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大宛齐—大北地区是塔里木盆地库车坳陷的重要油气勘探区,区域内原油以轻质油为主,其轻烃地球化学特征研究薄弱。采用气相色谱对大宛齐—大北地区的原油轻烃化合物进行分析和地球化学特征研究。研究区原油中C_4—C_7化合物组成特征和甲基环己烷指数均表明其为腐殖型母质来源的陆相油;Mango轻烃参数K1基本符合轻烃稳态催化动力学成因模式,其成因具有较好的一致性;庚烷值和异庚烷值显示其成熟度较高,根据原油形成温度与成熟度相互关系推测其母源成熟度R_O值约为0.8%~0.93%;轻烃的芳香度指数及链烷烃指数相关性和C_7轻烃蚀变参数相关性分析认为,原油轻烃不仅遭受了生物降解蚀变,还经历了蒸发分馏和水洗作用。研究结果对确定原油母源、成熟度及次生蚀变具有重要意义。
Dawanqi-Dabei area is an important oil and gas exploration area in the Kuqa Depression of the Tarim Basin. The crude oil in the area is mainly light oil, and its light hydrocarbon geochemical characteristics are weakly studied. The crude oil light hydrocarbon compounds in Dawanqi-Dabei area were analyzed by gas chromatography and the geochemical characteristics were studied. The composition of C_4-C_7 compounds and the methylcyclohexane index in crude oil of the study area all indicate that it is the continental oil from humus parent material. Mango light hydrocarbon parameter K1 is basically consistent with the light-hydrocarbon steady-state catalytic kinetic genesis model, With good consistency. The heptane and isoheptane values show high maturity. According to the correlation between the formation temperature and maturity of crude oil, the maturity R_O value of crude oil is about 0.8% -0.93% Aromatics index and paraffin index correlation and C_7 light hydrocarbon alteration parameter correlation analysis suggest that crude oil light hydrocarbons not only suffered biological degradation alteration, but also experienced evaporation fractionation and washing. The results of this study are of great significance for determining the source, maturity and secondary alteration of crude oil.