TYPES OF SEA-BOTTOM CHANNELS AND RELATED GASHYDRATE ACCULULATIONS IN THE SHENHU AREA, SOUTH CHINA SEA (SCS)

The drilling data collected from the Shenhu area in the years from 2007 to 2015 reveals that the area is rich in gas hydrate, which is greatly heterogenous in spatial distribution. There are many channels of different kinds developed in the study area. It is significant to study the types of channels and its bearing on gas hydrate accumulation as well as their impacts on future exploration. Through seismic interpretation and integrated analysis of seismic, logging and coring data, we made a classification of channel types and related hydrate accumulations. According to their shape and genesis, there are four kinds of channels: the "V" shaped channel, migrating "V" shaped channel, "U" shaped channel and saucer shaped channel. The characteristics of gas hydrate accumulation depend upon to some extent the types of channels. The gas hydrate reservoir in the "V" shape or migrating "V" shape channels, which usually have low hydrate abundance, are mostly located in the collapse deposits along the canyon wall. As to the "U" shaped channel, gas hydrates are mainly accumulated in the thalweg and levee deposits. In the Saucer shape channels, however, gas hydrates are mainly deposited in the coarse grained sediments of terminal lobes and overbank fans. The sedimentation rate and flow erosion rate are the main factors to the gas hydrate accumulation in variable shape d channels.