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CN-121995452-A - Reverse time migration imaging method, device and medium

CN121995452ACN 121995452 ACN121995452 ACN 121995452ACN-121995452-A

Abstract

The invention provides a reverse time migration imaging method, device and medium, and belongs to the migration imaging field. The method comprises the steps of 1, determining a checkpoint configuration strategy, generating a checkpoint list, 2, forward extending a shot-point wave field to obtain a checkpoint wave field, 3, receiving the reverse extension of the shot-point wave field, reaching a corresponding checkpoint and reading the shot-point wave field of the checkpoint, 4, forward extending the shot-point wave field by using the shot-point wave fields of the two time slices before and after the checkpoint, obtaining the shot-point wave field of one checkpoint, compressing and storing the shot-point wave field in a memory space, and 5, calculating to obtain a reverse time migration imaging field. According to the invention, a kanzi lossless compression strategy is adopted, and the storage efficiency is remarkably improved on the premise of not sacrificing the data integrity by specially aiming at the time slice wave field among check points.

Inventors

  • ZHANG YUANPENG
  • MENG XIANGBIN
  • LIU TONG

Assignees

  • 中国石油化工股份有限公司
  • 中石化石油物探技术研究院有限公司

Dates

Publication Date
20260508
Application Date
20241106

Claims (10)

  1. 1. A reverse time offset imaging method, comprising: Step 1, determining a checkpoint configuration strategy and generating a checkpoint list; Step 2, forward continuation of the shot wave field to obtain a check point wave field; step 3, receiving the reverse continuation of the point wave field, reaching a corresponding check point and reading the gun point wave field of the check point; Step 4, forward continuation is carried out by using the shot wave fields of the two time slices before and after the read check point, the shot wave field of one check point is obtained, and the shot wave field is compressed and stored in a memory space; and 5, calculating to obtain an inverse time offset imaging field.
  2. 2. The method of claim 1, wherein step 1, determining a checkpoint configuration strategy, generating a list of checkpoints, comprises: And determining the total duration, sampling interval, aperture size, grid size and the like of the finite difference calculation according to the reverse time offset calculation, and determining a check point configuration strategy by combining the available memory size, namely setting a check point every N steps to generate a check point list.
  3. 3. The method of claim 1, wherein step 2, shot wavefield forward continuation, obtaining a checkpoint wavefield, comprises: When the reverse time migration is calculated, firstly, starting from the shot position, adopting a finite difference algorithm to forward and outwards extend the wave field along a time axis, reaching a check point every N steps, obtaining the shot wave field of two time slices before and after the check point, and storing the shot wave field into a hard disk; repeating the above operation until the shot wave fields of all checkpoints in the checkpoint list generated in the step 1 are acquired, and storing the shot wave fields to a hard disk.
  4. 4. A method according to claim 3, characterized in that step 3, receiving a point wave field reverse continuation, arriving at the corresponding checkpoint and reading the shot point wave field of the checkpoint, comprises the specific operations of: And (2) reversely extending the wave field by adopting a finite difference algorithm from the receiving point, reversely propagating the seismic wave field along a time axis, suspending the wave field extension of the receiving point every time when one of the checkpoints determined in the step (1) is reached, and reading the gun point wave fields of two time slices before and after the checkpoint from a hard disk.
  5. 5. The method of claim 4, wherein step 4, forward continuation is performed by using the shot wavefield of the two time slices before and after the read checkpoint, the shot wavefield of one checkpoint is obtained, and the shot wavefield of one checkpoint is compressed and stored in the memory space, and the specific operations include: Starting from the current check point time, utilizing the shot wave fields of the two time slices before and after the read check point, adopting a finite difference algorithm to forward extend the wave fields outwards along a time axis, reaching one check point every N steps, obtaining the shot wave field at each moment of the check point, carrying out kanzi lossless compression on the shot wave field at each moment, and storing the compressed shot wave field in a corresponding memory space.
  6. 6. The method of claim 5, wherein the calculating of the reverse time offset imaging field in step 5 comprises: And (2) reversely extending the wave field by adopting a finite difference algorithm from the receiving point, reversely propagating the seismic wave field along a time axis, suspending the wave field extension of the receiving point every time when reaching one check point determined in the step (1), acquiring the shot wave field at the corresponding moment from a memory, decompressing the acquired shot wave field at the corresponding moment by adopting a kanzi algorithm, and carrying out cross-correlation on the decompressed wave field and the wave field of the receiving point to obtain a reverse time migration imaging field.
  7. 7. A reverse time offset imaging apparatus, comprising: the list generation unit is used for determining a check point configuration strategy and generating a check point list; the forward continuation unit is used for forward continuation of the shot wave field to obtain a check point wave field; The reverse continuation unit is used for receiving the point wave field reverse continuation, reaching a corresponding check point and reading the gun point wave field of the check point; the compressed storage unit is used for forward continuation by utilizing the shot wave fields of the two time slices before and after the read check point, acquiring the shot wave field of one check point and compressing and storing the shot wave field into a memory space; and the calculation unit is used for calculating and obtaining the reverse time offset imaging field.
  8. 8. The apparatus according to claim 7, wherein the reverse continuation unit is configured to receive a point wavefield reverse continuation, arrive at a corresponding checkpoint and read a shot wavefield at the checkpoint, and specifically perform the following operations: And (3) reversely extending the wave field by adopting a finite difference algorithm from the receiving point, reversely propagating the seismic wave field along a time axis, suspending the wave field extension of the receiving point every time when one check point in the check point list is reached, and reading the gun point wave fields of two time slices before and after the check point from the hard disk.
  9. 9. The apparatus of claim 8, wherein the compression storage unit is configured to perform forward continuation using the shot wavefield of the two time slices before and after the read checkpoint, obtain a shot wavefield of a checkpoint, and compress and store the shot wavefield in the memory space, and specifically perform the following operations: Starting from the current check point time, utilizing the shot wave fields of the two time slices before and after the read check point, adopting a finite difference algorithm to forward extend the wave fields outwards along a time axis, reaching one check point every N steps, obtaining the shot wave field at each moment of the check point, carrying out kanzi lossless compression on the shot wave field at each moment, and storing the compressed shot wave field in a corresponding memory space.
  10. 10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores at least one program executable by a computer, which when executed by the computer, causes the computer to perform the steps in the reverse time offset imaging method according to any one of claims 1-6.

