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CN-121995453-A - Reverse time migration imaging method, device and medium based on lossless compression

CN121995453ACN 121995453 ACN121995453 ACN 121995453ACN-121995453-A

Abstract

The invention provides a reverse time migration imaging method, device and medium based on lossless compression, and belongs to the field of seismic exploration data processing. The method comprises the steps of determining a checkpoint configuration strategy, generating a checkpoint list, enabling a shot wave field to be forward-delayed to obtain a checkpoint wave field, compressing and storing the obtained checkpoint wave field, receiving the reverse continuation of the checkpoint wave field, reaching a corresponding checkpoint and reading the shot wave field of the checkpoint, decompressing the shot wave field of the read checkpoint, calculating to obtain two time-sliced shot wave fields of the checkpoint, and calculating to obtain a reverse time migration imaging field. The invention reduces the storage requirement of the hard disk and improves the IO bandwidth at the same time, thereby improving the calculation efficiency of the integral reverse time offset.

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 lossless compression-based reverse time migration imaging method, comprising: Step 1, determining a checkpoint configuration strategy and generating a checkpoint list; Step 2, forward delaying the shot wave field to obtain a check point wave field; Step 3, compressing and storing the acquired check point wave field; step 4, 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 5, decompressing the shot wave field of the read check point, and calculating to obtain two time-sliced shot wave fields of the check point; and 6, calculating to obtain an inverse time offset imaging field.
  2. 2. The method of claim 1, wherein step 1, determining a checkpoint configuration policy, generating a checkpoint list, comprises: and determining the total duration, sampling interval, aperture size and grid size of finite difference calculation according to 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, the shot wavefield is forward-delayed, and the checkpoint wavefield is obtained, comprising: When the reverse time offset is calculated, firstly, starting from the shot position, adopting a finite difference algorithm to forward and outwards extend the wave field along the time axis, and reaching a check point every N steps to obtain the shot wave field of two time slices before and after the check point.
  4. 4. A method according to claim 3, wherein step 3, the acquired checkpoint wavefield is stored in compression, and the specific operations include: Based on the shot wave fields of the front and rear time slices of the check point obtained in the step 2, calculating gradient values of the two shot wave fields, specifically: Assuming that the first shot wave field is denoted as a and the second shot wave field is denoted as b, the gradient value Δa is calculated using the following formula: Δa=a-b; and performing floating point number lossless compression on the shot wave field a and the gradient value delta a by utilizing kanzi algorithm to obtain a compressed shot wave field, and storing the compressed shot wave field into a hard disk.
  5. 5. The method of claim 4, wherein step 4, receiving a point wavefield reverse continuation, arriving at a corresponding checkpoint and reading the checkpoint's shot wavefield, comprises: After completing the finite difference forward continuation of the shot-point wave field, starting the finite difference backward continuation wave field from the receiving point, back-propagating the seismic wave field along the time axis, suspending the receiving point wave field continuation every time a check point determined in step 1 is reached, and reading the shot-point wave field of the check point from the hard disk.
  6. 6. The method of claim 5, wherein step 5, decompressing the shot wavefield of the read checkpoint and calculating the shot wavefield of the two time slices of the checkpoint comprises: Reading the shot wave field of the check point read in the step 4 into a memory, and decompressing by utilizing kanzi algorithm to obtain a shot wave field a and a gradient value delta a of the check point; From the gradient values, the shot wavefield b=a- Δa is found, resulting in two time-sliced shot wavefields of the checkpoint.
  7. 7. The method of claim 6, wherein the calculating of the reverse time offset imaging field in step 6 comprises: Calculating to obtain two time-sliced shot wave fields of the check point by utilizing the step 5, adopting a finite difference algorithm, forward extending in a time domain, and calculating to obtain all shot wave fields between the current check point and the next check point; And respectively cross-correlating all shot wave fields between the current check point and the next check point with wave fields of the receiving points to obtain reverse time migration imaging fields.
  8. 8. A lossless compression-based reverse-time migration imaging apparatus, comprising: the checkpoint list generation module is used for determining a checkpoint configuration strategy and generating a checkpoint list; The forward continuation module is used for forward dragging of the shot wave field to obtain a check point wave field; The compression storage module is used for carrying out compression storage on the acquired check point wave field; The reverse continuation module 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 decompression module is used for decompressing the shot wave field of the read check point and calculating to obtain two time-sliced shot wave fields of the check point; And the calculation module is used for calculating and obtaining the reverse time offset imaging field.
  9. 9. The apparatus of claim 8, wherein the compressed storage module performs the following operations in particular: Based on the acquired shot wave fields of the front and rear time slices of the check point, gradient values of the two shot wave fields are calculated, specifically: Assuming that the first shot wave field is denoted as a and the second shot wave field is denoted as b, the gradient value Δa is calculated using the following formula: Δa=a-b; and performing floating point number lossless compression on the shot wave field a and the gradient value delta a by utilizing kanzi algorithm to obtain a compressed shot wave field, and storing the compressed shot wave field into a hard disk.
  10. 10. A computer-readable storage medium storing at least one program executable by a computer, the at least one program, when executed by the computer, causing the computer to perform the steps in the lossless compression-based reverse-time offset imaging method according to any one of claims 1 to 7.

