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Least square reverse time migration gradient precondition method based on direct wave field

A technology of least squares and reverse time migration, applied in measurement devices, instruments, scientific instruments, etc., can solve the problems of inaccurate geometric diffusion effect correction factors and suboptimal imaging results, and achieve high-precision imaging, Overcome the effects of inaccurate wavefield energy and accurate correction factors

Active Publication Date: 2019-12-03
OCEAN UNIV OF CHINA
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Problems solved by technology

However, in addition to the required direct wave field energy, the conventional seismic wave energy also contains other wave field energy such as reflected waves and multiple waves, which makes the correction factor of the geometric diffusion effect still not accurate enough, and thus makes the final imaging result not optimal

Method used

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  • Least square reverse time migration gradient precondition method based on direct wave field
  • Least square reverse time migration gradient precondition method based on direct wave field
  • Least square reverse time migration gradient precondition method based on direct wave field

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Embodiment 1

[0036] A least-squares reverse-time migration gradient preconditioning method based on the direct wave field proposed by the present invention, its implementation process is as follows figure 2 shown. The present invention uses the horizontal layered medium model (horizontal layered medium true velocity model such as image 3 shown) to simulate the real underground medium conditions in the field, the horizontal layered medium model has four layers, the velocity of the first layer is 2500m / s, the velocity of the second layer is 3000m / s, the velocity of the third layer is 3500m / s, the fourth layer The layer velocity is 3800m / s, the transverse length of the model is 3000m, and the longitudinal length is 2000m. Gaussian smoothing is performed on the velocity model of the horizontal layered medium to obtain the background model (the background velocity model of the horizontal layered medium is as follows Figure 4 shown), the theoretical reflection coefficient model can be obtai...

specific Embodiment approach

[0038](1) Based on the above-mentioned horizontal layered medium velocity model, the seismic data acquisition is carried out by using the full-array observation method. There are 61 shots in total, and each shot receives 401 traces. The shot interval is 50m, and the trace interval is 5m. 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.

[0039] (2) In the iterative calculation of the least squares reverse time migration (i>=1), input the reflection coefficient model M updated in the last iteration i-1 (Input the given initial velocity model M in the first iteration 0 ), based on the background velocity model v 0 , Reflection coefficient model M i-1 (The given initial velocity model M in the first iteration 0 ), using the finite-difference linearization forward modeling technology of the acoustic wave equation, and taking the source wavelet w as the disturbance, the seismic ...

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Abstract

The invention relates to a least square reverse time migration gradient precondition method based on a direct wave field, belongs to the field of seismic migration imaging. The method comprises the steps that: a seismic record is obtained by adopting the sound wave equation finite difference linearization forward modeling technology based on a background speed model and a reflection coefficient model in each iteration process of least squares reverse time migration, then timing 'approximate direct' wave field energy with shot point seismic source wavelets as disturbance and reverse 'approximate direct' wave field energy with the above seismic record obtained by linearization forward modeling as disturbance are obtained by simulation by using the non-reflection acoustic wave equation finitedifference forward modeling technology, and finally, the timing 'approximate direct' wave field energy and the reverse 'approximate direct' wave field energy are applied to perform precondition processing on the gradient. Model experiment results show that the defect of inaccurate wave field energy in a conventional gradient precondition method based on seismic wave energy can be effectively overcome, the precision of the gradient precondition is improved, so that the imaging effect of least square reverse time migration is remarkably improved.

Description

technical field [0001] The invention belongs to the field of seismic migration imaging, in particular to a gradient preconditioning method of least squares reverse time migration based on direct wave field. Background technique [0002] Accurate subsurface structural migration imaging can provide accurate structural information for subsequent seismic data interpretation, and has always been a research hotspot in the field of seismic exploration. Least squares reverse time migration is a high-precision imaging method. The conventional reverse time migration imaging problem is regarded as an inversion problem under the least squares framework. The inversion method is used to obtain the underground reflection coefficient model, which can Obtain high-precision, high-magnitude, high-resolution imaging results. In recent years, the research and development of least squares reverse time migration technology has received extensive attention from the industry. However, in the conve...

Claims

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Application Information

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