Quantitative prediction method for organic matter abundance of offshore non-well sag lacustrine source rock

Abstract

The application discloses a method for quantitatively predicting the organic matter abundance of offshore well-free depression lacustrine source rock, comprising the following steps: collecting the structural parameters and sedimentary parameters of the developed layer section of the proven hydrocarbon-generating depression lacustrine source rock, and calculating the structural and sedimentary factors according to the structural and sedimentary parameters; determining the average TOC value of the developed layer section of the proven hydrocarbon-generating depression lacustrine source rock; establishing the correlation chart of the structural factor and the sedimentary factor of the developed layer section of the proven hydrocarbon-generating depression lacustrine source rock and the average TOC value; collecting the structural parameters and sedimentary parameters of the developed layer section of the suspected lacustrine source rock in the well-free depression to be predicted, and calculating the structural and sedimentary factors according to the structural and sedimentary parameters; and respectively projecting the structural and sedimentary factors of the developed layer section of the suspected lacustrine source rock in the well-free depression to be predicted on the correlation chart to read the average TOC value of the developed layer section of the suspected lacustrine source rock in the well-free depression to be predicted. The application can quantitatively predict the organic matter abundance of the offshore well-free depression lacustrine source rock conveniently.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, and in particular to a method for quantitatively predicting the organic matter abundance of marine wellless depression lacustrine source rocks. Background Technology

[0002] The TOC value (organic matter abundance, or whole-rock organic carbon content) of lacustrine source rocks is limited by the number of wells drilled and the fact that drilled wells are often located in relatively sandy areas at the edge of the lake basin, making quantitative prediction difficult. This is especially true for depressions without wells to be predicted (meaning the hydrocarbon generation potential of depressions without wells has not yet been verified by drilling), where predicting the organic matter abundance of lacustrine source rocks is even more challenging. Current technologies mostly rely on qualitative judgments based on the structural, sedimentary, and geochemical characteristics of hydrocarbon-rich depressions to determine whether they are potentially hydrocarbon-rich. A few quantitative predictions require areas with high levels of seismic data and research, achieved by determining parameters such as the area of ​​the source area, the elevation difference of the source area, and the area of ​​mudstone in the sedimentary area. However, current technologies still struggle to quantitatively predict the organic matter abundance of lacustrine source rocks in marine depressions without wells, i.e., it is difficult to quantitatively evaluate the hydrocarbon generation potential of lacustrine source rocks in marine depressions without wells. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address at least one defect of the related technologies mentioned in the background: the existing technology is difficult to quantitatively predict the organic matter abundance of marine wellless lacustrine source rocks. Therefore, the present invention provides a method for quantitatively predicting the organic matter abundance of marine wellless lacustrine source rocks.

[0004] The technical solution adopted by this invention to solve its technical problem is: to establish a method for quantitative prediction of organic matter abundance in marine well-free lacustrine source rocks, including the following steps: S1: Statistical analysis has confirmed the structural and sedimentary parameters of the developed layers in the hydrocarbon source rocks of the hydrocarbon-generating depression lacustrine facies. S2: Based on the structural and sedimentary parameters of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks, calculate the structural and sedimentary factors of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks. S3: Determine the average TOC value of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; S4: Establish correlation charts between the tectonic and sedimentary factors of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks and the average TOC value; S5: Statistical analysis of structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the unpredicted depressions without wells; S6: Based on the structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted, calculate the structural and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted. S7: Plot the structural and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the well-free depression to be predicted on the correlation chart obtained in step S4, and read the average TOC value of the developed strata in the suspected lacustrine source rocks of the well-free depression to be predicted.

[0005] In the method for quantitatively predicting the organic matter abundance of marine wellless depression lacustrine source rocks, preferably, step S1 includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments in the confirmed hydrocarbon-generating depression lacustrine source rocks, the structural parameters of the developed segments in the confirmed hydrocarbon-generating depression lacustrine source rocks are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks, a sedimentary facies diagram of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks is determined, and sedimentary parameters of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks are statistically analyzed. The sedimentary parameters include depression area A1, fan area A2, maximum stratigraphic thickness H2, and sedimentary rate R2.

