A Method for Calculating the Initial Matrix of l-bfgs Applied to Least Squares Reverse Time Migration

A technology of L-BFGS and least squares, which is applied in the field of seismic exploration migration imaging, can solve problems such as accelerated convergence speed, insufficient geometric diffusion compensation, and unbalanced illumination, and achieves improved imaging accuracy, balanced underground illumination, and accurate correction factors Effect

Active Publication Date: 2021-04-13
OCEAN UNIV OF CHINA
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Problems solved by technology

The model experiment results show that this method can effectively overcome the defects of insufficient geometric diffusion compensation and unbalanced illumination in the acoustic least squares reverse time migration method based on the conventional method, and significantly improve the imaging accuracy of the least squares reverse time migration. Accelerated the convergence speed, thus laying a good foundation for subsequent seismic data interpretation work

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  • A Method for Calculating the Initial Matrix of l-bfgs Applied to Least Squares Reverse Time Migration
  • A Method for Calculating the Initial Matrix of l-bfgs Applied to Least Squares Reverse Time Migration
  • A Method for Calculating the Initial Matrix of l-bfgs Applied to Least Squares Reverse Time Migration

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Embodiment 1

[0039] The present invention adopts the L-BFGS algorithm of optimizing the initial matrix to realize the least squares reverse time migration, and the specific process is as follows figure 2 shown. The present invention adopts the Marmousi model to describe the specific implementation. The Marmousi model is one of the commonly used standard models in the field of seismic exploration, and it is often used to test the feasibility and accuracy of algorithms under complex media conditions. In order to improve the calculation efficiency, under the premise of ensuring the complexity of the model, the original Marmousi model is thinned out. The Marmousi true velocity model after thinning is as follows image 3 As shown, Gaussian smoothing can be performed on it to obtain the thinned Marmousi background velocity model (such as Figure 4 shown), the theoretical reflection coefficient model can be obtained from the real velocity model and the background velocity model (the Marmousi ...

specific Embodiment approach

[0041] (1) Based on the thinned-out Marmousi velocity model, the seismic data collection is carried out in a full-array observation mode. There are 116 shots in total, 576 traces are received for each shot, the shot interval is 40m, and the trace interval is 8m. The shot points and receiver points are at Surface, with a depth of 0m. The least squares reverse time migration imaging is performed based on the velocity model and the acquired seismic data.

[0042] (2) In the kth iterative calculation of the least squares reverse time migration, k>=1, based on the background velocity model v obtained after velocity model smoothing 0 , taking the source wavelet w as the disturbance, according to formula (1), we can get the timing wave field P 0 .

[0043]

[0044] In formula (1), v 0 is the background velocity model, t is time, x and z are space coordinates respectively, P 0 is the simulated positive wave field, w is the source wavelet;

[0045] (3) Based on the positive wav...

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Abstract

The invention relates to a method for obtaining an L-BFGS initial matrix applied to least squares reverse time migration, which belongs to the field of seismic exploration migration imaging, and the method is in each iteration process of least squares reverse time migration , firstly based on the background velocity model and reflection coefficient model, taking the source wavelet of the shot point as the disturbance, using the second-order scalar acoustic wave equation finite difference linearization forward modeling technology to obtain the time wave field and seismic records, and based on the time wave field calculation The one-way lighting compensation factor of the shot point is obtained, and the reverse time extension is carried out with the seismic record as the disturbance to obtain the reverse time wave field, and the one-way lighting compensation factor of the receiver point is obtained, and finally the shot-detection two-way lighting compensation factor is obtained. On this basis, the compensation factor is introduced into the L-BFGS algorithm as the initial approximate matrix of the inverse Hessian matrix, and a method for calculating the initial matrix of L-BFGS applied to the least squares reverse time migration is developed. This method can effectively improve the imaging precision of least squares reverse time migration and accelerate the convergence speed.

Description

technical field [0001] The invention belongs to the field of seismic exploration migration imaging, and in particular relates to a method for obtaining an L-BFGS initial matrix applied to least square reverse time migration. Background technique [0002] Seismic exploration is currently the most effective geophysical exploration method for proving underground geological structures and finding field oil and gas reservoirs. It mainly includes the following three links: field seismic data acquisition, seismic data processing, and seismic data interpretation. Seismic data processing is an important link connecting field seismic data acquisition and seismic data interpretation, and the migration imaging of underground structures is the core content of seismic data processing. Therefore, high-precision migration imaging technology has always been an important part of seismic exploration. research hotspots in the field. Compared with conventional reverse time migration, the least ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V1/28G01V1/34
CPCG01V1/282G01V1/345G01V2210/52G01V2210/74
Inventor 解闯宋鹏谭军李金山夏冬明姜秀萍赵波张超张锐埼张洪洋王绍文毛士博
Owner OCEAN UNIV OF CHINA
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