Water-or oil-based drilling fluid is the first foreign fluid that contacts the reservoir zone of a borehole. Most muds contain particles that are part of the mud formulation. These desirable mud solids can cause severe formation damage in the presence of a poor quality mudcake. Moreover, the cutting debris generated while drilling may produce enough micro-sized and colloidal particles to cause severe formation damage if a poor quality mudcake is deposited on the borehole wall. Hence, drilling muds that are unable to form a well-dispersed, tight, thin, plasterlike external mudcake on the borehole wall can cause serious formation damage because of the formation of an internal mudcake.