THE GENERATION OF IMMATURE OILS IN THE LACUSTRINE JIYANG MEGA-DEPRESSION, BOHAI BAY BASIN, CHINA
Zhang Linye*, Zhang Shouchun+*, Chen Zhilin*, Zhang Chunrong* and Hong Zhihua*
*Geological Scientific Research Institute of Shengli Oil Field Ltd. Co., SINOPEC, Dongying, Shandong, China.
+ author for correspondence, email firstname.lastname@example.org
The lacustrine Jiyang mega-depression (Bohai Bay Basin, eastern China) produces important volumes of immature oils. These oils were generated at shallow burial depths by source rocks which have not entered the conventional oil window. Oil-source correlation studies have determined that the oils were mainly generated by source rock intervals in the Es4 and Es1 Members of the Neogene Shahejie Formation, which were deposited in saline- to brackish-water lacustrine settings.
A comparison of the results of thermal simulation experiments with the naturally-occurring maturation profile shows that various factors influenced the generation of the immature oils. Firstly, the source intervals in the Es4 and Es1 Members are enriched in fresh-water algal material. Secondly, most of the immature oil is derived from soluble organic matter. Finally, the saline depositional environment was favorable for the preservation of the organic matter.
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