Acoustic response of gas hydrate formation in sediments from South China Sea

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• 作者：Gaowei Hu^a ; ^b ; ^c ; ^{hgw-623@163.com" class="auth_mail} ; Yuguang Ye^b ; ^c ; ^{yeyug@public.qd.sd.cn" class="auth_mail} ; Jian Zhang^b ; ^c ; Changling Liu^b ; ^c ; Qing Li^c
• 关键词：Gas hydrate ; South China Sea (SCS) ; Acoustic response ; Bender element ; Time domain reflectometry (TDR)
• 刊名：Marine and Petroleum Geology
• 出版年：April, 2014
• 年：2014
• 卷：52
• 期：Complete
• 页码：1-8
• 全文大小：2559 K

文摘

Gas hydrate has been recognized as a potential energy resource in South China Sea (SCS). Understanding the acoustic response of gas hydrate formation in the SCS sediments is essential for regional gas hydrate investigation and quantification. The sediments were obtained from gravity core sampling at E 115掳12.52363鈥?N 19掳48.40299鈥? Gas hydrate was formed within a 鈥済as聽+聽water-saturated SCS sediments鈥?system. Combination of a new bender element technique and coated time domain reflectometry (TDR) was carried out to study the acoustic response of hydrate occurrence in SCS sediments. The results show the acoustic signal becomes weak when hydrate saturation (S_h) is lower than 14%. The acoustic velocities (Vp, Vs) of the sediments increase with S_h during hydrate formation, and Vs increases relatively faster when S_h is higher than 14%. These results indicate that tiny hydrate particles may firstly float in the pore fluid, which causes a significant acoustic attenuation, but has little influence on shear modulus. As time lapses and S_h approaches 14%, numerous particles coalesce together and contact with sediment particles. As a result, Vs has a sharp increase when hydrate saturation exceeds 14%. Several velocity models were validated with the experimental data, which suggests a combination of the BGTL (Biot-Gassmann Theory modified by Lee) model and the Weighted Equation is suitable to estimate S_h in SCS.