Description

Reverse time migration imaging method, device and medium Technical Field The invention belongs to the field of offset imaging, and particularly relates to a reverse time offset imaging method, a reverse time offset imaging device and a reverse time offset imaging medium. Background The prestack reverse time migration is a migration imaging method based on a double-pass wave, and the position of a reflection interface is obtained by utilizing the cross-correlation of a forward wave field and an inverse wave field. The reverse time migration can be performed by utilizing complex wave field information such as a rotary wave, a rhombic wave and the like, and compared with other migration methods, the method has the advantages of high precision, no approximate treatment, no limitation of inclination angles and severe change of speeds, and therefore has better imaging effect. However, the reverse time migration has the problems of low calculation efficiency, large storage capacity and the like, and is seriously dependent on an initial velocity model. Along with the deep research and the improvement of computing power in recent years, pre-stack reverse time migration and corresponding full waveform inversion are greatly developed, wherein a new wave field compression storage strategy greatly reduces the requirements of computer hardware, so that high-resolution imaging of three-dimensional seismic data is feasible. Pre-stack reverse time migration geophysical methods based on the cross-correlation principle require reconstruction of the forward wavefield with significant computation and storage. The method mainly comprises the following steps of firstly, storing wave field states of all time sampling points in a memory or a hard disk by a direct preservation method, extracting the stored wave field and carrying out cross-correlation operation with an anti-transmission wave field when imaging is carried out at a certain moment, secondly, storing the surrounding effective boundary layer of each positive transmission wave field by an effective boundary method, carrying out inverse time propagation by utilizing the wave field sampled at the last two times, adding the effective boundary corresponding to each time sampling point into the anti-transmission wave field so as to reconstruct the wave field value of the time point, thirdly, setting a check point at certain time intervals and storing the wave field based on a random boundary condition wave field reconstruction method, repeatedly pushing and reconstructing the wave field at any moment from the check point, only needing to store a small amount of buffer points to effectively reconstruct the wave field, adopting a strategy of calculating and storing, repeatedly pushing and delivering the reconstructed wave field, increasing the number of times along with the increase of time sampling, thus having higher reconstruction rate, and fifthly, reconstructing the wave field based on a random boundary condition wave field reconstruction method, setting a check point at certain time interval, repeatedly pushing and carrying out a sampling algorithm, compressing the sampled wave field, and storing the sampled wave field, and carrying out a conventional algorithm. How to reasonably and effectively combine the check point technology and the wave field lossless compression algorithm, and utilize kanzi lossless compression algorithm to store more wave field time slices in a limited memory space while reducing the wave field recalculation rate, so that the calculation efficiency of reverse time migration is improved, and no better solution exists at present. Disclosure of Invention The invention aims to solve the problems in the prior art and provides a reverse time migration imaging method, a reverse time migration imaging device and a reverse time migration imaging medium, which adopt kanzi lossless compression strategies, are specially aimed at time slice wave fields among check points, and obviously improve the storage efficiency on the premise of not sacrificing the data integrity. The invention is realized by the following technical scheme: in a first aspect of the present invention, there is provided a reverse time offset imaging method comprising: Step 1, determining a checkpoint configuration strategy and generating a checkpoint list; Step 2, forward continuation of the shot wave field to obtain a check point wave field; step 3, receiving the reverse continuation of the point wave field, reaching a corresponding check point and reading the gun point wave field of the check point; Step 4, forward continuation is carried out by using the shot wave fields of the two time slices before and after the read check point, the shot wave field of one check point is obtained, and the shot wave field is compressed and stored in a memory space; and 5, calculating to obtain an inverse time offset imaging field. The invention further improves that: step 1, determining a check point con