Method and system for estimating buried total organic carbon and annual flux of lacustrine delta

Abstract

The invention belongs to the technical field of organic carbon burial estimation, and discloses a method and a system for estimating burial total organic carbon and annual flux of a lacustrine delta. The method comprises the following steps of: dividing a delta period, a top build-up layer, a front build-up layer and a bottom build-up layer; calculating the total oblique sectional area, the top lamination layer, the front lamination layer, the bottom lamination layer oblique sectional area, the total delta length, the width and the height of the target delta body; estimating the maximum width and the minimum width of the delta to obtain porosity values of lithology of a top build-up layer, a front build-up layer and a bottom build-up layer; the total organic carbon TOC average value of the delta formation period is obtained; the deposition rate of the delta forming period is collected; and calculating the organic carbon burial amount and the organic carbon annual flux of each part and the overall part of the delta. According to the invention, the annual flux of organic carbon can be dynamically estimated, and the carbon flux change on the time scale can be reflected.

Description

Technical Field

[0001] The present invention belongs to the technical field of estimating organic carbon burial, and particularly relates to a method and system for estimating the total organic carbon burial and annual flux in lacustrine deltas. Background Art

[0002] TOC (Total Organic Carbon): A core indicator characterizing the organic matter content in sediments, and its burial amount directly affects the carbon sequestration potential.

[0003] Annual organic carbon flux: Reflects the input efficiency of organic carbon into the sedimentary system per unit time, and is a key parameter for evaluating the carbon sink capacity.

[0004] Existing technologies mostly focus on marine sedimentary environments or modern lake systems, but there is insufficient research on the organic carbon burial characteristics of deep-time lacustrine deltas.

[0005] When directly applying marine models, existing methods lead to large deviations in TOC estimation due to ignoring the unique hydrodynamic conditions (such as seasonal water level fluctuations, terrigenous clastic input patterns) and biogeochemical environments in lacustrine systems.

[0006] Existing methods lack a dynamic assessment of the changes in organic carbon flux over time scales. Traditional models are mostly based on static geological parameters (such as fixed sedimentation rates), without considering the spatio-temporal variations in sedimentation rates and paleogeographic evolution processes during the delta formation period, thus unable to accurately quantify the long-term change trends of carbon flux.

[0007] Obtaining data on deep-time lacustrine deltas faces multiple challenges, such as incomplete preservation of geological records, scarcity of high-resolution seismic profiles and continuous core samples. Existing technologies often regard the delta as a homogeneous whole and simplify calculations using a single parameter (such as the average TOC value), resulting in insufficient accuracy in estimating burial amounts and fluxes, and particularly difficult to reflect the differences in carbon sequestration contributions of different sedimentary units. Summary of the Invention

[0008] To overcome the problems existing in related technologies, the disclosed embodiments of the present invention provide a method and system for estimating the total organic carbon burial and annual flux in lacustrine deltas, specifically related to a method for estimating the buried TOC in lacustrine deltas and the annual flux of delta TOC.

[0009] The technical solution is as follows: A method for estimating the total organic carbon burial and annual flux in lacustrine deltas, comprising the following steps: S1, interpreting the seismic profile of the target delta, and dividing the delta periods and the parts of the topset bed, foreset bed, and bottomset bed; S2, based on the selected seismic profile of the delta body, calculating the total inclined cross-sectional area, topset bed, foreset bed, bottomset bed inclined cross-sectional areas, total length, width, and height of the target delta body; S3. Based on the paleogeographic map of the delta, estimate the maximum width and minimum width of the delta by using the maximum width value and the minimum width value respectively; S4. According to the formation period of the delta and the lithological differences of the sedimentary layers, accurately assign density and porosity values to obtain the porosity values of the topset bed, foreset bed and bottomset bed lithologies respectively; S5. Use the logging method to obtain the average value of total organic carbon TOC during the formation period of the delta as the value of total organic carbon TOC in the formula; S6. Collect the sedimentation rate during the formation period of the delta based on the wells within the delta area; S7. Obtain the organic carbon burial amount and organic carbon annual flux of each part and the overall of the delta through the calculation formulas of organic carbon burial amount and organic carbon annual flux.

