Evaluation method for organic matter abundance and hydrocarbon generation amount of neonatozoic marine hydrocarbon source rock

Abstract

The invention belongs to the technical field of oil and gas exploration and development, and relates to a method for evaluating organic abundance and hydrocarbon generation quantity of a neonatozoic marine facies hydrocarbon source rock, which comprises the following steps of: extracting kerogen from the marine facies hydrocarbon source rock to obtain various hydrocarbon forming organisms and components thereof in the kerogen; performing kerogen enrichment on each of the hydrocarbon forming organisms; carrying out carbon element determination on the kerogen sample subjected to kerogen enrichment; calculating the organic matter abundance of the marine hydrocarbon source rock according to the measured carbon element content; counting the mass ratio of kerogen to rock in the hydrocarbon source rock of each sedimentary facies belt; according to the ratio of the kerogen mass to the rock mass, the organic matter abundance of the marine hydrocarbon source rock in different water depth ranges is predicted. According to the method, the distribution of different-quality and different-depth marine facies hydrocarbon source rocks in less-well and no-well areas and the hydrocarbon generation amount of the marine facies hydrocarbon source rocks can be accurately obtained, decision-making service is provided for oil-gas exploration and development, and the method has high application and popularization value.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the organic matter abundance and hydrocarbon generation amount of Cenozoic marine source rocks, and belongs to the technical field of oil and gas exploration and development. Background Art

[0002] Marine source rocks are one of the important sources of oil and gas discovered globally. The exploration wells of Cenozoic marine source rocks drilled in the offshore areas of China are very limited. The organic matter abundance of marine source rocks shows a trend of decreasing with the increase of the distance from the shore. How about the organic matter abundance and hydrocarbon generation amount in the vast marine strata is very important for offshore oil and gas exploration. For low-exploration areas with few or no wells, the seismic response characteristics can be used to identify and predict mudstones with high organic matter abundance to a certain extent. However, the organic matter abundance of Cenozoic marine source rocks in the offshore areas is low, and the seismic response characteristics are not obvious. At the same time, for the deep-water to ultra-deep-water areas in the northern South China Sea, the seismic imaging quality is poor, and it is difficult to implement the method of predicting marine source rocks using seismic facies. There is an urgent need to invent a new method that can be used to predict the organic matter abundance and hydrocarbon generation amount of marine source rocks in well-free areas. Summary of the Invention

[0003] Aiming at the above problems, the purpose of the present invention is to provide a method for evaluating the organic matter abundance and hydrocarbon generation amount of Cenozoic marine source rocks, which can accurately obtain the distribution and hydrocarbon generation amount of marine source rocks with different qualities and depths in areas with few or no wells, provide decision-making services for oil and gas exploration and development, and has great popularization and application value.

[0004] To achieve the above purpose, the present invention proposes the following technical solutions: A method for evaluating the organic matter abundance of Cenozoic marine source rocks, comprising the following steps: extracting kerogen from marine source rocks to obtain various hydrocarbon-generating organisms and their compositions in the kerogen; enriching kerogen for each of the hydrocarbon-generating organisms; measuring the carbon element content of the kerogen sample after kerogen enrichment; calculating the organic matter abundance of marine source rocks according to the measured carbon element content; counting the ratio of the mass of kerogen to the mass of rock in the source rocks of each sedimentary facies belt; predicting the organic matter abundance of marine source rocks within different water depth ranges according to the ratio of the mass of kerogen to the mass of rock.

[0005] Further, the method for obtaining various hydrocarbon-generating organisms and their compositions in the kerogen is as follows: subjecting the rock sample of marine source rock to acid treatment to obtain kerogen, weighing the kerogen, calculating the mass ratio of the kerogen to the rock sample, and counting the mass proportion of kerogen in marine source rocks under different sedimentary environments; identifying the hydrocarbon-generating organisms in the kerogen to obtain the area sum occupied by each of the hydrocarbon-generating organisms; determining the paleo-water depth during the deposition period of marine source rocks, constructing the relationship between the proportion of benthic organisms and the paleo-water depth, and dividing the paleo-water depth interval range according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-generating organisms and their compositions within each water depth interval range.

[0006] Furthermore, the paleo-water depth ranges include: the water depth range of 0 - 30 m, the water depth range of 30 - 60 m, the water depth range of 60 - 90 m, and the water depth range of 90 - 160 m; the hydrocarbon-generating organisms include terrestrial higher plants, seagrasses, benthic macroalgae, and acanthocystodinium.

[0007] Furthermore, the kerogen of various hydrocarbon-generating organisms is enriched so that the mass of the enriched kerogen is greater than 10 mg; or the kerogen of marine hydrocarbon source rocks with the proportion of the hydrocarbon-generating organisms greater than 90% is selected.

