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为了研究母质类型、热演化程度和运移方向等成藏要素对丁烷地球化学特征的影响,统计分析了塔里木盆地天然气中丁烷组分和碳同位素的变化特征.结果表明:该区丁烷含量变化较大,体积分数在0.02%~28.9%之间,平均值为1.89%;丁烷碳同位素较稳定,台盆区主频在-30‰~-28‰之间;前陆区主频在-24‰~-22‰之间;油型气iC4/nC4值小于0.8,δ13C4轻于-27.5‰;煤型气iC4/nC4值大于0.8,δ13C4重于-25.5‰;处于较高热演化阶段的天然气δ13iC4-δ13nC4值大于0;不同输导条件下,沿运移方向iC4/nC4值具有不同的变化趋势,在碎屑岩输导层中沿运移方向iC4/nC4值减小;通过盖层散失或是在碳酸盐岩风化壳中运移的天然气,沿运移方向iC4/nC4值增加.天然气中的丁烷可以为油气成藏研究提供丰富的地球化学信息,对其组成和碳同位素特征的研究具有重要的理论和实践意义.
In order to study the influence of hydrocarbon accumulation factors on the geochemical characteristics of butane in natural gas in the Tarim Basin, the characteristics of butane composition and carbon isotope variation in natural gas in Tarim Basin were studied in order to study the effects of parent material types, thermal evolution degree and migration direction on the hydrocarbon isotopes.The results show that: The content of carbon monoxide in the basin fluctuates between 0.02% and 28.9% with an average of 1.89%. Butane carbon isotope is relatively stable. The dominant frequency of the basin is between -30 ‰ and -28 ‰. Between -24 ‰ and -22 ‰; iC4 / nC4 value of oil gas is less than 0.8 and δ13C4 is less than -27.5 ‰; iC4 / nC4 value of coal gas is more than 0.8 and δ13C4 is more than -25.5 ‰; at higher thermal evolution stage Of δ13iC4-δ13nC4 values of natural gas are greater than 0. Under different transport conditions, the iC4 / nC4 values have different trends along the migration direction and decrease along the migration direction of clastic rock. The value of iC4 / The loss of layers or migration of natural gas in carbonate weathering crusts increases the value of iC4 / nC4 along migration direction, butane in natural gas can provide rich geochemical information for hydrocarbon accumulation research, and its composition and carbon Isotopic characteristics of the study has important theoretical and practical significance.