Methods for establishing a distribution model of hydrocarbon expulsion efficiency of lacustrine clay source rocks and methods for determining hydrocarbon expulsion efficiency of lacustrine clay source rocks

Abstract

This invention provides a method for establishing a distribution model of hydrocarbon expulsion efficiency of lacustrine clay source rocks and a method for determining the hydrocarbon expulsion efficiency of lacustrine clay source rocks. The template establishment method includes: acquiring multiple samples for model establishment in the study area; determining the lower limit of organic carbon content (TOC) and the maximum hydrocarbon generation per unit mass of organic matter in the study area based on the organic carbon content (TOC), hydrocarbon index (HCI), and residual hydrocarbons (S1) of each sample; determining the hydrocarbon expulsion efficiency of each sample with an organic carbon content (TOC) not lower than the lower limit of TOC based on the hydrocarbon index (HCI) and the maximum hydrocarbon generation per unit mass of organic matter; and determining the relationship model between hydrocarbon expulsion efficiency and organic carbon content (TOC) as the distribution model of hydrocarbon expulsion efficiency of lacustrine clay source rocks in the study area based on the hydrocarbon expulsion efficiency of each sample with an organic carbon content (TOC) not lower than the lower limit of TOC.

Description

Technical Field

[0001] This invention belongs to the field of petroleum geological exploration technology, and particularly relates to a method for establishing a hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks and a method for determining the hydrocarbon expulsion efficiency of lacustrine clay source rocks. Background Technology

[0002] Previous research has extensively explored the estimation of hydrocarbon expulsion efficiency from source rocks. The main methods rely on variations in soluble organic matter content and hydrocarbon molecule content from geological profiles of source rocks, the solubility of different components in crude oil within kerogen, residual hydrocarbons in source rocks, thermal simulation results, restoration of original hydrocarbon generation potential combined with pyrolysis parameters, hydrocarbon generation and expulsion simulation experiments, and comparisons of hydrocarbon generation amounts between thick and thin source rocks. However, existing methods for hydrocarbon expulsion efficiency involve various organic geochemical and geological parameters, leading to complex data acquisition and processing. Furthermore, parameter processing is primarily qualitative or semi-quantitative, making parameter control difficult in specific calculations. In addition, the abundance, type, maturity, thickness, and source-reservoir configuration of source rocks all influence hydrocarbon expulsion efficiency. Therefore, proposing a simple, rapid, and easy-to-operate quantitative method for calculating hydrocarbon expulsion efficiency is crucial. Summary of the Invention

[0003] The purpose of this invention is to provide a simple, quick, and easy-to-operate technical solution for quantitatively determining hydrocarbon expulsion efficiency. To achieve the above objective, this invention provides the following two technical solutions.

[0004] In a first aspect, the present invention provides a method for establishing a hydrocarbon expulsion efficiency distribution model for lacustrine clay source rocks, the method comprising:

[0005] Multiple samples were obtained from the study area for model building. These samples were lacustrine mudstone and shale samples with similar sedimentary conditions, similar organic parent material types, and similar degrees of organic matter thermal evolution. Among them, similar organic parent material types meant that more than 80% of the samples were type I, type II, or type III kerogen; similar degrees of organic matter thermal evolution meant that the difference in the highest pyrolysis peak temperature between the samples did not exceed 15℃.

[0006] Based on the models, the organic carbon content (TOC), hydrocarbon index (HCI), and residual hydrocarbon (S1) of the samples were established to determine the lower limit of the organic carbon content (TOC) of hydrocarbon source rocks in the study area and the maximum amount of hydrocarbon generated per unit mass of organic matter in the study area.

[0007] Based on models where the total organic carbon (TOC) content is not lower than the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area, the hydrocarbon index (HCI) of the samples is combined with the maximum hydrocarbon generation per unit mass of organic matter in the study area to determine the hydrocarbon expulsion efficiency of the samples used in the model establishment. The hydrocarbon expulsion efficiency is defined as: (maximum hydrocarbon generation per unit mass of organic matter in the study area - HCI) ÷ maximum hydrocarbon generation per unit mass of organic matter in the study area.

[0008] Based on models where the total organic carbon (TOC) content is not lower than the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area, hydrocarbon expulsion efficiency of samples is established, and the relationship between hydrocarbon expulsion efficiency and TOC content is determined as a distribution model for hydrocarbon expulsion efficiency of lacustrine clay source rocks in the study area.

[0009] According to the preferred embodiment of the first aspect, the samples used for model establishment also satisfy the requirement of large variation in organic matter abundance; wherein, large variation in organic matter abundance means that the difference between the maximum organic carbon content (TOC) and the minimum organic carbon content (TOC) is not less than 10%.

[0010] According to a preferred embodiment of the first aspect, obtaining multiple samples for model building in the study area includes:

[0011] Multiple lacustrine mudstone and shale samples with similar sedimentary conditions were found in the study area;

[0012] Determine the total organic carbon (TOC), residual hydrocarbons (S1), cracked hydrocarbons (S2), and highest pyrolysis peak temperature (T) of lacustrine mudstone and shale samples. max ;

[0013] The pyrolysis hydrocarbon production index PI of each lacustrine mudstone and shale sample was determined based on the residual hydrocarbon S1 and cracked hydrocarbon S2. The highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample was used to determine the pyrolysis hydrocarbon production index PI of each sample. max The thermal evolution degree of each lacustrine mudstone and shale sample was determined by the pyrolysis hydrocarbon production index PI (the industry usually classifies the thermal evolution degree into four levels: over-mature, mature, under-mature, and immature).

[0014] The organic parent material type of each lacustrine mudstone and shale sample was determined based on its total organic carbon (TOC) content and residual hydrocarbon (S1) content (in the industry, organic parent material types are generally classified into type I kerogen, type II kerogen, and type III kerogen, with type II kerogen including type II1 and type II2 kerogen); and / or the hydrogen index (HI) of each lacustrine mudstone and shale sample was determined based on its total organic carbon (TOC) content and cracked hydrocarbon (S2) content, and the hydrogen index (HI) and the highest pyrolysis peak temperature (T) of each lacustrine mudstone and shale sample were used to determine the type of parent material. max Determine the type of organic parent material in each lacustrine mudstone and shale sample;

[0015] Based on the thermal evolution degree and organic parent material type of each lacustrine mudstone and shale sample, lacustrine mudstone and shale samples with similar organic parent material type and similar organic thermal evolution degree were identified as samples for establishing multiple models in the study area.

