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Baiyun Deep-Water Fans in the Pearl River Mouth Basin, South China Sea: Architectures, Genesis Mechanism and Exploration Direction

Abstract

Baiyun deep-water fan in the Pearl River Mouth basin is the main deep-water hydrocarbon exploration target of China. Years of research and exploration practice prove that, characteristics and scales of deep-water reservoir in the basin differ greatly from that of typical passive continental margin basins, and lead to the different exploration direction. In order to make clear the deposition mechanism of deepwater reservoir, confirm the deepwater exploration direction, through sequence and sedimentary facies analysis, combined with tectonic movements, sea-level changes and responds on major geological events surrounding. The paper studied on the distribution characteristics and genesis mechanism of Baiyun deep-water fan, and pointed out the exploration direction based on 2D/3D seismic, drilling and core data. The results show that: 1)Architectures of the deep-water fans include channel, channel-levee complex and lobes. Among 7 3rd-order sequences from 23.8Ma to 10.5Ma, only SQ23.8, SQ21 and SQ13.8 are linked to deep-water sandbody, where SQ23.8 mainly develops shelf-margin delta, SQ21 develops lobes, channel and bank deposits, and SQ13.8 develops channel, channel levee and lobe deposits. 2)Formation of the deepwater sandbody is the result of multiple factors' reasonable matching:tectonic movements, on the one hand promote the expansion of the Pearl River, enhancing the supply capacity of the provenance, on the other hand control the combined pattern and sedimentary process of the deep-water fan system. Organical coordination of sea-level fluctuation and unconformities control the “valve” to open or close, further making the deepwater sandbody only deposit in SQ23.8, SQ21 and SQ13.8. Slope gradient has certain control effect on the sedimentary system. Since 23.8Ma, the basin can be divided into gentle-slope stage and steep-slope stage bounded by SB13.8:at the gentle-slope stage, the Pearl River depositional system is mainly of shelf margin delta-channel-deepwater fan sedimentary model, such as SQ23.8 and SQ21;at the steep-slope stage, the system is mainly of shelf delta-submarine valley-deepwater fan sedimentary model. 3)Major deepwater target formations are SQ23.8, SQ21.Shelf-margin deltas and deepwater fan are the main targets within SQ23.8, while shelf-margin Deltas, deep-water channels and lobes are the major target of SQ21.Lithologic-structural traps should be the preferred target. Acknowledgments:This study is funded by the National Basic Research Program of China(No.2009CB219407).