Application of Biomarkers and Compound Specific Sulfur Isotope in Oil-Source Rock Correlation in the Wenliu Oilfield, Bohai Bay Basin

Abstract

Summary Dongpu Depression is an important petroliferous depressions in the Bohai Bay Basin, eastern China, which is a typical saline lacustrine depression. Wenliu Oilfield is the biggest oilfield in the depression. There is still some controversy about the oil source for the Wenliu oilfield. The dispute is focused on the location (in-situ or the adjacent Qianliyuan Sag) and the horizons (the Es3M or the Es3L-Es4u) of the key source rocks. Quite a few geologists suggested that the Es3M in-situ should be the most important source rocks, which is primarily dark shales with great hydrocarbon generation potential. To help unravel the origin and source rocks of the Wenliu oils, a total of 44 rock samples and 66 oil samples were collected for study by conventional geochemical methods combined with compound specific carbon/sulfur isotopic analysis. We suggested that the Wenliu Oils are mixed sources derived from both the Es3M and the Es3L-Es4U strata, and the latter should be responsible for the majority of the crude oils in the Wenliu Oifleld based on oil-oil and oil-source correlation as well as semi-quantitative comparison of biomarkers abundances. The results would be instructive for further petroleum exploration and petroleum resource evaluation in the area.