A three-division correction method for time closure difference of 2D seismic data

Abstract

The present invention discloses a method for correcting the time closure error of two-dimensional seismic data using the three-part method, which is carried out in the following order: S1. For each set of survey networks, the two-dimensional data processed with amplitude, frequency, and phase consistency are used to select the layers that exist in the entire study area, are stable, and are continuous, and are picked for layers; S2. The layer files of the set of survey networks are output, and the intersections and the time closure errors of the intersections are calculated based on the layer files; S3. The system error correction amount is calculated; the survey line correction amount is calculated; and the drift correction amount is calculated. The present invention can effectively solve the problems of low efficiency, strong subjective factors, and false structures caused by cumulative errors in the existing technology during closure. The accuracy of the structural map based on this fully meets the industry standard and well reflects the structural appearance and morphology of the target reflection layer. The present invention belongs to the field of seismic data processing technology and can calculate the intersection position, closure error, and closure error correction amount of complex two-dimensional survey networks.

Description

Technical Field

[0001] The invention belongs to the technical field of seismic data processing, in particular to a method for correcting two-dimensional seismic data using a three-division time closure difference method. Background Art

[0002] In recent years, as exploration becomes increasingly complex, the amount of data required for comprehensive interpretation has increased in seismic data interpretation, leading to increasingly complex 2D survey networks. However, due to the limitations of seismic data, the acquisition and processing of large amounts of 2D survey lines often spans a significant period—over 20 years—and involves the simultaneous use of multiple survey networks. This can lead to the following challenges: a. varying acquisition parameters for data from different years; b. different processing software and processes; c. complex subsurface structures; and d. different datums used during processing between survey networks. These issues can lead to time differences between events of the same reflector layer at the intersection of 2D survey lines, known as misclosure. Misclosure is a common and challenging issue in 2D seismic data interpretation, directly impacting the accuracy and even correctness of structural maps.

[0003] Currently, the following methods are used to correct for time misclosure of 2D survey lines: 1. Manual interaction, which relies on interpreters observing intersecting survey lines at intersections and performing corrections line by line and point by point. This method is not only subject to interpreters' subjective judgment, but is also inefficient and prone to cumulative errors, leading to changes in profile morphology. 2. Sorting and grouping 2D survey lines based on factors such as construction time and line angles. This method still calculates the correction between the next group of survey lines and the previous group, closing them line by line, and uses interpolation and other methods to calculate the correction at points without intersections, which still poses the problem of changing the structural morphology of the profile. Furthermore, conventional methods ignore the acquisition of closure differences when calculating misclosure corrections.

[0004] Thomas N. Bishop proposed in 1995 to use an iterative method to calculate the closure correction value. This method is equivalent to the least squares method, as described below.

[0005] Assume there are m survey lines, n intersection points, t k(i) and t l(i) are the horizon times of the kth and lth survey lines at the i-th intersection, respectively. b(i) is defined as the inherent closure error of the profile at the i-th intersection, that is:

[0006] b(i)=t k(i) -t l(i) Formula ①

[0007] Under the least squares constraint, for profile j (j = 1, 2, ..., m), the estimated value of the closure error correction produced by the rth iteration process is Here r = 0, 1, ..., represents the number of iterations. In each iteration, the estimated correction value is corrected by adding the error between the average observed misclosure and the average calculated misclosure of the line. The updated misclosure correction value of profile j obtained in each iteration is the average of the difference between the inherent misclosure of all intersection points of profile j and the updated misclosure of the previous iteration, with appropriate consideration of its sign. So the estimated misclosure correction value for the r+1th iteration is Estimated value of the closure error correction at the rth iteration The following relationship exists:

[0008]

[0009] Where, To count the number of intersection points on the survey line j.

[0010] During the process, the convergence of the method is monitored by the inherent closure error of the profile b(i) and the root mean square error of the closure error corrected by the closure error correction amount generated in the rth iteration process.

