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ABSTRACT: Stratigraphic traps and hydrocarbon occurrence in a lacustrine sequence stratigraphic framework: an example from shoreline area of Shengli Oilfield, China

Jiang, Zaixing1, Yingchang Cao2, Yingxia Xu2, and Xilong Gao2
(1) University of Petroleum, Dongying Shandong, China 
(2) University of Petroleum

The Chengbei low relief on the western Bohai shoreline is covered with the lower Tertiary lacustrine and the upper Tertiary fluvial clastic sequence. The relief is bordered on the Chengbei depression with Chengbei growth fault in the west, and extends downdip into Shaleitian depression eastward with a ramp. Two sequences, each comprising low-stand (LST), lacustrine transgressive (LTST), high-stand (HST) and falling-stage (FSST) systems tract, have been distinguished in the lower Tertiary deposits. A tectonic analysis reveals that the FSST was formed from the upthrowing of Chengbei fault. As a result, successive deltaic systems prograding eastward were constructed in response to a quick lake shoreline shift basinward during the stage. Sedimentary facies, in addition to deltaic in the FSST, include valley-fan complex and semi-deep lake in the LST and LTST, and delta-turbidite in the HST. Two types of traps have been identified, i.e., valley-fan lithologic and FSST deltaic sandbodies terminated and sealed updip by overlying LTST black mudstones. Whereas, HST deltaic sandbodies commonly serve as aquifers in spite of their great thickness. This is because HST sandbodies generally onlap too landward and cannot be laterally sealed laterally and vertically. Combined with hydrocarbon migration analysis, two oil-enrichment and two oil non-enrichment models have been proposed.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia