1. . 
A class of water muds that use partially hydrolyzed polyacrylamide (PHPA) as a functional additive, either to control wellbore shales or to extend bentonite clay in a low-solids mud. As a shale-control mud, PHPA is believed to seal microfractures and coat shale surfaces with a film that retards dispersion and disintegration. KCl is used as a shale inhibitor in most PHPA mud designs. In low-solids muds, PHPA interacts with minimal concentrations of bentonite to link particles together and improve rheology without increased colloidal solids loading.
Alternate Form: PHPA
See: acrylamide polymer, acrylamide acrylate polymer, acrylate polymer, beneficiation, clay extender, clay-water interaction, clear-water drilling, encapsulation, flocculant, hardness ion, low-solids mud, potassium mud, seawater mud