Reverse time migration mass data OVT domain common imaging point gather manufacturing method and device

Abstract

The invention relates to the technical field of seismic exploration data processing, in particular to a reverse time migration mass data OVT domain common imaging point gather manufacturing method and device. The method comprises the steps of obtaining to-be-processed seismic work area fidelity processing shot gather data and a depth domain velocity model; presetting grid information output by the imaging gather; taking the shot point position as a center, constructing a stereo imaging space corresponding to single-shot reverse time migration, and obtaining a speed model in the stereo range; carrying out wave field continuation on the seismic source wave field and the single-shot data in the speed model by utilizing a seismic wave equation, and completing single-shot reverse time migration processing; and trace header information of each imaging seismic trace in single-shot reverse time migration is obtained, and partitioning processing is performed according to grid information output by a preset imaging trace gather and the size of a node memory, so that manufacturing of a reverse time migration OVT domain common imaging point trace gather is completed. According to the method provided by the invention, the production efficiency of the OVT domain imaging gather of the reverse time migration mass data is improved, and the error-tolerant rate is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic exploration data processing, and particularly relates to a method and device for producing common image point gathers in the OVT domain for reverse time migration of massive data. Background Art

[0002] The seismic wave reverse time imaging technology has less approximation to the seismic wave equation, can solve the multi-valued travel time problem, is suitable for imaging problems in cases such as arbitrary steep dips and relatively drastic lateral and longitudinal velocity variations, and can also accurately image wave fields such as multiple waves and converted reflection waves that are usually considered as interference wave types. Compared with the Kirchhoff prestack depth imaging technology and the one-way wave seismic depth imaging technology, the seismic wave reverse time imaging technology has significant technical advantages and is one of the technologies with relatively mature theory and the most accurate imaging in the current series of high-precision seismic imaging technologies. At present, it has been applied on a large scale in both marine and land data, and significant exploration and development application effects have been achieved.

[0003] It is found in practical applications that the current reverse time migration method mainly uses the migrated stack profile. Since the single-shot imaging data volume after migration is above 100 TB or PB level, which belongs to massive data, producing imaging gathers from the massive data has a huge amount of calculation and high cost. Currently, it mainly extracts the common image point offset gathers of a single azimuth target line, and mainly conducts fine excision and stacking processing on this basis, but the industrial research and application of producing reverse time migration imaging gathers based on massive data have not been realized. Therefore, the effective information such as formation azimuth hidden in the reverse time migration massive data common image point gathers has not been excavated. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] The present invention provides a method for producing common image point gathers in the OVT domain for reverse time migration of massive data to solve the defects in the prior art that only the migrated stack profile information is used, the huge amount of calculation brought by producing imaging gathers based on massive data is not efficiently solved, and the limitation of the computer node memory size is not broken through, etc. Therefore, the effective information such as formation azimuth hidden in the reverse time migration massive data has not been fully excavated.

[0006] (2) Technical Solutions

[0007] To solve the above problems, on the one hand, the present invention provides a method for producing common image point gathers in the OVT domain for reverse time migration of massive data, including:

[0008] Step S1: Obtain the preprocessed shot gather data Gather and the high-precision velocity model VEL in the depth domain after fidelity preprocessing of the seismic work area to be processed;

[0009] Step S2: Obtain the total number of shots shotnum in the gather data Gather in Step S1, and preset the grid information for the output of the imaging gather in the seismic work area to be processed;

[0010] Step S3: For any gather data Gather in Step S1, with the shot point position as the center, construct a three-dimensional imaging space corresponding to the single-shot reverse time migration according to the migration aperture aperture, imaging bin, migration depth Z, and migration step dz. The three-dimensional imaging space includes the range in the XY direction and the depth in the Z direction, and obtain the velocity model within this three-dimensional range from the high-precision velocity model VEL in Step S1;

[0011] Step S4: For the single-shot data and velocity model in Step S3, use the seismic wave equation to perform wavefield continuation on the source wavefield and the single-shot data in the velocity model, and apply the reverse time imaging condition and perform cumulative operations at each imaging point position at each time step of the wavefield continuation. Finally, complete the single-shot reverse time migration processing to obtain the single-shot reverse time migration data volume;

[0012] Step S5: According to the imaging output grid information in Step S2, obtain the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse time migration in Step S4;

[0013] Step S6: Perform block processing on the imaging output grid range corresponding to Step S2. At the same time, use the position of the header information in Step S5 to accumulate each imaging trace in the single-shot reverse time migration data volume in Step S4 to the corresponding imaging output grid after block processing, and complete the production of the OVT domain imaging gather for the entire work area.

