Amplitude-Preserved Wave Equation: An Example to Image the Gas Hydrate System

Jiachun You,Iván Vargas-Cordero,Sha Song,Umberta Tinivella,Michela Giustiniani

doi:10.3390/en14123700

Abstract

Natural gas hydrate is an important energy source. Therefore, it is extremely important to provide a clear imaging profile to determine its distribution for energy exploration. In view of the problems existing in conventional migration methods, e.g., the limited imaging angles, we proposed to utilize an amplitude-preserved one-way wave equation migration based on matrix decomposition to deal with primary and multiple waves. With respect to seismic data gathered at the Chilean continental margin, a conventional processing flow to obtain seismic records with a high signal-to-noise ratio is introduced. Then, the imaging results of the conventional and amplitude-preserved one-way wave equation migration methods based on primary waves are compared, to demonstrate the necessity of implementing amplitude-preserving migration. Moreover, a simple two-layer model is imaged by using primary and multiple waves, which proves the superiority of multiple waves in imaging compared with primary waves and lays the foundation for further application. For the real data, the imaging sections of primary and multiple waves are compared. We found that multiple waves are able to provide a wider imaging illumination while primary waves fail to illuminate, especially for the imaging of bottom simulating reflections (BSRs), because multiple waves have a longer travelling path and carry more information. By imaging the actual seismic data, we can make a conclusion that the imaging result generated by multiple waves can be viewed as a supplementary for the imaging result of primary waves, and it has some guiding values for further hydrate and in general shallow gas exploration.

Highlights

Gas hydrates (GHs) are ice-like crystalline solids composed of cages of water molecules that surround low-molecular-weight gas molecules, which form under low-temperature and high-pressure conditions, and when adequate gas concentration is available [1]
One-way wave equation migration is the focus of our concern because of its high efficiency
By dealing with the actual marine seismic data, amplitude-preserved one-way wave equation migration is capable of producing more accurate imaging results than the results obtained by using the conventional one-way wave equation

Summary

Introduction

Gas hydrates (GHs) are ice-like crystalline solids composed of cages of water molecules that surround low-molecular-weight gas molecules, which form under low-temperature and high-pressure conditions, and when adequate gas concentration is available [1]. [30] proposed to apply the matrix decomposition theory to calculate one-way true amplitude equations, which achieves a better imaging result compared with the one-way true amplitude equation migration method based on Taylor expansion. The theory, proposed by [33], uses the multiple waves as the receiver wavefield, while the primary waves as the source wavefield to perform seismic imaging based on the conventional migration methods. A layered velocity model is used to verify the advantage of multiples in imaging; secondly, a test is carried out to compare the imaging performance of the conventional and preserved-amplitude one-way wave equation migration methods; a carefully comparison is made between imaging results of primary and multiple waves

Data and Methods

Seismic Data Acquisition and Processing

Depth Migration Using Primary and Multiple Waves

Primary Wave Imaging

Conclusions