Offshore time-lapse seismic basic data shot point repeatability evaluation method

Abstract

The invention relates to an offshore time-lapse seismic basic data shot point repeatability evaluation method, which comprises the following steps of: determining the direction of a shot line, scanning the position of the shot line, and forming a pre-drawn shot line cluster; determining the direction of a tie line, and scanning the position of the tie line; on the basis of the pre-drawn shot line cluster, the pre-drawn shot line closest to the actual shot line is found; on the basis of the tie line position and the pre-drawn shot line cluster, determining pre-drawn grid intersection points; according to the actual shot line acquisition direction, determining the shot point position of the pre-drawn shot line; calculating a position error between the shot point of the previously drawn shot line closest to the actual shot line and the shot point of the corresponding actual shot line, and drawing a map; the repeatability of actual shot lines and shot points is evaluated, and the smaller the error is, the better the repeatability is.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas exploration technology, in particular to a method for evaluating the repeatability of shot points of marine time-lapse seismic basic data. BACKGROUND

[0002] Time-lapse seismic uses the difference between the two seismic data collected before and after the oilfield development to reveal the reservoir property changes and predict the distribution of remaining oil. Time-lapse seismic requires that the two seismic data collected and processed should have good repeatability. After matching processing, the difference between the two data of non-target layers is generally close to zero, and the difference is mainly concentrated in the oil-producing layer. Therefore, analyzing the position error of shot points and receiving points during data collection is of great significance to understanding the repeatability of data.

[0003] In the past, except for OBC / OBN and other seabed collection methods, the position disturbance of shot points in marine towed cable seismic collection has rarely been considered. This is mainly because the position disturbance of shot points (usually a few meters to tens of meters) can be ignored compared with the position drift of receiving points at a far offset distance of hundreds of meters or even thousands of meters caused by the towed cable feather. However, with the continuous development of time-lapse seismic processing technology and collection technology, marine towed cable time-lapse seismic collection has made great progress. Currently, time-lapse seismic monitoring data collection usually selects the same collection direction and time window as the basic data collection to ensure that the two collections produce approximately the same feather; and increases data redundancy during monitoring data collection to improve the success probability of matching the two collections. These measures significantly reduce the position error of receiving points (sometimes even lower than the position error of shot points). At this time, it is necessary to study the position disturbance of shot points in towed cable collection.

[0004] For example, as shown in Figure 1 , due to the influence of ocean currents and sea waves, the marine three-dimensional towed cable seismic collection shot lines in the South China Sea area along the south-north direction do not exhibit the expected parallel straight lines in the vertical direction (the scale of the contact line direction is intentionally enlarged, the aspect ratio is 1:2), but exhibit irregular curves with a certain distance. Obviously, the position of the shot points of the collected data has a large error compared with the regularly arranged pre-collection drawing positions.

[0005] Therefore, the position error of the shot points of the collected data is usually calculated by comparing the actual collected data with the pre-collection drawing in the prior art. However, after the seismic data collection is completed, the pre-collection drawing data is generally not saved as the result data. Years later, when the oilfield is preparing for the second three-dimensional collection, there is a lack of reference standard for evaluating the position error of the shot points of the previous three-dimensional data. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a marine time-lapse seismic base data shot point repeatability evaluation method, which makes up for the deficiency that the conventional marine time-lapse seismic streamer base data acquisition does not consider the influence of shot point error, and makes the repeatability evaluation of base data acquisition more comprehensive and reasonable.

[0007] To achieve the above purpose, the present application adopts the following technical solutions: The marine time-lapse seismic base data shot point repeatability evaluation method provided by the present application comprises the following steps: Determine the shot line direction and scan the shot line position to form a pre-drawn shot line cluster; Determine the tie line direction and scan the tie line position; On the basis of the pre-drawn shot line cluster, find the pre-drawn shot line closest to the actual shot line; On the basis of the tie line position and the pre-drawn shot line cluster, determine the pre-drawn grid intersection point; According to the actual shot line acquisition direction, determine the pre-drawn shot line shot point position; Calculate the position error between the pre-drawn shot line shot point closest to the actual shot line and the corresponding actual shot line shot point, and draw a drawing; Evaluate the repeatability of the actual shot line shot point, and the smaller the error is, the better the repeatability is.

