GEOCHEMICAL CHARACTERISTICS AND PRO-VENANCES OF CRUDE OIL IN THE NORTHERN MARGINAL FAULTED BLOCK ZONE OF QAIDAM BASIN

Using the data derived from the analyses of GC, carbon isotopes and hydrocarbon groups, this paper studies the geochemical characteristics and possible provenance of crude oil in the northern marginal faulted block zone of Qaidam Basin. These studies indicate. 1.The J₂d⁶ crude oil in Lenghu Area differs greatly from those in E₃ and N₁ formations and they are attributed to two different types. Together with another type of crude oil from Yuka-Lulehe, there are three types of crude oils in this area.The two types of crude oils in Lenghuare are resulted from different maturities of the source beds in different areas. 2.The J₂d⁶ crude oil in Lenghu No.3 Area comes from J₂d⁴-J₂d⁵ source beds in the same area, bearing no relation with the source beds in Lenghu No.4 and 5 areas; while the crude oils producing from E₃ and N₁ in No.4 and 5 areas are not related to the source beds in No.3 Area. A part of the crude oils may derive from J₂d⁴-J₂d⁵ beds, the other part probably comes from an unknown source area. 3.The crude oils from Yuka and Lulehe may have the same provenance,i.e. from J₂d⁶ and the underlying source beds bear no relationsh ip to J₂d⁷ bed.