[0016] Furthermore, the highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample was used to further investigate the effects. max The thermal evolution degree of lacustrine mudstone and shale samples was determined by the pyrolysis hydrocarbon production index (PI), including:

[0017] Each lacustrine mudstone and shale sample was analyzed according to its highest pyrolysis peak temperature T. max And the pyrolysis hydrocarbon production index PI, the point is set to the highest pyrolysis peak temperature T. max -The thermal evolution degree of each lacustrine mudstone and shale sample is determined by using the pyrolysis hydrocarbon production index (PI) thermal evolution degree classification template.

[0018] Furthermore, based on the organic carbon content (TOC) and residual hydrocarbon (S1) of each lacustrine mudstone and shale sample, the types of organic parent material for each lacustrine mudstone and shale sample were determined, including:

[0019] Each lacustrine mudstone and shale sample was plotted into an organic parent material type classification template based on its organic carbon content (TOC) and residual hydrocarbon (S1) to determine the organic parent material type of each lacustrine mudstone and shale sample.

[0020] Furthermore, the hydrogen index HI and the highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample were used to further analyze the results. max The types of organic parent material in each lacustrine mudstone and shale sample were determined, including:

[0021] Lacustrine mudstone and shale samples were classified according to their hydrogen index (HI) and highest pyrolysis peak temperature (T). max The point is set at the highest pyrolysis peak temperature T. max - The organic parent material type classification template based on the hydrogen index (HI) is used to determine the organic parent material type of each lacustrine mudstone and shale sample;

[0022] Furthermore, the organic carbon content (TOC), residual hydrocarbons (S1), cracked hydrocarbons (S2), and highest pyrolysis peak temperature (T) of each lacustrine mudstone and shale sample were determined. max This includes: preparing powder samples of each lacustrine mudstone and shale; and analyzing the organic carbon content (TOC), residual hydrocarbons (S1), cracked hydrocarbons (S2), and maximum pyrolysis peak temperature (T) of each lacustrine mudstone and shale powder sample. max The organic carbon content (TOC), residual hydrocarbons (S1), cracked hydrocarbons (S2), and highest pyrolysis peak temperature (T) of various lacustrine mudstone and shale samples were determined. max Furthermore, the particle size of the powder samples from various lacustrine mudstone and shale deposits ranged from 80 mesh to 120 mesh.

[0023] Furthermore, the pyrolysis hydrocarbon production index PI of each lacustrine mudstone and shale sample was determined using the following formula:

[0024] PI = S1 ÷ (S1 + S2)

[0025] In the formula, PI is the pyrolysis hydrocarbon production index, with a dimensionless unit; S2 is the cracked hydrocarbon, with a unit of mg hydrocarbon / g rock; and S1 is the residual hydrocarbon, with a unit of mg hydrocarbon / g rock.

[0026] Furthermore, the hydrogen index HI of each lacustrine mudstone and shale sample was determined using the following formula:

[0027] HI = S² × 100 ÷ TOC

[0028] In the formula, HI is the hydrogen index, in mg hydrocarbons / g TOC; S2 is cracked hydrocarbons, in mg hydrocarbons / g rock; TOC is the organic carbon content, in %;

[0029] Furthermore, the method also includes: based on the thermal evolution degree of each lacustrine mudstone and shale sample, the organic parent material type and total organic carbon (TOC) content of each lacustrine mudstone and shale sample, determining lacustrine mudstone and shale samples with similar organic parent material types, similar organic thermal evolution degrees, and large differences in organic matter abundance as samples for establishing multiple models in the study area; wherein, large differences in organic matter abundance means that the difference between the maximum and minimum organic carbon (TOC) content is not less than 10%;

[0030] Furthermore, the total organic carbon (TOC) content can be determined using a carbon-sulfur analyzer (such as a LECO CS230).

[0031] Furthermore, the residual hydrocarbon S1, the cracked hydrocarbon S2, and the highest pyrolysis peak temperature T... max The determination can be made using a rock-eval apparatus.

[0032] According to the preferred embodiment of the first aspect, the determination of the lower limit of the organic carbon content (TOC) of source rocks in the study area and the maximum hydrocarbon generation per unit mass of organic matter in the study area based on the establishment of the organic carbon content (TOC), hydrocarbon index (HCI), and residual hydrocarbons (S1) of the samples using each model includes:

[0033] Based on the various models, the lower limit of the organic carbon content (TOC) of hydrocarbon source rocks in the study area was determined by using samples according to their organic carbon content (TOC) and hydrocarbon index (HCI).

[0034] Based on the establishment of each model, the maximum amount of hydrocarbon generated per unit mass of organic matter in the study area was determined according to the organic carbon content (TOC) and residual hydrocarbon (S1) of the samples, combined with the lower limit of the organic carbon content (TOC) of hydrocarbon expulsion from source rocks in the study area.

[0035] Furthermore, based on the models established, the lower limit values ​​of the organic carbon content (TOC) of samples for hydrocarbon expulsion from source rocks in the study area were determined according to their total organic carbon (TOC) and hydrocarbon index (HCI), including:

[0036] The samples used to establish each model were plotted in a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon index (HCI) as the ordinate. The inflection point of the hydrocarbon index of mudstone and shale, which first increases and then decreases with organic carbon content (TOC), was determined as the lower limit of organic carbon content (TOC) for hydrocarbon expulsion from source rocks in the study area.

