Abstract:

Based on physical features, gross compositions and biomarker compounds, the crude oils in Daerqi oilfield are classified into two types with distinct maturations: low mature and mature oil. Oil-source correlation shows that the oils are derived from low mature source rock of the Duhongmu Formation and mature source rock of the Aershan Formation respectively. The oil maturation index between low and mature may be the mixture of two source rocks. The inference can be proved by the artificial oil mixing test and oil-bearing sand serial extraction. By analyzing the characteristics of oil distribution and the relationship between hydrocarbon migration and fault developing history, it is concluded that the mixing of oils derived from different source rocks is a key control factor in oil enrichment.

Key words: Daerqi oilfield, biomarker compound, mixed oil from different sources, oil enrichment