Method and system for quantitatively characterizing the distribution of different types of source rocks in areas with few wells

Abstract

The present application belongs to the technical field of oil and gas exploration and development, and relates to a method and system for quantitatively characterizing the distribution of different types of source rocks in areas with few wells. The method comprises the following steps: obtaining a post-stack seismic volume, a sedimentary facies map, acoustic transit time logging data, and density logging data for a target layer; obtaining seismic reflection characteristics of source rocks corresponding to different sedimentary deposits by intercepting a seismic profile obtained from the post-stack seismic volume; analyzing source rock types using the sedimentary facies map, and characterizing the planar distribution of different types of source rocks in the target layer based on the development characteristics and sedimentary facies of different types of source rocks predicted using the seismic reflection characteristics of the source rocks; obtaining the residual formation thickness of the target layer based on the post-stack seismic volume, predicting the formation sand-to-formation ratio of the target layer, and characterizing the thickness distribution of the source rocks in the target layer based on the residual formation thickness and the formation sand-to-formation ratio; and coupling the planar distribution of the source rocks with the source rock thickness distribution to obtain the spatial distribution of the source rocks. The present application quantitatively characterizes the distribution of different types of source rocks in areas with few wells.

Description

Technical Field

[0001] The present application belongs to the technical field of oil and gas exploration and development, and relates to acoustic wave remote detection imaging logging technology, and specifically to a method and system for quantitatively characterizing the distribution of different types of source rocks in areas with few wells. Background Art

[0002] In oil and gas exploration, source rock refers to rocks that have already formed, may form, or have the potential to generate oil and gas. Its distribution characteristics and its contact with transport pathways play a crucial role in controlling the migration and accumulation of oil and gas. Currently, conventional source rock evaluation methods are primarily based on single-well stratigraphic data. This involves determining the relative thickness of dark mudstone revealed by different wells relative to the stratigraphic thickness. This data is then digitized using sedimentary facies analysis to generate data such as the planar distribution of the dark mudstone to ground ratio. Subsequently, mudstone thickness is calibrated using seismic inversion profiles to infer the distribution of the source rock.

[0003] However, in underexplored areas, due to limited drilling and coring data, traditional source rock evaluation methods based on geochemical and logging data struggle to meet the requirements for high-precision resource calculations. In these areas, source rock identification and prediction rely heavily on seismic data, particularly seismic inversion techniques. Seismic inversion combines geophysical and geological data to calibrate seismic reflection characteristics and establish seismic identification models for source rocks. This method identifies the seismic characteristics and development patterns of source rocks, thereby predicting their spatial distribution. However, this method primarily serves to qualitatively characterize the distribution of source rocks and struggles to meet the requirements for high-precision resource assessment. Summary of the Invention

[0004] In response to the problems existing in the prior art, this application provides a method and system for quantitatively characterizing the distribution of different types of source rocks in areas with few wells. By combining seismic inversion with seismic multi-attribute analysis, source rocks can be directly predicted. The required data is simple and suitable for the identification and prediction of source rocks in areas with few wells, meeting the requirements of high-precision resource assessment.

[0005] In a first aspect, the present application provides a method for quantitatively characterizing the distribution of different types of source rocks in a well-poor area, the steps of which are as follows:

[0006] Data acquisition steps: obtaining target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data;

[0007] Data processing steps: intercepting the post-stack seismic volume to obtain a seismic profile, and obtaining the seismic reflection characteristics of the source rocks corresponding to different sediments through the seismic profile;

[0008] Steps for depicting the planar distribution of source rocks: Use sedimentary facies diagrams to analyze source rock types, use seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks, and depict the planar distribution of different types of source rocks in the target layer based on the development characteristics and sedimentary facies of different types of source rocks;

[0009] The steps for characterizing the vertical thickness distribution of the source rock are as follows: obtaining the residual formation thickness of the target layer based on the post-stack seismic volume, predicting the formation sand-to-stratigraphy ratio of the target layer using the seismic inversion method based on the post-stack seismic volume, acoustic transit time logging data, and density logging data, or predicting the formation sand-to-stratigraphy ratio of the target layer using the seismic attribute analysis method based on the post-stack seismic volume, and characterizing the thickness distribution of the source rock in the target layer based on the residual formation thickness and the formation sand-to-stratigraphy ratio;

[0010] Source rock distribution steps: Couple the plane distribution and thickness distribution of source rocks to obtain the spatial distribution of source rocks.

