A sand body characterization method based on seismic sedimentology analysis

Abstract

The present invention belongs to the field of oil and gas exploration technology, and is a technology that uses geological seismic combined with analysis methods to finely characterize the spatial distribution characteristics of sand bodies. First, based on the well logging and three-dimensional seismic data of the study area, combined with the interpretation of the well logging sedimentary phase, the sedimentary characteristics of the sand bodies in the study area are clarified, and the seismic response mode corresponding to the sand bodies is established through the seismic forward simulation method. Finally, the distribution of sand bodies in the work area is finely characterized by using multi-attribute optimization and fusion technology. This method mainly includes: clarifying the combination types and seismic reflection patterns of different types of sand bodies based on well logging and seismic data; further determining the seismic response characteristics of different sand body superposition styles through forward simulation technology; optimizing attributes and performing multi-attribute fusion through the correlation between sand-to-ground ratio and seismic attributes, improving the correlation between seismic attributes and sand-to-ground ratio, and then improving the accuracy of sand body characterization. The results obtained can provide technical support for subsequent sedimentary phase analysis, sweet spot prediction and drilling deployment.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and in particular to a method for sand body characterization by utilizing sedimentary geological information constraints and by optimizing and fusing seismic attributes. Background Art

[0002] The Sulige gas field in the Ordos Basin is an important super-large natural gas field. A block in the middle of the Sulige gas field is an important gas-producing block with huge exploration potential. The main gas-producing layers of the block, the Box 8 and the Mountain 1, have large sand body thickness and thin reservoirs. The sand body has strong vertical and horizontal heterogeneity, the distribution law of favorable sand body reservoirs is unclear, the reservoirs are relatively thin, the direct geological prediction is difficult, and the seismic data identification also has the problems of uncertainty and limited accuracy. It is necessary to carry out the main controlling factor analysis and quantitative characterization under the comprehensive constraints of effective sand body geology and geophysics. Due to the complex and diverse types of sand body combinations and strong multi-solution, unclear understanding of spatial distribution will lead to difficulties in geological selection in well site deployment. Therefore, it is urgent to propose a method based on geological and seismic combination to finely characterize the spatial distribution characteristics of effective sand bodies, clarify the types of different types of sand body combinations, genetic mechanisms and seismic reflection patterns, provide technical support for the vertical and horizontal combination types, differences and temporal and spatial distribution laws of sand bodies under the constraints of sedimentary microfacies, and predict high-quality phase belts, and guide the prediction of dense sand body sweet spots to achieve continuous and stable production in the block. Summary of the invention

[0003] The purpose of the present invention is to provide a sand body characterization method based on seismic sedimentology analysis. According to the well logging and three-dimensional seismic data of the study area, combined with the well logging sedimentary phase interpretation, the sedimentary characteristics of the sand body in the study area are clarified and the seismic response mode corresponding to the sand body is established through the seismic forward simulation method. Finally, the correlation analysis between the sand-to-ground ratio and the attribute is used to perform multi-attribute optimization and fusion to finely characterize the sand body distribution in the work area. The method of the present invention includes the following main steps:

[0004] (1) Analyze and process all well logging data in the study area, select wells with complete data for well-seismic calibration, clarify the seismic reflection characteristics of the layers through layer tracking, and establish an isochronous stratigraphic framework;

[0005] (2) Analyze the sedimentary facies of the connected wells based on the stratigraphic grid lines, clarify the sand body combination type, and match the seismic response characteristics corresponding to different sand body combination styles on the seismic profile in combination with the well-seismic calibration results:

[0006] Seis=Ana(Mode)

[0007] In the formula, Mode represents the type of different sand body combination styles, Ana(·) represents the analysis of the seismic response characteristics of different similar sand body combination styles, and Seis represents the corresponding seismic response characteristics established;

[0008] (3) On the basis of the established sand body combination style types, establish sand body geological models of different combination types and perform forward simulation, analyze the seismic reflection characteristics of different sand body combination styles, and verify whether the seismic response characteristics of different sand body combination types summarized in step (2) are reasonable through the forward modeling results;

[0009] (4) Based on the reasonable seismic reflection characteristics verified in step (3), the main characteristics of the sand body such as amplitude, frequency, phase, etc. are clarified;

