Analysis of Crude Oil Characteristics and Oil-source Correlation of the Sha-2 Member of Shahejie Formation in the Chengbei Low Step Fault

The Sha-2 Member of Shahejie Formation in the Chengbei low step fault is one of the key exploration targets of Dagang Oilfield in recent years. It is significant for oil and gas exploration to analyze the characteristics of the crude oil in the target horizons and conduct oil-source correlation. The study results shows that the crude oil generally exhibit high mature oil characteristics in physical property, with the characteristics of four low and one high, including low density, low viscosity, low gel and asphalt content, low sulfur content and high wax content. The crude oil geochemical properties and the characteristics of the crude oil biomarkers indicates that the source materialls deposited in the lacustrine weak reduction environment, reflecting high contribution of algae, with high mature oil characteristics. Study of four physical characteristics of the crude oil and correlation of biomarker characteristics between oils and source rocks, it is concluded that the oil and gas were sourced mainly from two ways, one was from the bidirectional oil supply from Qikou Sag and Qinan Sag, the other was from self-generation and self-reservoiring Sha-2 Member and high mature source rocks of Sha-3 Member.