AAPG Bulletin, V. 83 (1999), No. 6 (June 1999), P. 990-1003.

Petroleum Systems of the Zhu III Subbasin, Pearl River Mouth Basin, South China Sea¹

Zhu Weilin,² Li Mingbi,² and Wu Peikang³
 

©Copyright 1999.  The American Association of Petroleum Geologists.  All Rights Reserved
 

¹Manuscript received May 27, 1997; revised manuscript received June 2, 1998; final acceptance October 22, 1998.
²China Offshore Oil Exploration and Development Research Center, Gaobeidian, Hebei, 074000, China.
³East China Sea Oil Corporation, Shanghai, 200030, China.

We would like to thank the China National Offshore Oil Corporation for permission to publish this paper. We also thank Huang Zhengji for carrying out part of the geochemical study. We are grateful for the reviews and comments of L. B. Magoon, Neil Hurley, Kenneth M. Wolgemuth, S. Bachu, and others. 
 

ABSTRACT

The Zhu III subbasin is one of three subbasins in the Pearl River Mouth Basin in the northern shelf of the South China Sea. The Zhu III belongs to a rift basin initiated in the Paleogene, being a part of the rifting lake group of Paleogene age in the Pearl River Mouth Basin. The evolution of the Zhu III subbasin can be divided into three stages: lacustrine facies of the early stage (Paleocene-middle Oligocene), bay facies of the middle stage (late Oligocene), and open shallow marine of the late stage (Neogene), forming, respectively, source, reservoir, and seal rocks. The lacustrine sediments include the Wenchang Formation (oil source rock) and the Enping Formation (gas source rock), which are the source rocks of two petroleum systems in the study area. The Zhu III subbasin experienced three obvious tectonic movements, of which the tenso-shear movement in the late Oligocene and extensional movement at the end of the middle Miocene formed the main oil-bearing structures in the study area. Oil and gas exploration results, synthetic study of geochemical and thermal modeling of the two source rocks, diagenesis and organic inclusions, and basin modeling show that there are two petroleum systems in the Zhu III subbasin: the Wenchang-Zhujiang(.) petroleum system in Wenchang B sag, and the Enping-Zhuhai(.) petroleum system in the Wenchang A sag. In the two petroleum systems, hydrocarbon generation, migration, and accumulation peaks are late Miocene-Holocene.