油成甲烷碳同位素分馏的化学动力学及其初步应用

利用金管实验装置,在高压、恒速升温的条件下对塔里木盆地2个油样进行了热解成气实验,结合GC和碳同位素分析,得到了甲烷生成率、甲烷碳同位素与实验温度和升温速率的关系。由此建立并标定了油成甲烷及其碳同位素分馏的化学动力学模型。结果表明:2个油样生成甲烷气时的平均活化能差别不大,但活化能的分布有所差异;12C生成的活化能在低值区稍高,而在高值区稍低,从而使生成12C的平均活化能稍低于13C。正是12C、13C甲烷生成的活化能分布上的这一微小的差异,导致了甲烷生成时碳同位素的明显分馏。所得模型在塔里木盆地的初步应用显示,英南2气藏天然气主要为晚近期的阶段聚集气,而满东1气藏天然气可能为累积聚集。

Chemical Kinetics of Carbon Isotope Fractionation of Oil-Cracking Methane and Its Initial Application

By means of the gold tube thermal simulation equipments, 2 oil samples from Tarim Basin are carried out pyrolysis under high pressure and constant heating rate. Combining GC and carbon isotope analysis, the relationship between generation ratio of and carbon isotope ratio of methane and simulating temperature along with heating rate can be obtained. Based on the experiments above, the chemical kinetic models of methane generated from oil and its fractionation of carbon isotope are constructed and calibrated. The results indicate that the average value and distribution range of activation energy of methane generation are similar for the two oil samples with insignificant difference in distributional manner. The average activation energy of ~ 12 CH_4 generation is a little bit lower than that of the corresponding ~ 13 CH_4 because of relatively higher in low part of activation energy distribution of ~ 12 CH_4 compared to that of ~ 13 CH_4. There is a tiny difference between the activation energy distribution of ~ 12 CH_4 and ~ 13 CH_4 gene- ration that results the obvious fractionation of carbon isotope of the methane generated. The initial application of the calibrated models in Tarim Basin suggests that the gas pools in well Yingnan 2 comes mainly from the partial accumulation in late-and recent-period, and that of well Mandong 1 is cumulated gas.