A wellbore stability model for shale formations: Accounting for strength anisotropy and fluid induced instability

The presence of weak planes in rock fabric along with interactions of clay minerals with aqueous fluids are the major causes of instability in shale formations. Reviewing the current state-of-the art of wellbore stability models indicates that the interaction of aqueous fluids with clay minerals has been ignored or over-simplified due to the complexity of the processes. In this paper, a diffusion-sorption model, which is considered to be a...