[0011] In some embodiments, in the step of characterizing the vertical thickness distribution of the source rock, a method for predicting the formation sand-to-ground ratio using the seismic inversion method based on the post-stack seismic volume, acoustic time difference logging data, and density logging data is as follows:

[0012] Boundary value determination steps: Calculate the wave impedance values ​​of the sandstone and mudstone of the target layer based on the acoustic transit time logging data and density logging data, analyze the wave impedance characteristics of the sandstone and mudstone of the target layer, and determine the wave impedance boundary values ​​of the sandstone and mudstone;

[0013] Inversion steps: Use seismic inversion software to perform wave impedance inversion on the stacked seismic volume to obtain a wave impedance inversion profile;

[0014] Judgment steps: The lithology of each sampling point on the wave impedance inversion profile is determined based on the wave impedance limit values ​​of sandstone and mudstone. When the wave impedance value is greater than the wave impedance limit value of sandstone and mudstone, the corresponding stratum is determined to be sandstone; when the wave impedance value is less than the wave impedance limit value of sandstone and mudstone, it is determined to be mudstone;

[0015] Calculation steps: Within the target layer, for each seismic trace, count the number of sampling points Ns identified as sandstone and the total number of sampling points Nt, and calculate the sand-to-ground ratio of the seismic trace based on the number of sampling points Ns and the total number of sampling points Nt;

[0016] Sand ratio=Ns / Nt

[0017] Integration step: Integrate the sand-to-ground ratio of each seismic trace with the corresponding position information to obtain the sand-to-ground ratio of the target layer.

[0018] In some embodiments, in the step of characterizing the vertical thickness distribution of the source rock, a method for predicting the formation sand-to-ground ratio using a seismic attribute analysis method based on the post-stack seismic volume is:

[0019] Extraction step: converting the post-stack seismic volume into a seismic attribute volume, extracting the root mean square amplitude seismic attribute from the seismic attribute volume to obtain a seismic root mean square amplitude profile;

[0020] Steps for determining the root mean square amplitude: according to the distribution range of sedimentary facies, a virtual well is set up, the position corresponding to the virtual well is found on the seismic root mean square amplitude profile, and the root mean square amplitude value at the position is read;

[0021] Calculation steps: Substitute the read RMS amplitude value into the fitting relationship formula between sand-to-ground ratio and RMS amplitude to obtain the formation sand-to-ground ratio of the target layer.

[0022] In some embodiments, the fitting relationship between the sand-to-ground ratio and the root mean square amplitude is expressed as:

[0023] Sand ratio = 0.2002 · Root mean square amplitude – 0.0098.

[0024] In some embodiments, in the step of characterizing the vertical thickness distribution of the source rock, the method for obtaining the residual formation thickness based on the post-stack seismic volume is:

[0025] Identification steps: on the seismic profile, identify the seismic times t1 and t2 corresponding to the top and bottom interfaces of the target layer;

[0026] Depth calculation steps: Substitute the seismic times t1 and t2 into the actual drilling time-depth conversion relationship to obtain the formation depth corresponding to the top interface of the target layer and the depth corresponding to the bottom interface of the target layer;

[0027] Residual thickness calculation steps: The residual formation thickness of the target layer is obtained by subtracting the formation depth corresponding to the top interface of the target layer from the depth corresponding to the bottom interface of the target layer.

[0028] In a second aspect, the present application provides a system for quantitatively characterizing the distribution of different types of source rocks in an area with few wells, which is used to implement the method for quantitatively characterizing the distribution of different types of source rocks in an area with few wells described in the first aspect of the present application, comprising:

[0029] Data acquisition module, used to obtain target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data;

[0030] The data processing module intercepts the post-stack seismic volume to obtain a seismic profile, and obtains the seismic reflection characteristics of the source rocks corresponding to different sediments through the seismic profile;

[0031] The module for depicting the planar distribution of source rocks uses sedimentary facies maps to analyze source rock types, uses seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks, and depicts the planar distribution of different types of source rocks in the target layer based on their development characteristics and sedimentary facies.

[0032] The hydrocarbon source rock vertical thickness distribution characterization module obtains the residual formation thickness of the target layer based on the post-stack seismic volume, and uses the seismic inversion method to predict the formation sand-to-stratigraphy ratio of the target layer based on the post-stack seismic volume, acoustic time difference logging data, and density logging data, or uses the seismic attribute analysis method based on the post-stack seismic volume to predict the formation sand-to-stratigraphy ratio of the target layer. The hydrocarbon source rock thickness distribution in the target layer is characterized based on the residual formation thickness and the formation sand-to-stratigraphy ratio;

[0033] The source rock distribution module couples the planar distribution of source rocks with the thickness distribution of source rocks to obtain the spatial distribution of source rocks.

[0034] In some embodiments, the source rock plane distribution characterization module includes:

[0035] Sedimentary facies analysis module, which uses sedimentary facies diagrams to analyze source rock types;

[0036] Feature prediction module, which uses the seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks;

[0037] The plane distribution characterization module characterizes the plane distribution of different types of source rocks in the target layer according to their development characteristics and sedimentary facies.

[0038] In some embodiments, the source rock vertical thickness distribution characterization module includes:

[0039] The residual stratum thickness calculation module obtains the residual stratum thickness of the target layer based on the post-stack seismic volume.