[0037] Furthermore, based on the models established by the samples according to their organic carbon content (TOC) and residual hydrocarbons (S1), combined with the lower limit of the organic carbon content (TOC) of hydrocarbons expelled from source rocks in the study area, the maximum hydrocarbon generation per unit mass of organic matter in the study area was determined, including:

[0038] The samples used for model building were plotted on a coordinate system with organic carbon content (TOC) as the abscissa and residual hydrocarbon content (S1) as the ordinate for each model building sample. The linear relationship between organic carbon content (TOC) and residual hydrocarbon content (S1) of each model building sample passing through the zero point of the coordinate system was determined for samples with organic carbon content (TOC) not exceeding the lower limit of organic carbon content (TOC) of source rock hydrocarbon expulsion. The slope of the linear relationship fitting line was taken as the maximum hydrocarbon generation per unit mass of organic matter in the study area (the higher the slope, the higher the residual hydrocarbon generation conversion rate in the study area).

[0039] Furthermore, the method also includes: plotting the samples used in each model onto a coordinate system with total organic carbon (TOC) as the abscissa and hydrocarbon index (HCI) as the ordinate, and dividing the areas where the samples used in each model are located into regions based on the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area and the maximum hydrocarbon generation per unit mass of organic matter in the study area.

[0040] The regions with a total organic carbon (TOC) content not lower than the lower limit of the TOC content of source rocks in the study area are divided into three regions based on hydrocarbon expulsion index (HCI): the hydrocarbon expulsion region, the residual + hydrocarbon expulsion region, and the region dominated by residual hydrocarbons.

[0041] Areas with a total organic carbon (TOC) content lower than the lower limit of TOC for hydrocarbon emission from source rocks in the study area are considered residual hydrocarbon areas; source rocks in these areas generally do not emit hydrocarbons. Figure 5In the study, based on the slope hydrocarbon index (HCI), when TOC < 3%, the region corresponding to HCI < 60 mg hydrocarbon / g TOC is the residual hydrocarbon region; when TOC > 3%, the region corresponding to HCI between 12 and 60 mg hydrocarbon / g TOC is the hydrocarbon expulsion region; when TOC > 3%, the region corresponding to HCI between 7 and 12 mg hydrocarbon / g TOC is the residual hydrocarbon + hydrocarbon expulsion region; and when TOC > 3%, the region corresponding to HCI between 0 and 7 mg hydrocarbon / g TOC is the region dominated by residual hydrocarbons.

[0042] According to the preferred embodiment of the first aspect, the hydrocarbon expulsion efficiency of samples is established based on models where the total organic carbon content (TOC) is not lower than the lower limit of the TOC value for hydrocarbon expulsion from source rocks in the study area. The relationship between hydrocarbon expulsion efficiency and TOC is determined using these models as a distribution model for hydrocarbon expulsion efficiency of lacustrine clay source rocks.

[0043] For each model where the organic carbon content (TOC) is not lower than the lower limit of the organic carbon content (TOC) of the source rocks in the study area, the samples were plotted on a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon expulsion efficiency as the ordinate, and a scatter plot of organic carbon content (TOC) - source rock hydrocarbon expulsion efficiency was obtained.

[0044] The scatter plot of organic carbon content (TOC) versus hydrocarbon expulsion efficiency of source rocks was processed as follows: Starting from the lower limit of organic carbon content (TOC) for hydrocarbon expulsion from source rocks in the study area, the average value of hydrocarbon expulsion efficiency and the median value of organic carbon content (TOC) within each unit range of organic carbon content (TOC) were statistically analyzed. Virtual samples were constructed in which the organic carbon content (TOC) was equal to the median value of organic carbon content (TOC) within each unit range, and the hydrocarbon expulsion efficiency was equal to the average value of the hydrocarbon expulsion efficiency within that unit range of organic carbon content (TOC). Each virtual sample was plotted on a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon expulsion efficiency as the ordinate, resulting in a scatter plot of organic carbon content (TOC) versus hydrocarbon expulsion efficiency of source rocks.

[0045] Based on the scatter plot of the virtual sample of hydrocarbon expulsion efficiency from source rocks using the organic carbon content (TOC) as a basis, a correlation analysis of hydrocarbon expulsion efficiency and organic carbon content (TOC) was conducted to obtain the relationship model between the hydrocarbon expulsion efficiency and organic carbon content (TOC).

[0046] According to a preferred embodiment of the first aspect, the hydrocarbon index HCI is determined by the following formula:

[0047] HCI = S1 ÷ TOC

[0048] In the formula, HCl is the hydrocarbon index, in mg hydrocarbons / g rock; TOC is the organic carbon content, in %; and S1 is the residual hydrocarbon, in mg hydrocarbons / g rock.

[0049] Secondly, this invention provides a method for determining the hydrocarbon expulsion efficiency of lacustrine clay source rocks, the method comprising:

[0050] The hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area was established using the method for establishing the hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks provided in the first aspect of the present invention.

[0051] Obtain the total organic carbon (TOC) content of the target samples in the study area; wherein, the target samples have the same deposition conditions, organic parent material type, and degree of organic matter thermal evolution as most (more than 50%) of the samples used for model establishment.

[0052] The hydrocarbon expulsion efficiency of the target samples in the study area was determined by combining their total organic carbon (TOC) content with the hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area.

[0053] The technical solution provided by this invention is based on the following principle: When the source rock parent material type and thermal evolution degree are similar, the residual hydrocarbon S1 should increase with the increase of the total organic carbon (TOC) content. However, in reality, as the TOC content increases, when the residual hydrocarbon S1 value increases to a certain level, because the amount of generated hydrocarbons meets the saturation adsorption of the source rock, excess hydrocarbons will be discharged from the source rock, thus reducing the residual hydrocarbon S1 value. At this point, the residual hydrocarbon S1 value deviates from the normal trend with the increase of the TOC content, and the TOC content corresponding to the deviation point is equivalent to the lower limit of the TOC content of the discharged source rock. The significance of this value is that when the TOC content of the source rock is lower than this value, the amount of generated hydrocarbons is small and it is difficult to meet the saturation adsorption of the source rock, making it difficult for the generated hydrocarbons to be discharged; when the TOC content of the source rock is higher than this value, the amount of generated hydrocarbons can meet the saturation adsorption of the source rock itself, resulting in hydrocarbon discharge. Therefore, when hydrocarbon discharge occurs, the residual hydrocarbon S1 will be lower than the value corresponding to the normal trend line. For the portion of the total organic carbon (TOC) content above the lower limit, the HCl value of a sample point corresponds to the amount of residual hydrocarbons per unit of TOC, denoted as Qr. The portion exceeding the HCl value of that sample corresponds to the amount of hydrocarbons emitted, denoted as Qe. The sum of Qr and Qe is the total hydrocarbon generation, denoted as Qg. The hydrocarbon emission efficiency Ke is the ratio of the amount of hydrocarbons emitted Qe to the total hydrocarbon generation Qg, i.e.: Ke = Qe / Qg.

