A method for quickly determining seismic horizon by using depth domain migration velocity

Abstract

This invention discloses a method for rapidly determining seismic horizons using depth-domain migration velocity. This method analyzes the structural characteristics of depth-domain seismic migration velocities to quickly extract macroscopic seismic horizon information, providing reliable seismic horizon baseline data for structurally complex areas, significantly improving the efficiency of horizon identification and greatly reducing the workload of interpreters. The method is characterized by its adaptive updating capability in the horizon picking process, enabling rapid and stable extraction of macroscopic seismic horizon information for the work area, accurately reflecting the depth variation trend of subsurface structures, and ensuring the lateral continuity of seismic horizons.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas seismic exploration, specifically relating to a method for rapidly determining seismic horizons using depth domain migration velocity. Background Technology

[0002] Seismic horizon interpretation, a crucial component and fundamental step in seismic interpretation, aims to identify and trace stratigraphic interfaces for interpreting stratigraphic structure and properties, as well as constructing subsurface three-dimensional geological models. This process typically requires interpreters to manually extract specific seismic reflection phase axes from seismic data to trace key stratigraphic information and generate continuous horizon data—a labor-intensive and demanding undertaking. In tectonically complex areas, such as those with faults, folds, and salt domes, the interpretation difficulty increases, requiring interpreters to possess specialized geological knowledge and extensive practical experience to identify and differentiate complex seismic responses. This makes horizon tracing results highly susceptible to subjective human factors, thus affecting the accuracy and reliability of subsequent reservoir interpretation.

[0003] Oil and gas seismic exploration and development place increasingly higher demands on the accuracy and efficiency of seismic stratigraphic interpretation. Rapidly obtaining macroscopic seismic stratigraphic data of the work area is crucial for accurately reflecting the spatial distribution and contact relationships of subsurface structures and strata. This is essential for the subsequent description and precise characterization of stratigraphic and structural features at different scales (especially microscales), and forms the foundation for reliable fine-grained description and development of oil and gas reservoirs. Therefore, this invention aims to rapidly and effectively extract macroscopic seismic stratigraphic information of the work area while preserving the accuracy of the subsurface structural framework, thereby significantly improving the efficiency of subsequent fine-grained stratigraphic interpretation. Summary of the Invention

[0004] This invention proposes a method for rapidly determining seismic horizons using depth-domain migration velocity. This method utilizes tectonic feature information from depth-domain migration velocity data to quickly extract macroscopic seismic horizon information, providing reliable seismic horizon baseline data for tectonically complex areas, significantly improving the efficiency of horizon identification, and greatly reducing the workload of interpreters. The method of this invention includes the following main steps:

[0005] (1) After preprocessing the initial depth domain offset velocity data, the processed three-dimensional depth domain offset velocity data V is obtained. p (i,j,k), where i represents the depth index value, j represents the xline index value, and k represents the inline index value. Its depth range is H=[H(1),…,H(N)], and N is the number of depth sampling points;

[0006] (2) Estimated depth value of the target layer and estimated speed Set depth position weight w h and layer velocity weight wV , so that the sum of the two is 1;

[0007] (3) The processed three-dimensional depth domain offset velocity data V p Extract the maximum value V(m,j,k) and the depth position h(m,j,k) corresponding to the maximum value for each pass (i,j,k), where m represents the index value of the maximum value obtained for each pass;

[0008] (4) Based on the results of the previous step, the layer depth h1(j,k) of the j-th xline and the k-th inline is calculated using the following formula:

[0009]

[0010] (5) For the layer depth h1(j,k), the following steps are used for iteration:

[0011] ① Update depth position weight w h and layer velocity weight w V ;

[0012] ② For the layer depth h1(j,k) from the previous step, remove discontinuities, outliers, and jump points from the data, and mark their depth positions as 0 to obtain the effective layer depth h1′, and calculate the average layer velocity at the effective depth position.

[0013] ③ For the j-th xline and k-th inline with a depth position of 0, the depth of the adjacent traces is obtained by using a forward backtracking method, resulting in the initial depth h0(j,k), as shown in the following formula:

[0014]

[0015] Where m1 and m2 are the forward backtracking distances of xline and inline, respectively;

[0016] ④ Based on the results of the previous step, use the depth domain offset velocity V p The layer depth data h2(j,k) of the j-th xline and the k-th inline is calculated using the following formula:

[0017]

[0018] ⑤ Repeat steps ① to ④ until the extracted layer depth data meets the requirements;

[0019] (6) Perform two-dimensional smoothing on the layer depth data h2(j,k) to obtain the final seismic layer data h(j,k). Attached Figure Description

[0020] Figure 1This embodiment of the invention describes the process of picking seismic horizons using depth-domain migrated seismic data. The XLine trace numbers for this work area range from 1 to 391, totaling 391, while the InLine trace numbers range from 1 to 661, totaling 661. Figure 1 (a) is a top view of the seismic horizon picked in the first iteration. Figure 1 (b) is a top view of the seismic horizon picked in the second iteration. Figure 1 (c) is a top view of the seismic horizon picked in the third iteration. Figure 1 (d) is a top view of the final seismic horizon after smoothing. Figure 1 The vertical axis of (a)-(d) represents the InLine track number, and the horizontal axis represents the XLine track number. Figure 1 (a)-(d) The colors in the color charts indicate the depth of the selected layer. They share a single color scale, which ranges from 3.5km to 5.5km, and the unit is kilometers.