[0040] The sand-to-ground ratio prediction module uses the seismic inversion method to predict the formation sand-to-ground ratio of the target layer based on the post-stack seismic volume, acoustic time difference logging data and density logging data, or uses the seismic attribute analysis method to predict the formation sand-to-ground ratio of the target layer based on the post-stack seismic volume.

[0041] The thickness distribution characterization module characterizes the thickness distribution of source rocks in the target layer based on the residual formation thickness and the formation sand-to-ground ratio.

[0042] Compared with the prior art, the advantages and positive effects of this application are:

[0043] The method and system provided in this application for quantitatively characterizing the distribution of different types of source rocks in areas with few wells are based on multi-source data and, after data processing, characterize the planar distribution and vertical thickness distribution of source rocks. By using sedimentary phase maps and seismic reflection characteristics to characterize the planar distribution, the distribution range of different types of source rocks on the plane can be clearly presented; by combining seismic inversion or seismic attribute analysis with residual stratum thickness to characterize the thickness distribution, the vertical changes of source rocks can be accurately described. Finally, the planar and thickness distributions are coupled to obtain intuitive and comprehensive spatial distribution information of source rocks. The required data is simple, providing a complete solution for source rock research in areas with few wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of the method for quantitatively characterizing the distribution of different types of source rocks in a sparsely-welled area according to an embodiment of the present application;

[0045] Figure 2 A flow chart of a method for depicting the planar distribution of different types of source rocks in a target layer according to an embodiment of the present application;

[0046] Figure 3 A flow chart of a method for depicting the thickness distribution of source rocks in a target layer according to an embodiment of the present application;

[0047] Figure 4 This is a flow chart of a method for obtaining residual stratum thickness based on a post-stack seismic volume according to an embodiment of the present application;

[0048] Figure 5 This is a flow chart of a method for predicting the formation sand-to-sand ratio of a target layer using the seismic inversion method according to an embodiment of the present application;

[0049] Figure 6 This is a flow chart of a method for predicting the formation sand-to-sand ratio of a target layer using a seismic attribute analysis method according to an embodiment of the present application;

[0050] Figure 7 This is a structural block diagram of the system for quantitatively characterizing the distribution of different types of source rocks in areas with few wells as described in an embodiment of the present application;

[0051] Figure 8 This is a structural block diagram of the source rock plane distribution characterization module of the embodiment of the present application;

[0052] Figure 9 This is a structural block diagram of the hydrocarbon source rock vertical thickness distribution characterization module of the embodiment of the present application;

[0053] Figure 10 This is the seismic reflection characteristic map of the source rock of the target layer in Depression A of the present application;

[0054] Figure 11 This is the wave impedance analysis diagram of the sand and mudstone in Depression A of the present application;

[0055] Figure 12 This is the post-stack wave impedance inversion profile of the depression over-drilling in Example A of the present application;

[0056] Figure 13 Plane diagram of sand-mud ratio after wave impedance inversion for the purpose of depression in Example A of this application;

[0057] Figure 14 This is a correlation diagram of the root mean square amplitude attribute value and sand-to-ground ratio of the target layer in the depression A of the present application;

[0058] Figure 15This is a cross-sectional view of the root mean square amplitude of the depression through the virtual well in Example A of the present application;

[0059] In the figure, 1. Data acquisition module, 2. Data processing module, 3. Source rock plane distribution characterization module, 31. Sedimentary phase analysis module, 32. Feature prediction module, 33. Plane distribution characterization module, 4. Source rock vertical thickness distribution characterization module, 41. Residual formation thickness calculation module, 42. Sand-to-ground ratio prediction module, 43. Thickness distribution characterization module, 5. Source rock distribution module, W, well trajectory of actual drilling well A1, B, bottom interface of target layer, T, top interface of target layer, D, virtual well trajectory. DETAILED DESCRIPTION

[0060] The present application will be described in detail below with reference to exemplary embodiments in conjunction with the accompanying drawings. However, it should be understood that elements, structures, and features in one embodiment may also be beneficially combined in other embodiments without further description.

[0061] See also Figure 1 The first embodiment of the present application provides a method for quantitatively characterizing the distribution of different types of source rocks in a well-poor area, the steps of which are as follows:

[0062] S1. Data acquisition step: obtaining target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data.

[0063] Post-stack seismic volumes provide macroscopic information on the underground stratigraphic structure; sedimentary facies maps help understand the sedimentary environment and thus infer the type of source rocks; and acoustic transit time logging data and density logging data can be used for subsequent wave impedance calculations.

[0064] S2. Data processing step: intercepting the post-stack seismic volume to obtain a seismic profile, and obtaining the seismic reflection characteristics of the source rocks corresponding to different deposits through the seismic profile.

