Origin of the high waxy oils in Bohai Bay Basin, east China: Insight from geochemical and fluid inclusion analyses

An integrated approach of molecular sieve, molecular composition of fluid inclusion and compound specific isotope analysis was employed to investigate newly discovered oils reservoired in an Ordovician buried hill in the Dongying Depression of Bohai Bay Basin. The new discovered oils are characterized by high content of waxy alkanes (> 40%) with an extremely low concentration of cyclic biomarkers. The alkanes-removed waxy oil and the fluid inclusion oils correlate well with the source rocks of the Paleogene Kongdian Fm (Ek2). The δ13C values of the compound-specific isotope of the alkanes indicate that Ek2 is the primary source for the oils. This study demonstrates the existence of a new set of deeper source rocks with good oil-generation potential in the Dongying Depression.