Two condensate gas fields

i.e

Banqiao and Qianmiqiao

have been discovered in Qikou Sag.In addition

exploration breakthrough was also made in the Chenghai buried hill and the deep Paleogene in Qikou Sag

indicating good exploration prospect.This paper systematically analyzed the Paleogene natural gas reservoirs in Qikou Sag in terms of petroleum factors including source rocks

reservoirs and cap rocks

and described the key characte-ristics of the gas reservoirs.The result indicates that the natural gas mainly accumulate in the mid-deep strata of Shahejie Formation.The shallow secondary gas reservoirs mainly occur in structural traps.In contrast

the mid-deep gas reservoirs mainly occur in structural-lithologic compound traps.The genetic type of gas is dominated by humus type.The pore space of the reservoir is dominated by pores

with fractures occurring in the mid-deep layers

indicating dual porosity reservoir.Two regional cap rocks developed during the maximum flooding are overpressured and provide favorable preservation condition for gas reservoirs.The gas reservoirs mainly occur in areas with high gas generation intensity and are characterized by late hydrocarbon charging.The hydrocarbon distribution is characteri-zed by"gas in the north and oil in the south"and"oil in the upper interval and gas in the lower interval".