[0008] The marine time-lapse seismic base data shot point repeatability evaluation method, preferably, the determination of the shot line direction is obtained by the following way: Directly obtain the shot line direction from the acquisition report or the acquisition report; Estimate the shot line direction by linear fitting the shot line.

[0009] The marine time-lapse seismic base data shot point repeatability evaluation method, preferably, the estimation of the shot line direction by linear fitting the shot line comprises the following steps: ① Read a shot line to obtain the shot point coordinates of the shot line; ② Linearly fit the shot point distribution of the shot line to obtain the slope of the shot line k i ; ③ Convert the slope k i Into an azimuth θ i , and record it; ④ Repeat steps ①-③ to obtain the azimuths of all shot lines; ⑤ Sort the azimuths of all shot lines θ i , and take the average value of the azimuths of the middle 80% of the shot lines as the shot line direction of the entire work area θ .

[0010] The aforementioned method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data, preferably, involves the following steps in scanning the shot line location: Using the actual seismic shot line distribution of the foundation as the base map, the acquisition direction is drawn as follows: θ Spacing between gun lines dsl A parallel shot line cluster that is consistent with the base earthquake, which is required to cover the shot line distribution of the base earthquake. Add an overall offset to the gun line cluster along the liaison line direction. ofs Calculate the distance of each shot point from its nearest firing line. d ; offset ofs In plus or minus 1 dsl Sampling, repeated calculation of shot distance d Record the distance of the firing line. d With offset ofs Changes; Plot the average error (avg) of all shot points from the nearest shot line as a function of offset. ofs Find the optimal offset that minimizes the average error (avg) of the shot cluster from the variation graph. ofs-sln .

[0011] The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, includes the following method for determining the direction of the tie line: Determine the direction perpendicular to the artillery line; the direction perpendicular to the artillery line is the direction of the liaison line. When the direction of the liaison line is not perpendicular to the direction of the gun line, the direction of the liaison line is estimated by linearly fitting the distribution of gun points with the same gun number on each gun line.

[0012] The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, involves estimating the direction of the connecting line by linearly fitting the distribution of shot points with the same shot number along each shot line, and includes the following steps: ① Read all firing lines to obtain the firing line, firing number, and firing point coordinates of each firing point; ② Extract the cannon number from all cannon points j Information on the firing positions; ③ Linear fitting j Based on the distribution of firing points, the slope of the connecting line can be determined. k j ; ④ Slope k j Convert to azimuth And make a record; ⑤ Repeat steps ② to ④ to obtain the azimuth angles of all connecting lines except for the supplementary line; ⑥ Azimuth angles of all connecting lines Sort the connections and take the average azimuth of the middle 80% of the connections as the direction of the connections for the entire work area. .

[0013] The aforementioned method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, includes the following steps for scanning the contact line location: Using the distribution of seismic tie lines in the actual mining foundation as the base map, the direction is drawn as follows: Spacing between connecting lines dxl The parallel link clusters are consistent with the base earthquake, with the same number of links as the base data, and basically cover the distribution of the base earthquake link lines. Add an overall offset to the communication cluster along the line of fire. ofs Calculate the distance of each gun point from its nearest communication line. d ; ofs In positive and negative numbers dxl Sampling, repeated calculation d ,Record d Follow ofs Changes; Finally, plot the average error (avg) of all shot points from the nearest contact line as a function of offset. ofs Find the optimal offset that minimizes the average error (avg) from the change graph. ofs-xln .

[0014] The aforementioned method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, involves finding the pre-drawn shot line that is closest to the actual shot line, which includes the following steps: Calculate the average distance avg from each shot point on the current actual shot line to the previously drawn shot line cluster; The minimum value in avg corresponds to the foregrounded artillery line cluster that is closest to the actual artillery line.

