Lacustrine carbonates of Paleogene in Zhanhua Sag, Bohai Bay Basin, East China

Abstract

The lacustrine carbonate has become an important exploration target, as the carbonates in half-graben Zhanhua Sag, a typical petroliferous lacustrine deposit, are not well-documented. Here the depositional characteristics, distribution patterns and controlling factors of the lacustrine carbonate deposition in Zhanhua Sag were studied, using seismic, well logging and core data associated with optical petrography, XRD and geochemical analysis. We identified 11 microfacies and 5 facies associations. The distributions of each facies associations were clarified, with results of carbonate-developed high-gradient margins and carbonate-restricted low-gradient margins, which could be concluded into two depositional models of different structural settings in half-graben Zhanhua Sag. In addition, climate, the outcropped lithology in the catchment area and structural settings are the main factors controlling the lacustrine carbonate microfacies types and their distribution here. These results could serve as important supplements and references to other lacustrine carbonate researches.