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原油裂解气是高过成熟海相盆地的重要气源之一,但对其生气潜力的评价及气体特征还没有一个明确的认识.通过对塔里木盆地塔中62井志留系原油的连续热解与分步热解实验,发现在C1-5总气质量产率达到最大后(EasyRo=2.3%),原油残余物的最大生气潜力为43.4mL/g原油,仅为初始原油产气率的12%.结合动力学模拟结果,认为该原油样品裂解的主生气期对应的EasyRo值介于1.6%~2.3%之间.在封闭系统中,EasyRo>2.3%之后原油裂解气体积的增加主要与重烃气体的二次裂解有关,并不是原油进一步直接裂解的产物.实验结果表明,原油残余物裂解气具有干燥系数大(>92%)、甲烷碳同位素重的特征(介于28.7‰~26.7‰),与封闭体系中连续热解气存在明显的区别.甲烷碳同位素分馏动力学模拟结果表明,在一般地质条件下(2℃/Ma),主生气期内(EasyRo<2.3%)的原油裂解气甲烷碳同位素远低于原油的初始碳同位素值.本研究结果为高-过成熟盆地原油裂解气的客观评价提供了新的思路.
Crude cracked gas is one of the most important gas sources in the overripe marine basin, but there is not a clear understanding of its potential for gas generation and gas characteristics.Based on the continuous pyrolysis of Silurian 62 in Tarim Basin With the step-by-step pyrolysis experiment, it was found that the maximum gas potential of crude oil residue is 43.4mL / g crude oil after reaching the maximum gas mass production rate of C1-5 (EasyRo = 2.3%), only 12 % .According to the kinetic simulation results, the corresponding EasyRo values of the main gas-cracking period of the crude oil sample are between 1.6% and 2.3% .In a closed system, the increase of cracked gas volume after crude oil cracking with EasyRo> 2.3% Which is not related to the secondary cracking of hydrocarbon gas.It is not the product of further direct cracking of crude oil.The experimental results show that the cracked gas of crude oil residue has the characteristics of large drying coefficient (> 92%) and heavy carbon isotope of methane (ranging from 28.7 ‰ to 26.7 ‰ ), Which is obviously different from the continuous pyrolysis gas in the closed system.The simulation results of methane carbon isotope fractionation kinetics show that under the general geological conditions (2 ℃ / Ma), the crude oil cracking (EasyRo <2.3% Gas methane carbon isotopes are much lower than the crude carbon initial carbon . Isotope value of this study is the result of high - over mature basin objective evaluation of crude oil cracked gas it provides a new way of thinking.