1. n. 
In drilling fluid parlance, the absorption of a polymer film onto cuttings and wellbore walls to form a coat or barrier. The term is usually applied to shale encapsulation by long-chain, acrylamide-acrylate (PHPA) polymers. Negative sites on PHPA may bond to positive sites on the clays in shales, although it is not well-defined how (or how well) encapsulation works. A viscous polymer film, according to some test results, slows diffusion of water molecules into the shale and thus slows hydration and disintegration. This does not prevent wellbore problems but can delay their onset.