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采用PY-GC热模拟实验方法对塔里木盆地塔中地区海相烃源岩轻烃生成模式及热解气单体烃碳同位素进行研究,实验结果表明:轻烃大量生成在RO值为1.3%～1.9%阶段;在各类化合物组成中,链烷烃含量最高,环烷烃和芳烃含量比较接近;热解气苯和甲苯碳同位素值一般小于-25‰,环己烷和甲基环己烷碳同位素值小于-24.1‰。对塔里木盆地台盆区油型气轻烃组分及碳同位素组成分析认为,油型天然气轻烃组成以链烷烃为主,占45.4%～93.7%,平均为70.1%,其次是环烷烃,分布在5.4%～40.6%之间,平均为23.4%,芳烃含量较低;苯碳同位素值分布在-23.7‰～-28.6‰之间,甲苯碳同位素值分布在-23.7‰～-29.5‰之间,天然气中环己烷和甲基环己烷碳同位素值明显低于前陆区,一般都小于-26‰。结合塔中地区天然气碳同位素组成特征,对塔中地区气源进行了探讨。
The PY-GC thermal simulation experimental method was used to study the formation mode of light hydrocarbons and the carbon isotopes of hydrocarbon in the marine source rocks in Tazhong area, Tarim Basin. The experimental results show that the light hydrocarbons are abundantly produced at 1.3% 1.9%. The content of paraffins was the highest in all kinds of compounds, and the content of naphthenes and aromatics was relatively close. The carbon isotope values of benzene and toluene in pyrolysis were generally less than -25% o. The carbon isotopes of cyclohexane and methylcyclohexane Value is less than-24.1 ‰. Based on the analysis of the composition and carbon isotopic composition of light hydrocarbons in Tarim Basin, it is considered that the light hydrocarbons in oil-based natural gas are mainly paraffins, accounting for 45.4% ~ 93.7% with an average of 70.1%, followed by naphthenes Between 5.4% and 40.6%, with an average of 23.4% and lower aromatics content. The carbon isotope values of benzene distribute between -23.7 ‰ and -28.6 ‰, and the carbon isotope values of toluene distribute between -23.7 ‰ and -29.5 ‰ The carbon isotope values of cyclohexane and methylcyclohexane in natural gas are obviously lower than those in the foreland region, and are generally less than -26 ‰. Combined with the characteristics of carbon isotope composition of natural gas in Tazhong area, the gas source in Tazhong area was discussed.