开放体系和密闭体系恒速升温实验条件下有机质生烃动力学特征对比及意义

Characteristic Comparison of Hydrocarbon Generation Kinetics Under Open-Closed Systems with Constant Heating Rates and Its Significance

为了揭示不同实验条件下有机质生烃动力学特征及其地质应用的差异性,对松辽盆地煤样进行了开放体系(Rock-Eval)和密闭体系(金管)的恒速升温热模拟实验。根据实验产物产率与温度关系标定了开放系下的有机质成油、成气及密闭体系下有机质成气动力学模型;将标定的2种体系下的动力学参数以实验室升温速率和地质升温速率条件下进行外推,表明密闭体系下的成气转化率相对开放体系下的变化要慢,原因在于开放体系下煤样热解生气为初次裂解,而密闭体系下煤样生气是初次裂解和二次裂解共同贡献的结果。进一步将2种体系下获得的生气动力学参数结合松辽盆地徐家围子地区埋藏史、热史资料进行应用表明:应用开放体系获得的动力学参数外推计算的生气门限对应时间(115 Ma)要比实际生气门限对应时间(110 Ma)偏早;应用密闭体系获得的动力学参数外推计算的生气门限对应时间(92 Ma)要比实际生气门限对应时间偏晚。

In order to reveal the difference of hydrocarbon generation kinetics characteristics and its geologic application under different experiment conditions,two thermal simulation apparatus（open and closed systems） are employed to pyrolyze coal sample from Songliao basin.According to the relationship between experimental product yields and temperature,the kinetic models of the oil/gas generated from organic matter are calibrated.Then the kinetic parameters obtained from two experimental systems are extrapolated under the experimental heating rate and the geological heating rate,the results show that the TR（transformation ratio） increasing rate of the gas generation under closed system is slower than that under open system,the reason is that the coal sample pyrolysis to gas under open system is mainly primary cracking,but under closed system it is a common result of primary and secondary cracking.For further application,the hydrocarbon generation threshold is calculated,which combined the burial-thermal history of Xujiaweizi and the kinetic parameters obtained from two experimental systems.And the extrapolation result shows that the calculated geological time（115 Ma） corresponding to the threshold from open system is earlier than the geological time corresponding to the actual threshold（110 Ma）,and the calculated geological time（92 Ma） corresponding to the threshold from closed system is later than the geological time corresponding to the actual threshold.