[0015] The method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data, preferably, includes the following steps in determining the intersection points of the pre-drawn grid: Calculate the intersection point formed by the previously drawn gun line and the liaison line; If the line A 1 x + B 1 y + C 1=0 and A 2 x + B 2 y + C 2=0 respectively represent setting the gun line and the liaison line, then their intersection point ( x 0, y 0) is represented as:

[0016] in, , , These are the coefficients for the gun line; , , These are the coefficients of the connecting lines.

[0017] The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, involves determining the shot point locations of the pre-drawn shot line based on the actual shot line acquisition direction, including the following steps: The positions of the artillery points in the previous drawing are related to the data acquisition heading, and the artillery point numbers are consistent with the actual artillery lines acquired. Dual-source interval 2ds, positive acquisition at angle θ, even-number shot point coordinates are ( x pe , y pe ):

[0018] The coordinates of the cannon point for an odd number of cannons are ( x po , y po ):

[0019] Reverse acquisition, the coordinates of even-numbered shot points are ( x ne , y ne ):

[0020] The coordinates of the cannon point for an odd number of cannons are ( x no , y no ): .

[0021] The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data, preferably, involves calculating the positional error between the pre-drawn shot point closest to the actual shot line and the corresponding actual shot point, and then drawing a map. Specifically: Calculate the distance error between the pre-drawn blast line closest to the actual blast line and the same blast point on the actual blast line; When the distribution of the statistical bar chart of shot point errors varies greatly, a logarithmic coordinate axis should be used for the counting vertical axis to reduce the proportion of the difference. The average shot point error across the entire region is used as a reference indicator to measure the accuracy of shot point positioning in the acquisition of the four-dimensional seismic baseline data.

[0022] The present invention has the following advantages due to the adoption of the above technical solutions: (1) The method for evaluating the repeatability of shot points in marine time-shifted seismic basic data proposed in this invention makes up for the shortcomings of conventional marine time-shifted seismic towed cable basic data acquisition which does not consider the influence of shot point error, making the repeatability evaluation of basic data acquisition more comprehensive and reasonable.

[0023] (2) In the absence of a pre-drawing acquisition design, the present invention can estimate the shot point location of the pre-drawing design based on navigation files or seismic data trace information, providing a reference standard for quantitatively evaluating the shot point error of basic seismic acquisition.

[0024] (3) This invention can both quantitatively evaluate the repeatability of the overall shot points in the acquisition area and show the planar distribution of shot point errors, providing a basis for decision-making for marine time-shifting seismic acquisition construction.

[0025] (4) This invention is not only applicable to the repeatability evaluation of time-shifted seismic basic data acquisition, but also effective for the evaluation of the accuracy of shot point positioning in conventional marine towed cable three-dimensional seismic acquisition. Attached Figure Description

[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings: Figure 1 This is an example of shot line distribution in a 3D seismic acquisition using a towed cable in an oil field in the South China Sea, based on existing technology. Figure 2 This is a schematic diagram of the distribution of shot lines and the fitting of shot lines in the L oilfield. Figure 3 This is an estimation map of the firing line direction for the L oilfield. Figure 4 This is a schematic diagram of the initial pre-drawn shot line cluster for the L oilfield; Figure 5 This is a schematic diagram of the optimal offset scan for the shot line cluster in the L oilfield. Figure 6 This is a schematic diagram of the distribution and fitting of the connecting lines in the L oilfield; Figure 7 This is an estimated direction diagram of the L oilfield connecting line; Figure 8 This is a schematic diagram of the optimal offset scan of the pre-drawn connecting line cluster in the L oilfield; Figure 9 This is a schematic diagram showing the average distance from the actual production line #1 in the L oilfield to the previously drawn running line cluster; Figure 10 This is a schematic diagram showing the location and numbering of the blast points in the forward direction of the L oilfield; Figure 11 This is a schematic diagram showing the location and numbering of the blast points in the opposite direction of the L oilfield. Figure 12 This is a planar distribution map of the shot point location errors in the L oilfield basic data acquisition. Figure 13 This is a bar chart showing the error of shot point location in the basic data acquisition of L oilfield; Figure 14 This is a planar distribution map of the shot point location errors in the basic data acquisition of the G oilfield. Figure 15 This is a bar chart showing the error of the shot point location in the basic data acquisition of the G oilfield. Detailed Implementation

