Abstract: The faults development and evolution features in Chegu-20 burried hill as well as their vertical sealing mechanisms andaffected factors are analyzed. The main factors controlling vertical sealing faults are the pressure exerted on fault plane and theshale content. From the modeling result of compressive experiment,the plastically deformed limitation of mudstone is presented,and the method for prediction of sandy and shale contents in fault zone is established by its lithology and fault throw.Based onthese, the vertical sealing nature of Chegu-20 burried hill in Carboniferous-Permian to Paleogene are evaluated. It is pointed outthat the faults are all characterized by vertical sealing nature in C-P to Es* except for faults F3, F42 and F? in Line-298 and a-long Chegu-203-Chegu-20-Chegu-201. They show that this area possesses significant conditions for hydrocarbon accumulation andpreservation.

Key words: buried hill, fault, sealing, pressure, plasticity, deformation