[0008] Furthermore, the calculation formula for the organic matter abundance of the marine hydrocarbon source rocks is:

[0009] TOC 验证 =[∑(C i ×W i )]×W 干酪根 ÷λ

[0010] where TOC 验证 is the organic matter abundance of the marine hydrocarbon source rocks, C i is the carbon element content, W i is the sum of the areas occupied by the hydrocarbon-generating organisms, and λ is the content of kerogen organic matter in the whole rock organic matter. By adjusting λ, TOC 验证 is made consistent with the measured organic matter abundance of the marine hydrocarbon source rocks.

[0011] Furthermore, the sedimentary facies belts include the coast, enclosed shallow sea, and open shallow sea. In the hydrocarbon source rocks of each sedimentary facies belt, the ratios of the kerogen mass to the rock mass are respectively denoted as: W 滨海 , W 封闭浅海 and W 开阔浅海 .

[0012] Furthermore, the calculation formula for the organic carbon content OC 干酪根 of the kerogen in each water depth range is:

[0013] OC 干酪根 =∑(C i ×W i )

[0014] where C i is the carbon element content, and W i is the sum of the areas occupied by the hydrocarbon-generating organisms;

[0015] The calculation formula for the organic carbon content of the marine hydrocarbon source rocks in each water depth range is:

[0016] TOC′ 预测 =OC 干酪根 ×W 相带 ÷λ

[0017] Among them, TOC′ 预测 is the organic carbon content of marine hydrocarbon source rocks within a certain water depth range; W 相带 is the ratio of the mass of kerogen to the mass of rock in the hydrocarbon source rocks of each sedimentary facies zone, and the W 相带 includes W 滨海 , W 封闭浅海 or W 开阔浅海 .

[0018] The present invention also discloses a method for evaluating the hydrocarbon generation amount of hydrocarbon-generating organisms in Cenozoic marine hydrocarbon source rocks, including the following steps: extracting kerogen from marine hydrocarbon source rocks to obtain various hydrocarbon-generating organisms and their compositions in the kerogen; performing in-situ Fourier transform infrared spectroscopy analysis on the hydrocarbon-generating organisms to obtain the aliphatic hydrocarbon content and the aromatic hydrocarbon condensation coefficient; selecting modern biological species of the hydrocarbon-generating organisms and conducting hydrocarbon generation simulation experiments on modern organisms to obtain the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of modern organisms; using the aliphatic hydrocarbon content and the maximum liquid hydrocarbon production of modern organisms as the horizontal and vertical coordinates respectively to plot a graph and construct a liquid growth index fitting curve to predict the maximum liquid hydrocarbon production of various hydrocarbon-generating organisms; using the aromatic hydrocarbon condensation coefficient and the maximum gaseous hydrocarbon production of modern organisms as the horizontal and vertical coordinates respectively to plot a graph and construct a gaseous growth index fitting curve to predict the maximum gaseous hydrocarbon production of various hydrocarbon-generating organisms; predicting the hydrocarbon generation amount of marine hydrocarbon source rocks within different water depth ranges according to the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of the hydrocarbon-generating organisms.

[0019] Furthermore, the method for obtaining various hydrocarbon-generating organisms and their compositions in the kerogen is as follows: subjecting the rock sample of the marine hydrocarbon source rock to acid treatment to obtain kerogen, weighing the kerogen, calculating the mass ratio of the kerogen to the rock sample, and statistically analyzing the mass proportion of kerogen in marine hydrocarbon source rocks under different sedimentary environments; identifying the hydrocarbon-generating organisms in the kerogen to obtain the sum of the areas occupied by each hydrocarbon-generating organism; determining the paleo-water depth during the deposition period of the marine hydrocarbon source rock, constructing the relationship between the proportion of benthic organisms and the paleo-water depth, and dividing the paleo-water depth interval range according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-generating organisms and their compositions within each water depth interval range.

[0020] Furthermore, the calculation formula for the hydrocarbon generation amount of marine hydrocarbon source rocks within different water depth ranges is as follows:

[0021] Yeild = ∑(C i ×W i ×HC i )

[0022] Among them, C i is the carbon element content, W i is the sum of the areas occupied by the hydrocarbon-generating organisms, and HC i is the sum of the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of the hydrocarbon-generating organisms.

[0023] The technical solution of the present invention has at least the following technical effects or advantages: The present invention is mainly used in areas with low exploration degree. By calculating the distribution of hydrocarbon-forming organisms, it predicts the favorable development areas of marine hydrocarbon source rocks; through the composition and contribution amount of hydrocarbon-forming organisms, it accurately predicts the organic matter abundance and hydrocarbon generation amount of marine hydrocarbon source rocks, providing decision-making services for oil and gas exploration and development, and having great promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a distribution diagram of different hydrocarbon-forming organisms within each water depth range in an embodiment of the present invention;

[0025] Figure 2 It is a verification diagram of the accuracy of the calculation result of the organic matter abundance TOC of marine hydrocarbon source rocks in an embodiment of the present invention;

[0026] Figure 3 It is a fitting diagram of the growth index of hydrocarbon-forming organisms in an embodiment of the present invention, Figure 3 (a) is the fitting curve of the liquid growth index, Figure 3 (b) is the fitting curve of the gaseous growth index;

[0027] Figure 4 It is a prediction diagram of the distribution of hydrocarbon generation amount of marine hydrocarbon source rocks within different water depth ranges in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail through specific embodiments. However, it should be understood that the provision of the specific embodiments is only for better understanding of the present invention, and they should not be construed as limitations to the present invention. In the description of the present invention, it should be understood that the terms used are only for the purpose of description and cannot be construed as indicating or implying relative importance.

