See Inadvertent ReturnThe loss of drilling fluid, including slurry and lubrication, from the slurry or lubrication system. A special form of inadvertent return, where the fluid exceeds the strength and confining pressure of the ground and reaches the surface or waterway, is called a hydrofracture or frac-out. and HydrofractureA special form of inadvertent return in which drilling fluid reaches the surface or waterway. Also called a frac-out..
