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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/40449

Title: Velocity structures imaged from long-offset reflection data and four-component OBS data at Jiulong Methane Reef in the northern South China Sea
Authors: Tan K. Wang
Ting-Ren Chen
Jia-Ming Deng
Char-Shine Liu
Song-Chuen Chen
Contributors: 國立臺灣海洋大學:應用地球科學研究所
Keywords: Saturation
Bottom-simulating reflector (BSR)
Continental slope
Gas hydrate
Pre-stack depth migration (PSDM)
Date: 2015-08
Issue Date: 2017-01-19T02:32:18Z
Publisher: Marine and Petroleum Geology
Abstract: Abstract: In this study, P- and S-wave velocity models were built based on two pre-stack depth migration (PSDM) profiles of long-offset reflection data and 25 four-component ocean-bottom seismometers (OBS) data at Jiulong Methane Reef off SW Taiwan in the passive margin of the northern South China Sea (SCS). According to the velocity models, the average P-wave velocity and Vp/Vs ratio of the free gas beneath the bottom-simulating reflector (BSR) are 1.52-1.58km/s and 4.5-5.10, respectively. The depth of the BSR is found at 80-300m below the sea floor and the sedimentary thickness of the hydrate and the free gas are about 50-100m and 70-100m, respectively. P-wave velocity of about 1.75km/s in the hydrate-bearing sediment is southeastward increased to about 1.85km/s above the BSR. Similarly, Vp/Vs ratio of about 3.06 in the hydrate-bearing sediment is increased southeastward to about 3.48 above the BSR. Based on the pseudo-3D map of gas-hydrate saturation estimated from the PSDM and OBS models, the average saturations of hydrate and free gas at Jiulong Methane Reef are about 7% and 0.9-2.4%, respectively. The highest hydrate saturation (11%) is located at 5-20m above the BSR in the SE portion of the Jiulong Methane Reef. On the other hand, the highest gas saturation of about 2% is observed at 10-70m below the BSR in the NW portion of the Jiulong Methane Reef. We suggested that several normal faults dipping southeastward beneath the continental slope provided conduits for gas migrating northwestward at Jiulong Methane Reef. Therefore, the highest gas saturation is observed below the anticline in the NW portion of the Jiulong Methane Reef and the highest hydrate saturation (high P-wave velocity and high Vp/Vs ratio) is identified above the BSR in the SE portion of the Jiulong Methane Reef.
Relation: 68
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/40449
Appears in Collections:[應用地球科學研究所] 期刊論文

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