[0029] A hydrocarbon source rock refers to a rock rich in organic matter that can generate and expel a large amount of oil and gas, that is, a rock that can produce or has produced mobile hydrocarbons, including oil source rocks, gas source rocks, and oil and gas source rocks. Kerogen refers to the dispersed organic matter in sedimentary rocks that is insoluble in alkalis, non-oxidizing acids, and non-polar organic solvents, and it exists in large quantities in hydrocarbon source rocks.

[0030] A marine hydrocarbon source rock refers to a hydrocarbon source rock formed in a marine environment. Marine hydrocarbon source rocks are one of the important sources of oil and gas resources, mainly formed by a series of geological processes of organic matter deposited in a marine environment. These organic matters may come from planktonic algae, benthic thalloid plants, etc. In a specific sedimentary environment, these organic matters can be deposited and preserved in large quantities, and then form hydrocarbon source rocks.

[0031] The organic matter abundance refers to the percentage content of organic matter in the source rock per unit mass, and it is an important index for measuring and evaluating the hydrocarbon generation potential of the source rock.

[0032] The hydrocarbon generation amount refers to the maximum amount of hydrocarbon substances that can be generated by the organic matter in a certain volume or weight of source rock under natural geological conditions, including the amount of hydrocarbon that has been generated so far and the remaining hydrocarbon generation potential that has not been converted. Its basic unit is kilogram (kg) or ton (t) or cubic meter (m 3 ).

[0033] As mentioned above, for marine source rocks that are far from the shore and have a low organic matter abundance, it is impossible to accurately predict their organic matter abundance and hydrocarbon generation amount in the prior art. However, in the practice of oil and gas exploitation, it is very important to predict the organic matter abundance and hydrocarbon generation amount of marine source rocks, that is, it is necessary to evaluate whether they have exploitation value before oil and gas exploitation. Aiming at the problems existing in the prior art, the present invention proposes a method for quantitatively calculating the organic matter abundance and hydrocarbon generation amount of marine source rocks based on hydrocarbon-forming organisms. It obtains the kerogen mass obtained from the unit mass of marine source rock and calculates the proportion of hydrocarbon-forming organisms in the kerogen; by analogizing the organic carbon content of hydrocarbon-forming organisms to the hydrocarbon generation amount of modern organisms, the hydrocarbon generation amount of hydrocarbon-forming organisms is obtained, which can predict the distribution of Cenozoic marine source rocks, and at the same time predict the organic matter abundance and hydrocarbon generation amount of marine source rocks in different ranges. The following elaborates on the solution of the present invention in conjunction with the accompanying drawings.

[0034] Example 1

[0035] This example discloses a method for evaluating the organic matter abundance of Cenozoic marine source rocks, including the following steps:

[0036] S1 Extract kerogen from the marine source rock to obtain various hydrocarbon-forming organisms and their compositions in the kerogen.

[0037] The method for obtaining various hydrocarbon-forming organisms and their compositions in the kerogen is as follows:

[0038] S1.1 Conduct organic carbon determination on the rock sample of the marine source rock to obtain the actually measured organic matter abundance of the rock sample. Weigh 50 - 100 g of the measured rock sample and put it into an acid reaction tank for repeated acid treatment. The kerogen in the rock sample is insoluble in acid, while other parts of the rock sample are soluble in acid. Therefore, after acid treatment, kerogen can be obtained and weighed. Divide the weight of the kerogen by the weight of the original rock sample of the marine source rock, and the mass ratio of kerogen to the rock sample can be calculated.

[0039] Perform the operation in step S1.1 on marine source rocks in different sedimentary environments, and the mass proportion of kerogen in marine source rocks in different sedimentary environments can be counted, denoted as W 干酪根 .

[0040] In this embodiment, organic carbon was determined for 16 marine mudstones of the third member of the Linggezhuang Formation and 2 lacustrine mudstones of the Wenchang Formation. Among them, the lacustrine mudstones of the Wenchang Formation were used as the control group. Kerogens of all mudstone samples were obtained, and the mass ratio of kerogen to rock sample was obtained after weighing the kerogen. The TOC 测定 and W 干酪根 values are shown in Table 1.

