Application of balanced section technique to the study of positive inversion structure and hydrocarbon accumulation control in Xihu Depression of East China Sea

Balanced section technique has been applied to the study of the stage and strength of the Tertiary positive inversion structure in Xihu Depression of East China Sea. The Xihu Depression is recognized as a 3-stage inversion of early, medium and late inversion. The early inversion in late Eocene mainly occurred in the western slope of the basin, and the inversion strength increased from south to north in the study area. The medium reversion in late Oligocene mainly occurred in the eastern fault zone of the basin, and the inversion strength decreased from south to north in the study area. The late inversion in late middle-Miocene mainly occurred in the central uplift belt of the basin, and the inversion strength increased from south to north in the study area. The inversion action generally intensified along time. The inversion action had formed various structural traps which were large and intact, and very favorable to oil and gas migration and accumulation. Meanwhile, the inversion action also had a transformation effect on reservoir physical property. Present exploration shows that the three structural inversion belts are most favorable zones for oil and gas prospecting in Xihu Depression.