Abstract:

The oil in the west part of northern slope in Central Tarim Basin can be classified into two types (Ⅰ,Ⅱ) based on the distribution and composition of sterane and terpane. Type-I oil is characterized by relative tow ratio of tricyclic terpanes to hopanes, pregnanes to regular sterane and rearranged steranes to regular sterane, and by relative high ratio of Ts to Tm, C₂₈ to C₂₉ sterane and C₃₀ hopane to C₃₁ homohopanes. Type-Ⅱ oil has opposite biomarker characters to the type-I oil. The difference implies that there may be at least two oil sources in the study area The correlation between the oils and source rocks indicates that the oil of type-Ⅰ was derived from the Cambrian carbonate source rock,and the oil of type-Ⅱ was derived from the Middle-Upper Ordovician marl source rock.

Key words: Cambrian, Middle-Upper Ordovician, biomarker, oil-source correlation, north slope, Central Tarim