[0010] In step S2, calculate the total inclined cross-sectional area, topset bed, foreset bed, bottomset bed inclined cross-sectional areas, total length, width and height of the target delta body, including: using the cutting and patching method to convert the irregular delta graph into a regular graph and combining with the scale in the seismic profile, and using mathematical formulas for calculation.

[0011] Furthermore, use a graphic calculation tool to directly calculate the deltas of different periods that have been divided.

[0012] In step S3, based on the sedimentary facies belt changes, geomorphic turns or formation thickness mutation characteristics on the paleogeographic map, identify the two sides of the delta boundary, and estimate the maximum width according to the scale; Define the delta boundary based on sedimentary facies belts and formation contact relationship markers, and estimate the minimum width according to the scale.

[0013] In step S4, use logging curves to identify the lithology of sedimentary rocks or collect core samples to obtain the lithology of sedimentary rocks; the porosity range is determined according to the standard database, and the porosity is obtained based on laboratory core analysis data, and the density uses the density of quartz.

[0014] In step S5, use logging data to obtain the measured TOC data. The average value of the measured TOC data of different wells is the TOC average value. If there is no measured TOC data, use method to calculate the TOC average value data, and the expression is: ; ; In the formula, is the reading of the spacing between the resistivity curve and the acoustic travel time curve on the logarithmic resistivity coordinate, is an organic matter scale, reflecting the thermal evolution degree of organic matter, obtained from a large number of sample analyses or from the evaluation of burial history and thermal history; is the resistivity, with the unit of Ω·m; is the acoustic travel time difference, with the unit of μs / ft; is the resistivity when the organic carbon content in shale is zero, with the unit of Ω·m; is the acoustic travel time difference when the organic carbon content in shale is zero, with the unit of μs / ft.

[0015] In step S7, the calculation formula for the buried amount of organic carbon is: ; The calculation formula for the annual flux of organic carbon is: ; In the formula, is the sedimentation rate, is the density, is the porosity, is the cross-sectional area of the delta body, is the width of the delta, is the buried amount of organic carbon, is the annual flux of organic carbon, is the surface area of the delta.

[0016] Another object of the present invention is to provide a system for estimating the total buried organic carbon and annual flux of a lacustrine delta, which system implements the method for estimating the total buried organic carbon and annual flux of a lacustrine delta, and the system includes: A delta sedimentation stage and internal structure division module, used for interpreting the seismic profile of the target delta and dividing the delta stage and the topset bed, foreset bed and bottomset bed parts; A layered parameter calculation module, used for calculating the total cross-sectional area of the target delta body, the cross-sectional areas of the topset bed, foreset bed and bottomset bed, the total length, width and height of the delta according to the selected seismic profile of the delta body; A module for estimating the maximum width and minimum width of the delta, used for estimating the maximum width and minimum width of the delta according to the paleogeographic map of the delta plane respectively by using the maximum width value and the minimum width value; A module for obtaining porosity values, used for accurately assigning density and porosity according to the formation period of the delta and according to the lithology differences of sedimentary layers, and respectively obtaining the porosity values of the lithologies of the topset bed, foreset bed and bottomset bed; A module for obtaining the average value of total organic carbon TOC, used for obtaining the average value of total organic carbon TOC in the formation period of the delta by using well logging methods as the value of total organic carbon TOC in the formula; A sedimentation rate obtaining module, configured to collect the sedimentation rate during the delta formation period based on wells within the delta region; An organic carbon burial amount and annual organic carbon flux obtaining module, configured to obtain the organic carbon burial amount and annual organic carbon flux of each part and the overall of the delta through the calculation formulas of the organic carbon burial amount and annual organic carbon flux.

[0017] Furthermore, the lacustrine delta total organic carbon burial and annual flux estimation system is carried on a computer device, and the computer device includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, and when the processor executes the computer program, the functions in the above-mentioned lacustrine delta total organic carbon burial and annual flux estimation system are implemented.