[0027] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0028] This invention provides a method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data. It estimates the pre-acquisition shot point coordinates using the shot line number, shot point coordinates, and shot point number from the actual seismic data, and then statistically analyzes the errors between the actual seismic data and the estimated pre-acquisition shot point positions. This invention overcomes the deficiency of conventional marine time-lapse seismic towed cable baseline data acquisition, which does not consider the influence of shot point errors, making the repeatability evaluation of baseline data acquisition more comprehensive and reasonable.

[0029] The method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data provided by this invention includes the following steps: S1. Determine the direction of the firing line and scan its position to form a cluster of firing lines drawn in advance; S2. Determine the direction of the tie line and scan its location; S3. Based on the previously drawn artillery line cluster, find the artillery line that is closest to the actual artillery line. S4. Based on the location of the liaison line and the previously drawn gun line cluster, determine the intersection of the previously drawn grid. S5. Determine the location of the firing points of the previously drawn firing line based on the actual firing line acquisition direction; S6. Calculate the positional error between the pre-drawn shot point closest to the actual shot line and the corresponding actual shot point, and draw a map. S7. Evaluate the repeatability of actual shot lines and shot points; the smaller the error, the better the repeatability.

[0030] In the above embodiments, preferably, the determination of the shot line direction is obtained in the following manner: The direction of the shot line can be obtained directly from the collection report or collection report; The direction of the shot line is estimated by linearly fitting the shot line.

[0031] In the above embodiments, preferably, estimating the shot line direction by linear fitting of the shot line includes the following steps: ① Read a shot line (seismic data trace header or P1 / 90 navigation file) and obtain the shot point coordinates of the shot line; ② Linearly fit the distribution of shot points along the shot line to obtain the slope of the shot line. k i ; ③ Slope k i Convert to azimuth θ i And make a record; ④ Repeat steps ①-③ to obtain the azimuth angles of all gun lines; ⑤ Azimuth of all firing lines θ i Sort the shots and take the average azimuth of the middle 80% of the shot lines as the positive direction of the shot lines for the entire work area. θ .

[0032] In the above embodiments, preferably, the scanning of the shot line position includes the following steps: Using the actual seismic shot line distribution of the foundation as the base map, the acquisition direction is drawn as follows: θ Gun line spacing ( dsl A parallel shot line cluster that is consistent with the base earthquake, which is required to cover the shot line distribution of the base earthquake. Add an overall offset to the gun line cluster along the liaison line direction. ofs Calculate the distance of each shot point from its nearest firing line. d ; offset ofs In plus or minus 1 dsl Sampling, repeated calculation of shot distance d Record the distance of the firing line. d With offset ofs Changes; Plot the average error (avg) of all shot points from the nearest shot line. d With offset ofs The change graph was used to find the average error avg of the shot cluster. d Minimum optimal offset ofs-sln .

[0033] In the above embodiments, preferably, determining the direction of the communication line includes the following methods: Determine the direction perpendicular to the artillery line; the direction perpendicular to the artillery line is the direction of the liaison line. When the direction of the liaison line is not perpendicular to the direction of the gun line, the direction of the liaison line is estimated by linearly fitting the distribution of gun points with the same gun number on each gun line.

[0034] In the above embodiments, preferably, the step of estimating the direction of the connecting line by linearly fitting the distribution of the same shot number on each shot line includes the following steps: ① Read all shot lines (seismic data trace headers or P1 / 90 navigation files) to obtain the shot line, shot number, and shot point coordinates of each shot point; ② Extract the cannon number from all cannon points j Information on the firing positions; ③ Linear fitting j Based on the distribution of firing points, the slope of the connecting line can be determined. k j ; ④ Slope k j Convert to azimuth And make a record; ⑤ Repeat steps ② to ④ to obtain the azimuth angles of all connecting lines except for the supplementary line; ⑥ Azimuth angles of all connecting lines Sort the connections and take the average azimuth of the middle 80% of the connections as the direction of the connections for the entire work area. .