[0006] In the method for quantitatively predicting the organic matter abundance of marine wellless lacustrine source rocks, the preferred method is... The statistical analysis of the subsidence rate R1 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression includes: Determine the depositional duration T3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the subsidence rate R1 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock is calculated, R1=H1 / T3. The statistical analysis of the sedimentary rate R2 of the developed layers in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression includes: Determine the depositional duration T3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed section in the confirmed hydrocarbon-generating lacustrine source rock, the deposition rate R2 of the developed section in the confirmed hydrocarbon-generating lacustrine source rock is calculated, R2=H2 / T3.

[0007] In the method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks, preferably, step S2 includes: Based on the settling rate R1 and sedimentation rate R2 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the structural factor R3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock is calculated, R3=R2 / R1=H2 / H1. Based on the depression area A1 and fan area A2 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the sedimentary factor R4 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock is calculated, R4=A2 / A1.

[0008] In the method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine hydrocarbon source rocks, preferably, step S3 includes: Based on geochemical tests and experience from wells drilling in the proven hydrocarbon-generating lacustrine source rocks, the average TOC value of the developed intervals in the proven hydrocarbon-generating lacustrine source rocks was determined.

[0009] In the method for quantitatively predicting the organic matter abundance of marine well-free lacustrine source rocks, preferably, step S4 includes: Based on the tectonic and sedimentary factors of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks, correlation charts with the average TOC value were established using the normal distribution trend method.

[0010] In the method for quantitatively predicting the organic matter abundance of marine wellless depression lacustrine source rocks, preferably, step S5 includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments in the suspected lacustrine source rocks of the unpredicted depression, the structural parameters of the developed segments in the suspected lacustrine source rocks of the unpredicted depression are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed sections in the suspected lacustrine source rocks of the unpredicted depression, the sedimentary facies diagram of the developed sections in the suspected lacustrine source rocks of the unpredicted depression is determined, and the sedimentary parameters of the developed sections in the suspected lacustrine source rocks of the unpredicted depression are statistically analyzed. The sedimentary parameters include the depression area A1, the fan area A2, the maximum stratigraphic thickness H2, and the sedimentary rate R2.

[0011] In the method for quantitatively predicting the organic matter abundance of marine wellless lacustrine source rocks, the preferred method is... The statistical analysis of the subsidence rate R1 of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted includes: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rock of the wellless depression to be predicted; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted, the subsidence rate R1 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted is calculated, R1=H1 / T3. The statistical analysis of the sedimentary rate R2 of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted includes: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rock of the wellless depression to be predicted; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression, the deposition rate R2 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression is calculated, R2=H2 / T3.

[0012] In the method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks, preferably, step S6 includes: Based on the subsidence rate R1 and sedimentation rate R2 of the developed layer in the suspected lacustrine source rock of the unwell-predicted depression, the structural factor R3 of the developed layer in the suspected lacustrine source rock of the unwell-predicted depression is calculated, R3=R2 / R1=H2 / H1. Based on the depression area A1 and fan area A2 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression, the sedimentary factor R4 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression is calculated, R4=A2 / A1.

[0013] In the method for quantitatively predicting the organic matter abundance of marine wellless depression lacustrine source rocks, preferably, step S7 includes: The tectonic and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted are plotted on the correlation chart obtained in step S4. The average TOC value of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted is quantitatively predicted by combining the normal distribution correlation curve, and the source rock grade of the wellless depression to be predicted is evaluated.