[0018] Furthermore, the lacustrine delta total organic carbon burial and annual flux estimation system is carried on a computer-readable storage medium, and the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the functions in the above-mentioned lacustrine delta total organic carbon burial and annual flux estimation system can be implemented.

[0019] Combining all the above technical solutions, the beneficial effects of the present invention are as follows: First, aiming at the problem that traditional methods often rely on single geological parameters or simplified models, the present invention constructs a multi-dimensional calculation model by integrating multi-source data such as seismic profile interpretation, paleogeographic map analysis, lithology porosity / density data, logging TOC values, and sedimentation rates. Existing technologies mostly regard the delta as a homogeneous whole for estimation, ignoring the lithological differences of different sedimentary layers (topset bed, foreset bed, bottomset bed). The present invention innovatively calculates parameters such as the cross-sectional area and porosity for each sedimentary layer separately, and accumulates them step by step through formulas. It realizes a more refined evaluation of the organic carbon distribution and avoids the errors caused by simplified stratification in traditional methods. By introducing the sedimentation rate (SR) parameter and combining the paleogeographic data during the delta formation period, this method can dynamically estimate the annual organic carbon flux and reflect the carbon flux change on the time scale.

[0020] Second, the present invention focuses on the quantitative calculation of delta organic carbon. Organic carbon is one of the core indicators for oil and gas generation, enrichment, and evaluation. On the basin scale, areas with high organic carbon content (such as the center of ancient lakes, delta fronts, and deep-sea shelves) are often the "sweet spots" for the development of source rocks and also the key areas for oil and gas exploration. Therefore, for the calculation of organic carbon, its value lies not only in resource quantity estimation but also in guiding the efficient and safe development of oil and gas resources. In the future, with the in-depth exploration of unconventional oil and gas, the precise detection and analysis of organic carbon will become the key development direction of the industry.

[0021] Thirdly, while existing technologies mainly focus on marine sedimentary environments or modern lake systems, there is insufficient research on the organic carbon burial characteristics of deep-time lacustrine deltas. Obtaining data on deep-time lacustrine deltas faces multiple challenges, such as incomplete preservation of geological records, scarcity of high-resolution seismic profiles and continuous core samples. The present invention calculates parameters such as cross-sectional area and porosity for each sediment layer separately and accumulates them step by step through formulas, achieving a more refined assessment of organic carbon distribution and avoiding errors caused by simplified stratification in traditional methods. By introducing the sedimentation rate (SR) parameter and combining it with paleogeographic data during the delta formation period, this method can dynamically estimate the annual organic carbon flux and reflect the carbon flux changes on a time scale.

[0022] Fourthly, in the field of calculating the organic carbon burial in deltas, the quantitative calculation of organic carbon in deep-time lacustrine deltas has been a long-standing technical problem. Traditional methods of calculation must rely on 3D seismic attribute inversion (such as waveform classification and curvature analysis), resulting in high calculation costs. The present invention proposes to simplify the quantitative calculation of organic carbon in deltas in the form of mathematical formulas and through example calculations, and overcomes the shortcomings of existing technologies that mainly focus on marine sedimentary environments and modern lake systems, enabling more difficult calculations of organic carbon in deep-time lacustrine deltas, achieving an efficient and cost-saving method. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Figure 1 It is a flowchart of a method for estimating the total organic carbon burial and annual flux in a lacustrine delta provided by an embodiment of the present invention. Figure 2 It is a seismic profile of a delta in a certain city provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0025] Accurate estimation of the total organic carbon (TOC) burial and annual flux in lacustrine deltas is a core step in analyzing the carbon cycle of paleoecosystems and evaluating the potential of unconventional oil and gas resources. However, traditional methods are limited by static models driven by single parameters and are difficult to quantify the complex effects of dynamic changes in sedimentary environments on the process of organic carbon burial. The innovations of this invention are: (1) quantitative calculation of organic carbon in deep-time lacustrine deltas; (2) dynamic estimation of the annual flux of organic carbon in deep-time lacustrine deltas. This invention proposes a method for calculating organic carbon in lacustrine deltas, including quantitative calculation of organic carbon in deep-time lacustrine deltas and dynamic estimation of the annual flux of organic carbon in deep-time lacustrine deltas.

