VINCENT, STEPHEN J.¹, MARK B. ALLEN¹, DAVID I.M. MACDONALD¹, Ll GUO¹, and ZHAO XUN^2
1Cambridge Arctic Shelf Programme, Department of Earth Sciences, Cambridge University, England
²Chinese Academy of Geological Sciences, Beijing, China.

Abstract: Palaeofacies Reconstructions Of The Bohai Basin, Northeast China, During The Paleogene

The Bohai Basin is one of a family of early Cenozoic extensional basins that lie along the eastern margin of Asia, from Russia to Vietnam. It forms China's second most prolific producer of oil. There is active exploration in the basin's offshore sector, with recent discoveries by international and Chinese companies.

Source rocks in the basin are composed mainly of deep lacustrine syn-rift mudstones, particularly in the third member of the Shahejie Formation (Sha3). Reservoirs are a combination of pre-Tertiary rocks within fault block crests (buried hill reservoirs), and syn- and post-rift sediments. The latter currently forms the least productive category, whilst reservoir prediction in the first two categories is hampered by a lack of data on the complex nature of the structure, subcrop and syn-rift succession of the basin.

Six reconstructions of the syn-rift succession, subcrop lithology and fault trace distribution during the Paleogene are presented. The reconstructions illustrate the basin's structural and sedimentological evolution, and are important for reservoir prediction because: (1) the distribution of subcrop lithologies provides a direct means of identifying potential buried hill reservoirs where favourable lithologies are present in footwall crests. (2) fault trace data provide information on the position of structural traps, footwall- and hangingwall-derived clastic bodies and sediment transfer routes. (3) coarse clastic bodies in the syn-rift succession form the main reservoir type. Their provenance can be predicted from the source area lithologies in the adjacent subcrop.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas