Fluid loss is the measurement of filtrate passing drilling fluid into a porous permeable formation. Low fluid loss is a characteristic of good drilling fluids and the key to borehole integrity. The goal of a good drilling fluid is to create a thin filter cake on the sides of the borehole. This prevents the excessive loss of fluids into the formation. The drill pipe formation of filter cake or a layer of wet mud solids on the wall of the hole in the formation.