[0041] S1.2 Take pictures of the kerogens of the 16 marine mudstones of the third member of the Linggezhuang Formation after the above acid treatment, and identify various hydrocarbon-generating organisms existing in the kerogens through image recognition software, that is, identify the hydrocarbon-generating organisms in the kerogens. The hydrocarbon-generating organisms in the kerogens of the marine mudstones of the third member of the Linggezhuang Formation are terrestrial higher plant leaves, seagrasses, benthic macroalgae leaves, and acanthocystodinium. A large number of pediastrum were identified in the kerogens of the lacustrine mudstones of the Wenchang Formation. Also through image recognition software, calculate the area of each hydrocarbon-generating organism in the image, and add up the areas of the same type of hydrocarbon-generating organisms to obtain the sum of the areas occupied by each type of hydrocarbon-generating organism, which are respectively denoted as: W 陆生高等植物叶片 、W 海草 、W 底栖宏观藻叶片 and W 具刺沟鞭藻 。

[0042] Table 1 Parameter value table of marine mudstones of the third member of the Linggezhuang Formation and lacustrine mudstones of the Wenchang Formation

[0043] Number <![CDATA[TOC 测定 > <![CDATA[W 干酪根 > <![CDATA[W 陆生高等植物叶片 > <![CDATA[W 海草 > <![CDATA[W 底栖宏观藻叶片 > <![CDATA[W 具刺沟鞭藻 > Marine mudstone - 1 1.121 0.003 5 95 0 0 Marine mudstone - 2 0.997 0.012 15 75 0 10 Marine mudstone - 3 1.015 0.003 5 95 0 0 Marine mudstone - 4 1.251 0.006 5 95 0 0 Marine mudstone - 5 1.162 0.019 5 85 10 0 Marine mudstone - 6 0.797 0.025 5 85 10 0 Marine mudstone - 7 0.820 0.019 15 35 40 10 Marine mudstone - 8 0.968 0.016 10 25 45 20 Marine mudstone - 9 0.991 0.023 10 40 45 5 Marine mudstone - 10 0.496 0.002 35 45 5 15 Marine mudstone - 11 0.507 0.007 5 80 5 10 Marine mudstone - 12 0.596 0.013 10 85 0 5 Marine mudstone - 13 0.684 0.003 10 75 10 5 Marine mudstone - 14 0.702 0.008 30 55 15 0 Marine mudstone - 15 0.820 0.051 100 0 0 0 Marine mudstone - 16 1.175 0.107 100 0 0 0

[0044] S1.3 Determine the paleo-water depth during the deposition period of marine hydrocarbon source rocks based on methods such as benthic foraminifera, construct the relationship between the proportion of benthic organisms and the paleo-water depth, and generate a correlation diagram between the proportions of terrestrial higher plant leaves, seagrasses, benthic macroalgae leaves, and acanthocystodinium and the paleo-water depth. Since within the same water depth range, the composition of hydrocarbon-generating organisms is relatively consistent, based on this principle, divide the paleo-water depth interval range according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-generating organisms and their compositions within each water depth interval range. That is, determine which hydrocarbon-generating organisms are included within each water depth interval range, and the proportion of each type of hydrocarbon-generating organism. In this embodiment, such as Figure 1As shown in the figure, the paleo - water depth ranges include: the range of 0 - 30m water depth, the range of 30 - 60m water depth, the range of 60 - 90m water depth, and the range of 90 - 160m water depth; the hydrocarbon - forming organisms include terrestrial higher plants, seagrasses, benthic macro - algae, and acanthocyst dinoflagellates. Among them, within the water depth range of 0 - 30m, the proportion of terrestrial higher plants is 20%, seagrasses account for 55%, benthic macro - algae account for 20%, and acanthocyst dinoflagellates account for 5%; within the water depth range of 30 - 60m, the proportions of terrestrial higher plants, seagrasses, benthic algae, and acanthocyst dinoflagellates are 10%, 75%, 20%, and 5% in sequence; within the water depth range of 60 - 90m, the proportions of each organism are 5%, 35%, 55%, and 5% in sequence; within the water depth range of 90 - 160m, there is almost no terrestrial higher plant, seagrasses account for 10%, benthic algae account for 80%, and acanthocyst dinoflagellates account for 10%.

[0045] Based on the results of paleogeomorphic restoration during the deposition period of Member 3 of the Lingnan Formation, constrained by the calculated results of paleo - water depth revealed by wells during the deposition period of Member 3 of the Lingnan Formation, quantitative prediction of the distribution and composition of hydrocarbon - forming organisms in marine source rocks in the study area can be achieved.

[0046] S2 Enrich the kerogen for each hydrocarbon - forming organism.

[0047] Enrich the kerogen for the four hydrocarbon - forming organisms of terrestrial higher plants, seagrasses, benthic algae, and acanthocyst dinoflagellates detected in marine source rocks, and at the same time, enrich the kerogen of Pediastrum detected in lacustrine source rocks, so that the mass of the enriched kerogen is greater than 10mg; or select the kerogen of marine source rocks with a hydrocarbon - forming organism proportion greater than 90%.

[0048] S3 Determine the carbon element of the kerogen sample after kerogen enrichment to generate the carbon element content C i , and its unit is: (mg·organic carbon) / (g·organism). Among them, the organic carbon content per unit mass of terrestrial higher plants is 678mg, while those of seagrasses, benthic algae, and acanthocyst dinoflagellates are 389mg, 427mg, and 403mg respectively, and that of Pediastrum is 389mg.