Description

Reverse time migration imaging method, device and medium based on lossless compression Technical Field The invention belongs to the field of seismic exploration data processing, and particularly relates to a reverse time migration imaging method, device and medium based on lossless compression. 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 the novel wave field reconstruction method and storage strategy greatly reduce the requirements of computer hardware, so that the high-resolution imaging of the three-dimensional seismic data is feasible. Setting a check point at regular intervals in the forward transmission process based on the reconstruction method of the check point and storing two time-sliced wave fields of the check point, and starting from the check point, obtaining the wave field at any moment in the future through FDTD calculation based on the stored two time-sliced wave fields. The two time slice wave fields of the check point need to be stored in a hard disk, IO operation is involved in the actual calculation process, the time consumption of the IO operation is relatively long due to the fact that time slice data are relatively large, and a plurality of check point wave fields need to be stored in one offset calculation, so that a large amount of hard disk storage space is occupied. Therefore, how to optimize the storage size of the check point wave field and accelerate the read-write bandwidth of the wave field is a problem that needs to be solved at present. Disclosure of Invention The invention aims to solve the problems in the prior art and provide a reverse time migration imaging method, device and medium based on lossless compression, which can reduce the storage requirement of a hard disk and improve IO bandwidth at the same time, thereby improving the calculation efficiency of integral reverse time migration. The invention is realized by the following technical scheme: in a first aspect of the present invention, there is provided a reverse time migration imaging method based on lossless compression, comprising: Step 1, determining a checkpoint configuration strategy and generating a checkpoint list; Step 2, forward delaying the shot wave field to obtain a check point wave field; Step 3, compressing and storing the acquired check point wave field; step 4, 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 5, decompressing the shot wave field of the read check point, and calculating to obtain two time-sliced shot wave fields of the check point; and 6, calculating to obtain an inverse time offset imaging field. The invention further improves that: Step 1, determining a checkpoint configuration strategy, generating a checkpoint list, wherein the specific operations comprise: and determining the total duration, sampling interval, aperture size and grid size of finite difference calculation according to 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. The invention further improves that: step 2, forward delaying the shot wave field to obtain a check point wave field, wherein the specific operation comprises the following steps: When the reverse time offset is calculated, firstly, starting from the shot position, adopting a finite difference algorithm to forward and outwards extend the wave field along the time axis, and reaching a check point every N steps to obtain the shot wave field of two time slices before and after the check point. Further improvements of the invention are described in: step 3, compressing and storing the acquired check point wave field, wherein the specific operation comprises the following steps: Based on the shot wave fields of the front and rear time slices of the check point obtained in the step 2, calculating gradient values of the two shot wave fields, specifically: Assuming that the first sho