Abstract:

The northern shelf basins of South China Sea have the favorable conditions for the formation of non-structural reservoirs. In the geological history, frequent sea level fluctuations resulted in both vertical and lateral lithologic variations, leading to the formation of lithologic reservoirs, especially the low-level fans deposited on both the basin floor and slope during the lowstand. Frequent tectonic movements in the geological history resulted in many structural planes and structural unconformities, and so various types of unconformity reservoirs had correspondingly been formed. Exploration practices and research achievements show that the potential areas for non-structural reservoirs in offshore basins are as follows:(1) deep water areas where submarine fans are well developed, such as the central depression in Qiongdongnan basin, and Baiyun sag in Zhujiangkou basin; (2)frontal areas of large paleodeltas, such as Yingdong slope zone in Yinggehai basin and Yacheng 13-1 structural zone in Qiongdongnan basin; (3)sandbodies developed on the shelf, slope and basin floor around the diapiric structures in Yinggehai basin.

Key words: shelf basin, non-structural reservoir, exploration prospect, northern South China Sea