Organic Facies and Hydrocarbon Potential of Narrow-Long Fault Basin
CHEN JIAN YU, SUN YONG CHUAN, and HAO FANG, China University of Geosciences, Wuhan, China, and LIU YAO ZONG, Research Institute of Fuyu Petroleum Company, Fuyu City, China
Yishu basin is one of a great group of Mesozoic-Tertiary fault basins in Northeast China. It is a narrow-long oil-producing basin with a 7:1 ratio of length to width. The basin is filled by 2-6 km of Eocene to Miocene and is confined by two parallel normal faults. Its geometry and unsymmetry determine the spatial distribution and evolution of organic facies. Eocene dark mudstone of deep lake is the source rock, and interfan or filled lake swamps facies contain coal. Because of development of short transversal alluvial series and plentiful terrestrial matter, frequent gravity current disturbs the stagnant reducing environment and deteriorates organic matter. As a result, humic matter is dominant in source rock with TOC 0.7-1.3%, H/C ratio 0.6-1.1, IH less than 120 mg/g(TOC), and high P /Ph, C(13)-25.40% (PDB). Products of kerogen pyrolysis have rich aromatics. This basinproduces light oil with API 40-60 degrees and heavy gas with 20-40% of C(2)-C(5). Important implications for futher exploration are evident. Though this group of lacustrine fault basins is located within the same climatic plant zone, only those having enough subsidence rates with buried depth greater than 3 km tend to be oil-generating basins, of which the narrow-long one is inclined to produce light oil and condensate.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)