[0014] By implementing this invention, the following beneficial effects are achieved: This invention provides a novel method for quantitatively predicting the organic matter abundance of lacustrine source rocks in offshore well-free depressions. This method establishes the correlation between tectonic and sedimentary factors and organic matter abundance using known data from proven hydrocarbon-generating depressions. This correlation is then applied to well-free depressions to be predicted. Only the tectonic and sedimentary parameters of the depression to be predicted are needed to quantitatively predict organic matter abundance, eliminating the need for measured TOC data obtained from drilling. This solves the technical challenge of quantitatively predicting the organic matter abundance of lacustrine source rocks in the early stages of offshore exploration when drilling data is unavailable. This invention can accurately and conveniently quantitatively predict the organic matter abundance of lacustrine source rocks in offshore well-free depressions, thereby predicting their hydrocarbon generation potential. Furthermore, the prediction process is unaffected by the subjective experience of interpreters, resulting in stable and reliable results. This provides a reliable basis for evaluating the oil and gas resource potential of offshore well-free depressions. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 The flowchart of the present invention is shown. Figure 2 This diagram illustrates the maximum vertical displacement H1 and maximum stratigraphic thickness H2 of the depression-controlling fault in the Wenchang Formation, a lacustrine source rock in hydrocarbon-generating depressions (such as the N-depression), which has been verified by this invention. Figure 3 The sedimentary facies diagram of the Wenchang Formation, a lacustrine source rock in confirmed hydrocarbon-generating depressions (such as the N-depression), is shown. Figure 4 The diagram shows the relationship between the tectonic factors and the TOC of the Wenchang Formation, a proven hydrocarbon-generating lacustrine source rock in the Pearl River Estuary Basin, as well as a plotting diagram of depressions to be predicted without wells (such as depressions X, Y, and Z). Figure 5 The diagram shows the relationship between sedimentary factors and TOC of the Wenchang Formation, a proven hydrocarbon-generating lacustrine source rock in the Pearl River Estuary Basin, as well as plotting diagrams of depressions to be predicted without wells (such as depressions X, Y, and Z). Detailed Implementation

[0016] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0018] Lacustrine source rocks are a type of fine-grained sedimentary rocks rich in organic matter that can generate petroleum or natural gas, formed in inland fault-bounded or depression-like lake environments.

[0019] A depression refers to a third-order negative tectonic unit within a lacustrine basin (such as the Pearl River Estuary Basin), which is a subsidence center, sedimentation center, and potential hydrocarbon generation center during the rifting period.

[0020] Depression lacustrine source rocks refer to effective source rocks developed within the third-order negative tectonic units of a basin, formed by sedimentation in a semi-deep to deep lacustrine environment of a continental rift basin or depression lacustrine basin.

[0021] Exploration practice has shown that, due to the small overall sedimentary area and shallow water of terrestrial lacustrine basins, high-organic-matter source rock samples are mostly developed in environments with adequate terrigenous clastic material supply and relatively oxygen-deficient water conditions. Excessive or insufficient terrigenous clastic material supply is unfavorable, as is excessively shallow oxygen-rich or excessively deep oxygen-deficient water (mudstone thickness, settling rate, etc.). In other words, the water environment of the lacustrine basin and the degree of terrigenous clastic material deposition and infilling are approximately normally correlated with organic matter abundance, rather than being a unidirectional linear correlation. Based on this geological understanding, and addressing issues such as high exploration costs and lack of drilling at sea, such as... Figure 1 As shown, some embodiments of the present invention disclose a method for quantitatively predicting the organic matter abundance of marine wellless depression lacustrine source rocks based on geological understanding. Specifically, it is a method for quantitatively predicting the organic matter abundance of source rocks using a trend method based on geological understanding of tectonic and sedimentary infilling. The method includes the following steps: S1: Statistical analysis of the structural and sedimentary parameters of the developed sections in the lacustrine source rocks of confirmed hydrocarbon-generating depressions. Among them, confirmed hydrocarbon-generating depressions are adjacent to depressions without wells for prediction, or confirmed hydrocarbon-generating depressions are located around depressions without wells for prediction. Confirmed hydrocarbon-generating depressions refer to depressions whose hydrocarbon generation potential has been verified by drilling, while depressions without wells for prediction refer to depressions whose hydrocarbon generation potential has not yet been verified by drilling. S2: Based on the structural and sedimentary parameters of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks, calculate the structural and sedimentary factors of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks. S3: Determine the average TOC value (i.e., organic matter abundance, or whole-rock organic carbon content) of the developed layers in the confirmed hydrocarbon source rocks of the lacustrine facies of hydrocarbon-generating depressions. S4: Establish a correlation chart between the tectonic and sedimentary factors of the developed strata in confirmed hydrocarbon-generating lacustrine source rocks and the mean TOC value; S5: Statistical analysis of structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the unpredicted depressions without wells; S6: Based on the structural and sedimentary parameters of the developed sections in the suspected lacustrine source rocks of the unpredicted depression without wells, calculate the structural and sedimentary factors of the developed sections in the suspected lacustrine source rocks of the unpredicted depression without wells. S7: Plot the structural and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the unpredicted depression on the correlation chart obtained in step S4, and read the average TOC value of the developed strata in the suspected lacustrine source rocks of the unpredicted depression.

