Estimation of Methane Flux and Identification of Fluid Source in Gas Hydrate Potential Area Offshore Southwestern Taiwan
Date Issued
2012
Date
2012
Author(s)
Hu, Ching-Yi
Abstract
Previous studies reported that the widely distribution of BSRs (Bottom Simulating Reflection) and the geophysical modeling indicating a large amount of methane hydrates in offshore Southwestern Taiwan. In this study, we estimate the methane fluxes along passive and active margins from the measured data of the cored sediments collected during Marion Dufresne 178 cruise in 2010. Total changes of the dissolved inorganic carbon (DIC) fluxes (ΔDIC-Prod ) can be used to estimate the methane flux quantitatively, and we confirm that the sulfate depletion is mainly controlled by the anaerobic oxidation of methane (AOM) reaction and/or the sedimentary organic matter. Although BSRs are widely distributed both in the active margin and in the passive margin, the methane fluxes in active margin are greater than in passive margin of the coring sites. All the estimated methane fluxes in offshore SW Taiwan are higher than other gas hydrate and upwelling area.
Cl-, I- and Br- concentrations of pore water in cored sediments may be useful to indicate the existence of potential gas hydrates in study area. Compared the data with previous three studied cores in this area, we found that there is no evidence to indicate gas hydrate dissociation, formation or lateral fluid flow in studied area. The results shown in the I- vs. Br- diagrams, which can reflect these dissolved species in pore water, indicate the variations are mainly controlled by marine organic matter degradation. Since dissolved species in pore water can’t indicate the existence of gas hydrate in the studied samples (< 30 m), the high methane flux may result from deep gas hydrate reservoirs and/or free gas zones.
Subjects
gas hydrate
methane
halogen
cation
SMTZ
SDGs
Type
thesis
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