[0021] Figure 2 This describes the process of picking seismic horizons using depth domain migration velocity in the 461st InLine profile of this invention. The XLine trace numbers in this work area range from 1 to 391, totaling 391, with a depth range of 0 km to 6 km, a depth sampling interval of 5 m, and 1201 sampling points. Figure 2 (a) is a cross-sectional view of the seismic horizon picked in the first iteration. Figure 2 (b) is a cross-sectional view of the seismic horizon picked in the second iteration. Figure 2 (c) is a cross-sectional view of the seismic horizon picked in the third iteration. Figure 2 (d) is a cross-sectional view of the smoothed seismic horizon. Figure 2 The vertical axis of (a)-(d) represents the depth, ranging from 0km to 6km, with units of kilometers, and the horizontal axis represents the XLine track number. Figure 2 The black lines in (a)-(d) represent the corresponding extracted layers. Figure 2 The colors in (a)-(d) represent the offset velocity of the 461st InLine profile. They share a single color scale, ranging from 2.5 km / s to 4.0 km / s, in kilometers per second.

[0022] Figure 3This is a display image of the seismic horizons picked up from depth-domain migration seismic data for the 461st InLine profile in this embodiment of the invention. The XLine trace numbers for this work area range from 1 to 391, totaling 391, with a displayed depth range of 3.8 km to 5.6 km, a depth sampling interval of 5 m, and 361 sampling points. The colored background represents the depth-domain migration depth, with a velocity range of 2.5 km / s to 4.0 km / s (in kilometers per second). The seismic records in this profile are overlaid on the migration velocity map using a black waveform variable area display method, and the white curve in the image represents the smoothed final seismic horizons. Detailed Implementation

[0023] Figure 1-3 The present invention demonstrates a method for constructing seismic horizons, and its specific implementation includes the following steps:

[0024] (1) Preprocessing the depth domain offset velocity data to remove outliers, resulting in the processed 3D depth domain offset velocity data V. p (i,j,k), where i represents the depth index value, with a total of 1021 sampling points, j represents the xline index value, with a total of 391 xline sampling points, and k represents the inline index value, with a total of 661 inline sampling points. Its depth range is H=[H(1),…,H(N)], and N is the number of depth sampling points, which is 1021.

[0025] (2) Estimated depth value of the target layer and estimated speed Set depth position weight w h and layer velocity weight w V The sum of the two is 1;

[0026] (3) Extract the maximum value V(m,j,k) and the corresponding depth position h(m,j,k) of the three-dimensional depth domain migration velocity for each pass, where m represents the index value of the maximum value obtained for each pass. The method is as follows:

[0027] ① For the depth domain offset velocity of the j-th xline and the k-th inline, calculate its differential data ΔV. p (i,j,k), the formula is as follows:

[0028] ΔV p (i,j,k)=V p (i+1,j,k)-V p (i,j,k),

[0029] ② For the velocity difference data ΔV of the j-th xline and the k-th inline, p(i,j,k), for each sampling point i from 1 to N-1, filter out those that satisfy ΔV p (i,j,k)<0 and ΔV p The sampling point index value i is the point where (i+1,j,k)>0;

[0030] ③ Check the sampling point i from the previous step to determine if V is satisfied. p (i-1,j,k)<V p (i,j,k)<V p If (i+1,j,k) is a given value, then calculate the depth and velocity values ​​of its sampling point, using the following formula:

[0031]

[0032] (4) Calculate the layer depth h1(j,k) of the j-th xline and the k-th inline based on the results of the previous step, using the following formula.

[0033]

[0034] (5) Based on the initial layer depth h1(j,k) obtained in the previous step, the following steps are used for iteration:

[0035] ① Update depth position weight w h and layer velocity weight w V ;

[0036] ② Preprocess the stratigraphic depth result h1(j,k) from the previous step, removing obvious discontinuities, outliers, and jump points. Mark the depth of the removed locations as 0 to obtain the effective stratigraphic depth h1′(j,k), and calculate the average stratigraphic velocity at the effective depth location.

[0037] ③ When the layer depth of the j-th xline and the k-th inline is 0, the layer depth of the adjacent trace is obtained by backtracking forward, and the initial depth h0(j,k) is obtained, as shown in the following formula:

[0038]

[0039] Where m1 and m2 are the distances back along the xline and inline directions, respectively;

[0040] ④ Based on the results of the previous step, the layer depth h2(j,k) of the j-th xline and the k-th inline is calculated using the depth domain migration velocity Vp, as shown in the following formula:

[0041]

[0042] ⑤ Repeat steps ① to ④ until the extracted layer data meets the requirements;

[0043] (6) Perform two-dimensional smoothing on the layer data h2(j,k) obtained in the previous step to obtain the final seismic layer data h(j,k).