[0011]

[0012] The convergence criterion is δ is a very small number (usually taken as 0.00001).

[0013] This method can simply and effectively calculate the closure error correction value, and Bishop et al. have proved that the results obtained by this method are equivalent to the least squares solution.

[0014] Therefore, the problem is simplified to knowing the closed gap matrix B of a certain scale between all intersecting sections = {b1, b2, ..., b i ,...,b n} T , and the serial number of the intersecting section corresponding to the closure error, the correction amount required for each survey line can be easily calculated.

[0015] Introducing the above method into the time closure error of two-dimensional seismic data will solve the above problems existing in the prior art. Summary of the Invention

[0016] The purpose of the present invention is to provide a method for correcting the time closure difference of two-dimensional seismic data by three-division method. By decomposing the time closure difference into three parts, the method can protect the structural morphology of the section to the greatest extent.

[0017] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0018] A method for correcting time closure difference of two-dimensional seismic data by three-division method is carried out in the following steps:

[0019] S1. For each set of survey network, two-dimensional data processed with amplitude, frequency and phase consistency are used to select the layers that exist, are stable and are continuous in the whole study area for layer picking;

[0020] S2. Output the layer file of the survey network, and calculate the intersection points and the time closure difference of the intersection points according to the layer file;

[0021] S3. Calculate the three components of the closure error correction

[0022] First, calculate the first component of the closure error correction, that is, the systematic error correction;

[0023] Then, the second component of the closure error correction, i.e., the survey line correction, is calculated;

[0024] Finally, the third component of the closure error correction is calculated: the drift correction.

[0025] As a limitation: the layer file contains seven columns, namely, survey network number, layer name, survey line name, CMP number, X coordinate, Y coordinate, and layer time;

[0026] In step S2, the intersection and the intersection time closure difference are calculated based on the X, Y coordinates and the layer time of the layer file.

[0027] As a further limitation, the step of calculating the first component of the misclosure correction includes the following process:

[0028] In each measurement network, the average of the closure errors of all the intersection points of the survey lines is taken as the typical closure error value of the measurement network. The closure error correction of the measurement network, i.e., the systematic error correction, is calculated according to the following formula:

[0029]

[0030] As a further limitation, the step of calculating the second component of the misclosure correction comprises the following process:

[0031] The closure error of each intersection point is added to the systematic error correction to obtain a new closure error. The closure error correction of the survey line is calculated according to formula (2), that is, the survey line correction amount.

[0032] As a further limitation, the step of calculating the third component of the misclosure correction includes the following process:

[0033] The closure error of each intersection point is added to the systematic error correction to obtain a new closure error. The inverse of the new closure error is taken and evenly distributed to the intersection points. A cubic polynomial is used to interpolate the values ​​according to the intersection points to obtain the drift correction value of the entire survey line.

[0034] Due to the adoption of the above technical solution, the present invention has achieved the following technical advancements compared with the prior art:

[0035] (1) The present invention can effectively solve the problems of low efficiency, strong subjective factors, and false structures caused by cumulative errors in the existing technology during closure. The accuracy of the structural map based on this fully meets the industry standard and well reflects the structural appearance and morphology of the target reflective layer;

[0036] (2) The present invention calculates the system error correction value, which can be used to correct the time closure error caused by the different acquisition and processing times between measurement networks;

[0037] (3) The present invention calculates the survey line correction value, which can be used to correct the time closure error between survey lines;

[0038] (4) The present invention calculates the drift correction amount, which can be used to correct the closure error remaining after applying the first component and the second component of the correction amount.