[0065] S3. Step of characterizing the planar distribution of source rocks: characterize the planar distribution of different types of source rocks in the target layer.

[0066] Specifically, see Figure 2 The specific method for depicting the planar distribution of different types of source rocks in the target layer is:

[0067] S31. Use sedimentary facies diagrams to analyze source rock types.

[0068] S32. Use the seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks.

[0069] S33. Describe the planar distribution of different types of source rocks in the target layer based on their development characteristics and sedimentary facies.

[0070] The use of sedimentary facies maps and seismic reflection characteristics to depict planar distribution can clearly present the distribution range of different types of source rocks on the plane.

[0071] S4. Step of characterizing the vertical thickness distribution of source rocks: characterizing the thickness distribution of source rocks in the target layer.

[0072] Specifically, see Figure 3 , the specific method for describing the thickness distribution of source rocks in the target layer is:

[0073] S41. Obtain the residual stratum thickness of the target layer based on the post-stack seismic volume.

[0074] Specifically, in some embodiments, see Figure 4 , the method to obtain the residual stratum thickness based on the post-stack seismic volume is:

[0075] S411, identification step: identifying the earthquake times t1 and t2 corresponding to the top and bottom interfaces of the target layer on the seismic profile;

[0076] S412, depth calculation step: Substituting the earthquake times t1 and t2 into the actual drilling time-depth conversion relationship to obtain the formation depth corresponding to the top interface of the target layer and the depth corresponding to the bottom interface of the target layer;

[0077] S413. Residual thickness calculation step: Subtract the depth corresponding to the top interface of the target layer from the depth corresponding to the bottom interface of the target layer to obtain the residual formation thickness of the target layer.

[0078] By identifying the seismic time of the top and bottom interfaces of the target layer on the seismic profile, substituting the actual drilling time-depth conversion relationship into the corresponding depth, the residual formation thickness is calculated by subtracting the two. This method fully utilizes the combination of seismic data and actual drilling data to accurately determine the residual formation thickness of the target layer. Accurate residual formation thickness data is crucial for subsequent calculation of source rock thickness distribution based on sand-to-formation ratio, ensuring the vertical accuracy of the final source rock distribution characterization.

[0079] S42. Predict the formation sand-to-sand ratio of the target layer.

[0080] In some embodiments, see Figure 5 The formation sand ratio of the target layer is predicted using the seismic inversion method based on the post-stack seismic volume, acoustic time difference logging data and density logging data. The specific method is as follows:

[0081] S421, limit value determination step: calculating the wave impedance values ​​of the sandstone and mudstone of the target layer based on the acoustic transit time logging data and the density logging data, analyzing the wave impedance characteristics of the sandstone and mudstone of the target layer, and determining the wave impedance limit values ​​of the sandstone and mudstone;

[0082] S422, inversion step: performing wave impedance inversion on the stacked seismic volume using seismic inversion software to obtain a wave impedance inversion profile;

[0083] S423, determination step: performing lithology determination on each sampling point on the wave impedance inversion profile according to the wave impedance limit value of sandstone and mudstone; when the wave impedance value is greater than the wave impedance limit value of sandstone and mudstone, the corresponding formation is determined to be sandstone; and when the wave impedance value is less than the wave impedance limit value of sandstone and mudstone, the corresponding formation is determined to be mudstone;

[0084] S424, calculation step: within the target layer, for each seismic trace, count the number of sampling points Ns identified as sandstone and the total number of sampling points Nt, and calculate the sand-to-ground ratio of the seismic trace based on the number of sampling points Ns and the total number of sampling points Nt;

[0085] Sand ratio=Ns / Nt

[0086] S425, integration step: integrating the sand-to-ground ratio of each seismic trace with the corresponding position information to obtain the sand-to-ground ratio of the target layer.

[0087] In the embodiment of the present application, by calculating the wave impedance value based on the acoustic time difference logging data and the density logging data, and determining the wave impedance limit value of sandstone and mudstone, the lithology of each sampling point on the wave impedance inversion profile can be accurately determined. This determination method based on rock physical properties is more accurate and reliable than simply relying on seismic reflection characteristics to determine lithology, and reduces the possibility of misjudgment. Based on accurate lithology determination, the number of sampling points identified as sandstone and the total number of sampling points are statistically calculated to calculate the sand-to-ground ratio, so that the calculation result of the sand-to-ground ratio can truly reflect the proportion of sandstone in the formation. The sand-to-ground ratio of each seismic channel is integrated with the corresponding position information, and the sand-to-ground ratio data of the target layer obtained is spatially continuous and accurate, which provides high-precision data support for the subsequent calculation of the source rock thickness distribution in combination with the residual formation thickness.