[0026] Example 1, as Figure 1 shown, the method for estimating the total organic carbon burial and annual flux in lacustrine deltas provided by the embodiments of this invention (the method for estimating TOC burial amount and TOC annual flux) includes the following specific steps: S1, Interpret the seismic profile of the target delta, and divide the delta periods and the topset, foreset, and bottomset parts; The purpose of this invention is to clarify the delta sedimentation periods and internal structures, providing a spatial framework for layered calculation. The advantage is that through high-resolution seismic data, the internal heterogeneity of the delta can be accurately characterized.

[0027] S2, Based on the selected seismic profile of the delta body, calculate the total inclined cross-sectional area, topset, foreset, bottomset inclined cross-sectional areas, total length, width, and height of the target delta body; In CorelDRAW software, open the seismic profile diagram, use the brush tool to clearly draw the delta body to be calculated, and then select the clearly drawn delta body in the software and insert the graphic calculation tool script at the same time. It can be calculated.

[0028] Exemplarily, the calculation method of this step is as follows. In corelDRAW software, open the seismic profile diagram. Different periods of deltas are divided in the seismic profile. Take one of the periods as an example. The first method can use the integral method for calculation, but for the integral method, a suitable function needs to be fitted according to the digitized boundary data. The second method uses the cutting and patching method in mathematics to transform the irregular delta shape into a regular shape in combination with the scale in the seismic profile diagram; For example: The delta inclined cross-section is an irregular polygon. Auxiliary lines can be drawn along the key inflection points to divide it into combinations such as trapezoids + triangles + rectangles, etc. Topsets: Mostly horizontal or low-angle inclined layered, can be approximated as rectangles or trapezoids. Foresets: Have obvious inclined foreset reflections, can be approximated as triangles or trapezoids. Bottomsets: Located below the foresets, with a gentle slope, can be approximated as trapezoids or triangles. The total inclined cross-sectional area of the delta can be obtained by adding the areas of the regular shapes after cutting and patching. For example, the area formula of a trapezoid: (a, b are the lengths of the upper and lower bases, and h is the height). The area formula of a triangle is: The area formula of a rectangle is: The above parameters need to be converted into actual distances for calculation based on the actual scale.

[0029] Calculations can be performed using mathematical formulas. A third method involves using graphical calculation tools to directly calculate the delta for each stage. All of these methods can calculate the total cross-sectional area of the delta, the cross-sectional areas of the topset, foreset, and bottomset layers, and the total length, width, and height of the delta. The goal is to obtain basic parameters for calculating the volume of each sedimentary layer. The advantage lies in the independent calculation of layer parameters, laying the foundation for subsequent lithologic differentiation modeling.

[0030] S3, based on the planar paleogeographic map of the delta, the maximum and minimum widths of the delta were estimated using the maximum and minimum width values, respectively; For example, its role is to quantify the delta's planar distribution, reduce the uncertainty of paleogeographic parameters, and improve the accuracy of the results. Collect high-precision delta planar paleogeographic maps, ensuring they include complete information on stratigraphic age, sedimentary facies, and drainage distribution. Carefully examine the legends and scales to clearly identify the boundaries of each sedimentary unit and its key geomorphic features.

[0031] The maximum width is determined by looking for the direction of maximum width from one edge to the other, along the direction of the delta's greatest extent. This direction typically coincides with the long axis of the main river's estuary. Accurately identify the delta's boundaries based on features such as sedimentary facies changes, geomorphic transitions, or sudden changes in stratigraphic thickness on paleogeographic maps. The maximum width is then estimated based on the scale.

[0032] The minimum width is the direction along which the delta's horizontal span is smallest. This direction occurs at localized contractions of the delta, such as at the confluence of tributaries or at areas limited by paleo-geomorphic uplifts. Sedimentary facies, stratigraphic contacts, and other landmarks are also used to clearly define the delta's boundaries in this direction. The minimum width is estimated based on the scale.