[0014] Preferably, in Step S1, the fidelity preprocessing includes static correction, denoising, energy compensation, deconvolution seismic processing steps, and anti-spherical amplitude compensation processing, and at the same time perform regularization processing on spatially unevenly distributed data;

[0015] The gather is obtained by sorting the preprocessed common midpoint (CMP) gather data according to shot-trace or shot-offset, etc.;

[0016] The depth-domain velocity model is obtained by well-controlled and horizon-controlled structural constraint modeling or grid tomography inversion or full waveform inversion methods, and it is required that the velocity model can reflect the horizontal and vertical detailed changes of the geological structure.

[0017] Preferably, the grid information for the output of the OVT domain imaging gather in the seismic work area to be processed in Step S2 specifically includes LINE number, CDP number range, imaging bin bin, depth step dz, migration depth Z, starting direction of azimuth, number of azimuths azimuthnum, starting offset offsetstart, offset interval doffset, and number of offset groups offsetnum;

[0018] The imaging surface element bin is in the binx×biny format, and the calculation of the degree of each azimuth angle specifically includes:

[0019] Calculated according to the opposite azimuth angle, dazimuth = 180 / azimuthnum, and calculated according to a single azimuth angle: dazimuth = 360 / azimuthnum.

[0020] Preferably, obtaining the header information of each seismic trace at each imaging point in the single-shot reverse-time imaging data volume according to the imaging output header information in step S4 specifically includes the X and Y coordinates of the shot point, the X and Y coordinates of the imaging point position, the LINE number and CDP number corresponding to the imaging point position. At the same time, according to the azimuth starting direction and each azimuth angle calculation formula in step S2, the azimuth angle from the shot point to the imaging point position is obtained and rounded, and according to the starting offset and offset interval in step S2, the offset from the shot point to the imaging point position is obtained and rounded.

[0021] Preferably, in step S3, the offset aperture aperture is more than 1 times the buried depth of the target layer; the number of imaging surface elements binxnum occupied by the length of the 3D imaging space in the x direction = (int)[aperture / binx]+1, the number of imaging surface elements binynum occupied by the length in the y direction = (int)[aperture / biny]+1, and the number of imaging steps nZ occupied by the depth in the z direction = (int)[Z / dz]+1, where (int)[·] represents the rounding operation.

[0022] Preferably, in step S4,

[0023] The reverse-time imaging condition includes the cross-correlation reverse-time imaging condition, the normalized reverse-time imaging condition, or the reverse-time imaging condition based on traveling wave separation.

[0024] Preferably, in step S4,

[0025] The seismic wave equation includes the acoustic wave equation or the elastic wave equation;

[0026] The velocity model is an isotropic model or an anisotropic model.

[0027] Preferably, step S6 specifically includes:

[0028] Perform block division in advance according to the LINE number range LINEnum or CDP number range CDPnum of the offset gather. During specific extraction, complete the extraction of the reverse time migration gather body block by block serially or synchronously using multiple computing nodes, and finally complete the production of the common image point gather in the reverse time migration OVT domain for the entire work area. For each block of the reverse time migration gather body within the preset range, the specific extraction steps are as follows:

[0029] Step S61: Allocate a storage space in the memory of the computer node or generate a storage file on the disk. The size of this storage space is SIZE = dLINEnum × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes, and zero-fill this disk space. If this storage space is smaller than the memory of the computing node, use the above two methods to allocate disk space. Otherwise, perform block division to reduce the size of dLINEnum or dCDPnum when producing a single-block OVT image gather, or generate multiple storage space files on the disk;

[0030] Step S62: For the reverse time migration data volume of any shot, obtain the information on the LINE number and CDP number range of the imaging points in this shot's migration data volume. If the LINE number and CDP number range of the imaging points overlap with the block LINE number and CDP number ranges in Step S61, then perform the extraction work of the common image point gather in Step S63. Otherwise, do not extract this shot's imaging data volume.

