Angle-Weighted Reverse Time Migration With Wavefield Decomposition Based on the Optical Flow Vector

Chuang Xie,Peng Song,Jun Tan,Shaowen Wang,Bo Zhao,Xishuang Li

doi:10.3389/feart.2021.732123

Abstract

Reverse time migration (RTM) is based on the two-way wave equation, so its imaging results obtained by conventional zero-lag cross-correlation imaging conditions contain a lot of low-wavenumber noises. So far, the wavefield decomposition method based on the Poynting vector has been developed to suppress these noises; however, this method also has some problems, such as unstable calculation of the Poynting vector, low accuracy of wavefield decomposition, and poor effect of large-angle migration artifacts suppression. This article introduces the optical flow vector method to RTM to realize high-precision wavefield decomposition for both the source and receiver wavefields and obtains four directions of wavefields: up-, down-, left-, and right-going. Then, the cross-correlation imaging sections of one-way propagation components of forward- and back-propagated wavefields are optimized and stacked. On this basis, the reflection angle of each imaging point is calculated based on the optical flow vector, and an attenuation factor related to the reflection angle is introduced as the weight to generate the optimal stack images. The tests of theoretical model and field marine seismic data illustrate that compared with the conventional RTM with wavefield decomposition based on the Poynting vector, the angle-weighted RTM with wavefield decomposition based on the optical flow vector proposed in this article can achieve wavefield decomposition for both the source and receiver wavefields and calculate the reflection angle of each imaging point more accurately and stably. Moreover, the proposed method adopts angle weighting processing, which can further eliminate large-angle migration artifacts and effectively improve the imaging accuracy of RTM.

Highlights

Reverse time migration (RTM) was proposed in the 1980s (Baysal, 1983; McMechan, 1983; Whitmore, 1983), which is based on a two-way wave equation and applies zero-lag crosscorrelation imaging conditions to realize imaging
In Angle-Weighted RTM Imaging Based on the Optical Flow Vector, we show how to calculate the reflection angle of each imaging point underground based on the optical flow vector method and how to produce the final RTM image using an attenuation factor related to the reflection angles
We can conclude that the method in this article can more effectively eliminate low-wavenumber noises compared to other methods and it is suitable for RTM of real data

Summary

INTRODUCTION

Reverse time migration (RTM) was proposed in the 1980s (Baysal, 1983; McMechan, 1983; Whitmore, 1983), which is based on a two-way wave equation and applies zero-lag crosscorrelation imaging conditions to realize imaging. The optical flow vector method is introduced into RTM to decompose wavefields and calculate the reflection angle of each imaging point underground. The decomposed wavefields of both sources and receivers in the opposite direction are selected for imaging separately to avoid migration artifacts (Chen and He, 2014), using the following: FIGURE 3 | The wavefield direction near the reflection interface calculated: (A) based on the Poynting vector; (B) based on the optical flow vector. There is a risk of losing effective information if only the wavefields in the opposite direction are selected for imaging To address this problem, the reflection angle of each imaging point underground is first calculated based on the optical flow vector. We can conclude that the method in this article can more effectively eliminate low-wavenumber noises compared to other methods and it is suitable for RTM of real data

CONCLUSION

DATA AVAILABILITY STATEMENT