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| Genesis and characteristics of Paleogene overpressure in Zhanhua Depression, Jiyang Sub-basin |
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LIU Hua1,2,3, YUAN Feifei1,3, JIANG Youlu1,3, HAO Xuefeng4, FANG Xuqing4
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(1.Shandong Provincial Key Laboratory of Deep Oil and Gas, Qingdao 266580, China;2.Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;3.School of Geosciences in China University of Petroleum (East China), Qingdao 266580, China;4.Research Institute of Exploration and Development, Shengli Oilfield Company, SINOPEC, Dongying 257000, China)
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| Abstract: |
| According to sedimentation rate, mudstone content and source rock maturity, overpressure characteristics and its genetic mechanisms were analyzed. Results show that max overpressure coefficient reaches 1.8 and overpressure develops in Es1, Es3 and Es4, corresponding to three sets of source rocks vertically in Zhanhua Depression. The overpressured area is corresponding to Bonan Sag, Sikou Sag and Gubei Sag. Disequilibrium compaction and hydrocarbon generation are two main genetic mechanisms of overpressure in Zhanhua Depression, which play a role dependent on thermal maturation of source rocks. Mudstone content over 85% and sedimentation rate higher than 200 m/Ma are essential for disequilibrium compaction overpressure. Disequilibrium compaction overpressure is the main overpressure generation mechanism when Ro<0.7%, causing lower than 1.5 overpressure coefficient and hydrocarbon accumulation within source rock layer. Overpressure coefficient is over 1.5 when Ro>0.7%, then hydrocarbon generation becomes the main genetic mechanism, and hydrocarbon accumulates above the overpressure layer. |
| Key words: overpressure undercompaction pressurization hydrocarbon generation pressurization overpressure genetic mechanism Zhanhua Depression |
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