[0031] Step S63: For the reverse time migration data volume of a shot selected in Step S62, extract any imaging seismic trace. First, determine whether this seismic trace overlaps with the block LINE number and CDP number ranges in Step S61. If this trace is within this range, then accumulate it to the corresponding position in the storage space in Step S61 according to the LINE number, CDP number, azimuth, offset, and depth information in the trace header of this seismic trace. If this seismic trace is not within this range, do not process it;

[0032] Step S64: Complete the extraction process of the OVT gather for all imaging seismic traces in all shot migration data volumes according to Steps S62 and S63.

[0033] Preferably, in Step S61, the block division is to divide the data range along the LINE number or CDP number direction into Num parts. After block division, the required storage space for a single-block OVT image gather becomes SIZE1 = (int)[dLINEnum / Num] × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes or dLINEnum ×

[0034] (int) [dCDPnum / Num] × nZ × azimuthnum × offsetnum × sizeof(float), so that the storage space required for each block is less than the memory of the computing node.

[0035] On the other hand, the present invention provides an apparatus for making an OVT domain common image point gather for reverse time migration of massive data, comprising:

[0036] A first acquisition module, configured to acquire the shot gather data Gather after fidelity preprocessing of the seismic work area to be processed and the high-precision velocity model VEL in the depth domain;

[0037] A preset module, configured to obtain the total number of shots shotnum of the shot gather data Gather from the acquisition module, and preset the grid information of the imaging gather output of the seismic work area to be processed;

[0038] A construction module, for any shot gather data Gather, centered on the shot point position, according to the migration aperture aperture, imaging bin, migration depth Z, and migration step dz, construct a three-dimensional imaging space corresponding to the single-shot reverse time migration. The three-dimensional imaging space includes the range in the XY direction and the depth in the Z direction, and obtain the velocity model within this three-dimensional range from the high-precision velocity model VEL in the acquisition module;

[0039] A processing module, for the single-shot data and the velocity model, use the seismic wave equation to perform wavefield continuation of the source wavefield and the single-shot data in the velocity model, and apply the reverse time imaging condition and perform cumulative operation at each imaging point position at each time step of the wavefield continuation, and finally complete the single-shot reverse time migration processing to obtain the single-shot reverse time migration data volume;

[0040] A second acquisition module, according to the imaging output grid information, obtain the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse time migration;

[0041] A block-by-block accumulation module, perform block processing on the imaging output grid range in the above preset module, and at the same time, use the position of the header information in the second acquisition module to accumulate each imaging trace in the single-shot reverse time migration data volume to the corresponding imaging output grid after block processing, and complete the production of the OVT domain imaging gather for the entire work area.

[0042] (III) Advantageous Effects

[0043] The method for making an OVT domain common image point gather for reverse time migration of massive data provided by the present invention fully exploits the azimuth and other information hidden in the massive reverse time migration common image point gather data, is suitable for high-precision focused imaging processing of seismic data in complex structures or complex reservoirs, and provides important data support for pre-stack fracture prediction and imaging gather optimization processing in the depth domain, maximizing efficiency and reducing the error tolerance rate. Description of the Drawings

[0044] Figure 1 It is a schematic comparison diagram of the reverse time migration full azimuth common image point gather and the 6 opposite azimuth common image point gathers in the OVT domain;

[0045] Figure 2 It is a schematic comparison diagram of the reverse time migration full azimuth common image point gather and the multi-azimuth common image point gathers in the OVT domain;

[0046] Figure 3 It is a seismic profile based on the reverse time migration full azimuth common image point gather in the prior art;

[0047] Figure 4 It is a seismic profile after optimizing and stacking the reverse time migration massive data OVT domain common image point gather of the present invention;

[0048] Figure 5 It is a schematic flow diagram of the method for making the reverse time migration massive data OVT domain common image point gather according to the embodiment of the present invention. Detailed Embodiment

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0050] As Figures 1-5 shown, the present invention provides an embodiment of a method for making a reverse time migration massive data OVT domain common image point gather, which specifically includes the following steps:

[0051] Step S1, obtain the shot gather data Gather and the high-precision depth domain velocity model VEL after fidelity preprocessing of the seismic work area to be processed.

