CARBON ISOTOPIC FRACTIONATION EFFECT CAUSED BY MATURITY DURING THE GENERATION OF COAL-PYROLYSIS HYROCARBONS
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摘要: 通过半封闭体系下的生排烃热模拟实验研究了3种煤在不同热解温度下的碳同位素分馏效应。研究结果表明,煤的有机质类型不同,成熟度造成的热解烃的碳同位素分馏效应也有差别,腐植煤的热解烃基于成熟度的碳同位素分馏效应大,而煤本身的碳同位素值随成熟度的变化不大。在较高成熟度时,二次裂解的概率大大增加,导致热解烃尤其是残留烃的正构烷烃单体碳同位素组成明显变重。同一烃源岩在不同温度下的热解烃正构烷烃单体的碳同位素组成曲线具有很大的相似性,说明在油源对比中正构烷烃单体碳同位素值曲线的形状和其数值一样都是重要的对比依据。Abstract: The carbon isotopic fractionation effect of 3 types of coal under different pyrolysis temperatures has been studied through the hydrocarbon generation-expulsion pyrolysis simulation experiment in a semiClosed system.The results indicate that the carbon isotopic fractionation effect caused by the maturity differences changes with the different organic types of the coal.The fractionation effect of the pyrolysis hydrocarbons from the humous coal is significant,whereas the carbon isotope of the coal itself changes little with maturity.The possibility of the secondary cracking of the pyrolysis hydrocarbons increases greatly under a higher maturity level,resulting in the significant increase of the carbon isotopic compositions of the individual n-alkanes,especially the residual hydrocarbons.The isotopic distribution curves of the individual n-alkanes from the same source rock under different temperatures are very similar,indicating that,alike the value,the curve shape of the isotope may also provide a very important basis for oil-source correlation.
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