[0088] In other implementations of this application, see Figure 6 , based on the post-stack seismic volume, the seismic attribute analysis method is used to predict the formation sand-to-ground ratio of the target layer. The specific method is as follows:

[0089] S421, extraction step: converting the post-stack seismic volume into a seismic attribute volume, extracting root mean square amplitude seismic attributes from the seismic attribute volume to obtain a seismic root mean square amplitude profile;

[0090] S422, root mean square amplitude determination step: according to the sedimentary facies distribution range, a virtual well is established, a position corresponding to the virtual well is found on the seismic root mean square amplitude profile, and the root mean square amplitude value at the position is read;

[0091] S423, calculation step: Substitute the read root mean square amplitude value into the fitting relationship formula of sand-to-ground ratio and root mean square amplitude to obtain the formation sand-to-ground ratio of the target layer.

[0092] In the embodiment of the present application, the post-stack seismic volume is converted into a seismic attribute volume and the root mean square amplitude seismic attribute is extracted, and the intrinsic connection between the seismic attribute and the lithology and physical properties of the formation is utilized. The root mean square amplitude seismic attribute can reflect the characteristics of the formation to a certain extent. By setting up a virtual well to read the root mean square amplitude value, and then calculating the sand-to-ground ratio, an effective method for predicting the sand-to-ground ratio is provided for the lack of sufficient logging data in a well-sparse area. Compared with the above-mentioned seismic inversion method, the operation is simpler and the calculation amount is smaller. It is only necessary to obtain the post-stack seismic volume and perform attribute extraction, combined with the setting of the virtual well and the reading of the root mean square amplitude value, the formation sand-to-ground ratio of the target layer can be quickly obtained, which improves work efficiency and has strong practicality in a well-sparse area.

[0093] Specifically, in some embodiments of the present application, the fitting relationship formula between the sand-to-ground ratio and the root mean square amplitude is expressed as:

[0094] Sand ratio = 0.2002 · Root mean square amplitude – 0.0098.

[0095] In the examples of this application, a fitting relationship between sand-to-ground ratio and RMS amplitude is presented, providing a clear quantitative basis for calculating sand-to-ground ratio using RMS amplitude. This quantitative relationship allows for rapid and accurate calculation of sand-to-ground ratio in practice, as long as the RMS amplitude value is obtained. This reduces human error and improves the consistency and reliability of the sand-to-ground ratio calculation results.

[0096] S43. Characterize the distribution of source rock thickness in the target layer based on the residual formation thickness and the formation sand-to-ground ratio.

[0097] Specifically, the formula for calculating the thickness of the source rock in the target layer based on the residual formation thickness and the formation sand-to-ground ratio is expressed as:

[0098] Source rock thickness = residual formation thickness × (1 – formation sand-to-ground ratio)

[0099] Substituting the residual formation thickness obtained in step S41 and the formation sand-to-formation ratio obtained in step S42 into the above-mentioned source rock thickness calculation formula, the source rock thickness distribution can be obtained.

[0100] S5. Source rock distribution step: coupling the planar distribution of source rocks with the thickness distribution of source rocks to obtain the spatial distribution of source rocks.

[0101] In the above-mentioned method of quantitatively characterizing the distribution of different types of source rocks in areas with few wells in this application, the integration of multi-source data is achieved by obtaining the target post-stack seismic body, sedimentary phase map, acoustic time difference logging data and density logging data. On the basis of data processing, the plane distribution and vertical thickness distribution of the source rock are characterized respectively. By using sedimentary phase map and seismic reflection characteristics to characterize the plane distribution, the distribution range of different types of source rocks on the plane can be clearly presented; by combining the seismic inversion method or seismic attribute analysis method with the residual stratum thickness to characterize the thickness distribution, the vertical changes of the source rock are accurately described. Finally, the plane and thickness distribution are coupled to obtain intuitive and comprehensive spatial distribution information of the source rock, which solves the problem of quantitative distribution characterization of source rocks in areas with few wells and provides a complete solution for the study of source rocks in areas with few wells.

[0102] The second embodiment of the present application provides a system for quantitatively characterizing the distribution of different types of source rocks in a region with few wells, which is used to implement the method for quantitatively characterizing the distribution of different types of source rocks in a region with few wells described in the first embodiment of the present application, see Figure 7 , the system comprising:

[0103] Data acquisition module 1, used to obtain target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data;

[0104] Data processing module 2 intercepts the post-stack seismic volume to obtain a seismic profile, and obtains the seismic reflection characteristics of the source rocks corresponding to different sediments through the seismic profile;

[0105] Module 3 for characterizing the plane distribution of source rocks: using sedimentary facies maps to analyze source rock types, using seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks, and characterizing the plane distribution of different types of source rocks in the target layer based on their development characteristics and sedimentary facies;

[0106] The hydrocarbon source rock vertical thickness distribution characterization module 4 obtains the residual formation thickness of the target layer based on the post-stack seismic volume, predicts the formation sand-to-stratigraphy ratio of the target layer using the seismic inversion method based on the post-stack seismic volume, acoustic time difference logging data and density logging data, or predicts the formation sand-to-stratigraphy ratio of the target layer using the seismic attribute analysis method based on the post-stack seismic volume, and characterizes the hydrocarbon source rock thickness distribution in the target layer based on the residual formation thickness and the formation sand-to-stratigraphy ratio;

[0107] The source rock distribution module 5 couples the planar distribution of the source rock with the thickness distribution of the source rock to obtain the spatial distribution of the source rock.

