ANALYSIS ON THE INVERSION STRUCTURES AND OIL-GAS CONDITIONS OF THE QIONGHAI SAG

A large number of inversion oil-gas reservoirs and oil-bearing structures have been discovered in Z-3 Depression of Pearl River Mouth Basin, yet the research on the inversion structure belts in Qionghai Sag in the north of the Depression was in low level. The methods of growth index and displacement-distance curve are adopted to analyze the period and intensity of inversion structures. The source rocks, reservoirs and caprock conditions are evaluated through sedimentary analysis and quantitative simulation. The results show that the structural inversion started in the middle Miocene, with the Eocene source rocks and Oligocene-Miocene reservoir-caprock assemblages developed in the inverted structure belts. The inversion period is matched with the main expulsion stage of source rocks in the upper Wenchang Formation, thus it is concluded that the inversion structural belt is a favorable exploration direction for Qionghai Sag.