The role of moisture adsorption in wellbore stability of shale formations: Mechanism and modeling

In this study, the constitutive equations are generalized to consider the case of non-ideal solutions. The coupled transport equations are solved using a finite difference method and numerical computations are conducted to predict the stability of the wellbore. Having developed a transient model that predicts the instantaneous moisture content around the wellbore, it is possible to update the rock compressive strength as a function of its moisture content using available empirical correlations in the literature. The results of this analysis indicate that the range of safe mud weight reduces substantially due to moisture adsorption. Comparisons of several compressive failure criteria indicate that stability reduction of the wellbore due to moisture transport is a common pattern based on the selected criteria. The results of this investigation assist in drilling fluid optimization and address wellbore stability issues in troublesome shale formations.