[0052] Among them, the fidelity preprocessing includes static correction, denoising, energy compensation, deconvolution seismic processing steps and anti-spherical amplitude compensation processing, and at the same time regularize the spatially unevenly distributed data;

[0053] The gather is obtained by sorting the common midpoint CMP gather data after preprocessing according to shot-channel or shot-offset distance, etc.;

[0054] The depth domain velocity model is obtained by well-controlled and horizon-controlled structure constraint modeling or grid tomography inversion or full waveform inversion method, and it is required that the velocity model can reflect the horizontal and vertical detail changes of the geological structure.

[0055] Step S2: Obtain the total number of shots shotnum = 38490 of the gather data in Step 1, and preset the grid information for the output of the imaging gather in the seismic working area to be processed.

[0056] Among them, the grid information for the output of the OVT-domain imaging gather in the seismic working area to be processed includes LINE number, CDP number range, imaging bin, depth step dz, migration depth Z, starting direction of azimuth angle, number of azimuth angles azimuthnum, starting offset offsetstart, offset interval doffset, and number of offset groups offsetnum;

[0057] The imaging bin is in the form of binx × biny. The calculation of the degree of each azimuth angle specifically includes:

[0058] Calculated according to the opposite azimuth angle, dazimuth = 180 / azimuthnum; calculated according to the single azimuth angle: dazimuth = 360 / azimuthnum.

[0059] In this embodiment, the grid information specifically includes: LINE number and CDP number range, imaging bin (binx = 25m, biny = 25m), depth step dz = 10, migration depth Z = 10km, starting direction of azimuth angle (0 degrees along the LINE direction), number of azimuth angles azimuthnum = 6, starting offset offsetstart = 100, offset interval doffset = 100, number of offset groups offsetnum = 70. Here, the degree of each azimuth angle is calculated according to the opposite azimuth angle, dazimuth = 180 / azimuthnum = 30.

[0060] Step S3: For any gather data Gather in Step S1, with the shot point position as the center, construct a 3D imaging space corresponding to the single-shot reverse time migration according to the migration aperture aperture, imaging bin, migration depth Z, and migration step dz. The 3D imaging space includes the range in the XY direction and the depth in the Z direction, and obtain the velocity model within this 3D range from the high-precision velocity model VEL in Step S1.

[0061] Specifically, for any gather data Gather in step 1, due to the irregular spatial distribution of shot points and geophone points, centering on the shot point position, according to the migration aperture (diameter) aperture = 10000 m, imaging bin (binx = 25 m, biny = 25 m), migration depth Z = 10 km, and migration step size dz = 10 m, a three-dimensional imaging space corresponding to single-shot reverse-time migration (including the range in the XY direction and the depth in the Z direction) is constructed, and the velocity model within this three-dimensional range is obtained from the high-precision velocity model VEL in step S1.

[0062] Here, the migration aperture (diameter) aperture should take into account the depth of the target layer, and aperture = 10000 m is taken; the number of imaging bins binxnum occupied by the length of the three-dimensional imaging space in the x direction is 401, the number of imaging bins binynum occupied by the length in the y direction is 401, and the number of imaging step sizes nZ occupied by the depth in the z direction is 1001.

[0063] In this step, the migration aperture aperture is more than 1 times the buried depth of the target layer; the number of imaging bins binxnum occupied by the length of the three-dimensional imaging space in the x direction is (int)[aperture / binx]+1, the number of imaging bins binynum occupied by the length in the y direction is (int)[aperture / biny]+1, and the number of imaging step sizes nZ occupied by the depth in the z direction is (int)[Z / dz]+1, where (int)[·] represents the rounding operation.

[0064] Step S4: For the single-shot data and velocity model in step S3, use the seismic wave equation to perform wavefield continuation of the source wavefield and the single-shot data in the velocity model, and apply the reverse-time imaging condition and perform cumulative operations at each imaging point position at each time step of the wavefield continuation, and finally complete the single-shot reverse-time migration processing to obtain the single-shot reverse-time migration data volume.

[0065] Among them, the reverse-time imaging condition in this embodiment can include the cross-correlation reverse-time imaging condition, the normalized reverse-time imaging condition, the reverse-time imaging condition based on traveling wave separation, etc.

[0066] The seismic wave equation in this embodiment can include the acoustic wave equation, the elastic wave equation, etc., and the velocity model can be an isotropic model or an anisotropic model, etc.

[0067] Step S5: According to the imaging output grid information in step S2, obtain the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse-time migration in step S4.

[0068] According to the imaging output header information in step S4, obtain the header information of each seismic trace at the imaging points in the single-shot reverse-time imaging data volume, specifically including the X and Y coordinates of the shot point, the X and Y coordinates of the imaging point position, the LINE number and CDP number corresponding to the imaging point position. At the same time, according to the azimuth starting direction and each azimuth angle calculation formula in step S2, obtain the azimuth from the shot point to the imaging point position and round it off. According to the starting offset and offset interval in step S2, obtain the offset from the shot point to the imaging point position and round it off.

[0069] Step S6: Perform block processing on the imaging output grid range corresponding to step S2. At the same time, use the header information position in step S5 to accumulate each imaging trace in the single-shot reverse-time migration data volume in step S4 to the corresponding imaging output grid after block processing, and complete the production of the OVT domain imaging trace gather for the entire work area.

[0070] Considering the huge amount of data in the reverse-time migration OVT trace gather, performing block processing on the reverse-time migration trace gather to be output first can improve efficiency and reduce the error tolerance rate.

[0071] Specifically, perform block extraction in advance according to the LINE number range LINEnum or CDP number range CDPnum of the migration trace gather. When specifically extracting, complete the extraction work of the reverse-time migration trace gather serially block by block or using multiple computing nodes synchronously. Finally, complete the production of the common imaging point gather in the reverse-time migration OVT domain for the entire work area. For each block of the reverse-time migration trace gather within the preset range, the specific extraction steps are as follows:

[0072] Step S61: Allocate a storage space in the computer node memory or generate a storage file on the disk. The size of this storage space is SIZE = dLINEnum × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes, and zero-fill this disk space. If this storage space is smaller than the computer node memory, use the above two methods to allocate disk space. Otherwise, perform block processing to reduce the size of dLINEnum or dCDPnum when producing a single-block OVT imaging trace gather, or generate multiple storage space files on the disk.

[0073] In this step, the block processing is to divide the data range along the LINE number or CDP number direction into Num parts. After block processing, the storage space required for a single-block OVT imaging trace gather becomes SIZE1 = (int)[dLINEnum / Num] × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes or dLINEnum ×

[0074] (int)[dCDPnum / Num] × nZ × azimuthnum × offsetnum × sizeof(float), so that the storage space required for each block is less than the memory of the computing node.

[0075] Step S62: For any shot reverse time migration data volume, obtain the information of the range of the LINE number and CDP number of the imaging points in the shot migration data volume. If the range of the LINE number and CDP number of the imaging points overlaps with the range of the block LINE number and CDP number in Step S61, then perform the common image point gather extraction work in Step S63. Otherwise, do not extract this shot imaging data volume.

[0076] Step S63: For the reverse time migration data volume of a shot selected in Step S62, extract any imaging seismic trace. First, determine whether this seismic trace overlaps with the range of the block LINE number and CDP number in Step S61. If this trace is within this range, then accumulate it to the corresponding position in the storage space in Step S61 according to the LINE number, CDP number, azimuth, offset, and depth information in the trace header information of this seismic trace. If this seismic trace is not within this range, then do nothing.