[0054] When using the technical solution provided by this invention, the new method for estimating the hydrocarbon expulsion efficiency of lacustrine source rocks based on the basic principle of hydrocarbon generation and expulsion requires that the source rocks have similar sedimentary conditions, organic parent material types, and thermal evolution levels. Therefore, a large number of source rock sample analysis data should be available.

[0055] The technical solution provided by this invention is a new technique for estimating the hydrocarbon expulsion efficiency of lacustrine source rocks. Compared with existing technologies, the technical solution provided by this invention fully considers the basic principles of hydrocarbon generation and expulsion from source rocks, reasonably explains the relationship between the relative hydrocarbon generation, expulsion, and relative residual hydrocarbon content of source rocks, and determines the maximum relative hydrocarbon generation. The organic geochemical analysis data of source rocks used in the method are mainly conventional test data, which are easy to collect and organize in actual research. The plots are simple to draw, and the maximum relative hydrocarbon generation curve in the figure is intuitive and highly operable. It solves the problems of complex calculation of hydrocarbon expulsion efficiency of source rocks and the need to consider many factors, and has broad application prospects. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the points of each saline lacustrine shale sample in Example 1 of the present invention, plotted in the coordinate system of organic carbon content (TOC) and hydrocarbon generation potential (PG).

[0057] Figure 2 The highest pyrolysis peak temperature T for each saline lacustrine shale sample in Example 1 of this invention. max -A schematic diagram in the Hydrogen Index (HI) Organic Parent Material Type Classification Template.

[0058] Figure 3 This is a schematic diagram of the application points of each saline lacustrine shale sample in Example 1 of the present invention to the organic carbon content (TOC) - residual hydrocarbon (S1) organic parent material type classification template.

[0059] Figure 4 The highest pyrolysis peak temperature T for each saline lacustrine shale sample in Example 1 of this invention. max - A schematic diagram in the pyrolysis hydrocarbon production index (PI) thermal evolution degree classification template.

[0060] Figure 5 The graphs obtained by plotting the sample points in a coordinate system with the organic carbon content (TOC) as the abscissa and the residual hydrocarbon (S1) as the ordinate are used to establish the models in Embodiment 1 of the present invention.

[0061] Figure 6 The graphs obtained by plotting samples onto a coordinate system with total organic carbon (TOC) as the abscissa and hydrocarbon index (HCI) as the ordinate are used to establish the models in Embodiment 1 of the present invention.

[0062] Figure 7 This is a scatter plot of the organic carbon content (TOC) and hydrocarbon source rock expulsion efficiency in Example 1 of the present invention.

[0063] Figure 8 This is a scatter plot of a virtual sample of the organic carbon content (TOC) and hydrocarbon source rock expulsion efficiency in Example 1 of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0065] Organic carbon (TOC) refers to the amount of carbon in a rock excluding inorganic carbon found in carbonates, graphite, etc. It includes carbon from insoluble organic matter—kerogen—as well as carbon from soluble organic matter. TOC is used to reflect the abundance of organic matter because organic carbon generally constitutes the majority of organic matter and its content is relatively stable.

[0066] Residual hydrocarbons (S1) refer to the content of residual hydrocarbons (or free hydrocarbons or pyrolytic hydrocarbons) in rocks that have been generated by organic matter but have not yet been expelled.

[0067] Cracking hydrocarbon S2 refers to the content of organic matter in rocks that can generate hydrocarbons but does not, mainly corresponding to the hydrocarbon-producing portion of insoluble organic matter.

[0068] Hydrocarbon generation potential (PG) refers to the sum of hydrocarbons already generated and those potentially generated in a source rock, but does not include the portion that has been expelled from the source rock after generation (also known as hydrocarbon generation potential or hydrocarbon generation capacity).

[0069] The highest pyrolysis peak temperature Tmax refers to the temperature corresponding to the peak of the cracked hydrocarbon S2 peak obtained by the pyrolysis analyzer, which corresponds to the temperature at which the pyrolysis hydrocarbon production rate is the highest.

[0070] Kerogen from different sources of organic matter in different sedimentary environments varies greatly in properties and oil and gas generation potential. Kerogen can be classified into three main types: Type I kerogen, also known as saprophytic kerogen, can come from algal sediments and has a high oil generation potential; Type II kerogen, which comes from marine plankton and microorganisms, with Type II1 kerogen (humic-saprophytic type) tending to generate oil and having a moderate oil generation potential, and Type II2 kerogen (saprophytic-humic type) tending to generate gas; and Type III kerogen, also known as humic type, which comes from higher terrestrial plants and has a high gas generation potential.

[0071] Example 1:

[0072] This embodiment provides a method for establishing a hydrocarbon expulsion efficiency distribution model for lacustrine clay source rocks.

[0073] This embodiment uses the Chang 7 Member source rocks of the Yanchang Formation in Basin A as an example. The lithology of the Chang 7 Member source rocks in Basin A includes black shale and dark mudstone. Black shale is mainly developed in the Chang 73 Member, while dark mudstone is developed in the Chang 71, Chang 72, and Chang 73 Members. The Chang 73 Member has the thickest black shale and dark mudstone with the best continuity, while the Chang 71 and Chang 72 Members are mainly composed of dark mudstone. From a macroscopic perspective of rock types, both mudstone and shale belong to clay-type source rocks, often deposited in quiet, oxygen-deficient sedimentary environments such as shallow seas, deltas, and lakes. They are rich in plankton or terrestrial organic matter, which is deposited and preserved along with clay minerals. In this embodiment, the black shale and dark mudstone of the Chang 7 Member in Basin A are considered as a single entity, hereinafter collectively referred to as "Chang 7 Member mudstone and shale." This embodiment uses the organic geochemical characteristic analysis method of the Chang 7 Member lacustrine mudstone and shale as an example to illustrate the method for establishing the hydrocarbon expulsion efficiency distribution model of lacustrine clay-type source rocks according to this invention.

