Mixing Characteristics of Oil Inclusions with Different Thermal Maturities in the Wenliu Uplift, Dongpu Depression, Bohai Bay Basin, North China

Multiple types of oil inclusions with different fluorescence colors have been detected in the northern Dongpu depression. Recent evidences show that these inclusions may have been trapped simultaneously or during a very short period. Therefore, whether these oils were mixed before trapping is unknown. In this study, we analyzed the petrography and fluorescence spectral characteristics of oil inclusions in the Wenliu uplift in the northern Dongpu depression, and assessed the data with the oil mixing ratio curve obtained in the previous experiment. The results show that there are three types of oil inclusions (type I, type II and type III) with yellow, green and blue fluorescence colors, corresponding to low-mature, medium-mature and high-mature oil, respectively. The “pure” oil inclusions, do exist in type II and type III group of oil inclusions, showing the medium-mature oil was generated from the source rock rather than being formed by the mixture of high-mature and low-mature end oils. Most of the oil inclusions are mixtures of high-mature and medium-mature end oils from the sub-sags to the Wenliu uplift, the mixing degree increases to close to 50%. The oil between the Qianliyuan sub-sag and the Wenliu uplift was mainly mixed by medium mature oils, whereas the oil between the Liutun sub-sag and the Wenliu uplift was mainly mixed by high mature oil.