US Patent 7678742 Drill-in fluids and associated methods

Of the many methods provided herein, the present invention provides a method comprising: providing a drill-in fluid that comprises an aqueous base fluid, a viscosifier, a relative permeability modifier fluid loss control additive, and a degradable bridging agent comprising a degradable material capable of undergoing an irreversible degradation downhole; placing the drill-in fluid in a subterranean formation; and allowing the relative permeability modifier fluid loss control additive to reduce fluid loss from the drill-in fluid to the subterranean formation. Another example is a method of degrading a filter cake in a subterranean formation comprising: providing a filter cake produced by a drill-in fluid that comprises an aqueous base fluid, a viscosifier, a relative permeability modifier fluid loss control additive, and a degradable bridging agent comprising a degradable material capable of undergoing an irreversible degradation downhole; and allowing the degradable bridging agent to degrade.