Seismic analysis of the gas hydrate system at Pointer Ridge offshore SW Taiwan.

Han, Wei-Chung, Chen, Liwen, Liu, Char-Shine , Berndt, Christian and Chi, Wu-Cheng (2019) Seismic analysis of the gas hydrate system at Pointer Ridge offshore SW Taiwan. Open Access Marine and Petroleum Geology, 105 . pp. 158-167. DOI 10.1016/j.marpetgeo.2019.04.028.

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Supplementary data:

Abstract

Highlights

• Present original 2D/3D seismic data to reveal the geologic setting of a potential gas hydrate prospect off SW Taiwan.
• Active fluid flow processes are studied by analyzing water column and seismic data.
• A conceptual model is proposed for the gas hydrate system of Pointer Ridge by detailed seismic attribute analysis.
• Potential gas hydrate reservoirs that might be targets for future exploration are identified.

Abstract

Pointer Ridge is a gas hydrate prospect on the South China Sea continental slope offshore SW Taiwan. It is characterized by densely distributed bottom simulating reflections (BSRs), active gas seepage, and potential sandy gas hydrate reservoirs. To understand how the fluids have migrated toward the seafloor, and the role of geological processes in the gas hydrate system, we have collected and analyzed high-quality 2D and 3D reflection seismic data. We first mapped the spatial distribution of the BSRs, and interpreted a major normal fault, Pointer Ridge Fault (PR Fault). The NE-SW trending fault dips to the east, and separates the erosional regime to the west from the depositional regime to the east. One active vent site was identified directly above the PR Fault, while another is located on a topographic high to the west of the fault. On the hanging block of the fault we found at least one major unconformity. The seismic data indicate refilled channels with coarser-grained sediments in the hanging wall of the normal fault. Seismic attribute analysis shows subsurface fluid conduits and potential gas hydrate reservoirs. We propose two types of gas chimneys, which are separated by the fault. Gas plumes derived from hydroacoustic data are mostly from the footwall block of the fault. We infer that fluid flow is more active in the erosional environment compared to the depositional one, and that this is the result of reduced overburden. The methane-bearing fluids migrate upward along the PR Fault and chimneys and form hydrates above the base of the gas hydrate stability zone. Based on seismic interpretation and seismic attribute analysis, we postulate that the channel infill constitutes the most promising hydrate reservoirs in this geological setting. In the surveyed area of Pointer Ridge these channels occur mainly below the gas hydrate stability zone.

Document Type: Article
Keywords: 3D seismic, Gas hydrates, Neural networks, Seismic attributes, Taiwan
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Date Deposited: 06 May 2019 06:50
Last Modified: 31 Jan 2022 09:14
URI: https://oceanrep.geomar.de/id/eprint/46575

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