[0035] In the above embodiments, preferably, the scanning of the contact line location includes the following steps: Using the distribution of seismic tie lines in the actual mining foundation as the base map, the direction is drawn as follows: Spacing between connecting lines ( dxl A cluster of parallel contact lines that is consistent with the base earthquake, with the same number of contact lines as the base data, and basically covering the distribution of contact lines of the base earthquake; Add an overall offset to the communication cluster along the line of fire. ofs Calculate the distance of each gun point from its nearest communication line. d ; ofs In positive and negative numbers dxl Sampling, repeated calculation d ,Record d Follow ofs Changes; Finally, plot the average error (avg) of all shot points from the nearest communication line. d With offset ofs Find the average error avg from the change graph. d Minimum optimal offset ofs-xln .

[0036] In the above embodiments, preferably, finding the pre-drawn gun line that is closest to the actual gun line includes the following steps: Calculate the average distance (avg) from each shot point on the current actual firing line to the previously drawn shot line cluster. d ); avg( d The minimum value in the range corresponds to the front-drawn blast line that is closest to the actual blast line in the front-drawn blast line cluster.

[0037] In the above embodiments, preferably, determining the intersection points of the previously drawn meshes includes the following steps: Calculate the intersection point formed by the previously drawn gun line and the liaison line; If the line A 1 x + B 1 y + C 1=0 and A 2 x + B 2 y + C 2=0 respectively represent setting the gun line and the liaison line, then their intersection point ( x 0, y 0) is represented as:

[0038] in, , , These are the coefficients for the gun line; , , These are the coefficients of the connecting lines.

[0039] In the above embodiments, preferably, determining the location of the shot points along the pre-drawn shot line based on the actual shot line acquisition direction includes the following steps: The positions of the artillery points in the previous drawing are related to the data acquisition heading, and the artillery point numbers are consistent with the actual artillery lines acquired. Dual-source interval 2ds, positive angle acquisition (shot point numbers from smallest to largest, even on the left and odd on the right), the coordinates of even-numbered shot points are ( x pe , y pe ):

[0040] The coordinates of the cannon point for an odd number of cannons are ( x po , y po ):

[0041] Reverse data acquisition (shot point numbers from largest to smallest, even on the left and odd on the right), the coordinates of even-numbered shot points are ( x ne , y ne ):

[0042] The coordinates of the cannon point for an odd number of cannons are ( x no , y no ): . In the above embodiments, preferably, the step of calculating the positional error between the pre-drawn gun point closest to the actual gun line and the corresponding actual gun point, and then drawing the map, specifically involves: Calculate the distance error between the pre-drawn gun line closest to the actual gun line and the same gun point on the pre-drawn gun line; When the distribution of the statistical bar chart of shot point errors varies greatly, a logarithmic coordinate axis should be used for the counting vertical axis to reduce the proportion of the difference. The average shot point error across the entire region is used as a reference indicator to measure the accuracy of shot point positioning in the acquisition of the four-dimensional seismic baseline data.

[0043] Example 1: The following explanation uses the L oil field as an example: 1) Determine the direction of the firing line The L oilfield data collection report indicates that the shot line direction was 60º / 240º. In the absence of relevant information, the shot line direction can be estimated by linearly fitting the shot line. Figure 2 The distribution of shot lines in the L oilfield is shown, totaling 52 shot lines including supplementary lines. Linear fitting is used to obtain the azimuth angle of each shot line. θ i Then, the azimuth angles of all gun lines were determined. θ i Sort the shots and take the average azimuth of the middle 80% of the shot lines as the positive direction of the shot lines for the entire work area. θ .like Figure 3 As shown, θ i After removing the first 10% minimum and the last 10% maximum values, the positive azimuth of the shot line was collected in the L oilfield. θ The mean is 59.3º.

