Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea

doi:10.1007/s11001-007-9020-y

CORC > 海洋研究所 > 中国科学院海洋研究所 > 海洋地质与环境重点实验室

	Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea
	Wu, Shiguo ; Wang, Xiujuan ; Wong, How Kin ; Zhang, Guangxue
刊名	MARINE GEOPHYSICAL RESEARCHES
	2007-06-01
卷号	28 期号:2 页码:127-138
关键词	Bottom Simulating Reflectors Gas Hydrates Free Gas Saturation South China Sea
ISSN号	0025-3235
DOI	10.1007/s11001-007-9020-y
文献子类	Article
英文摘要	The passive northern continental margin of the South China Sea is rich in gas hydrates, as inferred from the occurrence of bottom-simulating reflectors (BSR) and from well logging data at Ocean Drilling Program (ODP) drill sites. Nonetheless, BSRs on new 2D multichannel seismic reflection data from the area around the Dongsha Islands (the Dongsha Rise) are not ubiquitous. They are confined to complex diapiric structures and active fault zones located between the Dongsha Rise and the surrounding depressions, implying that gas hydrate occurrence is likewise limited to these areas. Most of the BSRs have low amplitude and are therefore not clearly recognizable. Acoustic impedance provides information on rock properties and has been used to estimate gas hydrate concentration. Gas hydrate-bearing sediments have acoustic impedance that is higher than that of the surrounding sediments devoid of hydrates. Based on well logging data, the relationship between acoustic impedance and porosity can be obtained by a linear regression, and the degree of gas hydrate saturation can be determined using Archie's equation. By applying these methods to multichannel seismic data and well logging data from the northern South China Sea, the gas hydrate concentration is found to be 3-25% of the pore space at ODP Site 1148 depending on sub-surface depth, and is estimated to be less than values of 5% estimated along seismic profile 0101. Our results suggest that saturation of gas hydrate in the northern South China Sea is higher than that estimated from well resistivity log data in the gas hydrate stability zone, but that free gas is scarce beneath this zone. It is probably the scarcity of free gas that is responsible for the low amplitudes of the BSRs.; The passive northern continental margin of the South China Sea is rich in gas hydrates, as inferred from the occurrence of bottom-simulating reflectors (BSR) and from well logging data at Ocean Drilling Program (ODP) drill sites. Nonetheless, BSRs on new 2D multichannel seismic reflection data from the area around the Dongsha Islands (the Dongsha Rise) are not ubiquitous. They are confined to complex diapiric structures and active fault zones located between the Dongsha Rise and the surrounding depressions, implying that gas hydrate occurrence is likewise limited to these areas. Most of the BSRs have low amplitude and are therefore not clearly recognizable. Acoustic impedance provides information on rock properties and has been used to estimate gas hydrate concentration. Gas hydrate-bearing sediments have acoustic impedance that is higher than that of the surrounding sediments devoid of hydrates. Based on well logging data, the relationship between acoustic impedance and porosity can be obtained by a linear regression, and the degree of gas hydrate saturation can be determined using Archie's equation. By applying these methods to multichannel seismic data and well logging data from the northern South China Sea, the gas hydrate concentration is found to be 3-25% of the pore space at ODP Site 1148 depending on sub-surface depth, and is estimated to be less than values of 5% estimated along seismic profile 0101. Our results suggest that saturation of gas hydrate in the northern South China Sea is higher than that estimated from well resistivity log data in the gas hydrate stability zone, but that free gas is scarce beneath this zone. It is probably the scarcity of free gas that is responsible for the low amplitudes of the BSRs.
学科主题	Geochemistry & Geophysics ; Oceanography
URL标识	查看原文
语种	英语
WOS记录号	WOS:000248425000006
公开日期	2010-12-24
内容类型	期刊论文
源URL	[http://ir.qdio.ac.cn/handle/337002/5075]
专题	海洋研究所_海洋地质与环境重点实验室
作者单位	1.Chinese Acad Sci, Inst Oceanol, Qingdao, Peoples R China 2.Chinese Acad Sci, Key Lab Marine Geol & Environm, Qingdao, Peoples R China 3.Univ Hamburg, Inst Biogeochem & Marine Chem, D-20146 Hamburg, Germany 4.Guangzhou Marine Geol Survey MLR, Guangzhou 510760, Peoples R China
推荐引用方式 GB/T 7714	Wu, Shiguo,Wang, Xiujuan,Wong, How Kin,et al. Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea[J]. MARINE GEOPHYSICAL RESEARCHES,2007,28(2):127-138.
APA	Wu, Shiguo,Wang, Xiujuan,Wong, How Kin,&Zhang, Guangxue.(2007).Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea.MARINE GEOPHYSICAL RESEARCHES,28(2),127-138.
MLA	Wu, Shiguo,et al."Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea".MARINE GEOPHYSICAL RESEARCHES 28.2(2007):127-138.