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Gas Hydrate Related Fluid Flow Study Offshore Southwestern Taiwan

Abstract

Fluid migration pattern is important for understanding hydrocarbon exploration. However, these patterns are difficult to measure on the seafloor. Using phase properties of the gas hydrates, we studied the fluid flow patterns offshore southwestern Taiwan from bottom-simulating-reflectors (BSR), which is interpreted as the bottom of the gas hydrate stability zone. It provides us an opportunity to study possible fluid flow patterns at several hundred meters sub-bottom depths of the marine sediments. 3D seismic reflection data provide detailed information on the physical properties of the crust, which can be used for hydrocarbon exploration. Recently, scientists from Taiwan and Germany are collaborating on a project to use P-Cable seismic system to study gas hydrates offshore southwest Taiwan. In this study, I used 2 cubes with a wide-spread BSR covering the active and passive margins in Formosa and Four-Way Closure Ridges, respectively. We derived static-state thermal conduction models from in-situ thermal measurements on seafloor and bathymetry, then we studied fluid migration patterns from the discrepancies of the BSR-based and model-based temperature fields. We found the temperature discrepancies can be correlated with the geological processes or fluid migrations. Through 3D seismic attribute analysis, we interpret the space evolution of a gas chimney structure in the passive margin site and their correlation to the occurrences of the sediment waves. In active margin, the different flanks of the anticline ridge might have different geological process to trigger the fluid migration in the strata. Our preliminary results show that there are different fluid migration patterns above the BSR in the gas hydrate stability zone. Such results are very important in hydrocarbon exploration and will help us to evaluate some proposed sites for future drilling programs.