Lacustrine Turbiditic Reservoirs in the Jiyang Superdepression, Bohai Bay Basin
Dongxia Chen1, Xiongqi Pang1, Maowen Li2, Jianhui Zeng1,
and Zhenxue Jiang1
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