SACK BLACK shale inhibitor additive is a partially water-soluble, water-dispersable, coupled Gilsonite. It helps reduce HPHT and dynamic fluid losses, torque, drag, and filter-cake thickness. The coupler enhances inhibitor wettability in water-based fluids and requires no additional coupler when added to a mud system. 

The free-flowing powder is added directly to the mud system through the mixing hopper. SACK BLACK additive is ~80% non-soluble in water and therefore remains in a particulate phase in the mud system, becoming a malleable solid that deforms as needed to seal microfractures in shales and to reduce filtrate invasion in sands.