AUTHOR=Chen Yuanzhong , Zong Jingjing , Liu Chengxin , Cao Zhonglin , Duan Pengfei , Li Jianguo , Hu Guangmin 

TITLE=Offshore subsurface characterization enabled by fiber-optic distributed acoustic sensing (DAS): An East China Sea 3D VSP survey example

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1033456

DOI=10.3389/feart.2023.1033456

ISSN=2296-6463

ABSTRACT=Recent advances in Distributed Acoustic Sensing (DAS) technology have encouraged more intense measurements of the subsurface and environment events, providing better chances for geohazards monitoring and subsurface characterization as well as development. This study discusses the subsurface evaluation enabled by the DAS-Vertical Seismic Profiling (DAS-VSP) system acquired in the East China sea, China. Taking advantage of a continuous recording of the vibrational wavefields through the strain deformation of the fiber deployed along the borehole, DAS-VSP is considered an emerging and promising alternative borehole acquisition method. It provides a wider-spectrum range of recordings in a cheaper, denser, and more continuous tense compared with conventional geophones. We explore the 3D DAS-VSP signal processing and imaging strategy. In particular, based on a set of 3D DAS-VSP data of exceptional quality, this study reviews the common processing challenges and practical solutions for de-noise, de-ghosting, de-multiple, and wavefield separation that arouse from the DAS acquisition mechanism in the offshore VSP scenario. On the other hand, the high-quality down-going multiples are separated and imaged using the pre-stack Gaussian beam depth migration in addition to the primary reflection wavefield, providing a significant amount of additional illumination to support the subsurface evaluation. The current results validate the efficiency of the DAS-VSP survey and encourage better geological interpretation.