[0077] Step S64: Complete the extraction process of the OVT gather for all imaging seismic traces in all shot migration data volumes according to Step S62 and Step S63.

[0078] As Figure 1 and Figure 2 shown, Figure 1 is the comparison between the reverse time migration omnidirectional common image point gather and the OVT domain six opposite azimuth common image point gathers. It can be analyzed that the reverse time migration omnidirectional common image point gather superimposes the seismic information of all azimuths, so the azimuth information is lost, while the OVT domain six opposite azimuth common image point gathers contain richer geological information related to the formation structure.

[0079] Figure 2 For the comparison between the reverse time migration omnidirectional common image point gather and the OVT domain multi-azimuth common image point gathers, it can be seen that the OVT domain multi-azimuth common image point gathers have obvious azimuthal anisotropy characteristics, which is helpful for the development of work such as pre-stack fracture prediction.

[0080] Figure 3 For the seismic profile based on the reverse time migration omnidirectional common image point gather, the result is not clear in depicting the contact relationship of complex structural strata, while Figure 4 in the seismic profile optimized and superimposed based on the reverse time migration OVT domain multi-azimuth common image point gathers, the contact relationship of complex structural strata is depicted more clearly and explicitly, which is helpful for the development of fine oil and gas exploration and development work.

[0081] On the other hand, the present invention provides an apparatus for making OVT domain common image point gathers of reverse time migration of massive data, including:

[0082] A first acquisition module, configured to acquire the shot gather data Gather after fidelity preprocessing and the high-precision depth domain velocity model VEL of the seismic work area to be processed;

[0083] A preset module, configured to obtain the total number of shots shotnum of the shot gather data Gather from the acquisition module, and preset the grid information of the imaging gather output of the seismic work area to be processed;

[0084] A construction module, for any shot gather data Gather, centered on the shot point position, according to the migration aperture aperture, imaging bin, migration depth Z, and migration step dz, construct a three-dimensional imaging space corresponding to the single-shot reverse time migration. The three-dimensional imaging space includes the range in the XY direction and the depth in the Z direction, and obtain the velocity model within this three-dimensional range from the high-precision velocity model VEL in the acquisition module;

[0085] A processing module, for the single-shot data and the velocity model, use the seismic wave equation to perform wavefield continuation of the source wavefield and the single-shot data in the velocity model, and apply the reverse time imaging condition and perform cumulative operation at each imaging point position at each time step of the wavefield continuation, finally complete the single-shot reverse time migration processing, and obtain the single-shot reverse time migration data volume;

[0086] A second acquisition module, according to the imaging output grid information, obtain the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse time migration;

[0087] A block-by-block accumulation module, perform block-by-block processing on the imaging output grid range in the above preset module, and at the same time, use the position of the header information in the second acquisition module to accumulate each imaging trace in the single-shot reverse time migration data volume to the corresponding imaging output grid after block-by-block processing, and complete the production of the OVT domain imaging gathers of the entire work area.

[0088] The method for making OVT domain common image point gathers of reverse time migration provided by the embodiments of the present invention fully exploits the information such as azimuth hidden in the massive reverse time migration common image point gather data. Starting from the input gather data position and wavefield information, through reverse time imaging processing, the massive reverse time migration common image point gather data output is reconstructed according to the OVT vector slice grid for seismic data, and the OVT domain common image point gathers of reverse time migration are constructed, providing a data basis for subsequent fracture prediction and gather optimization.

