Depositional pattern and exploration prospect of the deepwater sediments in Shuangfeng basin

The South China Sea is an important region offshore China for exploration of oil and gas resources and gas hydrate. As the exploration in the shallow waters is moving into a mature stage, the deep water area in the northern part of the South China Sea has gradually become a research hotspot. The study of the Shuangfeng Basin in the deep water basins of the northern South China Sea is obviously lagged behind the others. In this paper, seismic geophysical exploration theories and analogy methods are applied to study the tectono-sedimentary pattern and oil and gas exploration prospects of the basin, based on the 2D multi-channel seismic data and the drilling data of the basin and surrounding areas. A large amount of seismic data were processed and analyzed, and seven reflection horizons traceable recognized in the Shuangfeng basin. Three sets of the seismic sequence are established according to unconformable boundaries. Data shows that after mid-Late Miocene, the basin entered into a bathyal-pelagic depositional environment dominated by deep water sediments, such as undercut channel-fillings, deep water fans and slump deposits. The Cenozoic in the basin is quite thick. Analogy analysis of drilling data and basin modeling suggest that the Oligocene lacustrine-gulf facies in the western and northern depressions have reached the maturity or early maturity stage and had certain hydrocarbon generation capacity. The alluvial fan and fan deltaic deposits developed around the periphery, and the slope fan and the pelvic fan developed in the basin center could be good reservoirs. The bathyal mudstone deposited since Early Miocene are good in quality as regional cap rocks. Excellent source-reservoir-cap systems are available for oil and gas accumulation.