Geochemical Characteristics of Aromatic Hydrocarbon in Crude Oils from the Xifeng Oilfield of the Ordos Basin

Crude oil samples were collected systematically from the Xifeng Oilfield in Ordos Basin and analyzed by means of high-resolution GC-MS. In this paper, biomarkers of aromatic hydrocarbon in crude oils were studied, and the oil-source correlation and their genesis were investigated. The results show that the studied oils are of the same genetic type, and that alkylnaphthalene and aromatic sulfur compounds are indicative of depositional environment and thermal maturation. The oil-forming matrixes are algae and higher plants, and the higher plants have made an especially great contribution to the oil formation. The crude oils were formed under weak reduction and fresh water environments and are now mature. Geochemical characteristics of crude oils are closely correlated to those of the Upper Triassic Chang-7 subsection,suggesting that crude oils mainly originated from the Chang-7 oi1 bed group.