[0089] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A method for making OVT domain common image point gathers of reverse time migration massive data, characterized in that, it includes: Step S1, obtain the shot gather data Gather after fidelity preprocessing and the high-precision depth domain velocity model VEL of the seismic work area to be processed; Step S2, obtain the total number of shots shotnum of the shot gather data Gather in Step S1, and preset the grid information of the imaging gather output of the seismic work area to be processed; Step S3, for any shot gather data Gather in Step S1, with the shot point position as the center, construct a three-dimensional imaging space corresponding to single-shot reverse time migration according to the migration aperture aperture, imaging bin, migration depth Z, and migration step dz. The three-dimensional imaging space includes the range in the XY direction and the depth in the Z direction, and obtain the velocity model within this three-dimensional range from the high-precision velocity model VEL in Step S1; Step S4, for the single-shot data and velocity model in Step S3, use the seismic wave equation to perform wavefield continuation on the source wavefield and the single-shot data in the velocity model, and apply the reverse time imaging condition and perform cumulative operation at each imaging point position at each time step of the wavefield continuation, and finally complete the single-shot reverse time migration processing to obtain the single-shot reverse time migration data volume; Step S5, according to the imaging output grid information in Step S2, obtain the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse time migration in Step S4; Step S6, perform block processing on the imaging output grid range corresponding to Step S2, and at the same time, use the position of the header information in Step S5 to accumulate each imaging trace in the single-shot reverse time migration data volume in Step S4 to the corresponding imaging output grid after block processing, and complete the production of the OVT domain imaging gather of the entire work area.

2. The method for making OVT domain common image point gathers of reverse time migration massive data according to claim 1, characterized in that, in the Step S1, the fidelity preprocessing includes static correction, denoising, energy compensation, deconvolution seismic processing steps and anti-spherical amplitude compensation processing, and at the same time perform regularization processing on spatially unevenly distributed data; The gather is obtained by sorting the common midpoint CMP gather data after preprocessing according to shot-trace or shot-offset distance, etc.; The depth domain velocity model is obtained by well-controlled and horizon-controlled structural constraint modeling or grid tomography inversion or full waveform inversion method, and it is required that the velocity model can reflect the horizontal and vertical detail changes of the geological structure.

3. The method for making OVT domain common image point gathers of reverse time migration massive data according to claim 1, characterized in that, the grid information of the OVT domain imaging gather output of the seismic work area to be processed in the Step S2 specifically includes LINE number, CDP number range, imaging bin bin, depth step dz, migration depth Z, starting direction of azimuth angle, number of azimuth angles azimuthnum, starting offset offsetstart, offset interval doffset, and number of offset groups offsetnum; The imaging bin bin is in the form of binx×biny, and the calculation of the degree of each azimuth angle specifically includes: Calculated according to the opposite azimuth, dazimuth = 180 / azimuthnum. Calculated according to the single azimuth: dazimuth = 360 / azimuthnum.

4. The method for producing an OVT domain common image point gather of reverse time migration massive data as claimed in claim 1, characterized in that obtaining the header information of each seismic trace of the single-shot reverse time migration data volume according to the imaging output header information in step S4, specifically including the X and Y coordinates of the shot point, the X and Y coordinates of the imaging point position, the LINE number and CDP number corresponding to the imaging point position, and at the same time, according to the azimuth starting direction and each azimuth angle calculation formula in step S2, obtaining and rounding the azimuth from the shot point to the imaging point position, and according to the starting offset and offset interval in step S2, obtaining and rounding the offset from the shot point to the imaging point position.

5. The method for producing an OVT domain common image point gather of reverse time migration massive data as claimed in claim 1, characterized in that in step S3, the offset aperture aperture is more than 1 times the buried depth of the target layer; the number of imaging bins binxnum occupied by the length of the stereoscopic imaging space in the x direction = (int)[aperture / binx] + 1, the number of imaging bins binynum occupied by the length in the y direction = (int)[aperture / biny] + 1, and the number of imaging steps nZ occupied by the depth in the z direction = (int)[Z / dz] + 1, where (int)[·] represents the rounding operation.

6. The method for producing an OVT domain common image point gather of reverse time migration massive data as claimed in claim 1, characterized in that in step S4, the reverse time imaging condition includes the cross-correlation reverse time imaging condition, the normalized reverse time imaging condition or the reverse time imaging condition based on traveling wave separation.

7. The method for producing an OVT domain common image point gather of reverse time migration massive data as claimed in claim 1, characterized in that in step S4, the seismic wave equation includes the acoustic wave equation or the elastic wave equation; the velocity model is an isotropic model or an anisotropic model.