[0022] This invention provides a novel method for quantitatively predicting the organic matter abundance of lacustrine source rocks in offshore well-free depressions. This method establishes the correlation between tectonic and sedimentary factors and organic matter abundance using known data from proven hydrocarbon-generating depressions. This correlation is then applied to well-free depressions to be predicted. Only the tectonic and sedimentary parameters of the depression to be predicted are needed to quantitatively predict organic matter abundance, eliminating the need for measured TOC data obtained from drilling. This solves the technical challenge of quantitatively predicting the organic matter abundance of lacustrine source rocks in the early stages of offshore exploration when drilling data is unavailable. This invention can accurately and conveniently quantitatively predict the organic matter abundance of lacustrine source rocks in offshore well-free depressions, thereby predicting their hydrocarbon generation potential. Furthermore, the prediction process is unaffected by the subjective experience of interpreters, resulting in stable and reliable results. This provides a reliable basis for evaluating the oil and gas resource potential of offshore well-free depressions.

[0023] In some embodiments, the source rock development strata include different stratigraphic levels, such as boundaries, systems, series, formations, and sections, where a group is, for example, the Wenchang Formation.

[0024] In some embodiments, step S1 (statistically analyzing the structural and sedimentary parameters of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression) specifically includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments (such as the Wenchang Formation) in the lacustrine source rocks of confirmed hydrocarbon-generating depressions (such as depressions A to N), the structural parameters of the developed segments in the lacustrine source rocks of confirmed hydrocarbon-generating depressions are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed strata (such as the Wenchang Formation) in the lacustrine source rocks of confirmed hydrocarbon-generating depressions (such as depressions A to N), sedimentary facies maps of the developed strata in the lacustrine source rocks of confirmed hydrocarbon-generating depressions (such as the sedimentary facies maps of the developed strata) are determined. Figure 3 As shown in the figure, the sedimentary parameters of the developed sections in the confirmed hydrocarbon source rocks of the lacustrine facies of the hydrocarbon-generating depression are statistically analyzed. The sedimentary parameters include the depression area A1, the fan area A2, the maximum stratigraphic thickness H2, and the sedimentary rate R2.

[0025] In this context, the depression area A1 refers to the total area of ​​the depression on a plane. The fan area A2 refers to the sum of the planar distribution areas of braided river deltas, fan deltas, and nearshore underwater fan sedimentary units of lacustrine terrestrial clastic origin. For example, Table 1 below shows some sedimentary parameters of the Wenchang Formation, a lacustrine source rock in a confirmed hydrocarbon-generating depression (such as the N depression), with a depression area A1 of 1604 km² and a fan area A2 of 841 km².

[0026] Table 1 In some embodiments, the subsidence rate R1 of the developed strata in the proven lacustrine source rocks of hydrocarbon-generating depressions is statistically analyzed, specifically including: The depositional duration T3 of the developed layer in the confirmed hydrocarbon source rocks of the lacustrine facies of the hydrocarbon-generating depression was determined; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the subsidence rate R1 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock is calculated as R1 = H1 / T3.

[0027] In some embodiments, the depositional rate R2 of the developed layers in the proven hydrocarbon-generating lacustrine source rocks of hydrocarbon-generating depressions is statistically analyzed, specifically including: The depositional duration T3 of the developed layer in the confirmed hydrocarbon source rocks of the lacustrine facies of the hydrocarbon-generating depression was determined; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks, the deposition rate R2 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks is calculated as R2 = H2 / T3.

[0028] In some embodiments, the depositional duration T3 of the developed strata in the proven hydrocarbon-generating lacustrine source rocks of hydrocarbon-generating depressions is determined, specifically including: Determine the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed segments in the confirmed hydrocarbon source rocks of the lacustrine facies of the hydrocarbon-generating depression; Based on the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks, the depositional duration (i.e. development duration) T3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks is calculated as T3 = T1 - T2.