[0044] 2) Scan the position of the gun line like Figure 4As shown, using the base seismic shot line distribution as the base map, a cluster of 39 parallel shot lines with a 60º acquisition direction and a shot line spacing consistent with the base seismic data (400m) is drawn. This shot line cluster covers the base seismic shot line distribution. Then, an overall offset is added to the shot line cluster along the connecting line direction. ofs Calculate the distance of each shot point from its nearest firing line. d . ofs Sample at several positive and negative shot line intervals and repeat the calculation. d ,Record d Follow ofs The changes. Understanding the distance error. d With offset ofs After understanding the pattern of change, it can be reduced. ofs The sampling range and sampling interval are adjusted to improve the accuracy of the analysis. Figure 5 Showing ofs The average error avg of all shot points from the nearest shot line in 101 samples within [88,288] is calculated. d With offset ofs The change graph was used to find the average error avg of the shot cluster. d Minimum optimal offset ofs-sln It is approximately 188m.

[0045] 3) Determine the direction of the connecting line Generally, the direction perpendicular to the shot line is the direction of the connecting line; in the L oil field, the connecting line direction is 150º. When the shot line direction is unknown or the connecting line direction is not perpendicular to the shot line direction, it can still be estimated using a linear fitting method. Figure 6 The distribution of connecting lines in the L oilfield is shown, with the smallest shot number being 881 and the largest being 2377, with a shot number interval of 1, totaling 1497 connecting lines. For ease of display, a shot number interval of 34 is used here, resulting in 45 connecting lines. Linear fitting is performed on each connecting line, and then the azimuth angles of all connecting lines are calculated. Sort the data and take the average of the middle 80% of the azimuth angles of the connecting lines as the positive direction of the connecting lines for the entire work area. .like Figure 7 As shown, After removing the first 10% minimum and the last 10% maximum values, the positive azimuth of the connecting line in the L oilfield was obtained. The average value is 150º, which is consistent with the actual situation.

[0046] 4) Scan the location of the communication line Using the actual seismic tie-line distribution as the base map, a cluster of parallel tie-lines with a 150° orientation and a tie-line spacing consistent with the base seismic data (25m) was drawn, with the same number of tie-lines as the base data (1497), covering the base seismic tie-line distribution. Then, an overall offset was added to the tie-line cluster along the shot line direction. ofsCalculate the distance of each gun point from its nearest communication line. d . ofs Sample at positive and negative tie line intervals and repeat the calculation. d ,Record d Follow ofs The change. Plot the average error (avg) of all gun points from the nearest contact line. d With offset ofs The graph shows the changes in the average error avg( d Minimum optimal offset ofs-xln Understanding distance error d With offset ofs After understanding the pattern of change, it can be reduced. ofs The sampling range and sampling interval are adjusted to improve the accuracy of the analysis. Figure 8 Showing ofs The average error avg of all shot points from the nearest communication line in 101 samples within [150, 200] is calculated. d With offset ofs The change graph was used to find the average error avg of the connection cluster. d Minimum optimal offset ofs-xln It is approximately 176m.

[0047] 5) Locate the pre-drawn firing line that is closest to the actual firing line. Find the pre-drawn shot line that is closest to the actual shot line. The method is: ① Calculate the average distance (avg) from each shot point on the current actual shot line to the pre-drawn shot line cluster. d );②avg( d The minimum value in the range corresponds to the front-drawn blast line that is closest to the actual blast line in the front-drawn blast line cluster. Figure 9 The average distance from the blasting point on the actual blasting line #1 to the 39 previously drawn blasting lines is shown. It can be seen that the actual blasting line #1 is closest to the previously drawn blasting line #8.

