Squence Stratigraphic Architecture and Favorable Reservoir Sandbodies of the Hanjiang Formation on the Northern Slope of the Baiyun Sag, Pearl River Mouth Basin

Abstract

Baiyun Sag is the key area of oil and gas exploration in the Pearl River Mouth Basin, South China Sea. Based on the drilling, logging and 3D seismic data, under the guidance of sequence stratigraphy, seismic sedimentology and seismic geomorphology, the succession of middle Hanjiang Formation on the northern slope of Baiyun Sag can be divided into two third-order sequences. Each third-order sequence can be subdivided into low standard systems tract (LST), transgression systems tract (TST), high standard systems tract (HST) and forced regressive systems tract (FSST). The two depositional systems of shelf–edge delta and abyssal fan are recognized within the middle of Hanjiang Formation, and the planar distribution and morphology of sedimentary facies in each depositional system are analyzed within the high-accuracy sequence stratigraphic framework. The shelf-edge delta depositional system develops in the forced regressive systems tract, corresponding to the period of relative sea-level falling, while the abyssal fan depositional system belongs to the low standard systems tract, corresponding to the period of relative sea-level rising. In seismic attributes maps and slices, typical sedimentary architectures in the two depositional systems are recognized and depicted, including distributary channels, longshore sandbar, sheet sand, deepwater channels and lobes. On this basis, we predict the distribution of the favorable reservoir facies belts and the types of traps, which have a great prospect for oil and gas exploration. Besides we observe that the migratory direction of the depocenter of shelf-edge delta has changed from east to west at the 13.8Ma, which probably is influenced by enhanced ocean current caused by the climate change and the tectonic uplifting of Dongsha area.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018