[0039] The invention belongs to the technical field of seismic data processing and can calculate the intersection position, closure error and closure error correction amount of a complex two-dimensional survey network. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0041] In the attached figure:

[0042] Figure 1 Schematic diagram of a flow chart of an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of picking layers according to an embodiment of the present invention;

[0044] Figure 3 A two-dimensional measurement network system difference monitoring diagram according to an embodiment of the present invention;

[0045] in, Figure 3 a is the time closure error plane diagram of the original data;

[0046] Figure 3 b is the time closure error histogram of the original data;

[0047] Figure 3 c is the time misclosure plane after applying the first component of the correction;

[0048] Figure 3 d is the histogram of time closure error after applying the first component of the correction;

[0049] Figure 4This is a monitoring diagram before and after the application of the minimum square correction amount of the two-dimensional measurement network according to an embodiment of the present invention;

[0050] in, Figure 4 a is the time misclosure plane after applying the first component of the correction;

[0051] Figure 4 b is the histogram of time closure error after applying the first component of the correction;

[0052] Figure 4 c is the time misclosure plane after applying the first component + second component of the correction;

[0053] Figure 4 d is the histogram of time closure error after applying the first component + second component of the correction;

[0054] Figure 5 : This is a cross-sectional view (arbitrary line) before time closure error correction according to an embodiment of the present invention;

[0055] Figure 6 This is a cross-sectional view after time closure error correction according to an embodiment of the present invention (arbitrary line);

[0056] Figure 7 This is a cross-sectional view (any survey line) before time closure error correction according to an embodiment of the present invention;

[0057] Figure 8 This is a cross-sectional diagram after time closure error correction according to an embodiment of the present invention (any survey line, this method);

[0058] Figure 9 This is the time closure error correction profile (any survey line) obtained by processing the conventional method of the prior art of the present invention. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0060] Example 1: A method for correcting time closure difference of two-dimensional seismic data using the three-division method

[0061] like Figure 1 As shown, this embodiment is carried out in the following steps in sequence:

[0062] A method for correcting time closure difference of two-dimensional seismic data by three-division method is carried out in the following steps:

[0063] S1. Data Preparation

[0064] S11. Perform amplitude, frequency and phase consistency processing on the post-stack seismic profiles of the entire work area;

[0065] S12. For each set of measurement network, the two-dimensional data after amplitude, frequency and phase consistency processing is used to select the layers that exist, are stable and continuous in the whole study area for layer picking, such as Figure 2 , which is a schematic diagram of picking layers in this embodiment;

[0066] S13. Divide all survey lines into several survey networks based on the different years of acquisition and processing in the work area where the survey lines are located. It is considered that the closure errors between the survey networks need to be corrected using the first component of the closure error correction, i.e., the systematic error correction, and output the layer file of the entire work area.

[0067] In this embodiment, the output layer file contains seven columns: survey network number, layer name, survey line name, CMP number, X coordinate, Y coordinate, and layer time;

[0068] S2. Calculate the intersection and intersection time closure error based on the layer file

[0069] S21. Calculate the intersection position of the entire work area according to the layer file and store the corresponding information, including the survey network number, survey line name, CMP number, X coordinate, coordinate, and layer time;

[0070] S22, subtract the horizon time at the intersection of the two survey lines to obtain the closure error of the intersection;

[0071] S3. Calculate the three components of the closure error correction

[0072] S31, calculating the first component of the closure error correction, that is, the systematic error correction;

[0073] S32, calculating the second component of the closure error correction, i.e., the survey line correction;

[0074] S33. Calculate the third component of the closure error correction: that is, the drift correction.

[0075] Specifically, step S31 includes the following process:

[0076] First, within each measurement network, the mean of the closure errors of all the intersection points of the survey lines is taken as the typical closure error value of the measurement network. The closure error correction value of the measurement network, i.e., the systematic error correction value, is calculated according to formula ②.

[0077] make

[0078] This step is used to correct the time closure error caused by different acquisition and processing times between measurement networks. This value is unique to a set of measurement networks.

[0079] When there is a systematic error correction, the time closure error plane distribution map of the work area has a larger range, such as Figure 3As shown in a, at the same time, the histogram has a bimodal or even multimodal distribution feature as shown in Figure 3 As shown in b;

[0080] After applying the system error correction, the time closure error distribution map of the work area is reduced from -150 to 43 to -30 to 43. Figure 3 As shown in c, at the same time, the bimodal feature of the histogram disappears and becomes a single peak as shown in Figure 3 As shown in d.

[0081] Step S32 includes the following process:

[0082] First, add the closure error of each intersection point to the systematic error correction to obtain the new closure error after eliminating the systematic error;

[0083] Then, the closure error correction of the survey line is calculated according to formula ②.

[0084] Calculate the survey line correction value, which is used to correct the time closure error between survey lines. This value is unique for a survey line.

[0085] After applying the line correction, the time closure error distribution range of the work area is as follows: Figure 4 -30~43 shown in b is reduced to Figure 4 d shows -15 to 18, the closing error plane after applying the survey line correction Figure 4 c than before application Figure 4 a Small color difference.

[0086] Step S33 involves time-shifting the original profile based on the correction value at each cmp point, completing the three-part time misclosure correction for the 2D seismic data. Specifically, the misclosure at each intersection is added to the systematic error correction value to obtain a new misclosure value. The inverse of this value is then averaged across the intersection points. Interpolation is then performed using a cubic polynomial based on the intersection locations to obtain the drift correction for the entire survey line.

[0087] Depending on the specific situation, the three components of the time closure correction can be flexibly applied: if complete closure is required at the intersection, the time closure correction to be applied is the sum of the three components; if the profile morphology is strictly required to remain unchanged, the time closure correction to be applied is the sum of the first component and the second component.

[0088] The result after applying the method provided in the embodiment to correct any line is as follows: Figure 6 As shown, Figure 5 Compared with the uncorrected profile shown, the time closure error within the rectangular box has been effectively resolved.

[0089] Select any survey line to compare the method provided by this embodiment with the conventional method of the prior art: the conventional method is corrected as follows: Figure 9 As shown, Figure 7Compared with the uncorrected cross section shown in the figure, a false structure is clearly present in the rectangular frame. After correction using the method provided in this embodiment, the results are as follows: Figure 8 As shown, it can be seen that the cross-sectional morphology has hardly changed.

[0090] In summary, the method provided in this embodiment has a protective effect on the cross-sectional morphology.

Claims

1. A method for correcting time closure difference of two-dimensional seismic data by three-division method, characterized in that Follow these steps in order: S1. For each set of survey network, two-dimensional data processed with amplitude, frequency and phase consistency are used to select the layers that exist, are stable and are continuous in the whole study area for layer picking; S2. Output the layer file of the survey network, and calculate the intersection points and the time closure difference of the intersection points according to the layer file; S3. Calculate the three components of the closure error correction First, calculate the first component of the closure error correction, that is, the systematic error correction; Then, the second component of the closure error correction, i.e., the survey line correction, is calculated; Finally, calculate the third component of the closure error correction: the drift correction; The steps for calculating the first component of the misclosure correction include the following: In each measurement network, the average of the closure errors of all the intersection points of the survey lines is taken as the typical closure error value of the measurement network. The closure error correction of the measurement network, i.e., the systematic error correction, is calculated according to the following formula: The steps for calculating the second component of the misclosure correction include the following: Add the closure error of each intersection point to the systematic error correction to obtain the new closure error. Calculate the closure error correction of the survey line according to formula ②, i.e., the survey line correction amount. The steps for calculating the third component of the misclosure correction include the following: The closure error of each intersection point is added to the systematic error correction to obtain a new closure error. The inverse of the new closure error is taken and evenly distributed to the intersection points. A cubic polynomial is used to interpolate the values ​​according to the intersection points to obtain the drift correction value of the entire survey line.

2. The method for correcting time closure difference of two-dimensional seismic data using the three-division method according to claim 1, characterized in that: The layer file contains seven columns, namely, survey network number, layer name, survey line name, CMP number, X coordinate, Y coordinate, and layer time; In step S2, the intersection and the intersection time closure difference are calculated based on the X, Y coordinates and the layer time of the layer file.

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