[0074] (1) TOC determination and pyrolysis analysis of mudstone and shale

[0075] Samples of mudstone and shale from section 7 of the Long 7 Formation were collected. After being crushed, the mudstone and shale samples from section 7 of the Long 7 Formation were sieved through a 100-mesh sieve to obtain powder samples. The total organic carbon (TOC) of the powder samples from section 7 of the Long 7 Formation was determined using a carbon-sulfur analyzer. Then, the residual hydrocarbons (S1), cracked hydrocarbons (S2), and the highest pyrolysis peak temperature (Tmax) of the powder samples from section 7 of the Long 7 Formation were determined using a rock-eval pyrolysis analyzer.

[0076] Using PI = S1 ÷ (S1 + S2), HI = S2 × 100 ÷ TOC, PG = S1 + S2, and HCI = S1 ÷ TOC, combined with the organic carbon content TOC, residual hydrocarbons S1, cracked hydrocarbons S2, and the highest pyrolysis peak temperature Tmax of each Chang 7 mudstone and shale sample, the hydrocarbon generation potential PG, hydrogen index HI, hydrocarbon index HCI, and pyrolysis hydrocarbon production index PI of each Chang 7 mudstone and shale sample were determined.

[0077] The results are shown in Table 1.

[0078] Table 1. Statistical data on basic geochemical characteristics of the Chang 7 section mudstone and shale.

[0079]

[0080]

[0081] (2) Drawing and comprehensive comparison of source rock characteristic maps

[0082] ① The organic matter abundance distribution of each Chang 7 mudstone and shale sample was determined by plotting its total organic carbon (TOC) content and hydrocarbon generation potential (PG) onto a TOC-PG coordinate system. The results are shown in [reference needed]. Figure 1 .from Figure 1 As can be seen, the abundance of organic matter in the samples is highly dispersed, with TOC content ranging from 0.37% to 36.83%. This meets the condition of large variation in organic matter abundance.

[0083] ② The shale samples of each of the seven sections were analyzed according to their hydrogen index (HI) and highest pyrolysis peak temperature (T). max The point is set at the highest pyrolysis peak temperature T. max The organic parent material type was determined using the HI (hydrogen index) organic parent material classification template for each of the 7th section mudstone and shale samples. The results are shown in [link to template]. Figure 2 Each of the shale samples from section 7 of the Changde Formation was plotted into an organic parent material type classification template based on its total organic carbon (TOC) and residual hydrocarbon (S1) content, thereby determining the organic parent material type of each sample. The results are shown in [link to template]. Figure 3 .Depend on Figure 2 It can be seen that the mudstone and shale samples of Chang 7 are mainly concentrated in the II1 and II2 type areas; from Figure 3 It can be seen that the mudstone and shale samples of Chang 7 are mainly distributed in the Type II2 region, followed by the Type II1 region. Therefore, considering... Figure 2 , Figure 3 It can be seen that the organic parent material of the Chang 7 section mudstone and shale samples is mainly of type II1 and type II2 kerogen, which are similar in type, and the source rocks are mainly oil-generating.

[0084] ③ Each of the seven sections of mudstone and shale samples was analyzed according to its highest pyrolysis peak temperature T. max And the pyrolysis hydrocarbon production index PI, the point is set to the highest pyrolysis peak temperature T. max The thermal evolution degree of each Chang 7 mudstone and shale sample was determined using the pyrolysis hydrocarbon production index (PI) thermal evolution degree classification template. See the results below. Figure 4 .Depend on Figure 4 It can be seen that the mudstone and shale samples of the Chang 7 section are mainly concentrated in the "mature" area. Therefore, it can be concluded that the maturity of the mudstone and shale samples of the Chang 7 section is close and mainly in the "mature" stage, indicating that a certain amount of oil and gas has been generated, and that it has exploration potential and research value.

[0085] ④ Based on the results of steps ①②③ above: the organic matter abundance of the Chang 7 mudstone and shale samples varies greatly; the main organic parent material types are type II1 and type II2 kerogen, and the source rocks are mainly oil-generating; the thermal evolution is mainly in the "mature" stage. Furthermore, the sedimentary conditions, organic parent material types, and thermal evolution of the Chang 7 mudstone and shale samples are highly similar, meeting the basic conditions for establishing a hydrocarbon expulsion efficiency distribution model for source rocks. Therefore, each Chang 7 mudstone and shale sample will be used as the model sample.

[0086] (3) Analyze and establish a hydrocarbon excretion model

[0087] ① The samples used for model establishment, namely the shale samples of each Chang 7 Formation, were plotted on a coordinate system with TOC as the abscissa and HCI as the ordinate, according to their organic carbon content (TOC) and hydrocarbon index (HCI). The inflection point where the hydrocarbon index of the shale first increases and then decreases with TOC was determined. The TOC value at this inflection point was used as the lower limit of the TOC value for hydrocarbon expulsion from the source rocks of the Chang 7 Formation in Basin A. The results are as follows: Figure 6 As shown. By Figure 6 It can be seen that as the total organic carbon (TOC) content of the mudstone and shale samples increases, the hydrocarbon index (HCI) shows a characteristic of first increasing and then decreasing. By analyzing the distribution of sample scatter points, the inflection point at which the HCI of mudstone and shale continuously decreases with the increase of TOC content is determined. The abscissa corresponding to this inflection point is the lower limit of the TOC content of the source rocks of the Chang 7 Member of the Yanchang Formation in Basin A (hereinafter referred to as the lower limit of the TOC content). In this example, the lower limit of the TOC content is 3%.

