Guangzhou Marine Geologic Survey
Guangzhou Marine Geologic Survey
Liang J.,Guangzhou Marine Geologic Survey |
Zhang Z.,Fugro |
Su P.,Guangzhou Marine Geologic Survey |
Sha Z.,Guangzhou Marine Geologic Survey |
Yang S.,Guangzhou Marine Geologic Survey
Interpretation | Year: 2017
Continuous Bottom-simulating reflection (BSR) is commonly considered to mark the base of gas hydrate stability zone. Below this depth, gas hydrate gives away to free gas or water filling with pore spaces of sediments. We integrated and analyzed seismic data collected in 2008, and LWD (logging while drilling) data and coring results acquired by the Fugro Voyager in 2015 in the Shenhu area on the northern slope of the South China Sea. Based on seismic and well logs correlation, the BSR with typical characteristics of gas hydrates and free gas was identified at 237 m, below the mudline (BML). However, LWD data reveal a 63-m thick hydrate layer from 205 m to 268 m, BML. Increases in resistivity and velocity at 262 m, BML indicate gas hydrate is likely presented below the BSR. The observed pore water freshening with depth and infrared image of core samples are consistent with geophysical interpretation. Seismic and well interpretations reveal continuous, discontinuous, and pluming BSRs in the Shenhu area. The continuous BSR indicates the base of methane gas hydrate stability zone and structure II gas hydrate is likely presented below the BSR. Deep thermogenic fluid locally entrapped within shallow-buried sediments may reinforce gas hydrate accumulations near the discontinuous and pluming BSRs. We conclude that seismic responses of structure II gas hydrate can be distinct from Structure I gas hydrate. Understanding the seismic characterizations of structures I and II will help in evaluation of gas hydrate reservoirs and inferring the presence of deep thermogenic reservoirs. © 2017 Society of Exploration Geophysicists and American Association of Petroleum Geologists.
Zhang G.,Guangzhou Marine Geologic Survey |
Chen F.,Guangzhou Marine Geologic Survey |
Yang S.,Guangzhou Marine Geologic Survey |
Su X.,China University of Geosciences |
And 4 more authors.
Chinese Journal of Oceanology and Limnology | Year: 2012
The large deep-sea area from the southwestern Qiongdongnan Basin to the eastern Dongsha Islands, within the continental margin of northern South China Sea, is a frontier of natural gas hydrate exploration in China. Multiform of deep-sea sedimentations have been occurred since late Miocene, and sediment waves as a potential quality reservoir of natural gas hydrate is an most important style of them. Based on abundant available data of seismic, gravity sampling and drilling core, we analyzed the characteristics of seismic reflection and sedimentation of sediment waves and the occurrence of natural gas hydrate hosted in it, and discussed the control factors on natural gas hydrate accumulation. The former findings revealed the deep sea of the northern South China Sea have superior geological conditions on natural gas hydrate accumulation. Therefore, it will be of great significance in deep-sea natural gas hydrate exploration with the study on the relationship between deep-sea sedimentation and natural gas hydrate accumulation. © 2012 Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg.