Applying seismic attribute analysis for gas hydrate distribution and characterization in the Yung-An Ridge area offshore southwestern Taiwan
碩士 === 國立臺灣大學 === 海洋研究所 === 100 === Yung-An Ridge is a structural high located in the accretionary complex of the Luzon subduction-collision system offshore southwestern Taiwan. Bottom simulating reflectors (BSRs) are widespread in the region, and combined geophysical and geochemical investigations...
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| Format: | Others |
| Language: | zh-TW |
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2012
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| Online Access: | http://ndltd.ncl.edu.tw/handle/49169200001571881895 |
| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 100 === Yung-An Ridge is a structural high located in the accretionary complex of the Luzon subduction-collision system offshore southwestern Taiwan. Bottom simulating reflectors (BSRs) are widespread in the region, and combined geophysical and geochemical investigations have revealed that large amount of gas hydrates and free gases are accumulated beneath the ridge and adjacent slope basins on both sides of the Yung-An Ridge where high priority drilling sites for gas hydrate investigation are proposed. It is thus important to have a good understanding of the potential gas hydrate reservoir characters there. This study applies seismic attribute analysis (SAA) technique to analyse a 3D seismic volume data and three large offset multi-channel seismic reflection data in the Yung-An Ridge area. Seismic attribute analyses of the 3D seismic data help us to better constrain the geological features identified in the 3D seismic volume. The reflection strength analyses show that in addition to the high amplitude character of BSRs, we have also observed some very strong reflection signals below BSRs in the slope basins on both sides of the Yung-An Ridge. Instantaneous frequency images show that there are low frequency patches beneath BSRs which may reflect gas-bearing strata. The analyses of instantaneous phase images help to identify faults easily. The SAA results suggest that there is little or no gas hydrate presence beneath the Penghu Canyon, while in the slope basin to the west of the Yung-An Ridge, characters of buried channel deposits are clearly visible. There are widely distributed high amplitude reflections in the slope basin to the east of the Yung-An Ridge suggesting the presence of large amount of free gases. A fault structure has been identified at the eastern edge of the slope basin which terminates the high amplitude reflections. The gas chimney character of the fault feature suggest that this fault forms a good conduit for gas migration.
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