by the well positions with a smaller correlation are determined to be in other groups.

13. A system for dividing the boundary of crude oil groups by the similarity of bicyclic aromatic hydrocarbon compounds, characterized in that, The system for dividing the crude oil group boundary using the similarity of bicyclic aromatic hydrocarbon compounds analyzes the similarity of crude oil components using the method for dividing the crude oil group boundary using the similarity of bicyclic aromatic hydrocarbon compounds described in any one of Claims 1 - 12.

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