8. The method for producing an OVT domain common image point gather of reverse time migration massive data as claimed in claim 1, characterized in that step S6 specifically includes: blocking in advance according to the LINE number range LINEnum or CDP number range CDPnum of the offset gather. Specifically, when extracting, the extraction of the reverse time migration gather body is completed serially block by block or by using multiple computing nodes synchronously, and finally the production of the OVT domain common image point gather of the whole work area reverse time migration is completed; for each block of the reverse time migration gather body within the preset range, the specific extraction steps are as follows: Step S61: Allocate a storage space in the memory of the computer node or generate a storage file on the disk. The size of this storage space is SIZE = dLINEnum × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes, and zero-fill the disk space. If the storage space is smaller than the memory of the computing node, use the above two methods to allocate disk space. Otherwise, perform block processing to reduce the size of dLINEnum or dCDPnum when making a single-block OVT imaging gather, or generate multiple storage space files on the disk. Step S62: For any shot's reverse time migration data volume, obtain the range information of the LINE number and CDP number of the imaging points in the shot migration data volume. If the range of the LINE number and CDP number of the imaging points overlaps with the range of the block LINE number and CDP number in Step S61, then perform the common imaging point gather extraction work in Step S63. Otherwise, do not extract this shot's imaging data volume. Step S63: For the reverse time migration data volume of a shot selected in Step S62, extract any imaging seismic trace. First, determine whether this seismic trace overlaps with the range of the block LINE number and CDP number in Step S61. If this trace is within this range, then accumulate it to the corresponding position in the storage space in Step S61 according to the LINE number, CDP number, azimuth, offset, and depth information in the trace header information of this seismic trace. If this seismic trace is not within this range, do nothing. Step S64: Complete the extraction process of the OVT gathers of all imaging seismic traces in all shot migration data volumes according to Steps S62 and S63.

9. The method for making a common imaging point gather in the reverse time migration OVT domain as claimed in claim 8, characterized in that, in Step S61, the block processing divides the data range along the LINE number or CDP number direction into Num parts. After block processing, the storage space required for a single-block OVT imaging gather becomes SIZE1 = (int)[dLINEnum / Num] × dCDPnum × nZ × azimuthnum × offsetnum × sizeof(float) bytes or dLINEnum × (int)[dCDPnum / Num] × nZ × azimuthnum × offsetnum × sizeof(float), so that the storage space required for each block is smaller than the memory of the computing node.

10. An apparatus for making a common imaging point gather in the reverse time migration massive data OVT domain, characterized in that, it includes: A first acquisition module for acquiring the shot gather data Gather and the high-precision velocity model VEL in the depth domain after fidelity preprocessing of the seismic work area to be processed; A preset module for obtaining the total number of shots shotnum of the shot gather data Gather from the acquisition module and presetting the grid information for outputting the imaging gather of the seismic work area to be processed; A building module is used to construct a three-dimensional imaging space corresponding to single-shot reverse-time migration centered on the shot point position for any gather data, according to the migration aperture, imaging bin, migration depth Z, and migration step dz. The three-dimensional imaging space includes the range in the XY direction and the depth in the Z direction, and a velocity model within this three-dimensional range is obtained from the high-precision velocity model VEL in the acquisition module. A processing module performs wavefield continuation of the source wavefield and the single-shot data in the velocity model using the seismic wave equation for the single-shot data and the velocity model, and applies the reverse-time imaging condition and performs cumulative operations at each imaging point position at each time step of the wavefield continuation, finally completing the single-shot reverse-time migration processing to obtain a single-shot reverse-time migration data volume. A second acquisition module obtains the header information of each imaging seismic trace in the three-dimensional imaging space corresponding to the single-shot reverse-time migration according to the imaging output grid information. A block cumulative module performs block processing on the imaging output grid range in the above preset module, and at the same time, using the position of the header information in the second acquisition module, accumulates each imaging trace in the single-shot reverse-time migration data volume to the corresponding imaging output grid after block processing, completing the production of the OVT domain imaging gather for the entire work area.

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