AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
The Northern South China Sea Deepwater Basin: Characteristics of Hydrocarbon Accumulation and Exploration Potential
(1) CNOOC, Beijing, China.
(2) China University of Petroleum, Beijing, China.
The northern South China Sea (SCS) deepwater basins, with area larger than 120,000 square kilometers, are composed of basins and depressions deeper than 500 meters.
The northern SCS deepwater basins experienced initial rifting and thermal depression, then were overprinted by neotectonics. Three types of source rocks were deposited in the SCS deepwater basins: (1) early rifting-controlled lacustrine dominated source rock, (2) late rifting-controlled continent-marine transitional coal-bearing source rock, and (3) thermal depression-controlled marine source rock. The Oligocene coal-bearing source rock provides the primary hydrocarbon contribution in the area. The Miocene marine source rock was first-time identified as a significant HC contributor, and has extensive distribution in the Pearl River Mouth Basin (PRMB) and QiongDongNan Basin (QDNB )deepwater basins. Enhanced by high heat flow in northern SCS deepwater and ultra-deepwater basins, the marine source rock could potentially generate significant HC resource, which extends the exploration potential in the area.
In Baiyun Depression in the PRMB, the continental marginal deltaic depositional system developed distributaries channels, river mouth sand bars, slope canyons, slope fans and turbiditic lobes. In the deltaic system, giant reservoirs could potentially be developed by the well-sorted rocks that could have good physical properties. A recently discovered Red River deltaic ocean bottom fan system is extensively distributed in the PRMB, and its distribution are thousands of square kilometers. There are also carbonate reefs developed in the QDNB deepwater basin. Gas zones have been encountered at the edge of the deltaic system during previous drilling activities.
In summary, there are series of deepwater and ultra-deepwater basins developed in the northern SCS, with multiple and extensively distributed source rocks. High heat flow and pressure in the deepwater basins enhance generating hydrocarbon. The depositional conditions in these basins provide the potential to develop high quality reservoir rocks. There are also many mid to large size structural and stratigraphic traps including the carbonate reefs. The deepwater and ultra-deepwater basins in the northern SCS have huge exploration potential that are gradually proving by deepwater drilling activities.