[0048] 6) Calculate the intersections of the previously drawn mesh. Calculate the intersection point of the two line clusters based on their equations. If the line... A 1 x + B 1 y + C 1=0 and A 2 x + B 2 y + C 2=0 represent a certain gun line and a communication line, respectively. Then their intersection point ( x 0, y 0) can be represented as:

[0049] 7) Determine the positions of the gun points along the pre-drawn gun line. The previously drawn shot point locations are related to the data acquisition heading, and the shot point numbers are consistent with the actual data acquisition shot lines. For the L oilfield, the dual-source interval is 2ds=50m, with a θ=60º angle for forward data acquisition (Southwest => Northeast, shot point numbers from smallest to largest, even on the left and odd on the right). The coordinates of even-numbered shot points are (…). x pe , y pe ):

[0050] The coordinates of the cannon point for an odd number of cannons are ( x po , y po ):

[0051] Reverse data acquisition (northeast => southwest, shot point numbers from largest to smallest, even on the left and odd on the right), the coordinates of even-numbered shot points are ( x ne , y ne ):

[0052] The coordinates of the cannon point for an odd number of cannons are ( x no , y no ): . Figure 10 and Figure 11 Examples of the numbering of the foreground blast point locations in the L oilfield, in the forward direction (60º) and the reverse direction (240º). "+" indicates the location of the blast point on the foreground blast line, "•" indicates the location of the actual blast point, and the numbers are the blast point numbers. All foreground blast points fall on the connecting line, and the numbering rules are consistent with those for the blast points on the actual blast line.

[0053] 8) Calculate the shot point errors and draw a plane distribution map of the shot point errors. Calculate the distance error between the nearest actual shot line and the same shot point on the previously drawn shot line. When the distribution of shot point error statistics in the histogram varies significantly, a logarithmic coordinate axis is used for the counting axis to reduce the proportion of difference. The average shot point error for the entire area is used as a reference indicator to measure the accuracy of shot point positioning in this 4D seismic baseline data acquisition. Figure 12 and Figure 13 These are a planar distribution map and a bar chart showing the positional error of the shot points in the L oilfield basic data acquisition. The average positional error of the shot points is 137m. Figure 14 and Figure 15The images show a planar distribution map and a bar chart of the shot point location error for the overseas G oilfield, with an average shot point location error of 7.13m. It is clearly evident that the shot points acquired from the basic seismic acquisition of the G oilfield exhibit better repeatability.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data, characterized in that, Includes the following steps: Determine the direction of the artillery line and scan its position to form a cluster of artillery lines to be drawn in advance; Determine the direction of the tie line and scan its location; Based on the pre-drawn artillery line cluster, find the pre-drawn artillery line that is closest to the actual artillery line; Based on the location of the liaison line and the pre-drawn gun line cluster, determine the intersection points of the pre-drawn grid; Determine the location of the artillery points along the actual artillery line based on the actual direction of the artillery line data collection. Calculate the positional error between the pre-drawn shot point closest to the actual shot line and the corresponding shot point on the actual shot line, and draw a map; The repeatability of actual shot lines and shot points is evaluated; the smaller the error, the better the repeatability.

2. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, The direction of the firing line is determined in the following way: The direction of the shot line can be obtained directly from the collection report or collection report; The direction of the shot line is estimated by linearly fitting the shot line.

3. The method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data according to claim 2, characterized in that, The method of estimating the shot line direction by linear fitting includes the following steps: ① Read a firing line and obtain the coordinates of the firing point of that firing line; ② Linearly fit the distribution of shot points along the shot line to obtain the slope of the shot line. k i ; ③ Slope k i Convert to azimuth θ i And make a record; ④ Repeat steps ①-③ to obtain the azimuth angles of all gun lines; ⑤ Azimuth of all firing lines θ i Sort the shots and take the average azimuth of the middle 80% of the shot lines as the positive direction of the shot lines for the entire work area. θ .

4. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, The scanning of the shot line location includes the following steps: Using the actual seismic shot line distribution of the foundation as the base map, the acquisition direction is drawn as follows: θ Spacing between gun lines dsl A parallel shot line cluster that is consistent with the base earthquake, which is required to cover the shot line distribution of the base earthquake. Add an overall offset to the gun line cluster along the liaison line direction. ofs Calculate the distance of each shot point from its nearest firing line. d ; offset ofs In plus or minus 1 dsl Sampling, repeated calculation of shot distance d Record the distance of the firing line. d With offset ofs Changes; Plot the average error (avg) of all shot points from the nearest shot line as a function of offset. ofs Find the optimal offset that minimizes the average error (avg) of the shot cluster from the variation graph. ofs-sln .