[0010] (5) The ratio of the sand body thickness to the formation thickness of each well, i.e., the sand-to-formation ratio, is calculated by using the formation thickness and sand body thickness of multiple wells in the target layer segment. Multiple seismic attributes of the target layer segment are extracted in a targeted manner according to the analysis results in step (4), and the cross analysis is performed with the sand-to-formation ratio at the well point to calculate the correlation coefficient, and select the seismic attributes with higher correlation:

[0011] A opt =cross[(A1,…,A n ), R]

[0012] In the formula, A represents the seismic attribute, n represents the number of selected attributes, R represents the sand-to-ground ratio at the well point, cross(·) represents the intersection analysis of multiple seismic attributes and the sand-to-ground ratio at the well point, and A opt Indicates the preferred attribute;

[0013] (6) Based on the result of attribute optimization in step (5), the correlation between multiple seismic attributes is calculated, and attributes with poor correlation are selected for data fusion. The correlation with the sand-to-ground ratio at the well point is improved by the calculated fused attributes, wherein the attribute fusion is calculated by the following formula:

[0014]

[0015] In the formula, A i represents the i-th selected seismic attribute, N is the total number of selected seismic attributes, max(·) represents the maximum value, ∑[·] represents the summation operation, A fusion Indicates the final fused attributes;

[0016] (7) The fused seismic attributes obtained in step (6) are used to finely characterize the shape of the river channel sand body.

[0017] Repeat the above steps (1) to (7) until the data interpretation of all target layers in the entire work area is processed, and the characterization results of the sand bodies in all target layers in the entire work area can be obtained. This result has important indicative significance for subsequent sedimentary facies interpretation and sweet spot prediction.

[0018] The present invention is a sand body characterization method based on seismic sedimentology analysis, which has the following advantages:

[0019] (1) Combined with logging data analysis, by establishing geological models of different sand body combination types for seismic forward modeling, the seismic reflection characteristics of various sand body combination types can be clarified and verified, which can provide support for the subsequent optimization of seismic attributes and improve the accuracy of attribute analysis.

[0020] (2) Based on the seismic phase and combined with the sand-to-ground ratio of the sedimentary seismic concept as a constraint, a bridge between seismic sedimentation was established. The results of sand body characterization obtained by optimizing properties through the analysis of seismic sedimentology are more in line with geological laws.

[0021] (3) The integration of multiple seismic attributes can effectively improve the correlation between seismic attributes and sand-to-ground ratio, which in turn helps predict the planar distribution of sand bodies and make the characterization results more accurate. The analysis of multiple seismic attributes eliminates the problem of multiple solutions of a single seismic attribute and can accurately characterize the distribution characteristics of sand bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the technical roadmap of the method of the present invention.

[0023] Figure 2 This is a well-connected seismic-sedimentary facies cross-section diagram of the work area in the embodiment of the present invention, wherein: Figure 2 a is the well logging interpretation diagram of the river channel sand body in the working area of ​​the embodiment, Figure 2 b is the seismic interpretation map of the river channel sand body in the example work area.

[0024] Figure 3 This is a forward simulation analysis of different sand body combination types in the working area of ​​the embodiment of the present invention, wherein: Figure 3 a is the geological model diagram of different types of sand body combinations. Figure 3 b is the corresponding forward modeling result.

[0025] Figure 4 It is a box 8 of the working area of ​​the embodiment of the present invention. 3-4 Results of correlation analysis between layer sand-to-ground ratio and seismic attributes.

[0026] Figure 5 It is a box 8 of the working area of ​​the embodiment of the present invention. 3-4 The results of seismic attributes of the selected layers and their correlation with each other.

[0027] Figure 6 It is a box 8 of the working area of ​​the embodiment of the present invention. 3-4 The final selected seismic attributes and fusion result map of the layer segment and the correlation map of each attribute and the sand-to-ground ratio of the layer segment, where: Figure 6 a is the maximum absolute amplitude and its difference with box 83-4 Correlation diagram of layer sand-to-soil ratio, Figure 6 b is the maximum amplitude and its difference with box 8 3-4 Correlation diagram of layer sand-to-soil ratio, Figure 6 c is the average absolute amplitude and its difference with box 8 3-4 Correlation diagram of layer sand-to-soil ratio, Figure 6 d is the attribute after the fusion of the three and its relationship with box 8 3-4 Correlation diagram of sand-to-sand ratio of each layer.

