【摘要】 以甲烷的量子化模型及正构二十四烷(n-C24)金管限定体系裂解成气实验为基础,从理论上进一步论述了量子化模型应用于重烃气体(乙烷和丙烷)碳同位素动力学模拟的适应性,计算了甲烷、乙烷及丙烷生烃动力学与碳同位素动力学参数,重点探讨了δ13C2与δ13C3变化的主控因素。研究结果表明,n-C24裂解生成的气态烃碳同位素与早期报道的n-C18、n-C25及原油裂解生成的气态烃碳同位素具有可比性,可应用于地质条件下解释原油裂解气的某些地球化学特征。n-C24生烃地质模型表明,其在150～160℃是稳定的,主要裂解温度介于180～200℃之间,与目前所报道的原油裂解地质模型吻合。随热解程度的增加,δ13C2与δ13C3体现了比δ13C1更明显的变化。气藏充注历史控制的同位素累积效应对天然气碳同位素有很大的影响,与累积聚集气相比,阶段聚集气的δ13C变重,并在更大程度上影响了演化曲线的分异。在此基础上,应用n-C24裂解成气碳同位素分馏地质模型探讨了塔里木盆地某些油气藏天然气碳同位素值变化的原因。更多还原

【Abstract】 Based on quantitative modeling and experimental data on n-tetracosane cracking to generate gaseous hydrocarbons in a confined system,we calculated the generation kinetics and carbon isotope kinetics of methane,ethane and propane and determined the main controlling factors influencing the variation of δ13C2 and δ13C3.The carbon isotope of gaseous hydrocarbons from nC24 cracking to gas are comparable to those from crude oil reported recently,and they can be used to investigate the geochemical characteristics of crude oil cracking to gas under geological conditions.The geological model of nC24 cracking suggests it is stable at 150～160℃ and its cracking temperature ranges 180℃ to 200℃,consistent with geological models of crude oil cracking currently reported.With increasing degree of thermal stress,the changes in δ13C2 and δ13C3 are larger than that of δ13C1.It is shown that isotope accumulation controlled by the recharging history of a reservoir has a considerable impact on the carbon isotope distribution of natural gas.Compared to that of cumulative gas,the carbon isotope ratio of partly accumulation gas is heavier and influences the fractionation of the δ13C2 and δ13C3 curves to a greater extent.The geological model of nC24 cracking to gas has been used to interpret the origin of carbon isotopic variation of natural gas in some reservoirs in the Tarim basin.更多还原