Abstract:

The leakage of fluid （CO₂, brine and freshwater） along fault is a crucial issue that cannot be ignored during CO₂ 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 CO₂ 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 CO₂ leakage, the extended duration and the increased leakage amount of CO₂, with CO₂ injection rate and reservoir permeability increasing. Meanwhile, the initial time and duration of CO₂ leakage are unchanged while the leakage amount of CO₂ 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 CO₂ injection rate and reservoir permeability. The numerical results show that brine starts to leak earliest, followed by CO₂, freshwater. Meanwhile, the duration of CO₂ leakage along a fault is the longest, while the duration of brine leakage is the shortest. Additionally, the leakage amount of CO₂ is the largest, followed by brine leakage amount and the freshwater leakage amount.

Key words: CO₂ storage, geological fault, fluid leakage, leakage time, leakage amount