Gas hydrates characterization in the southern Hikurangi margin using full waveform inversion

Abstract

Scientific issues with relation to seafloor stability and finding alternative energy sources can be tackled by studying gas hydrates. The southern Hikurangi margin happens to have world-class gas hydrate deposits as evident by the widespread of the distinctive seismic signature of the base of the hydrate layer - bottom simulating reflection (BSR) – on numerous seismic profiles acquired in the region. Hydrates have always been characterized using traditional velocity analysis and ray-based tomography, which provide limited velocity models in accuracy and resolution. However, the full waveform inversion (FWI) provides a powerful alternative to the traditional methods as it uses phase and amplitude information to produce structurally accurate subsurface models. In this study, we applied the elastic FWI along 13 Km long 2D multichannel seismic profile on the southern Hikurangi margin. The workflow included: (1) Redatuming the seismic data to the seafloor, (2) 2D traveltime tomography, and (3) FWI of refracted and reflected energy. We will present the resulting high-resolution velocity model from our processing sequence and estimates of hydrate and free gas saturations.

AAPG Datapages/Search and Discovery Article #90348 © 2019 AAPG Asia Pacific Region Geosciences Technology Workshop, Gas Hydrates – From Potential Geohazard to Carbon-Efficient Fuel?, Auckland, New Zealand, April 15-17, 2019