[0049] S4 Calculate the organic matter abundance of marine source rocks based on the measured carbon element content.

[0050] The calculation formula for the organic matter abundance of marine source rocks is as follows:

[0051] TOC 验证 =[Σ(C i ×W i )]×W 干酪根 ÷λ

[0052] Among them, TOC 验证 is the organic matter abundance of marine source rocks, C i is the carbon element content, W iThe sum of the areas occupied by hydrocarbon-generating organisms is \(S\), and \(\lambda\) is the content of kerogen organic matter in the total rock organic matter. In classical petroleum geology, it is considered that the kerogen organic matter accounts for 80%-99% of the total rock organic matter. Therefore, the value range of \(\lambda\) is within 0.8-0.99. By adjusting \(\lambda\), the TOC 验证 is consistent with the measured organic matter abundance of marine hydrocarbon source rocks, that is, TOC 验证 = \(k\times\) TOC 测定 , and \(k = 1\). In actual verification, when the value of \(\lambda\) satisfies \(k>0.95\) and the correlation coefficient \(r 2 >0.7\), it is considered that the coincidence degree of TOC 验证 and TOC 测定 is relatively high. Only by selecting a reasonable value range of \(\lambda\) can reasonable results of the organic carbon content of each hydrocarbon-generating organism and the proportion of each hydrocarbon-generating organism in marine hydrocarbon source rocks be given. As Figure 2 shown, in this embodiment, \(\lambda\) is selected as 0.8. At this time, TOC 验证 = \(0.98\times\) TOC 测定 , \(R 2 = 0.707, indicating that in this embodiment, \(\lambda\) is reasonably selected and the organic matter abundance of marine hydrocarbon source rocks can be calculated more accurately.

[0053] S5 Statistically analyze the ratio of the mass of kerogen to the mass of rock in the hydrocarbon source rocks of each sedimentary facies belt.

[0054] The sedimentary facies belts include coastal, restricted shallow sea and open shallow sea. In the hydrocarbon source rocks of each sedimentary facies belt, the ratios of the mass of kerogen to the mass of rock are respectively denoted as: \(W 滨海 , \(W 封闭浅海 and \(W 开阔浅海 . In this embodiment, the ratio of kerogen in the marine hydrocarbon source rock to the mass of rock \(W 滨海 in the coastal environment is 0.016; the ratio of kerogen in the marine hydrocarbon source rock to the mass of rock \(W 封闭浅海 in the restricted shallow sea environment is 0.028, and the ratio of kerogen in the marine hydrocarbon source rock to the mass of rock \(W 开阔浅海 in the open shallow sea environment is 0.013.

[0055] S6 Predict the organic matter abundance of marine hydrocarbon source rocks within different water depth ranges based on the ratio of the mass of kerogen to the mass of rock.

[0056] The composition of hydrocarbon-generating organisms is relatively consistent within each water depth range. Therefore, the calculation formula for the organic carbon content \(OC 干酪根 of kerogen within each water depth range is:

[0057] OC 干酪根 = \(\sum(C i \times W i )

[0058] where \(C i is the carbon element content, with the unit of mg, and \(Wi It is the sum of the areas occupied by hydrocarbon-generating organisms;

[0059] Then the calculation formula for the organic carbon content of marine hydrocarbon source rocks within this water depth range is:

[0060] TOC′ 预测 = OC 干酪根 ×W 相带 ÷λ

[0061] Among them, TOC′ 预测 is the organic carbon content of marine hydrocarbon source rocks within a certain water depth range; W 相带 is the ratio of the mass of kerogen to the mass of rock in the hydrocarbon source rocks of each sedimentary facies belt. W 相带 includes W 滨海 , W 封闭浅海 or W 开阔浅海 .

[0062] Calculations show that for mudstone in the coastal environment within the water depth range of 0 - 30m, TOC′ 预测 is 0.94%, for mudstone in the semi-enclosed shallow sea within the water depth range of 30 - 60m, TOC′ 预测 is 1.56%, and within the range of 60 - 90m, TOC′ 预测 is 1.48%; for the open shallow sea within the water depth range of 30 - 60m, TOC′ 预测 is 0.72%, within the range of 60 - 90m, TOC′ 预测 is 0.69%, and within the range of 90 - 160m, TOC′ 预测 is 0.65%.

[0063] Example 2

[0064] Based on the same inventive concept, this example discloses a method for evaluating the hydrocarbon generation amount of hydrocarbon-generating organisms in Cenozoic marine hydrocarbon source rocks, including the following steps:

[0065] S1 Extract kerogen from the marine hydrocarbon source rock to obtain various hydrocarbon-generating organisms and their compositions in the kerogen.

[0066] The method for obtaining various hydrocarbon-generating organisms and their compositions in the kerogen is:

[0067] S1.1 Conduct an organic carbon determination on the rock sample of the marine hydrocarbon source rock to obtain the actually measured organic matter abundance of the rock sample. Weigh 50 - 100g of the measured rock sample and put it into an acid reaction tank for repeated acid treatment. The kerogen in the rock sample is insoluble in acid, while other parts of the rock sample are soluble in acid. Therefore, after acid treatment, kerogen can be obtained and weighed. Divide the weight of the kerogen by the weight of the original rock sample of the marine hydrocarbon source rock to calculate the mass ratio of kerogen to the rock sample.

