This study is focused on the development of a fluid dynamic model for fluid leakage dynamics through the cement sheath within the casing-liner overlap, assuming the existence of a microannulus. The model is based on computational fluid modeling using Darcy's law under transient conditions. The effects of permeability, porosity, microannulus size, casing-liner cement overlap length, pressure, and temperature on fluid leakage were investigated. The model showed that higher permeability, larger microannuli, and shorter casing-liner cement overlap lengths significantly enhance the leakage rates, while lower porosity has an adverse effect. It was further observed that high operating pressures enhance leakage flow rates significantly, while temperature variations moderately affect the leakage rates. Additionally, the compressibility of the fluid plays a critical role by amplifying leakage rates at high pressures due to increased gas expansivity, leading to a more pronounced flow behavior under transient conditions. These results provide a strong foundation to optimize casing-liner overlap cement sheath properties and configurations to ensure good integrity under different well conditions.
Elzenary et al. (Wed,) studied this question.