[0108] In this embodiment, the system achieves modular integration of functions by dividing it into a data acquisition module 1, a data processing module 2, a source rock planar distribution characterization module 3, a source rock vertical thickness distribution characterization module 4, and a source rock distribution module 5. Each module performs its own function, yet collaborates with each other, enabling the entire process of quantitatively characterizing the distribution of different source rock types in areas with few wells to run efficiently and orderly. This modular design facilitates system maintenance, upgrades, and expansion, improving its stability and flexibility.

[0109] In some embodiments of this application, see Figure 8 The source rock plane distribution characterization module 3 includes:

[0110] Sedimentary facies analysis module 31, analyzing source rock types using sedimentary facies diagrams;

[0111] Feature prediction module 32, predicting the development characteristics of different types of source rocks using seismic reflection characteristics of source rocks;

[0112] The plane distribution characterization module 33 characterizes the plane distribution of different types of source rocks in the target layer according to the development characteristics and sedimentary facies of different types of source rocks.

[0113] In this embodiment, the source rock planar distribution characterization module is further subdivided into a sedimentary facies analysis module 31, a feature prediction module 32, and a planar distribution characterization module 33. Sedimentary facies analysis module 31 uses sedimentary facies maps to analyze source rock types, providing a foundation for subsequent analysis. Feature prediction module 32 uses seismic reflection characteristics to predict source rock development characteristics, enhancing the scientific nature of the prediction. Planar distribution characterization module 33 integrates the results of the first two modules to precisely characterize the planar distribution of different types of source rocks in the target layer, making the planar distribution characterization results more accurate and detailed, and facilitating a deeper understanding of the planar distribution patterns of source rocks.

[0114] In some embodiments, see Figure 9 The hydrocarbon source rock vertical thickness distribution characterization module 4 includes:

[0115] The residual stratum thickness calculation module 41 obtains the residual stratum thickness of the target layer according to the post-stack seismic volume.

[0116] The sand-to-ground ratio prediction module 42 predicts the formation sand-to-ground ratio of the target layer using the seismic inversion method based on the post-stack seismic volume, acoustic time difference logging data and density logging data, or predicts the formation sand-to-ground ratio of the target layer using the seismic attribute analysis method based on the post-stack seismic volume.

[0117] The thickness distribution characterization module 43 characterizes the thickness distribution of the source rock in the target layer according to the residual formation thickness and the formation sand-to-formation ratio.

[0118] In the embodiments of the present application, the module for characterizing the vertical thickness distribution of source rock is subdivided into a residual formation thickness calculation module, a sand-to-formation ratio prediction module, and a thickness distribution characterization module. The residual formation thickness calculation module accurately obtains the residual formation thickness; the sand-to-formation ratio prediction module predicts the sand-to-formation ratio using different methods; and the thickness distribution characterization module combines the results of the two to accurately characterize the thickness distribution of source rock in the target layer. This subdivided module design makes the thickness distribution characterization process more rigorous and scientific, improves the accuracy of the source rock thickness distribution characterization results, and provides a strong guarantee for comprehensively and accurately presenting the spatial distribution of source rock.

[0119] In order to verify the effectiveness of the method and system for quantitatively characterizing the distribution of different types of source rocks in a well-poor area described in the above embodiments of the present application, the following specific embodiments are used for illustration.

[0120] Example: Taking Sag A as an example, obtain post-stack seismic data, sedimentary facies maps, acoustic time-of-day logging data, and density logging data for the area.

[0121] First, the source rock types were analyzed using the sedimentary facies of the target layer in Depression A. Generally, source rocks are divided into medium-deep lake source rocks and shallow lake source rocks according to their sedimentary facies.

[0122] according to Figure 10 The figure shows the seismic reflection characteristic map of the source rock in the target layer of Depression A. Seismic sections are selected at equal intervals to predict the development characteristics of different types of source rocks.

[0123] The rock physical analysis of the well logging wave impedance curve of the target layer in Depression A was carried out, such as Figure 11 The following figure shows the sand-mud ratio plane of the target layer after stacking in Sag A using impedance inversion. The longitudinal wave impedance has a strong ability to distinguish sandstone and mudstone. The impedance limit between sandstone and mudstone is 8500 (unit: g / cm 3 m / s), high wave impedance represents sandstone, and low wave impedance represents mudstone.