[0088] ② Plot the samples used for model establishment, i.e., each 7-section mudstone and shale sample, onto a coordinate system with TOC as the abscissa and S1 as the ordinate, according to their organic carbon content (TOC) and residual hydrocarbons (S1). Determine the linear relationship between TOC and S1 for each sample passing through the zero point of the coordinate system, provided that the TOC does not exceed the lower limit of the TOC for hydrocarbon expulsion from the source rock. The slope of this linear relationship fitting line is taken as the maximum hydrocarbon generation per unit mass of organic matter in the study area (hereinafter referred to as the maximum hydrocarbon generation per unit mass of organic matter). The results are as follows: Figure 5 As shown. By Figure 5It can be seen that when the total organic carbon (TOC) content is low (TOC < 3%), the residual hydrocarbon S1 increases with the increase of TOC. At this time, the slope of the straight line corresponding to the scatter plot trend is approximately the hydrocarbon index HCI = 60 mg hydrocarbon / g TOC. In this example, the maximum hydrocarbon generation by organic matter is 60 mg hydrocarbon / g TOC. When the total organic carbon (TOC) content is high (TOC > 3%), the residual hydrocarbon S1 deviates from the normal trend with the increase of TOC. At this time, the slope of the straight line corresponding to the scatter plot trend becomes significantly slower, that is, the hydrocarbon index HCI decreases significantly. The deviation indicates that hydrocarbons have been discharged from the source rock. This area is a hydrocarbon discharge area, a residual hydrocarbon + hydrocarbon discharge area, and a residual hydrocarbon-dominated area. According to the slope hydrocarbon index (HCI), when TOC < 3%, the region corresponding to HCI < 60 mg hydrocarbon / g TOC is the residual hydrocarbon region; when TOC > 3%, the region corresponding to HCI between 12-60 mg hydrocarbon / g TOC is the hydrocarbon expulsion region; when TOC > 3%, the region corresponding to HCI between 7-12 mg hydrocarbon / g TOC is the residual hydrocarbon + hydrocarbon expulsion region; when TOC > 3%, the region corresponding to HCI between 0-7 mg hydrocarbon / g TOC is the residual hydrocarbon-dominated region. Figure 5 ).

[0089] ③ In the plot obtained in step ①, the regions where the samples used for each model are located are divided based on the lower limit of organic carbon content (TOC) and the maximum hydrocarbon generation value of organic matter: Regions with TOC content lower than the lower limit of organic carbon content for hydrocarbon expulsion from source rocks in the study area are considered residual hydrocarbon regions, where source rocks generally do not expel hydrocarbons; regions with TOC content not lower than the lower limit of organic carbon content for hydrocarbon expulsion from source rocks in the study area are further divided into three regions based on the hydrocarbon index (HCI): hydrocarbon expulsion region, residual + hydrocarbon expulsion region, and residual hydrocarbon-dominated region. See the results below. Figure 6 .

[0090] ④ The hydrocarbon expulsion efficiency of each model based on the organic carbon content (TOC) not lower than the lower limit of the organic carbon content (TOC) of the source rocks in the study area was determined by combining the hydrocarbon index (HCI) of the sample with the maximum hydrocarbon generation per unit mass of organic matter in the study area; where the hydrocarbon expulsion efficiency Ke = (maximum hydrocarbon generation value of organic matter - hydrocarbon index (HCI)) ÷ maximum hydrocarbon generation value of organic matter.

[0091] by Figure 6Taking Sample 1 as an example, TOC = 21.44%, HCl = 31.67 mg hydrocarbons / g TOC. The HCl value of this sample corresponds to the residual hydrocarbon amount per unit TOC content, denoted as Qr, Qr = 31.67 mg hydrocarbons / g TOC. The portion of the HCl value higher than that of Sample 1 corresponds to the emission amount, denoted as Qe, Qe = 60 - 31.67 = 28.33 mg hydrocarbons / g TOC. The sum of Qr and Qe is the total hydrocarbon generation, denoted as Qg, Qg = 60 mg hydrocarbons / g TOC. According to the definition of hydrocarbon emission efficiency Ke, it is the ratio of hydrocarbon generation Qe to total hydrocarbon generation Qg, that is: Ke = Qe / Qg = 28.33 ÷ 60 = 0.47. The above is the process of determining the hydrocarbon emission efficiency Ke of one sample. Based on this, the hydrocarbon emission efficiency of the remaining samples can be determined.

[0092] ⑤ For models where the organic carbon content (TOC) is not less than 3% of the lower limit of TOC, samples were plotted on a coordinate system with TOC as the abscissa and hydrocarbon expulsion efficiency as the ordinate, resulting in a scatter plot of TOC-source rock hydrocarbon expulsion efficiency. The results are shown below. Figure 7 As shown.

[0093] ⑥ Processing the scatter plot of organic carbon content (TOC) versus source rock hydrocarbon expulsion efficiency: Starting from the lower limit of organic carbon content (TOC), calculate the average value of hydrocarbon expulsion efficiency within each unit of organic carbon content (TOC) variation range, and the median value of organic carbon content (TOC) within each unit of organic carbon content (TOC) variation range. Construct virtual samples where organic carbon content (TOC) equals the median value of organic carbon content (TOC) within each unit of organic carbon content (TOC) variation range, and hydrocarbon expulsion efficiency equals the average value of hydrocarbon expulsion efficiency within that unit of organic carbon content (TOC) variation range. Plot each virtual sample according to its organic carbon content (TOC) and hydrocarbon expulsion efficiency onto a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon expulsion efficiency as the ordinate. This yields the scatter plot of organic carbon content (TOC) versus source rock hydrocarbon expulsion efficiency virtual samples. The results are as follows: Figure 8 As shown in the figure, a scatter plot of virtual samples of source rock hydrocarbon expulsion efficiency based on total organic carbon (TOC) content was used to conduct a correlation analysis between hydrocarbon expulsion efficiency and TOC content, thus obtaining a relationship model between the hydrocarbon expulsion efficiency and TOC content.

[0094] Taking a unit organic carbon content (TOC) variation range of 3%-4% as an example, the horizontal axis of the virtual sample corresponding to this unit organic carbon content TOC variation range is set to 3.5%, and the vertical axis is the average hydrocarbon expulsion efficiency within the 3%-4% TOC variation range. Similarly, the hydrocarbon expulsion efficiency and organic carbon content (TOC) of the virtual samples corresponding to the remaining unit organic carbon content TOC variation ranges are determined.