[0029] For example, if T1 is 47.8 Ma (47.8 million years ago), T2 is 38.0 Ma (38 million years ago), then T3 is 9.8 Ma (9.8 million years ago).

[0030] In some embodiments, the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed segment in the confirmed hydrocarbon-generating lacustrine source rock of the hydrocarbon-generating depression are determined, specifically including: The semi-deep to deep lacustrine facies range of the confirmed hydrocarbon-generating depression was determined by sedimentary environment analysis. Then, stratigraphic dating (e.g., zircon dating) was performed on the developed sections in the lacustrine source rocks of the confirmed hydrocarbon-generating depression to determine the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed sections in the lacustrine source rocks of the confirmed hydrocarbon-generating depression.

[0031] In some embodiments, such as Figure 2 As shown, in the seismic work area, the dashed line represents the stratigraphic interpretation, the red solid line represents the fault interpretation, and the time-depth relationship refers to the fact that the vertical coordinate of the seismic work area is in the time domain. By using the time-depth relationship established by the drilled wells, the depth can be calculated from the vertical time.

[0032] The depression-controlling fault is the main fault that controls the formation and evolution of the depression. The maximum vertical displacement H1 of the depression-controlling fault is on the section perpendicular to the fault strike (i.e., Figure 2 The maximum vertical elevation difference between the two blocks (the upside and downside blocks of a fault) is measured on the seismic profile. The two blocks are the upside and downside blocks of the fault, and the same marker layer is a seismic reflection interface that can be continuously tracked and isochronous on the seismic profile.

[0033] The maximum stratigraphic thickness H2 refers to the maximum thickness of the hydrocarbon source rock development section within the depression, which is the maximum value of the two-way travel time difference between the top and bottom of the strata picked up by the main survey line and the connecting line through the sedimentary center. Here, "through the sedimentary center" means that the survey line passes through the point where the water is deepest in the depression. The main survey line and the connecting line refer to two mutually perpendicular directions in 3D seismic exploration. The two-way travel time refers to the time it takes for a seismic wave to travel from the seismic source on the ground to a certain rock interface (such as the bottom of the Wenchang Formation) and be reflected back and received by the ground geophone.

[0034] For example, such as Figure 2 As shown, the maximum vertical displacement H1 of the controlling fault in the N Wenchang Formation of the hydrocarbon-generating depression has been confirmed to be 1820 ms, and the maximum stratigraphic thickness H2 of the N Wenchang Formation of the hydrocarbon-generating depression has been confirmed to be 910 ms.

[0035] In some embodiments, step S2 (calculating the tectonic and sedimentary factors of the developed segments in the proven hydrocarbon-generating lacustrine source rocks based on the tectonic and sedimentary parameters of the developed segments in the proven hydrocarbon-generating depression lacustrine source rocks) specifically includes: Based on the settling rate R1 and sedimentation rate R2 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks, the structural factor R3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks is calculated, specifically R3=R2 / R1=H2 / H1. Based on the depression area A1 and fan area A2 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks, the sedimentary factor R4 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rocks is calculated as R4 = A2 / A1.

[0036] For example, R3=H2 / H1=910ms / 1820ms=0.5; R4=A2 / A1=841km² / 1604km²=0.52. Table 2 below shows the tectonic factors, sedimentary factors, and average TOC values ​​of the Wenchang Formation, a lacustrine source rock in confirmed hydrocarbon-generating depressions (such as depressions A to N).

[0037] Table 2 In some embodiments, step S3 (determining the average TOC value of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression) specifically includes: Based on geochemical tests and experience from wells that have been confirmed to be source rocks in lacustrine hydrocarbon-generating depressions, the average TOC value of the developed intervals in the confirmed source rocks of lacustrine hydrocarbon-generating depressions was determined.

[0038] In some embodiments, step S4 (establishing correlation charts between tectonic and sedimentary factors of the developed strata in confirmed hydrocarbon-generating lacustrine source rocks and the average TOC value) specifically includes: Based on the tectonic and sedimentary factors of the developed layers in the proven hydrocarbon-generating lacustrine source rocks of hydrocarbon-generating depressions, correlation charts with the average TOC value were established using the normal distribution trend method, as follows: Figure 4 and Figure 5 As shown.