[0124] Jason seismic inversion software was used to perform wave impedance inversion on the post-stack seismic body of the target layer in Depression A, and the post-stack wave impedance inversion profile of Depression A was obtained. Figure 12 shown. Figure 12 In the figure, W represents the well trajectory of the actual drilling well A1, B represents the bottom interface of the target layer, and T represents the top interface of the target layer. Figure 12 The seismic wave impedance profile is generally consistent with the actual drilling wave impedance. Combined with the wave impedance limit value of 8500 (unit: g / cm) of the target layer sandstone and mudstone in Depression A, the seismic wave impedance profile is generally consistent with the actual drilling wave impedance. 3 m / s), can effectively distinguish the sand and mudstone of the target layer in Sag A, and then obtain the sand-to-ground ratio distribution of the target layer in Sag A (such as Figure 13 Show). Figure 13 In the figure, A1 and A2 represent actual drilling wells.

[0125] like Figure 14 The following figure shows the correlation between the RMS amplitude attribute value and the sand-to-formation ratio of the target layer in Sag A. The sand-to-formation ratio of the target layer in Sag A is well correlated with the RMS amplitude seismic attribute. Based on the distribution range of sedimentary facies, a virtual well was established. The RMS amplitude value of the virtual well was read on the seismic RMS amplitude profile (see Figure 15 The virtual well sand-to-ground ratio is calculated based on the RMS amplitude reading using the following formula: Sand-to-ground ratio = 0.2002·RMS amplitude – 0.0098. Figure 15 In the figure, B represents the bottom interface of the target layer, T represents the bottom interface of the target layer, and D represents the virtual well trajectory.

[0126] The thickness distribution of source rocks is characterized based on the residual formation thickness and sand-to-ground ratio.

[0127] The spatial distribution of source rocks is obtained by coupling the planar distribution of source rocks with the thickness distribution of source rocks.

[0128] The above embodiments are used to explain the present application rather than to limit the present application. Any modifications and changes made to the present application within the spirit of the present application and the protection scope of the claims shall fall within the protection scope of the present application.

Claims

1. A method for quantitatively characterizing the distribution of different types of source rocks in a well-polluted area, characterized in that: The steps are: Data acquisition steps: obtaining target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data; Data processing steps: intercepting the post-stack seismic volume to obtain a seismic profile, and obtaining the seismic reflection characteristics of the source rocks corresponding to different sediments through the seismic profile; Steps for depicting the planar distribution of source rocks: Use sedimentary facies diagrams to analyze source rock types, use seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks, and depict the planar distribution of different types of source rocks in the target layer based on the development characteristics and sedimentary facies of different types of source rocks; The steps for characterizing the vertical thickness distribution of source rocks are as follows: the residual formation thickness of the target layer is obtained based on the post-stack seismic volume; the formation sand-to-stratigraphy ratio of the target layer is predicted using the seismic inversion method based on the post-stack seismic volume, acoustic transit time logging data, and density logging data; or the formation sand-to-stratigraphy ratio of the target layer is predicted using the seismic attribute analysis method based on the post-stack seismic volume; the thickness distribution of the source rock in the target layer is characterized based on the residual formation thickness and the formation sand-to-stratigraphy ratio; the calculation formula for calculating the thickness of the source rock in the target layer based on the residual formation thickness and the formation sand-to-stratigraphy ratio is expressed as follows: Source rock thickness = residual formation thickness × (1 – formation sand-to-ground ratio) Source rock distribution steps: The plane distribution of source rocks is coupled with the thickness distribution of source rocks to obtain the spatial distribution of source rocks.

2. The method for quantitatively characterizing the distribution of different types of source rocks in a well-polluted area according to claim 1, wherein: In the step of characterizing the vertical thickness distribution of source rocks, the method for predicting the formation sand-to-ground ratio using the seismic inversion method based on post-stack seismic volumes, acoustic transit time logging data, and density logging data is as follows: Boundary value determination steps: Calculate the wave impedance values ​​of the sandstone and mudstone of the target layer based on the acoustic transit time logging data and density logging data, analyze the wave impedance characteristics of the sandstone and mudstone of the target layer, and determine the wave impedance boundary values ​​of the sandstone and mudstone; Inversion steps: Use seismic inversion software to perform wave impedance inversion on the stacked seismic volume to obtain a wave impedance inversion profile; Judgment steps: The lithology of each sampling point on the wave impedance inversion profile is determined based on the wave impedance limit values ​​of sandstone and mudstone. When the wave impedance value is greater than the wave impedance limit value of sandstone and mudstone, the corresponding stratum is determined to be sandstone; when the wave impedance value is less than the wave impedance limit value of sandstone and mudstone, it is determined to be mudstone; Calculation steps: Within the target layer, for each seismic trace, count the number of sampling points Ns identified as sandstone and the total number of sampling points Nt, and calculate the sand-to-ground ratio of the seismic trace using the following formula; Sand ratio=Ns / Nt Integration step: Integrate the sand-to-ground ratio of each seismic trace with the corresponding position information to obtain the sand-to-ground ratio of the target layer.