[0028] Figure 7 It is a box 8 of the working area of ​​the embodiment of the present invention. 3-4 The result of plane characterization of sand bodies using fused seismic attributes. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is as follows:

[0030] (1) Analyze and process all well logging data in the study area, select wells with complete data for well-seismic calibration, clarify the seismic reflection characteristics of the layers through layer tracking, and establish an isochronous stratigraphic framework;

[0031] (2) Based on the stratigraphic grid analysis of the well-connected sedimentary facies, four types of sand body combinations were identified (isolated, lateral, vertical, and composite). The seismic response characteristics corresponding to different sand body combination styles were matched on the seismic profile in combination with the well-seismic calibration results.

[0032] (3) Based on the established sand body combination style types, four sand body geological models of different combination types are established and forward simulation is performed to analyze the seismic reflection characteristics of different sand body combination styles. The forward modeling results are used to verify whether the seismic response characteristics of different sand body combination types summarized in step (2) are reasonable;

[0033] (4) Based on the reasonable seismic reflection characteristics verified in step (3), the main characteristics of the sand body such as amplitude, frequency, phase, etc. are clarified;

[0034] (5) calculating the ratio of the sand body thickness to the formation thickness of each well, i.e., the sand-to-formation ratio, based on the formation thickness and sand body thickness of multiple wells in the target layer segment, and extracting multiple seismic attributes of the target layer segment in a targeted manner according to the analysis results in step (4), performing intersection analysis with the sand-to-formation ratio at the well point, calculating the correlation coefficient, and selecting the seismic attributes with higher correlation;

[0035] (6) Based on the result of attribute optimization in step (5), the cross-correlation between multiple seismic attributes is calculated, and attributes with poor correlation are selected for data fusion, so as to improve the correlation with the sand-to-ground ratio at the well point through the calculated fused attributes;

[0036] (7) The fused seismic attributes obtained in step (6) are used to finely characterize the shape of the river channel sand body.

[0037] Repeat the above steps (1) to (7) until the data interpretation of all target layers in the entire work area is processed, and the characterization results of the sand bodies in all target layers in the entire work area can be obtained. This result has important indicative significance for subsequent sedimentary facies interpretation and sweet spot prediction.

[0038] In order to more clearly express the technical advantages of the present invention, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings.

[0039] Figure 1 This is the technical roadmap of the present invention, which shows a method for depicting the plane distribution of sand bodies using the technology of the present invention. The plane distribution characteristics of sand bodies can be accurately depicted through this technical route.

[0040] Figure 2 This is a well-connected seismic-sedimentary facies cross-section diagram of the work area in the embodiment of the present invention. Figure 2 a is the well logging interpretation diagram of the river channel sand body in the working area of ​​the embodiment, Figure 2 b is the seismic interpretation map of the river channel sand body in the working area of ​​the embodiment. It can be seen from the seismic profile that: Box 8 1-2 The seismic response characteristics of the meandering river are continuous reflection of medium-weak amplitude wave crests, 3-4 The seismic response characteristics of the meandering river in Section 1 are intermittent reflections with medium-weak amplitude peaks, and the seismic response characteristics of the meandering river in Section 2 are continuous reflections with medium-strong amplitude troughs; Box 8 1-2 The seismic response characteristics of the braided river section are relatively continuous reflection of medium-weak amplitude trough, box 8 3-4 The seismic response characteristics of the braided river in the first section are discontinuous reflection with medium-weak amplitude troughs, and the seismic response characteristics of the braided river in the mountain 1 section are continuous reflection with medium-strong amplitude peaks.

[0041] Figure 3 This is a forward simulation diagram of the sand body configuration in the working area of ​​the embodiment of the present invention. There are 4 types of sand body combinations in the forward model, namely isolated, lateral combination, vertical combination and composite. From the forward modeling results, it can be seen that: there are differences in the seismic reflection characteristics of the isolated sand bodies in Shan 1 and Box 8 sections, mainly due to the difference in the sandstone and mudstone they contain; the seismic reflection characteristics of the lateral combination sand bodies in Shan 1 and Box 8 sections are basically the same, both of which are mainly manifested as trough seismic reflection; the seismic reflection characteristics of the vertical combination sand bodies in Shan 1 and Box 8 sections are basically the same, both of which are mainly manifested as trough seismic reflection; the composite sand body is mainly developed in Box 8 section, and the seismic reflection characteristics are mainly manifested as weak amplitude trough intermittent reflection.

