Correlation of oils and source rocks and genesis of high wax oils in Gaoshangpu area, Nanpu Sag, Bohai Bay Basin

There are significant differences between crude oil properties and enrichment horizon across the Gaoliu Fault in the Gaoshangpu area of the Nanpu Sag.Oils are mainly enriched in the third member of Shahejie Formation (Es₃) to the north of the Gaoliu Fault, and are characterized by a high wax content.However, oils are mainly enriched in the Minghuazhen, Guantao and Dongying formations to the south of the Gaoliu Fault, and are normal crude oils with a low wax content. The biomarkers and compound specific isotopes of crude oils from different layers show that the origin of the high wax content oils in the Es₃ is different from that of the oils to the south of the Gaoliu Fault. The former is derived from the source rocks of the Es₃⁴ and the latter is sourced from the third member of the Dongying Formation (Ed₃) in the Linque Sub-Sag to the south of the Gaoliu Fault. The source rocks of the Es₃⁴ contain abundant terrigenous higher plants and lower hydrobionts, which provide the wax source. The microbe reformation, low thermal evolution degree and abnormal high pressure in the Es₃ are key factors in the formation, migration and preservation of high wax oils.