[0044] Figure 1 This embodiment of the invention describes the process of picking seismic horizons using depth-domain migration seismic data. First, maxima are identified in the depth-domain migration velocity data for regions near specific depth locations, thereby obtaining... Figure 1 (a) shows the preliminary results of seismic horizon picking. Based on this, by excluding... Figure 1 (a) identified significant discontinuities, outliers, and jump points. A forward-looking approach was used, replacing the depth of the removed points with the depth of neighboring layers to ensure layer continuity in the XLine and InLine directions. Using predefined depth and layer velocity weights, the new layer positions were optimized, resulting in… Figure 1 (b) Seismic horizon picking optimization results. The method of this invention progressively increases the depth location weight during the iteration process to enhance the continuity of seismic horizons in the XLine and InLine directions, ultimately achieving a result comparable to... Figure 1 (a) and Figure 1 (b) More stable seismic horizon results, such as Figure 1 As shown in (c), after three iterations and using a two-dimensional smoothing technique, the final result is... Figure 1 (d) Seismic horizon.

[0045] Figure 2 This demonstrates the process of seismic horizon picking on the 461st InLine depth domain migration velocity profile in this embodiment of the invention. Figure 2 In (a), the black lines represent the seismic horizons picked up in the first iteration. In the initial iteration phase, because the initial depth was set to a fixed value and the horizon velocity weight was high, horizon jumps occurred in areas with significant tectonic changes. In the second iteration, these anomalous horizons were removed during the preprocessing of the initial depth. The depth of adjacent horizons was used as the location depth for excluding anomalous horizons, thus initiating a new round of iterations and generating... Figure 2 (b) shows a more reasonable seismic horizon. After three iterations, Figure 2 (c) shows that the stratigraphic level gradually stabilizes, meeting the requirements for interpretation. Finally, the iteratively obtained stratigraphic results were smoothed to ensure continuity in the XLine and InLine directions, resulting in... Figure 2 (d) Seismic horizon.

[0046] Figure 3This figure illustrates the smoothed seismic horizon on the 461st InLine seismic data profile in this embodiment of the invention. The white curve in the figure represents the smoothed seismic horizon, and its trend is consistent with the seismic reflection phase axis of the seismic profile, accurately depicting the changing trend of the subsurface structure. This seismic horizon line can serve as a reference horizon for interpretation, laying the foundation for subsequent fine seismic interpretation. Furthermore, as can be seen from the figure, the method of this invention only requires three iterations to obtain high-quality horizon information, fully demonstrating the effectiveness and reliability of the method.

[0047] The advantages of the method of the present invention are: (1) Based on the structural features in the depth domain migration velocity, the macroscopic seismic horizon information of the work area can be extracted quickly, which can accurately reflect the depth change trend of the underground structure; (2) The method fully considers the positional change of the seismic horizon in depth, ensures the continuity in the XLine and InLine directions, and realizes the adaptive update of the seismic horizon picking process by applying different weight coefficients; (3) In practical applications, the present invention shows high efficiency and extremely high stability.

[0048] The above embodiments are only used to illustrate the present invention. The implementation steps of the method can be varied. Any equivalent transformations and improvements made on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for rapidly determining seismic horizons using depth-domain migration velocity, comprising the following main steps: (1) After preprocessing the initial depth domain offset velocity data, the processed three-dimensional depth domain offset velocity data V is obtained. p (i,j,k), where i represents the depth index value, j represents the xline index value, and k represents the inline index value. Its depth range is H=[H(1),…,H(N)], and N is the number of depth sampling points; (2) Estimated depth value of the target layer and estimated speed Set depth position weight w h and layer velocity weight w V , so that the sum of the two is 1; (3) The processed three-dimensional depth domain offset velocity data V p Extract the maximum value V(m,j,k) and the depth position h(m,j,k) corresponding to the maximum value for each pass (i,j,k), where m represents the index value of the maximum value obtained for each pass; (4) Based on the results of the previous step, the layer depth h1(j,k) of the j-th xline and the k-th inline is calculated using the following formula: (5) For the layer depth h1(j,k), the following steps are used for iteration: ① Update depth position weight w h and layer velocity weight w V ; ② For the layer depth h1(j,k) from the previous step, remove discontinuities, outliers, and jump points from the data, and mark their depth positions as 0 to obtain the effective layer depth h1′, and calculate the average layer velocity at the effective depth position. ③ For the j-th xline and k-th inline with a depth position of 0, the depth of the adjacent traces is obtained by using a forward backtracking method, resulting in the initial depth h0(j,k), as shown in the following formula: in, m1 and m2 are the forward backtracking distances of xline and inline, respectively; ④ Based on the results of the previous step, use the depth domain offset velocity V p The layer depth data h2(j,k) of the j-th xline and the k-th inline is calculated using the following formula: ⑤ Repeat steps ① to ④ until the extracted layer depth data meets the requirements; (6) Perform two-dimensional smoothing on the layer depth data h2(j,k) to obtain the final seismic layer data h(j,k).

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