[0042] Figure 4 Box 8 of the working area of ​​the embodiment of the present invention 3-4The results of the correlation analysis between the layer sand-to-ground ratio and seismic attributes. The correlation coefficients of the seven selected seismic attributes are all greater than 0.48, including root mean square amplitude, average reflection intensity, maximum amplitude, maximum absolute amplitude, average absolute amplitude, variance, and average peak amplitude.

[0043] Figure 5 Box 8 of the working area of ​​the embodiment of the present invention 3-4 The seismic attributes of the selected layers and their correlation results. The correlation between the average absolute amplitude, the maximum absolute amplitude and the maximum amplitude is poor, and they are used as the basic attributes for fusion.

[0044] Figure 6 Box 8 of the working area of ​​the embodiment of the present invention 3-4 The final selected seismic attributes of the layer segment and the fusion result map as well as the correlation map between each attribute and the sand-to-ground ratio of the layer segment. The maximum absolute amplitude, maximum amplitude and average absolute amplitude are selected as the basic attributes of fusion. Figure 6 a is the maximum absolute amplitude and its correlation with the sand-to-ground ratio, Figure 6 b is the maximum amplitude and its correlation with the sand-to-ground ratio, Figure 6 c is the average absolute amplitude and its correlation with the sand-to-ground ratio, Figure 6 d is the fused attribute and its correlation with the sand-to-land ratio, given by Figure 6 d It can be seen that the obtained fusion attribute is the same as box 8 3-4 After the sand-to-formation ratios at the well points of the intervals converged, the correlation improved significantly, with the correlation coefficient reaching 0.775.

[0045] Figure 7 Box 8 of the working area of ​​the embodiment of the present invention 3-4 The result of plane characterization of sand bodies using fused seismic attributes.

[0046] The above embodiments are only used to illustrate the present invention, wherein the various implementation steps of the method can be changed, and any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A sand body characterization method based on seismic sedimentology analysis, characterized in that Use the following specific steps: ⑴ Analyze and process all logging data in the study area, select wells with complete data for well-seismic calibration, clarify the seismic reflection characteristics of the layers through layer tracking, and establish an isochronous stratigraphic framework; (2) Analyze the sedimentary facies of the connected wells according to the stratigraphic grid line, clarify the sand body combination type, and match the seismic response characteristics corresponding to different sand body combination styles on the seismic section in combination with the well-seismic calibration results: Seis= Ana (Mode) In the formula, Mode represents the type of different sand body combination styles, It indicates the analysis of the seismic response characteristics of different similar sand body combination styles. Seis indicates the corresponding seismic response characteristics established. ⑶ On the basis of the established sand body combination style types, establish sand body geological models of different combination types and conduct forward simulation, analyze the seismic reflection characteristics of different sand body combination styles, and verify whether the seismic response characteristics of different sand body combination types summarized in step ⑵ are reasonable through the forward modeling results; (4) Based on the reasonable seismic reflection characteristics verified in step (3), clarify the main characteristics of the amplitude, frequency and phase factors of the sand body; (5) Calculate the ratio of the sand body thickness to the formation thickness of each well, i.e., the sand-to-formation ratio, through the formation thickness and sand body thickness of multiple wells in the target layer segment. According to the analysis results in step (4), extract multiple seismic attributes of the target layer segment, conduct intersection analysis with the sand-to-formation ratio at the well point, calculate the correlation coefficient, and select the seismic attributes with higher correlation: A opt = cross[(A1,…,A n ),R] In the formula, A represents the seismic attribute, n represents the number of selected attributes, R represents the sand-to-ground ratio at the well point, Represents the intersection analysis of multiple seismic attributes and the sand-to-ground ratio at the well point, A opt Indicates the selected attribute; (6) Based on the attribute selection results in step (5), the cross-correlation between multiple seismic attributes is calculated, and attributes with poor correlation are selected for data fusion. The calculated fusion attributes are used to improve the correlation with the sand-to-ground ratio at the well point. The attribute fusion is calculated by the following formula: ； In the formula, A i represents the i-th seismic attribute selected, N is the total number of seismic attributes selected, It means to find the maximum value. represents the sum operation, A fusion Indicates the final fused attributes; ⑺ Use the fused seismic attributes obtained in step ⑹ to finely characterize the shape of the river channel sand body; Repeat the above steps (1) to (7) until the data interpretation of all target layers in the entire work area is processed, and the characterization results of the sand bodies in all target layers in the entire work area can be obtained.

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