A Coupled Geomechanical and Flow Model for Evaluating the Impact of Drilling Fluid Imbibition in Reservoir Shale Formations

Imbibition of drilling fluid into shale formations significantly changes the mechanical properties of shales potentially causing swelling or disintegration of shale matrix and resulting in time dependent well integrity. This requires an accurate evaluation of the shale mechanical properties, fluid pressure and in situ stress alterations as a result of the imbibition and swelling. Single-phase flow models are currently utilized for modeling the imbibition of water into hydrocarbon-bearing shale formations in most of wellbore stability analysis. The effects of the natural fractures, wettability, and swelling have not been accounted for in those models making them not suitable for wellbore stability analysis in naturally fractured hydrocarbon-bearing formations.