Abstract: Kenli 16 Oilfield is located in the Laizhouwan sag with high sulfur content. Crude oil generally has mixed sources, but the degree and distribution characteristics of mixed sources of crude oil are not clear. In view of the above problem, biomarker compounds and saturated hydrocarbon carbon isotope methods were comprehensively used to identify mixed-source oil, and the mixed-source degree is quantitatively analyzed. The results show that the crude oil in Kenli 16 Oilfield generally has the characteristics of mixed sources, and the mixed-source degree of crude oil is basically the same on plane; in vertical direction, the mixed-source degree of crude oil is correlated with the strata. In which, the mixing proportion of salinized crude oil in the upper sub-member of the third Member of the Shahejie Formation is the highest, with an average of 89%; while that in the lower sub-member of the third Member of the Shahejie Formation is the lowest, with an average of 25%. The discovery of the mixed-source oil in Kenli 16 Oilfield confirms the contribution of salinized source rock to the fourth member of the Shahejie Formation in the main trough of the Laizhouwan sag, and indicates that the deep fourth member of the Shahejie Formation in the main trough and the southern slope zone contains great exploration potential. For the first time, the hydrocarbon generation and supply capacity of the southern trough is clearly defined, which is expected to open up the exploration situation in the periphery zones of the southern trough.

Key words: mixed-source oil, biomarker, carbon isotope of saturated hydrocarbons, source rock, quantitative judgment, Laizhouwan Sag