ORIGIN AND WHOLE-HYDROCARBON GEOCHEMICAL CHARACTISTICS OF OIL AND GAS FROM MAHAI AREA,NORTH EDGE OF QAIDAM BASIN
柴北缘马海地区油气全烃地球化学特征与成因

The paper adopts some methods such as gas composition, light hydrocarbon,carbon isotope, middle-molecular hydrocarbon and biomarker to illustrate whole-hydrocarbon geochemical charactistics of oil and gas from Mahai area and identify the genetic type and source of the different genetic oil. The result shows that gas from Nanbaxian and Mabei oil-gas field is the same genetic type, But the gas of Nanbaxian field is mainly high-over mature coal formed gas ,which is associated with lower Jurassic coal source rock in Yibei depression. Natural gas from Mabei structure is mainly wet gas of high mature early period, which is associate with Jurassic humic source rock in Gaqiu depression and Gaxi hypo-depression. Crude oil is mainly coal formed oil in Nanbaxian field, while crude oil is mainly sapropel-type oil in Mabei structure.