塔北隆起北缘原油轻烃单体烃碳同位素特征

Compound specific carbon isotope composition of light hydrocarbons in crude oils from the north of the Northern Tarim Uplift

对塔北隆起北缘原油进行了轻烃单体烃碳同位素组成分析,刻画了原油的轻烃组成特征。所有轻烃化合物中,环戊烷系列化合物碳同位素在不同原油之间差异最小,对原油成因的鉴别意义小于其他化合物。优选的其他化合物碳同位素在不同成因原油中呈现出显著规律,轮台油气田煤成油轻烃单体烃碳同位素较重,主要位于-21‰～-19‰之间;大涝坝油气田湖相油次之,位于-25‰～-21‰之间;雅克拉油气田海相油最轻,位于-31.5‰～-28‰之间。典型寒武系—下奥陶统来源的YN2井原油分布特征独特。上述分布特征揭示轻烃单体烃碳同位素组成可作为可靠的原油成因判识指标,尤其对于凝析油与轻质油更为有效。

Compound specific carbon isotope compositions of different fractions and different original crude oils were analyzed to investigate light hydrocarbon characteristics of crude oils in the north of the Northern Tarim Up- lift. Compound specific carbon isotope divergences of cyclopentane compounds in different crude oils were the least, which indicated that cyelopentanes had poor diagnosis in light hydrocarbons. A significant law can be found by compound specific carbon isotope compositions of optimized light hydrocarbons. Compound specific car- bon isotope of light hydrocarbons in coal-formed oils from the Luntai Oilfield was the highest, ranging from -21‰ to -19‰. Lacustrine oils from the Dalaoba Oiifield took the second place, ranging from -25‰ to -21‰. Marine oils in the Yakela Oilfield were the lowest, ranging from -31.5‰ to -28‰. Compound specific carbon isotope composition of light hydrocarbons in crude oils which derived from Cambrian-Lower Ordovician in well YN2 was unique. It is suggested that compound specific carbon isotope composition of light hydrocarbons can be a diagnosis index for group crude oil, especially for gas-condensate and light oils.