[0068] By performing the operation in step S1.1 on marine hydrocarbon source rocks in different sedimentary environments, the mass ratio of kerogen in marine hydrocarbon source rocks in different sedimentary environments can be statistically obtained, denoted as W 干酪根 .

[0069] In this embodiment, the organic carbon of 16 marine mudstones of the third member of the Linggezhuang Formation and 2 lacustrine mudstones of the Wenchang Formation was measured. Among them, the lacustrine mudstone of the Wenchang Formation was a comparative example. The kerogen of all mudstone samples was obtained, and after weighing the kerogen, the mass ratio of the kerogen to the rock sample was obtained.

[0070] S1.2 Take pictures of the kerogen of 16 marine mudstones of the third member of the Linggezhuang Formation after the above acid treatment, and identify various hydrocarbon-generating organisms existing in the kerogen through image recognition software, that is, identify the hydrocarbon-generating organisms in the kerogen. The hydrocarbon-generating organisms in the kerogen of the marine mudstone of the third member of the Linggezhuang Formation are terrestrial higher plant leaves, seagrass, benthic macroalgae leaves and acanthocystis. A large number of pediastrum were identified in the kerogen of the lacustrine mudstone of the Wenchang Formation. Also through image recognition software, calculate the area of each hydrocarbon-generating organism in the image, add up the areas of the same type of hydrocarbon-generating organisms, and obtain the sum of the areas occupied by each type of hydrocarbon-generating organism, which are respectively denoted as: W 陆生高等植物叶片 、W 海草 、W 底栖宏观藻叶片 and W 具刺沟鞭藻 .

[0071] S1.3 Based on methods such as benthic foraminifera, determine the paleo-water depth during the deposition period of marine hydrocarbon source rocks, construct the relationship between the proportion of benthic organisms and the paleo-water depth, and generate a correlation diagram between the proportions of terrestrial higher plant leaves, seagrass, benthic macroalgae leaves and acanthocystis and the paleo-water depth. Since within the same water depth range, the composition of hydrocarbon-generating organisms is relatively consistent, based on this principle, divide the paleo-water depth interval range according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-generating organisms and their composition within each water depth interval range. That is, determine which hydrocarbon-generating organisms are included within each water depth interval range, and the proportion of various hydrocarbon-generating organisms. In this embodiment, as Figure 1 shown, the paleo-water depth interval range includes: 0-30m water depth interval range, 30-60m water depth interval range, 60-90m water depth interval range and 90-160m water depth range; the hydrocarbon-generating organisms include terrestrial higher plants, seagrass, benthic macroalgae and acanthocystis. Among them, within the 0-30m water depth range, the proportion of terrestrial higher plants is 20%, the proportion of seagrass is 55%, the proportion of benthic macroalgae is 20%, and the proportion of acanthocystis is 5%; within the 30-60m water depth range, the proportions of terrestrial higher plants, seagrass, benthic algae and acanthocystis are 10%, 75%, 20% and 5% in turn; within the 60-90m water depth range, the proportions of each organism are 5%, 35%, 55% and 5% in turn; within the 90-160m water depth range, there is almost no terrestrial higher plant, seagrass accounts for 10%, benthic algae accounts for 80%, and acanthocystis accounts for 10%.

[0072] Based on the paleogeomorphic restoration results during the deposition period of Member Ling 3, with the calculation results of the paleo-water depth revealed by wells during the deposition period of Member Ling 3 as constraints, the quantitative prediction of the distribution and composition of hydrocarbon-generating organisms in the marine hydrocarbon source rocks in the study area can be realized.

[0073] In-situ Fourier transform infrared spectroscopy analysis was carried out on the hydrocarbon-generating organisms. Taking the peak heights of the C-H absorption bands of aliphatic and aromatic groups as parameters, the aliphatic hydrocarbon content and the aromatic hydrocarbon condensation coefficient were obtained, so as to quantitatively characterize the differences in the oil and gas generation capabilities of the hydrocarbon-generating organisms. The aliphatic hydrocarbon content and the aromatic hydrocarbon condensation degree coefficient of terrestrial higher plant leaves, seagrass, benthic macroalgae leaves, acanthocystis and pediastrum are shown in Table 2.

