ABSTRACT: Petroleum system and large oilfields formation in Jiyang Sub-basin

Changgu, Li, and Yang Shenbiao , Shengli Admin. Petro. Bur, Dongying Shangdong, China

Jiyang Sub-basin is located in the northern portion of Shandong Province and belongs to the Hydrocarbon-Bearing Basin of Bahai Bay. It is in the Yellow River's downstream and estuarine delta, which coordinate is roughly 116°-40'-119° of longitude and 37°-38° of north latitude. It is bounded by Chengning uplift in the north and Luxi uplift in the south. Including part of beach strand the total area is 29,000 km².

Jiyang sub-basin is a Mesozoic-Cenozoic rift type lacustrine basin, whose formation and development is controlled by the block faulting movement during the Yanshan and Himalayan orogeny. Up to now, among the 66 oilfields there are eight large composite oilfields (OOIP is more than 100 million tons). By the end of 1998, 60 oilfields were successfully put into development with the accumulative oil production of 600 million tons.

According to the difference of Petroleum System element and character were divided two Petroleum System. Southern area petroleum system was evolved early and source rock maturity is high. The critical moment is 24.6 Ma. Sedimentary facies of Shahejie Formation is estuarine delta. Fault and fracture are primary path of oil and gas migration. The synsedimentary structures include rollover, inherited anticline and ductile bed diapir. Northern area petroleum system was evolved late. The critical moment is 5.0 Ma. Fault activity continued from Cretaceous period to Miocene Epoch. Draping structure and fluvial facies sediment in the Miocene are traps and reservoir of large oilfield.

The distribution of enriched oil and gas is controlled by petroleum system characteristic. Oil and gas has the character of ring or semi-ring distribution with the source sub-depression as their centers.

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