[0095] The relationship model between hydrocarbon expulsion efficiency and total organic carbon (TOC) is as follows:

[0096] Ke = 19.846ln(TOC) + 4.4941

[0097] R 2 =0.7249

[0098] Since the lower limit of total organic carbon (TOC) content in the source rocks of the Chang 7 member of the Yanchang Formation in Basin A is 3% (>0), the relationship model between hydrocarbon expulsion efficiency and TOC content indicates that as TOC content increases, hydrocarbon expulsion efficiency also increases, showing a good positive correlation. Figure 8 It can be seen from the data that the highest hydrocarbon expulsion efficiency of the source rocks in the Chang 7 section of the Yanchang Formation in Basin A is close to 80%, while the lowest hydrocarbon expulsion efficiency is below 40%.

[0099] Example 2

[0100] This embodiment provides a method for determining the hydrocarbon expulsion efficiency of lacustrine clay source rocks.

[0101] This embodiment uses the Chang 7th section of the Yanchang Formation in Basin A as the research area to determine the hydrocarbon expulsion efficiency of certain mudstones and shale within the research area.

[0102] The method includes:

[0103] A. A hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area was established according to the method provided in Example 1.

[0104] B. Obtain the total organic carbon (TOC) content of the target samples in the study area.

[0105] C. The hydrocarbon expulsion efficiency of the target samples in the study area is determined by combining their total organic carbon (TOC) content with the hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area.

[0106] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for establishing a hydrocarbon expulsion efficiency distribution model for lacustrine clay source rocks, the method comprising: Obtain multiple samples from the study area for model building; The samples used to establish the model are lacustrine mudstone and shale samples with the same sedimentary conditions, similar organic parent material types, and similar degrees of organic matter thermal evolution. Among them, having similar organic parent material types means that more than 80% of the samples are type I, type II, or type III kerogen; having similar degrees of organic matter thermal evolution means that the difference in the highest pyrolysis peak temperature between the samples does not exceed 15℃. Based on the models, the organic carbon content (TOC), hydrocarbon index (HCI), and residual hydrocarbon (S1) of the samples were established to determine the lower limit of the organic carbon content (TOC) of hydrocarbon source rocks in the study area and the maximum amount of hydrocarbon generated per unit mass of organic matter in the study area. Based on models where the total organic carbon (TOC) content is not lower than the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area, the hydrocarbon index (HCI) of the samples is combined with the maximum hydrocarbon generation per unit mass of organic matter in the study area to determine the hydrocarbon expulsion efficiency of the samples used in the model establishment. The hydrocarbon expulsion efficiency is calculated as follows: (maximum hydrocarbon generation per unit mass of organic matter in the study area - HCI) ÷ maximum hydrocarbon generation per unit mass of organic matter in the study area. Based on models where the total organic carbon content (TOC) is not lower than the lower limit of the TOC for hydrocarbon expulsion from source rocks in the study area, hydrocarbon expulsion efficiency of samples is established, and the relationship between hydrocarbon expulsion efficiency and TOC is determined as a model for the distribution of hydrocarbon expulsion efficiency of lacustrine clay source rocks in the study area. The samples obtained from the study area for model building include: Multiple lacustrine mudstone and shale samples with similar sedimentary conditions were found in the study area; Determine the total organic carbon (TOC), residual hydrocarbons (S1), cracked hydrocarbons (S2), and highest pyrolysis peak temperature (T) of lacustrine mudstone and shale samples. max ; The pyrolysis hydrocarbon production index PI of each lacustrine mudstone and shale sample was determined based on the residual hydrocarbon S1 and cracked hydrocarbon S2. The highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample was used to determine the pyrolysis hydrocarbon production index PI of each sample. max The thermal evolution degree of each lacustrine mudstone and shale sample was determined by the pyrolysis hydrocarbon production index (PI). The organic parent material type of each lacustrine mudstone and shale sample was determined based on its total organic carbon (TOC) content and residual hydrocarbon (S1); and / or the hydrogen index (HI) of each lacustrine mudstone and shale sample was determined based on its total organic carbon (TOC) content and cracked hydrocarbon (S2) content, and the hydrogen index (HI) and the highest pyrolysis peak temperature (T) of each lacustrine mudstone and shale sample were used to determine the type of organic parent material of each sample. max Determine the type of organic parent material in each lacustrine mudstone and shale sample; Based on the thermal evolution degree and organic parent material type of each lacustrine mudstone and shale sample, lacustrine mudstone and shale samples with similar organic parent material type and similar organic thermal evolution degree were selected as samples for establishing multiple models in the study area.

2. The method according to claim 1, wherein, The samples used for model establishment also need to meet the requirement of large variation in organic matter abundance; where large variation in organic matter abundance means that the difference between the maximum organic carbon content (TOC) and the minimum organic carbon content (TOC) is not less than 10%.

3. The method according to claim 1, wherein, The highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample was used to determine the optimal pyrolysis temperature. max The thermal evolution degree of lacustrine mudstone and shale samples was determined by the pyrolysis hydrocarbon production index (PI), including: Each lacustrine mudstone and shale sample was analyzed according to its highest pyrolysis peak temperature T. max And the pyrolysis hydrocarbon production index PI, the point is set to the highest pyrolysis peak temperature T. max - The pyrolysis hydrocarbon production index (PI) thermal evolution degree classification template is used to determine the thermal evolution degree of each lacustrine mudstone and shale sample; and / or Based on the organic carbon content (TOC) and residual hydrocarbon (S1) of the lacustrine mudstone and shale samples, the types of organic parent material for each lacustrine mudstone and shale sample were determined as follows: Each lacustrine mudstone and shale sample was plotted into an organic parent material type classification template based on its total organic carbon (TOC) and residual hydrocarbon (S1) content, thereby determining the organic parent material type of each lacustrine mudstone and shale sample; and / or The hydrogen index HI and the highest pyrolysis peak temperature T of each lacustrine mudstone and shale sample were used respectively. max The types of organic parent material in each lacustrine mudstone and shale sample were determined, including: Lacustrine mudstone and shale samples were classified according to their hydrogen index (HI) and highest pyrolysis peak temperature (T). max The point is set at the highest pyrolysis peak temperature T. max - The organic parent material type classification template based on the hydrogen index (HI) is used to determine the organic parent material type of each lacustrine mudstone and shale sample.