[0074] Table 2 Aliphatic hydrocarbon content and aromatic hydrocarbon condensation degree coefficient table of hydrocarbon-generating organisms

[0075] Hydrocarbon - forming organisms Aliphatic hydrocarbons / (aliphatic hydrocarbons + aromatic hydrocarbons) Degree of aromatic hydrocarbon condensation Spiniferites 0.794 0.222 Benthic macroalgae leaves 0.304 0.628 Seagrass leaves 0.143 0.785 Higher plant leaves 0.117 0.810 Pediastrum 0.417 0.432

[0076] S3 Select the modern biological species of hydrocarbon-generating organisms, carry out hydrocarbon generation simulation experiments on modern organisms, and obtain the maximum liquid hydrocarbon yield O i (mg / g) and the maximum gaseous hydrocarbon yield G i (mg / g). In this embodiment, among the hydrocarbon-generating organisms detected in the hydrocarbon source rock, acanthocystis and benthic algae have clear modern biological species. For the results of the hydrocarbon generation simulation experiments on acanthocystis and laver (modern benthic algae), the maximum liquid hydrocarbon yield of acanthocystis is 376 mg / g and the gaseous hydrocarbon yield is 40 mg / g, and the maximum liquid hydrocarbon yield of laver is 140 mg / g and the gaseous hydrocarbon yield is 160 mg / g.

[0077] S4 Use the aliphatic hydrocarbon content and the maximum liquid hydrocarbon yield O of modern organisms i as the horizontal and vertical coordinates respectively to plot a graph, and construct a liquid growth index fitting curve, as Figure 3 (a) shown. In this embodiment, the maximum liquid hydrocarbon yield of various hydrocarbon-generating organisms is predicted. As Figure 3 shown, use the aliphatic hydrocarbon content and the maximum liquid hydrocarbon yields of acanthocystis and laver as the horizontal and vertical coordinates respectively to plot a graph, and construct a liquid growth index fitting curve.

[0078] S5 Use the aromatic hydrocarbon condensation coefficient and the maximum gaseous hydrocarbon yield G of modern organisms i as the horizontal and vertical coordinates respectively to plot a graph, and construct a gaseous growth index fitting curve, as Figure 3 (b) shown, to predict the maximum gaseous hydrocarbon yield of various hydrocarbon-generating organisms. As Figure 3 shown, in this embodiment, use the aliphatic hydrocarbon content and the maximum liquid hydrocarbon yields of acanthocystis and laver as the horizontal and vertical coordinates respectively to plot a graph, and construct a liquid growth index fitting curve.

[0079] S6 predicts the hydrocarbon generation amount of marine source rocks within different water depth ranges based on the maximum liquid hydrocarbon yield and the maximum gaseous hydrocarbon yield of hydrocarbon-forming organisms.

[0080] The formula for calculating the hydrocarbon generation amount of marine source rocks within different water depth ranges is as follows:

[0081] Yeild = ∑(C i ×W i ×HC i )

[0082] Among them, C i is the carbon element content, W i is the sum of the areas occupied by hydrocarbon-forming organisms, and HC i is the sum of the maximum liquid hydrocarbon yield and the maximum gaseous hydrocarbon yield of hydrocarbon-forming organisms. In this embodiment, HC 陆生高等植物叶片 = 273 mg / g; HC 海草 = 273 mg / g, HC 底栖宏观藻叶片 = 313 m / g, HC 具刺沟鞭草 = 649 mg / g.

[0083] As Figure 4 shown, in this embodiment, within the water depth range of 160 m, in the shore-shallow sea to shallow sea environment, the maximum hydrocarbon generation amount is in the enclosed shallow sea environment within the water depth range of 60 - 90 m. The hydrocarbon generation amount of unit mass of marine mudstone is 5.16 mg of total hydrocarbons, and the oil generation amount accounts for nearly 50%. Secondly, it is the enclosed shallow sea environment within the water depth range of 30 - 60 m, with a total hydrocarbon yield of 4.93 mg and an oil generation amount of 1.59 mg.

[0084] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention. The above content is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or replacements, which should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for evaluating the abundance of organic matter in Cenozoic marine source rocks, characterized in that: The following steps are involved: Extract kerogen from marine source rocks to obtain various hydrocarbon-forming organisms and their composition in the kerogen; Conducting kerogen enrichment on each of the hydrocarbon-forming organisms; Carry out carbon element determination on the kerogen sample after kerogen enrichment to obtain the carbon element content; Calculate the abundance of organic matter in marine source rocks based on the measured carbon content; The ratio of kerogen mass to rock mass in source rocks of each sedimentary facies belt was calculated; Based on the kerogen mass to rock mass ratio, the organic matter abundance of marine source rocks within different water depths is predicted.

2. The method for evaluating organic matter abundance of Cenozoic marine source rocks according to claim 1, characterized in that: The method for obtaining various hydrocarbon-forming organisms and their compositions in kerogen is: Acid treatment is performed on the rock sample of the marine source rock to obtain kerogen, the kerogen is weighed, the mass ratio of the kerogen to the rock sample is calculated, and the mass proportion of the kerogen in the marine source rock under different sedimentary environments is counted; Identify hydrocarbon-forming organisms in the kerogen, and obtain the sum of the areas occupied by each hydrocarbon-forming organism; Determine the paleo-water depth during the deposition of marine source rocks, construct the relationship between the proportion of benthic organisms and paleo-water depth, and divide the paleo-water depth intervals according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-forming organisms and their composition in each water depth interval.

