Abstract: 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 ¹²CH₄ generation is a little bit lower than that of the corresponding ¹³CH₄ because of relatively higher in low part of activation energy distribution of ¹²CH₄ compared to that of ¹³CH₄. There is a tiny difference between the activation energy distribution of ¹²CH₄ and ¹³CH₄ 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.

Key words: oil cracking gas, isotope fractionation, chemical kinetics, quantitative model