考虑地质断层激活后的CO_(2)封存流体泄漏模型及数值分析

Mathematical model and numerical analysis for leakage of fluid along geological fault during CO_(2) storage

地质断层活化后,流体(CO_(2)、盐水、淡水)沿断层泄漏是CO_(2)地质封存中不可忽视的关键问题,因此,推导了不同阶段流体沿断层的泄漏速度方程,并结合质量守恒方程和能量守恒方程,建立地质活化断层的CO_(2)封存流体泄漏模型,获取了流体沿断层泄漏的关键参数(泄漏时间和泄漏量)。模拟不同参数对流体泄漏时间和泄漏量的影响:随着CO_(2)注入速度增快和储层渗透率增大,CO_(2)沿断层泄漏的初始时间提前,持续时间延长,泄漏量增加;随着断层渗透率的增加,CO_(2)沿断层泄漏的初始时间和持续时间没有变化,而CO_(2)泄漏量增加;相较于CO_(2)注入速度和储层渗透率,断层渗透率对盐水和淡水泄漏影响最大。综上所述:流体沿断层泄漏的先后顺序为盐水、CO_(2)、淡水;流体沿断层泄漏的持续时间由长到短依次为:CO_(2)、淡水、盐水;流体沿断层的泄漏量由大到小为CO_(2)、盐水、淡水。

The leakage of fluid(CO_(2),brine and freshwater)along fault is a crucial issue that cannot be ignored during CO_(2) geological storage.For this reason,the equations to describe the fluid leakage rate along faults in different stages are derived.Then,these equations are combined with mass and energy conservation equations to establish the fluid leakage model in CO_(2) storage processes by considering geologically activated faults.In such case,the crucial parameters(i.e.,leakage time and leakage amount)for fluid leakage along a fault are obtained.The results of the effects of different parameters on leakage time and amount show the advanced initial time of CO_(2) leakage,the extended duration and the increased leakage amount of CO_(2),with CO_(2) injection rate and reservoir permeability increasing.Meanwhile,the initial time and duration of CO_(2) leakage are unchanged while the leakage amount of CO_(2) is increased,when increasing the fault permeability.In addition,the fault permeability has the greatest impact on the leakage amount of brine and freshwater,compared to CO_(2) injection rate and reservoir permeability.The numerical results show that brine starts to leak earliest,followed by CO_(2),freshwater.Meanwhile,the duration of CO_(2) leakage along a fault is the longest,while the duration of brine leakage is the shortest.Additionally,the leakage amount of CO_(2) is the largest,followed by brine leakage amount and the freshwater leakage amount.