Study on multi-period hydrocarbon accumulation process in Sanhecun subsag of Zhanhua sag

Key words:  accumulation process  Sanhecun subsag  oil and gas source  accumulation stage

Abstract:

The dynamic process of hydrocarbon accumulation in Sanhecun subsag of Zhanhua sag was studied by analyzing the sedimentary burial history and hydrocarbon generation history, taking advantage of the abundant drillings and available test datum. The results show that the crude oil in Sanhecun subsag originated from Bonan subsag, and the crude oil can be classified into three different types. The three stages of evolution in the hydrocarbon accumulation include the Ed formation, the Ng formation and the Nm formation, respectively. The crude oil of reservoirs formed in the Ed formation originated from the matured source rocks of Es₄ before the formation of the Kenxi low uplift. The crude oil from Bonan subsag migrated along the slope through fault-unconformity carrier system to Sanhecun subsag and was accumulated in the Es₃ and the following strata. The reservoirs formed at this stage were thickened by curing and biodegradation in the later stage. The crude oil of reservoirs formed in the Ng formation originated from the source rocks of Es₃ and Es₄ after the formation of the Kenxi low uplift. The crude oil from Bonan subsag migrated along the meshwork-carpet system to Sanhecun subsag and accumulated above the Es₃, and the reservoirs formed at this stage were thickened by biodegradation in the later stage. The crude oil of reservoirs formed in the Ng formation originated from the source rocks of Es₃, and the crude oil also migrated through the meshwork-carpet system and accumulated in the Neogene.