Lacustrine Turbiditic Reservoirs in the Jiyang Superdepression, Bohai Bay Basin

Dongxia Chen¹, Xiongqi Pang¹, Maowen Li², Jianhui Zeng¹, and Zhenxue Jiang^1
1 Petroleum University, China, Beijing, China
² Geological Survey of Canada, Calgary, AB

Exploration efforts in the past three decades have led to the discovery of more than 12 oil fields from the Tertiary lacustrine turbidite plays in the Jiyang Superdepression of Bohai Bay Basin. Based on wireline log data, core observations and thin-section analyses, this poster presents reservoir property data from several case studies and discusses the geological factors governing the hydrocarbon accumulation in turbidite reservoirs. The studied lacustrine turbidite bodies are typically distributed in an area of 0.5-1.0 sq. km, with a thickness of 5-10 m. The porosity and permeability of the reservoir rocks usually range from 8.3 to 21.7% and less than 1 to 400 mD, respectively. The porosities are dominantly secondary, including intergranular and granular solution pores, whereas the primary porosities are usually filled by compaction and carbonate cements. Two types of carbonate cements were identified, one from the precipitation from porous waters during sedimentation and another from the secondary precipitation in sandstones of the organic acid-dissolved carbonate minerals from source rocks. The sandstone porosity and permeability correlate negatively with increasing carbonate content. Turbidite sandstone properties control the reservoir physical quality and reservoir vertical and lateral heterogeneities. High quality oil-bearing sandstones in the Jiyang Superdepression are generally found in thick mudstone and medium to thick sandstone interbeds, with more than 15% porosity, more than 10 mD permeability and less than 5% carbonate cement.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005