4. The method according to claim 3, wherein, The method also includes: based on the thermal evolution degree of each lacustrine mudstone and shale sample, the organic parent material type and total organic carbon (TOC) content of each lacustrine mudstone and shale sample, determining lacustrine mudstone and shale samples with similar organic parent material types, similar organic thermal evolution degrees, and large differences in organic matter abundance as samples for establishing multiple models in the study area; wherein, large differences in organic matter abundance means that the difference between the maximum and minimum organic carbon (TOC) content is not less than 10%.

5. The method according to claim 1, wherein, Based on the models established for the organic carbon content (TOC), hydrocarbon index (HCI), and residual hydrocarbons (S1) of the samples, the lower limit of the organic carbon content (TOC) for hydrocarbon expulsion from source rocks in the study area and the maximum hydrocarbon generation per unit mass of organic matter in the study area were determined, including: Based on the various models, the lower limit of the organic carbon content (TOC) of hydrocarbon source rocks in the study area was determined by using samples according to their organic carbon content (TOC) and hydrocarbon index (HCI). Based on the establishment of each model, the maximum hydrocarbon generation per unit mass of organic matter in the study area was determined according to the organic carbon content (TOC) and residual hydrocarbons (S1) of the samples, combined with the lower limit of the organic carbon content (TOC) of hydrocarbons discharged from the source rocks in the study area.

6. The method according to claim 5, wherein, Based on the models established, the lower limit of the organic carbon content (TOC) of hydrocarbons expelled from source rocks in the study area was determined according to the samples' total organic carbon (TOC) and hydrocarbon index (HCI). The samples used to establish each model were plotted on a coordinate system with TOC as the abscissa and HCI as the ordinate, according to their organic carbon content (TOC) and hydrocarbon index (HCI). The inflection point of the hydrocarbon index of mudstone and shale, which first increases and then decreases with TOC, was determined. The TOC value at this inflection point was used as the lower limit of the organic carbon content (TOC) for hydrocarbon expulsion from source rocks in the study area.

7. The method according to claim 6, wherein, Based on the models established using samples according to their total organic carbon (TOC) content and residual hydrocarbons (S1), combined with the lower limit of the TOC content of source rocks in the study area, the maximum hydrocarbon generation per unit mass of organic matter in the study area was determined as follows: Each model-building sample was plotted on a coordinate system with organic carbon content (TOC) as the abscissa and residual hydrocarbons (S1) as the ordinate. The linear relationship between organic carbon content (TOC) and residual hydrocarbons (S1) of each model-building sample passing through the zero point of the coordinate system was determined for samples whose organic carbon content (TOC) does not exceed the lower limit of organic carbon content (TOC) for hydrocarbon expulsion from source rocks. The slope of this linear relationship fitting line was taken as the maximum hydrocarbon generation per unit mass of organic matter in the study area.

8. The method according to claim 7, wherein, The method also includes: plotting the samples used in each model onto a coordinate system with total organic carbon (TOC) as the abscissa and hydrocarbon index (HCI) as the ordinate, and dividing the areas where the samples used in each model are located into plots, based on the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area and the maximum hydrocarbon generation per unit mass of organic matter in the study area. The region with a total organic carbon (TOC) content lower than the lower limit of the TOC content of source rocks in the study area is the residual hydrocarbon region. The regions with a total organic carbon (TOC) content not lower than the lower limit of the TOC content of source rocks in the study area are divided into three regions based on hydrocarbon expulsion index (HCI): the hydrocarbon expulsion region, the residual + hydrocarbon expulsion region, and the region dominated by residual hydrocarbons.

9. The method according to claim 1, wherein, Models based on the total organic carbon (TOC) content of samples not lower than the lower limit of TOC for hydrocarbon expulsion from source rocks in the study area were established to determine the hydrocarbon expulsion efficiency of samples and the relationship between hydrocarbon expulsion efficiency and TOC content. These models serve as distribution models for hydrocarbon expulsion efficiency of lacustrine clay source rocks. For each model where the organic carbon content (TOC) is not lower than the lower limit of the organic carbon content (TOC) of the source rocks in the study area, the samples were plotted on a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon expulsion efficiency as the ordinate, and a scatter plot of organic carbon content (TOC) - source rock hydrocarbon expulsion efficiency was obtained. The scatter plot of organic carbon content (TOC) versus hydrocarbon expulsion efficiency of source rocks was processed as follows: Starting from the lower limit of organic carbon content (TOC) for hydrocarbon expulsion from source rocks in the study area, the average value of hydrocarbon expulsion efficiency and the median value of organic carbon content (TOC) within each unit range of organic carbon content (TOC) were statistically analyzed. Virtual samples were constructed in which the organic carbon content (TOC) was equal to the median value of organic carbon content (TOC) within each unit range, and the hydrocarbon expulsion efficiency was equal to the average value of the hydrocarbon expulsion efficiency within that unit range of organic carbon content (TOC). Each virtual sample was plotted on a coordinate system with organic carbon content (TOC) as the abscissa and hydrocarbon expulsion efficiency as the ordinate, resulting in a scatter plot of organic carbon content (TOC) versus hydrocarbon expulsion efficiency of source rocks. Based on the scatter plot of the virtual sample of hydrocarbon expulsion efficiency from source rocks using the organic carbon content (TOC) as a basis, a correlation analysis of hydrocarbon expulsion efficiency and organic carbon content (TOC) was conducted to obtain the relationship model between the hydrocarbon expulsion efficiency and organic carbon content (TOC).

10. A method for determining the hydrocarbon expulsion efficiency of lacustrine clay source rocks, the method comprising: A hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area was established using the method described in any one of claims 1-9. Obtain the total organic carbon (TOC) content of the target samples in the study area; wherein, the target samples have the same deposition conditions, organic parent material type, and degree of organic matter thermal evolution as more than 50% of the samples used in model establishment. The hydrocarbon expulsion efficiency of the target samples in the study area was determined by combining their total organic carbon (TOC) content with the hydrocarbon expulsion efficiency distribution model of lacustrine clay source rocks in the study area.

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