PHPA (Partially Hydrolyzed Polyacrylamide) powder is a high-molecular-weight, anionic, water-soluble polymer used in drilling fluids to stabilize boreholes by preventing shale swelling and erosion, acting as a fluid loss reducer by forming a filter cake, and encapsulating drill cuttings. It functions as a viscosifier, friction reducer, and flocculant, enhancing hole stability and facilitating efficient solids removal in various water-based mud systems, including fresh water, brine, and KCl.