注CO_(2)提高页岩气采收率实验研究

Experimental study of enhancing shale gas recovery by CO_(2) injection

注CO_(2)提高页岩气采收率(CO_(2)-ESGR)是一种既可以提高CH4采收率,又可以实现CO_(2)安全封存的技术,研究CH_(4)和CO_(2)在页岩上的动态吸附有助于更好理解CO_(2)-ESGR的动力学机制.以页岩样品为研究对象,利用高压吸附仪进行了不同温压条件下的吸附动力学实验.结果表明,CH_(4)和CO_(2)在页岩上的动态吸附均分为初期的快速吸附和后期的吸附平衡阶段,整个过程中气体的过剩吸附量和吸附速率都随压力增大而增大,随温度升高而减小.温度的升高虽然加快了气体的扩散,但却降低了气体的吸附量,总的结果是降低了气体在页岩上的吸附速率.当压力小于5 MPa时,CO_(2)在竞争吸附中占据优势,有利于CO_(2)-ESGR的实施.同时,利用准一级动力学模型计算了吸附速率常数,结果与实验结果相吻合.

CO_(2)enhanced shale gas recovery(CO_(2)-ESGR)is a technology that not only improves the recovery of CH4,but also realizes the safe storage of CO_(2).Research on the dynamic adsorption process of CH_(4) and CO_(2)on shale can give a better understanding for the kinetics mechanism of CO_(2)-ESGR.Using a high pressure adsorption apparatus,adsorption kinetics experiments of shale samples were carried out under different temperature and pressure conditions.The results show that the dynamic adsorption of CH_(4) and CO_(2)on shale is divided into the initial stage of rapid adsorption and the later stage of adsorption equilibrium.During the whole process,the excessive adsorption amount and adsorption rate ascend with the increase in pressure,while decline with the increase in temperature.Although the increase in temperature accelerates the diffusion of gas,it remarkably reduces the adsorption capacity of gas,therefore,the overall result is that the adsorption rate of gas on shale declines.When the pressure is less than 5 MPa,CO_(2) has an advantage in competitive adsorption,which is beneficial to the implementation of CO_(2)-ESGR.At the same time,the adsorption rate constant is calculated using the quasi-first order kinetic model,and the result is consistent with the experimental results.