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Mechanism of Overpressure Generation in the Paleocene Shahejie Formation in in the Linnan Sag, Eastern China
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 82nd EAGE Annual Conference & Exhibition, Oct 2021, Volume 2021, p.1 - 5
Abstract
Summary
In this paper, the log response–vertical effective stress and acoustic velocity-density crossplots are used to identify the characteristics and generation mechanisms of the overpressure in the Linnan Sag. The analyses of the acoustic velocity/density–vertical effective stress and acoustic velocity-density crossplots demonstrate that the overpressured points consistent with the loading curve. So, the disequilibrium compaction of the thick Paleocene mudstones is the fundamental mechanism resulting in overpressures. Hydrocarbon generation and vertical transfer may be the main unloading mechanisms, that correspond to the overpressure points that deviate from the loading curves. Since organic matter cracking may occur in formations at depths deeper than 3800m, the contribution of hydrocarbon generation to overpressuring should be limited. The transfer of overpressure via opening faults is therefore considered as the main cause of higher overpressure in local sandstones. The results of this analysis provide an indication of the magnitude, mechanism and distribution of the overpressure. This understanding will help to guide further exploration activities in the Linnan Sag and similar geological basins.
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