5. The method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data according to claim 1, characterized in that, The determination of the direction of the connecting line includes the following methods: Determine the direction perpendicular to the artillery line; the direction perpendicular to the artillery line is the direction of the liaison line. When the direction of the liaison line is not perpendicular to the direction of the gun line, the direction of the liaison line is estimated by linearly fitting the distribution of gun points with the same gun number on each gun line.

6. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 5, characterized in that, The method of estimating the direction of the connecting line by linearly fitting the distribution of shot points with the same shot number on each shot line includes the following steps: ① Read all firing lines to obtain the firing line, firing number, and firing point coordinates of each firing point; ② Extract the cannon number from all cannon points j Information on the firing positions; ③ Linear fitting j Based on the distribution of firing points, the slope of the connecting line can be determined. k j ; ④ Slope k j Convert to azimuth And make a record; ⑤ Repeat steps ② to ④ to obtain the azimuth angles of all connecting lines except for the supplementary line; ⑥ Azimuth angles of all connecting lines Sort the connections and take the average azimuth of the middle 80% of the connections as the direction of the connections for the entire work area. .

7. The method for evaluating the repeatability of shot points in marine time-lapse seismic baseline data according to claim 1, characterized in that, The scanning of the contact line location includes the following steps: Using the distribution of seismic tie lines in the actual mining foundation as the base map, the direction is drawn as follows: Spacing between connecting lines dxl The parallel link clusters are consistent with the base earthquake, with the same number of links as the base data, and basically cover the distribution of the base earthquake link lines. Add an overall offset to the communication cluster along the line of fire. ofs Calculate the distance of each gun point from its nearest communication line. d ; ofs In positive and negative numbers dxl Sampling, repeated calculation d ,Record d Follow ofs Changes; Finally, plot the average error (avg) of all shot points from the nearest contact line as a function of offset. ofs Find the optimal offset that minimizes the average error (avg) from the change graph. ofs-xln .

8. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, Finding the pre-drawn gun line that is closest to the actual gun line includes the following steps: Calculate the average distance avg from each shot point on the current actual shot line to the previously drawn shot line cluster; The minimum value in avg corresponds to the foregrounded artillery line cluster that is closest to the actual artillery line.

9. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, Determining the intersection points of the previously drawn grid includes the following steps: Calculate the intersection point formed by the previously drawn gun line and the liaison line; If the line A 1 x + B 1 y + C 1=0 and A 2 x + B 2 y + C 2=0 respectively represent setting the gun line and the liaison line, then their intersection point ( x 0, y 0) is represented as: in, , , These are the coefficients for the gun line; , , These are the coefficients of the connecting lines.

10. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, The process of determining the location of the shot points along the pre-drawn shot line based on the actual shot line acquisition direction includes the following steps: The positions of the artillery points in the previous drawing are related to the data acquisition heading, and the artillery point numbers are consistent with the actual artillery lines acquired. Dual-source interval 2ds, positive acquisition at angle θ, even-number shot point coordinates are ( x pe , y pe ): The coordinates of the cannon point for an odd number of cannons are ( x po , y po ): Reverse acquisition, the coordinates of even-numbered shot points are ( x ne , y ne ): The coordinates of the cannon point for an odd number of cannons are ( x no , y no ): 。 11. The method for evaluating the repeatability of shot points in marine time-shifted seismic baseline data according to claim 1, characterized in that, The calculation of the positional error between the pre-drawn gun point closest to the actual gun line and the corresponding actual gun point, and the creation of a map, specifically involves: Calculate the distance error between the pre-drawn blast line closest to the actual blast line and the same blast point on the actual blast line; When the distribution of the statistical bar chart of shot point errors varies greatly, a logarithmic coordinate axis should be used for the counting vertical axis to reduce the proportion of the difference. The average shot point error across the entire region is used as a reference indicator to measure the accuracy of shot point positioning in the acquisition of the four-dimensional seismic baseline data.

Images