3. The method for quantitatively characterizing the distribution of different types of source rocks in a well-polluted area according to claim 1, wherein: In the step of characterizing the vertical thickness distribution of source rocks, the method for predicting the formation sand-to-ground ratio using seismic attribute analysis based on the post-stack seismic volume is as follows: Extraction step: converting the post-stack seismic volume into a seismic attribute volume, extracting the root mean square amplitude seismic attribute from the seismic attribute volume to obtain a seismic root mean square amplitude profile; Steps for determining the root mean square amplitude: according to the distribution range of sedimentary facies, a virtual well is set up, the position corresponding to the virtual well is found on the seismic root mean square amplitude profile, and the root mean square amplitude value at the position is read; Calculation steps: Substitute the read RMS amplitude value into the fitting relationship formula between sand-to-ground ratio and RMS amplitude to obtain the formation sand-to-ground ratio of the target layer.

4. The method for quantitatively characterizing the distribution of different types of source rocks in a well-polluted area according to claim 3, wherein: The fitting relationship formula between sand-to-ground ratio and root mean square amplitude is expressed as: Sand ratio = 0.2002 · Root mean square amplitude – 0.0098.

5. The method for quantitatively characterizing the distribution of different types of source rocks in a well-polluted area according to any one of claims 1 to 4, wherein: In the step of characterizing the vertical thickness distribution of source rocks, the method for obtaining the residual formation thickness based on the post-stack seismic volume is as follows: Identification steps: on the seismic profile, identify the seismic times t1 and t2 corresponding to the top and bottom interfaces of the target layer; Depth calculation steps: Substitute the seismic times t1 and t2 into the actual drilling time-depth conversion relationship to obtain the formation depth corresponding to the top interface of the target layer and the depth corresponding to the bottom interface of the target layer; Residual thickness calculation steps: The residual formation thickness of the target layer is obtained by subtracting the formation depth corresponding to the top interface of the target layer from the depth corresponding to the bottom interface of the target layer.

6. A system for quantitatively characterizing the distribution of different types of source rocks in a region with few wells, for implementing the method for quantitatively characterizing the distribution of different types of source rocks in a region with few wells as claimed in any one of claims 1 to 5, characterized in that: include: Data acquisition module, used to obtain target post-stack seismic volume, sedimentary facies map, acoustic time difference logging data and density logging data; The data processing module intercepts the post-stack seismic volume to obtain a seismic profile, and obtains the seismic reflection characteristics of the source rocks corresponding to different deposits through the seismic profile; The module for depicting the planar distribution of source rocks uses sedimentary facies maps to analyze source rock types, uses seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks, and depicts the planar distribution of different types of source rocks in the target layer based on their development characteristics and sedimentary facies. The hydrocarbon source rock vertical thickness distribution characterization module obtains the residual formation thickness of the target layer based on the post-stack seismic volume, and uses the seismic inversion method to predict the formation sand-to-stratigraphy ratio of the target layer based on the post-stack seismic volume, acoustic time difference logging data, and density logging data, or uses the seismic attribute analysis method based on the post-stack seismic volume to predict the formation sand-to-stratigraphy ratio of the target layer. The hydrocarbon source rock thickness distribution in the target layer is characterized based on the residual formation thickness and the formation sand-to-stratigraphy ratio; The source rock distribution module couples the planar distribution of source rocks with the thickness distribution of source rocks to obtain the spatial distribution of source rocks.

7. The system for quantitatively characterizing the distribution of different types of source rocks in a well-poor area according to claim 6, characterized in that: The source rock plane distribution characterization module includes: Sedimentary facies analysis module, which uses sedimentary facies diagrams to analyze source rock types; Feature prediction module, which uses the seismic reflection characteristics of source rocks to predict the development characteristics of different types of source rocks; The plane distribution characterization module characterizes the plane distribution of different types of source rocks in the target layer according to their development characteristics and sedimentary facies.

8. The system for quantitatively characterizing the distribution of different types of source rocks in a well-poor area according to claim 6, characterized in that: The source rock vertical thickness distribution characterization module includes: The residual stratum thickness calculation module obtains the residual stratum thickness of the target layer based on the post-stack seismic volume. The sand-to-ground ratio prediction module uses the seismic inversion method to predict the formation sand-to-ground ratio of the target layer based on the post-stack seismic volume, acoustic time difference logging data and density logging data, or uses the seismic attribute analysis method to predict the formation sand-to-ground ratio of the target layer based on the post-stack seismic volume. The thickness distribution characterization module characterizes the thickness distribution of source rocks in the target layer based on the residual formation thickness and the formation sand-to-ground ratio.

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