The Characteristics and Origin of Overpressure in Damingtun Depression of Liaohe Basin and Petroleum Exploration Signif icance

Integrating logging, geological, seismic and drilling data and by means of equivalent depth, four types of compaction style in Damingtun depression are recognized from the view of sedimentation and hydrocarbon generation. They are stong overpressure, overpressure, local overpressure and normal compaction. From the point of plane, the high overpressure occurred in the center of sag. From the point of vertical, there exists relative high overpressure in the bottom of S₃³ formation, S₃⁴ and S₄ formation. The highest overpressure factor is up to 1.55. Overpressure is strong and exists widely. The faults act as important shelf for the occurrence of overpressure. Overpressure is mainly due to fast sedimentation and hydrocarbon generation.