3. The method for evaluating the organic matter abundance of Cenozoic marine source rocks according to claim 2, characterized in that: The ancient water depth intervals include: 0-30m water depth interval, 30-60m water depth interval, 60-90m water depth interval and 90-160m water depth range; the hydrocarbon-forming organisms include terrestrial higher plants, seaweeds, benthic macroscopic algae and spiny dinoflagellates.

4. The method for evaluating organic matter abundance of Cenozoic marine source rocks according to claim 2, characterized in that: The kerogen of various hydrocarbon-forming organisms is enriched so that the mass of the enriched kerogen is greater than 10 mg; or the kerogen of marine source rocks in which the hydrocarbon-forming organisms account for more than 90% is selected.

5. The method for evaluating the organic matter abundance of Cenozoic marine source rocks according to claim 2, characterized in that: The calculation formula for the organic matter abundance of the marine source rock is: TOC 验证 =[Σ(C i ×W i )]×W 干酪根 ÷λ Among them, TOC 验证 is the abundance of organic matter in marine source rocks, C i is the carbon content, W i is the area occupied by hydrocarbon-forming organisms, λ is the content of kerogen organic matter in the whole rock organic matter. By adjusting λ, TOC 验证 This is consistent with the measured abundance of organic matter in marine source rocks.

6. The method for evaluating organic matter abundance of Cenozoic marine source rocks according to claim 2, characterized in that: The sedimentary facies belts include coastal, closed shallow sea and open shallow sea. In the source rocks of each sedimentary facies belt, the ratio of kerogen mass to rock mass is recorded as: W 滨海 , W 封闭浅海 and W 开阔浅海 .

7. The method for evaluating organic matter abundance of Cenozoic marine source rocks according to claim 6, characterized in that: Kerogen organic carbon content (OC) in each water depth range 干酪根 The calculation formula is: OC 干酪根 =∑(C i ×W i ) Among them, C i is the carbon content, W i is the area occupied by hydrocarbon-forming organisms and; The calculation formula for the organic carbon content of marine source rocks in each water depth range is: TOC′ 预测 =OC 干酪根 ×W 相带 ÷λ Among them, TOC′ 预测 is the organic carbon content of marine source rocks within a certain water depth range; W 相带 is the ratio of kerogen mass to rock mass in the source rocks of each sedimentary facies belt, and W 相带 Including W 滨海 , W 封闭浅海 or W 开阔浅海 .

8. A method for evaluating the hydrocarbon generation of hydrocarbon-forming organisms in Cenozoic marine source rocks, characterized in that: The following steps are involved: Extract kerogen from marine source rocks to obtain various hydrocarbon-forming organisms and their composition in the kerogen; Performing in-situ Fourier transform infrared spectroscopy analysis on the hydrocarbon-forming organisms to obtain the aliphatic hydrocarbon content and the aromatic hydrocarbon condensation coefficient; Selecting modern biological species of the hydrocarbon-generating organisms, conducting hydrocarbon generation simulation experiments of modern organisms, and obtaining the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of the modern organisms; Plotting the aliphatic hydrocarbon content and the maximum liquid hydrocarbon production of the modern organisms as horizontal and vertical coordinates, respectively, to construct a liquid growth index fitting curve to predict the maximum liquid hydrocarbon production of various hydrocarbon-forming organisms; Plotting the aromatic hydrocarbon polycondensation coefficient and the maximum gaseous hydrocarbon production of the modern organisms as horizontal and vertical coordinates, respectively, to construct a gas growth index fitting curve to predict the maximum gaseous hydrocarbon production of various hydrocarbon-forming organisms; The hydrocarbon generation amount of the marine source rock in different water depths is predicted based on the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of the hydrocarbon-forming organisms.

9. The method for evaluating hydrocarbon generation by hydrocarbon-forming organisms of Cenozoic marine source rocks according to claim 8, characterized in that: The method for obtaining various hydrocarbon-forming organisms and their compositions in kerogen is: Acid treatment is performed on the rock sample of the marine source rock to obtain kerogen, the kerogen is weighed, the mass ratio of the kerogen to the rock sample is calculated, and the mass proportion of the kerogen in the marine source rock under different sedimentary environments is counted; Identify hydrocarbon-forming organisms in the kerogen, and obtain the sum of the areas occupied by each hydrocarbon-forming organism; Determine the paleo-water depth during the deposition of marine source rocks, construct the relationship between the proportion of benthic organisms and paleo-water depth, and divide the paleo-water depth intervals according to the proportion of benthic organisms, so as to obtain the corresponding hydrocarbon-forming organisms and their composition in each water depth interval.

10. The method for evaluating hydrocarbon generation of hydrocarbon-forming organisms in Cenozoic marine source rocks according to claim 8, characterized in that: The calculation formula for the hydrocarbon generation amount of the marine source rocks in different water depth ranges is: Yeild=∑(C i ×W i ×HC i ) Among them, C i is the carbon content, W i is the area occupied by hydrocarbon-forming organisms and HC i It is the sum of the maximum liquid hydrocarbon production and the maximum gaseous hydrocarbon production of the hydrocarbon-forming organism.

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