[0033] S4, based on the formation period of the delta and the differences in sedimentary lithology, accurately assign density and porosity values to obtain the porosity values of the top-accumulation layer, foreset layer, and bottom-accumulation layer respectively; For example, well logging curves such as gamma ray (GR) and acoustic transit time (AC) are used to identify sedimentary rock lithology or to obtain sedimentary rock lithology through core sampling. Porosity is determined based on the SPWLA (Society of Well Analysts) standard database and laboratory core analysis data. Density refers to the overall density of the delta, and the density of quartz can be used as an example.

[0034] S5. Obtain the average value of total organic carbon (TOC) during the delta formation period by logging methods, which is used as the value of TOC in the formula. Exemplarily, during the delta formation period, there are multiple wells in the same delta. Using logging data, the measured TOC data can be obtained. The average value of the measured TOC data from different wells is the TOC average value. If there is no measured TOC data, the method can be used to calculate the TOC data, and the formula is: ; ; In the formula, is the reading of the distance between the resistivity curve and the acoustic travel time curve on the logarithmic resistivity coordinate, is the organic matter scale, reflecting the thermal evolution degree of organic matter, obtained from a large number of sample analyses or from burial history and thermal history evaluations; is the resistivity, with the unit of Ω·m; is the acoustic travel time, with the unit of μs / ft; is the resistivity when the organic carbon content in the mudstone is zero, with the unit of Ω·m; is the acoustic travel time when the organic carbon content in the mudstone is zero, with the unit of μs / ft.

[0035] S6. Based on the wells within the delta area, collect the sedimentation rate during the delta formation period; Combine the static TOC data with the dynamic SR parameters to achieve spatio-temporal coupling analysis of carbon flux. Through the formula for calculating the annual organic carbon flux in the present invention, the SR parameter in the formula changes with the time scale, and the SR parameters in different geological ages are different. That is, the annual carbon flux in different geological ages can be obtained through this independent variable SR parameter, realizing the annual flux results across time and space.

[0036] S7. Through the formulas for calculating the organic carbon burial amount and the annual organic carbon flux, obtain the organic carbon burial amount and the annual organic carbon flux of each part and the whole of the delta; The formula for calculating the organic carbon burial amount is: ; The formula for calculating the annual organic carbon flux is: ; In the formula, is the sedimentation rate, is the density, is the porosity, is the cross-sectional area of the delta body, is the width of the delta, is the organic carbon burial amount, is the annual flux of organic carbon, is the surface area of the delta.

[0037] Example 2. The lacustrine delta total organic carbon and annual flux estimation system provided by the embodiments of the present invention includes: Delta sedimentary stage and internal structure division module, which is used to interpret the seismic profile of the target delta and divide the delta stage and the progradational, foreset, and bottomset parts.

[0038] Stratification parameter calculation module, which is used to calculate the total oblique cross-sectional area, progradational, foreset, bottomset oblique cross-sectional areas, total length, width, and height of the target delta body based on the selected seismic profile of the delta body.

[0039] Delta maximum width and minimum width estimation module, which is used to estimate the maximum width and minimum width of the delta according to the paleogeographic map of the delta plane. When estimating, the maximum width value and the minimum width value can be used respectively.

[0040] Porosity value obtaining module, which is used to accurately assign density and porosity according to the formation period of the delta and the lithological differences of the sedimentary layers, and obtain the porosity values of the lithologies of the progradational, foreset, and bottomset layers respectively.

[0041] Total organic carbon TOC average value obtaining module, which is used to obtain the average value of total organic carbon TOC during the formation period of the delta by logging method, as the value of total organic carbon TOC in the formula.

[0042] Sedimentation rate obtaining module, which is used to collect the sedimentation rate during the formation period of the delta according to the wells within the delta area.

[0043] Organic carbon burial amount and organic carbon annual flux obtaining module, which is used to obtain the organic carbon burial amounts and organic carbon annual fluxes of each part and the overall of the delta respectively through the organic carbon burial amount and organic carbon annual flux calculation formulas.

[0044] To further illustrate the related effects of the embodiments of the present invention, the following experiment is carried out.

