James W. Granath

ABSTRACT: Finding the Pearl in the Pearl River Mouth Basin, Offshore China: A Deepwater Turbidite Oil Play?

The Pearl River Mouth Basin (PRB), offshore China, is reexamined in light of advances in understanding deepwater depositional systems; better data analysis and display tools and techniques; recent experience in South Atlantic margin basins and offshore Borneo illustrating correlations between potential field data and controls on sediment distribution systems. The Pearl River Mouth Basin is a passive margin rift system composed of three subbasins. The southernmost of these, the Zhu II subbasin, is significantly extended in a new interpretation that integrates potential fields data with geological literature in a GIS-based visual database. The PRB formed over Mesozoic continental crust and inherited the pre-existing tectonic zones of weakness of that crust (Pigott & Ru, 1994). Paleogene extension that formed the depocenters of the PRB occurred mainly from Late Eocene to Late Oligocene and included a component of dextral shear (Edwards, 1992). The shear may originate from reactivation of NW-SE trending strike slip faults (Xia & Zhou, 1993). These basement trends are well suited to imaging with potential fields data. The strike-slip faults appear to control some edges of subbasins and uplifts, including the Shenhu Uplift boundary with the Zhu II Depression. The shear trend also seems to influence the paleo-Pearl River drainage. The initiation of seafloor spreading is marked by the 30 Ma “breakup” or T7 unconformity, a key boundary separating the more isolated depocenters containing lacustrine source-prone rift fill from the succeeding and widespread paleo-Pearl River deltaics (Chen et al., 1994). The deltaic reservoirs in the Zhu I and Zhu III subbasins have been the target of most PRB exploration. Few wells have tested the edge of the Zhu II subbasin, where a lack of reservoir quality sands has been perceived (Letsch et al., 1994). Recent advances in understanding deepwater depositional systems (i.e., Posamentier, 2000; Dickson & Macurda, 2001) predict turbidite reservoirs well outboard of the deltaic environments explored to date. AAPG Search and Discovery Article #90007©2002 AAPG Annual Meeting, Houston, Texas, March 1-13, 2002