[0039] Figure 4 In the diagram, A~N represent the correlation plotting points between the sedimentation rate / settlement rate and the average TOC value of the Wenchang Formation, a lacustrine source rock in different confirmed hydrocarbon-generating depressions. Depressions X, Y, and Z are depressions without wells to be predicted. Figure 5 In the diagram, A~N represent the correlation plotting points between the fan area / depression area and the average TOC value of the Wenchang Formation in different proven hydrocarbon-generating lacustrine source rocks. Depressions X, Y, and Z are depressions without wells to be predicted.

[0040] pass Figure 4 Statistical analysis revealed that the tectonic factors (sedimentation rate R2 / subsidence rate R1) of the Wenchang Formation, a hydrocarbon source rock in the confirmed hydrocarbon-generating depression lacustrine rock of the Pearl River Estuary Basin, generally exhibit a normal distribution with respect to the average TOC value. When 0.47 ≤ tectonic factor ≤ 1.08, high-quality hydrocarbon source rocks are developed; when 0.35 ≤ tectonic factor < 0.47, or 1.08 < tectonic factor ≤ 1.22, medium-quality hydrocarbon source rocks are developed; and when tectonic factor < 0.35, or tectonic factor > 1.22, poor-quality hydrocarbon source rocks are developed. pass Figure 5 Statistical analysis revealed that the sedimentary factors (fan area A2 / depression area A1) of the Wenchang Formation, a hydrocarbon source rock in the confirmed hydrocarbon-generating depression lacustrine rock of the Pearl River Estuary Basin, generally exhibit a normal distribution relationship with the average TOC value. When the sedimentary factor is 0.15 ≤ sedimentary factor ≤ 0.5, high-quality hydrocarbon source rocks are developed; when 0.1 ≤ sedimentary factor < 0.15, or 0.5 < sedimentary factor ≤ 0.55, medium-quality hydrocarbon source rocks are developed; and when the sedimentary factor < 0.1, or sedimentary factor > 0.55, poor-quality hydrocarbon source rocks are developed.

[0041] In some embodiments, step S5 (statistically analyzing the structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the unpredicted depression) specifically includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments in the suspected lacustrine source rocks of the unpredicted depressions (such as X, Y, and Z depressions), the structural parameters of the developed segments in the suspected lacustrine source rocks of the unpredicted depressions are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed sections in the suspected lacustrine source rocks of the unpredicted depressions (such as depressions X, Y, and Z), sedimentary facies diagrams of the developed sections in the suspected lacustrine source rocks of the unpredicted depressions were determined, and sedimentary parameters of the developed sections in the suspected lacustrine source rocks of the unpredicted depressions were statistically analyzed. The sedimentary parameters include depression area A1, fan area A2, maximum stratigraphic thickness H2, and sedimentary rate R2.

[0042] In some embodiments, the subsidence rate R1 of the developed strata in the suspected lacustrine source rocks of the unpredicted depression is statistically analyzed, specifically including: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rocks of the depression without wells to be predicted; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted, the subsidence rate R1 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted is calculated as R1=H1 / T3.

[0043] In some embodiments, the depositional rate R2 of developed layers in suspected lacustrine source rocks of unpredicted depressions is statistically analyzed, specifically including: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rocks of the depression without wells to be predicted; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed layer in the suspected lacustrine source rock of the unpredicted depression without wells, the deposition rate R2 of the developed layer in the suspected lacustrine source rock of the unpredicted depression without wells is calculated as R2=H2 / T3.

[0044] In some embodiments, the depositional duration T3 of the developed strata in the suspected lacustrine source rocks of the un-well-predicted depression is determined, specifically including: Determine the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed layer in the suspected lacustrine source rocks of the depression without wells to be predicted. Based on the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed segment in the suspected lacustrine source rock of the unpredicted depression, the depositional duration (i.e. development duration) T3 of the developed segment in the suspected lacustrine source rock of the unpredicted depression is calculated as T3 = T1 - T2.