[0045] Step 1. Analyze the seismic profile of the delta in a certain city, and then divide the delta bodies of different sedimentary stages. Take a stage of the delta with relatively regular morphological development and well-developed progradational, foreset, and bottomset layers as an example.

[0046] Step 2. Calculate the oblique cross-sectional area D of the delta body of this stage according to the seismic profile. The oblique cross-sectional area D is approximately 0.087 km 2 The progradational oblique cross-sectional area is 0.015 km 2 , and the foreset oblique cross-sectional area is 0.046 km 2, the cross-sectional area of the bottom set bed is 0.026 km 2 . Based on the delta seismic profile of a certain city Figure 2 It can also be obtained that the length L of the delta is about 24 km and the height H is about 8.68 km.

[0047] Step 3, based on the paleogeographic map of the delta in a certain city, the width W of the delta is measured. The widest and narrowest parts of the delta are 29.9 km and 13.5 km respectively, and the calculated average value is 21.7 km. Therefore, the width W is set to 21.7 km ± 8.2 km in the calculation. The surface area A of the delta is 84.89 km 2 .

[0048] Step 4, in order to obtain the density ρ and porosity φ of each part of the delta, the Eocene profile is selected. The lithology of the foreset bed and progradational bed is mainly medium-fine sandstone, and the lithology of the bottom set bed is mainly mudstone. The porosity of sandstone is selected as 20%; the porosity of mudstone is selected as 4.5%. The density of the delta is selected as 2650 kg / m 3 ; the overall porosity of the delta is 18%.

[0049] Step 5, the organic carbon data selects the average TOC data of Well Wang 46 in a certain sag of a city: 0.52%, and substitutes it into the formula.

[0050] Step 6, the selection of the sedimentation rate SR. Well Wang 46 in the Dongying Sag is selected as a representative, and the sedimentation rate is selected as 0.195 mm / yr.

[0051] Step 7, substitute the data selected in each step into the calculation formula: Moc = TOC × D × W × (1 - φ) × ρ, and the TOC content buried in the delta can be estimated; that is, M 顶积层、前积层 = 0.52% × 0.061 km 2 × 21.7 km × (1 - 0.2) × 2650 kg / m 3 = 14.59; M 底积层 = 0.52% × 0.026 km 2 × 21.7 km × (1 - 0.45) × 2650 kg / m 3 = 4.28; then substitute OC annual flux = TOC × A × SR × (1 - φ) × ρ to estimate the annual flux of organic carbon in the delta; OC annualflux = TOC × A × SR × (1 - φ) × ρ = 0.52% × 84.89 km 2 × 0.195 mm / yr × (1 - 0.18) × 2650 kg / m 3 = 0.19 (kt OC yr).

[0052] As described above, it is only a relatively preferred specific embodiment 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, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A method for estimating the total buried organic carbon and annual flux in lacustrine deltas, characterized in that, The method includes the following steps: S1. Interpret the target delta seismic profile, and divide the delta stages and the parts of the topset bed, foreset bed, and bottomset bed; S2. Based on the selected seismic profile of the delta body, calculate the total inclined cross-sectional area, topset bed, foreset bed, bottomset bed inclined cross-sectional areas, total length, width, and height of the target delta body; S3. According to the paleogeographic map of the delta, estimate the maximum width and minimum width of the delta by using the maximum width value and the minimum width value respectively; S4. According to the formation period of the delta and the lithological differences of the sedimentary layers, accurately assign the density and porosity, and obtain the porosity values of the lithologies of the topset bed, foreset bed, and bottomset bed respectively; S5. Use the logging method to obtain the average value of total organic carbon TOC during the formation period of the delta, and use it as the value of total organic carbon TOC in the formula; S6. Collect the sedimentation rate during the formation period of the delta according to the wells within the delta area; S7. Through the calculation formulas of organic carbon burial amount and annual organic carbon flux, obtain the organic carbon burial amount and annual organic carbon flux of each part and the whole of the delta.

2. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 1, wherein In step S2, calculating the total inclined cross-sectional area, topset bed, foreset bed, bottomset bed inclined cross-sectional areas, total length, width, and height of the target delta body includes: using the cutting and patching method to convert the irregular delta figure into a regular figure, and combining with the scale in the seismic profile diagram for calculation.

3. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 2, wherein Use a graphic calculation tool to calculate the deltas of different divided stages.

4. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 1, wherein In step S3, based on the sedimentary facies belt changes, geomorphic turning points, or sudden changes in formation thickness characteristics on the paleogeographic map, identify the two sides' boundaries of the delta, and estimate the maximum width according to the scale; Based on the sedimentary facies belt and formation contact relationship marks, define the boundaries of the delta, and estimate the minimum width according to the scale.

5. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 1, characterized in that, In step S4, use logging curves to identify the lithology of sedimentary rocks or collect core samples to obtain the lithology of sedimentary rocks; the porosity range is determined according to the standard database, and the porosity is obtained according to the laboratory core analysis data, and the density uses the density of quartz.

6. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 1, characterized in that, In step S5, using logging data, the measured TOC data is obtained. The average value of the measured TOC data of different wells is the TOC average value. If there is no measured TOC data, the method is used to calculate the TOC average value data, and the expression is: ； ； Wherein, is the reading of the spacing between the resistivity curve and the acoustic travel time curve on the logarithmic resistivity coordinate, is the organic matter scale; is the resistivity, is the resistivity when the organic carbon content in the shale is zero, is the acoustic travel time, is the acoustic travel time when the organic carbon content in the shale is zero.

7. The method for estimating the total buried organic carbon and annual flux in lacustrine deltas according to claim 6, wherein, In step S7, the calculation formula for organic carbon burial amount is: ； The calculation formula for annual organic carbon flux is: ； In the formula, is the burial amount of organic carbon, is the cross-sectional area of the delta body, is the width of the delta, is the porosity, is the density, is the annual flux of organic carbon, is the surface area of the delta, is the sedimentation rate.

8. A system for estimating the total buried organic carbon and annual flux in lacustrine deltas, characterized in that, The system implements the method for estimating the total buried organic carbon and annual flux of lacustrine deltas as described in any one of claims 1 - 7. The system includes: A delta sedimentary stage and internal structure division module, which is used to interpret the target delta seismic profile and divide the delta stages and the parts of the topset bed, foreset bed, and bottomset bed; A layered parameter calculation module, which is used to calculate the total inclined cross-sectional area, topset bed, foreset bed, bottomset bed inclined cross-sectional areas, total length, width, and height of the target delta body based on the selected seismic profile of the delta body; A delta maximum width and minimum width estimation module, which is used to estimate the maximum width and minimum width of the delta by using the maximum width value and the minimum width value respectively according to the paleogeographic map of the delta; A porosity value obtaining module, which is used to accurately assign the density and porosity according to the formation period of the delta and the lithological differences of the sedimentary layers, and obtain the porosity values of the lithologies of the topset bed, foreset bed, and bottomset bed respectively; The total organic carbon (TOC) average value obtaining module is used to obtain the average value of the total organic carbon (TOC) during the delta formation period by well logging methods, and use it as the value of the total organic carbon (TOC) in the formula. The sedimentation rate obtaining module is used to collect the sedimentation rate during the delta formation period based on the wells within the delta area. The organic carbon burial amount and organic carbon annual flux obtaining module is used to obtain the organic carbon burial amount and organic carbon annual flux of each part and the whole of the delta through the calculation formulas of the organic carbon burial amount and organic carbon annual flux.

9. The lacustrine delta buried total organic carbon and annual flux estimation system according to claim 8, characterized in that, The lacustrine delta buried total organic carbon and annual flux estimation system is installed on a computer device, which includes: at least one processor, a memory, and a computer program stored in the memory and operable on the at least one processor. When the processor executes the computer program, the functions in the above-mentioned lacustrine delta buried total organic carbon and annual flux estimation system are realized.

10. The lacustrine delta buried total organic carbon and annual flux estimation system according to claim 8, wherein The lacustrine delta buried total organic carbon and annual flux estimation system is installed on a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the functions in the above-mentioned lacustrine delta buried total organic carbon and annual flux estimation system can be realized.

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