[0045] In some embodiments, determining the absolute age T1 of the development period and the absolute age T2 of the end of development of the developed segment in the suspected lacustrine source rock of the depression to be predicted without a well specifically includes: The semi-deep lacustrine to deep lacustrine facies range of the depression to be predicted was determined by sedimentary environment analysis. Then, stratigraphic dating was performed on the developed sections in the suspected lacustrine source rocks of the depression without wells to determine the absolute age T1 of the development and formation period and the absolute age T2 of the end of development of the developed sections in the suspected lacustrine source rocks of the depression without wells.

[0046] In some embodiments, step S6 (calculating the structural and sedimentary parameters of the developed sections in the suspected lacustrine source rocks of the un-well-predicted depression based on the structural and sedimentary parameters of the developed sections) specifically includes: Based on the settling rate R1 and sedimentation rate R2 of the developed layer in the suspected lacustrine source rock of the unpredicted depression, the structural factor R3 of the developed layer in the suspected lacustrine source rock of the unpredicted depression is calculated, specifically R3=R2 / R1=H2 / H1. Based on the depression area A1 and fan area A2 of the developed layer in the suspected lacustrine source rock of the unpredicted depression without wells, the sedimentary factor R4 of the developed layer in the suspected lacustrine source rock of the unpredicted depression without wells is calculated as R4=A2 / A1.

[0047] In some embodiments, step S7 (plotting the tectonic and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted onto the correlation chart obtained in step S4, and reading the average TOC value of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted) specifically includes: The structural factor R3 and sedimentary factor R4 of the developed strata in the suspected lacustrine source rocks of the unpredicted depression were respectively plotted at... Figure 4 and Figure 5 On the correlation chart shown, the average TOC value of the developed layer in the suspected lacustrine source rocks of the unpredicted depression is quantitatively predicted by combining the normal distribution correlation curve, and the source rock grade of the unpredicted depression is evaluated. Specifically, the source rock grade of the unpredicted depression is evaluated according to the source rock grade classification standard.

[0048] This example classifies source rocks into three categories: excellent, medium, and poor. Poor source rocks have an average TOC value of <1%, medium source rocks have an average TOC value of 1% to 2%, and excellent source rocks have an average TOC value of >2%.

[0049] Table 3 below shows the predicted evaluation of tectonic factors, sedimentary factors, and average TOC values ​​of the Wenchang Formation in suspected lacustrine source rocks of unpredicted depressions (such as depressions X, Y, and Z). For example, the predicted average TOC values ​​of the developed layers in the suspected lacustrine source rocks of unpredicted depressions are 5.7%, 1.3%, and 0.5%, respectively, and their source rock grades are high-quality, medium-quality, and poor-quality, respectively.

[0050] Table 3 It is understood that the above embodiments only illustrate some implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above embodiments or technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. That is, the embodiments described in "some embodiments" can be freely combined with any of the embodiments above and below. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for quantitatively predicting the organic matter abundance of marine wellless lacustrine source rocks, characterized in that, Includes the following steps: S1: Statistical analysis has confirmed the structural and sedimentary parameters of the developed layers in the hydrocarbon source rocks of the hydrocarbon-generating depression lacustrine facies. S2: Based on the structural and sedimentary parameters of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks, calculate the structural and sedimentary factors of the developed sections in the confirmed hydrocarbon-generating lacustrine source rocks. S3: Determine the average TOC value of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; S4: Establish correlation charts between the tectonic and sedimentary factors of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks and the average TOC value; S5: Statistical analysis of structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the unpredicted depressions without wells; S6: Based on the structural and sedimentary parameters of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted, calculate the structural and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted. S7: Plot the structural and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the well-free depression to be predicted on the correlation chart obtained in step S4, and read the average TOC value of the developed strata in the suspected lacustrine source rocks of the well-free depression to be predicted.

2. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 1, characterized in that, Step S1 includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments in the confirmed hydrocarbon-generating depression lacustrine source rocks, the structural parameters of the developed segments in the confirmed hydrocarbon-generating depression lacustrine source rocks are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks, a sedimentary facies diagram of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks is determined, and sedimentary parameters of the developed sections in the confirmed hydrocarbon-generating depression lacustrine source rocks are statistically analyzed. The sedimentary parameters include depression area A1, fan area A2, maximum stratigraphic thickness H2, and sedimentary rate R2.

3. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 2, characterized in that, The statistical analysis of the subsidence rate R1 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression includes: Determine the depositional duration T3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the subsidence rate R1 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock was calculated. The statistical analysis of the sedimentary rate R2 of the developed layers in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression includes: Determine the depositional duration T3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks of the hydrocarbon-generating depression; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed section in the confirmed hydrocarbon-generating lacustrine source rock, the deposition rate R2 of the developed section in the confirmed hydrocarbon-generating lacustrine source rock was calculated.

4. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 2, characterized in that, Step S2 includes: Based on the settling rate R1 and sedimentation rate R2 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks, the structural factor R3 of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks is calculated. Based on the depression area A1 and fan area A2 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock, the sedimentary factor R4 of the developed layer in the confirmed hydrocarbon-generating lacustrine source rock is calculated.

5. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 1, characterized in that, Step S3 includes: Based on geochemical tests and experience from wells drilling in the proven hydrocarbon-generating lacustrine source rocks, the average TOC value of the developed intervals in the proven hydrocarbon-generating lacustrine source rocks was determined.

6. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 1, characterized in that, Step S4 includes: Based on the tectonic and sedimentary factors of the developed strata in the confirmed hydrocarbon-generating lacustrine source rocks, correlation charts with the average TOC value were established using the normal distribution trend method.

7. The method for quantitative prediction of organic matter abundance in marine wellless lacustrine source rocks according to claim 1, characterized in that, Step S5 includes: Based on the stratigraphic interpretation, fault interpretation, and time-depth relationship of the developed segments in the suspected lacustrine source rocks of the unpredicted depression, the structural parameters of the developed segments in the suspected lacustrine source rocks of the unpredicted depression are statistically analyzed. The structural parameters include the maximum vertical displacement H1 of the depression-controlling fault and the subsidence rate R1. Based on the tectonic setting, lithology, well logging facies, and seismic facies of the developed sections in the suspected lacustrine source rocks of the unpredicted depression, the sedimentary facies diagram of the developed sections in the suspected lacustrine source rocks of the unpredicted depression is determined, and the sedimentary parameters of the developed sections in the suspected lacustrine source rocks of the unpredicted depression are statistically analyzed. The sedimentary parameters include the depression area A1, the fan area A2, the maximum stratigraphic thickness H2, and the sedimentary rate R2.

8. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 1, characterized in that, The statistical analysis of the subsidence rate R1 of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted includes: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rock of the wellless depression to be predicted; Based on the maximum vertical displacement H1 of the depression-controlling fault and the deposition duration T3 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted, the subsidence rate R1 of the developed layer in the suspected lacustrine source rock of the depression without wells to be predicted is calculated. The statistical analysis of the sedimentary rate R2 of the developed strata in the suspected lacustrine source rocks of the well-less depression to be predicted includes: Determine the depositional duration T3 of the developed layer in the suspected lacustrine source rock of the wellless depression to be predicted; Based on the maximum stratigraphic thickness H2 and deposition duration T3 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression, the deposition rate R2 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression was calculated.

9. The method for quantitative prediction of organic matter abundance in marine wellless depression lacustrine source rocks according to claim 7, characterized in that, Step S6 includes: Based on the subsidence rate R1 and sedimentation rate R2 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression, the structural factor R3 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression is calculated. Based on the depression area A1 and fan area A2 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression, the sedimentary factor R4 of the developed layer in the suspected lacustrine source rock of the un-well-predicted depression is calculated.

10. The method for quantitative prediction of organic matter abundance in marine wellless lacustrine source rocks according to claim 1, characterized in that, Step S7 includes: The tectonic and sedimentary factors of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted are plotted on the correlation chart obtained in step S4. The average TOC value of the developed strata in the suspected lacustrine source rocks of the wellless depression to be predicted is quantitatively predicted by combining the normal distribution correlation curve, and the source rock grade of the wellless depression to be predicted is evaluated.

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