Abstract: Novel completion fluid compositions for fluid loss control during completion conducted on a wellbore penetrating a subterranean formation are disclosed. In particular, the composition described herein has an aqueous base fluid, a suspension polymer, a fluid loss control additive, and a degradable bridging agent. These novel compositions provide a means to temporarily seal a wellbore communicating with a subterranean formation to enable completion or workover operations to be performed, after which the composition can be removed by contact with a mild clean-up composition.

Abstract: Drill-in fluids disclosed herein comprise an aqueous base fluid, a viscosifier, a fluid loss control additive, and a degradable bridging agent comprising a degradable high strength polymetaphosphate material capable of undergoing an irreversible degradation downhole. The present disclosure further relates to a method for controlling fluid loss through a subterranean surface by using the drill-in fluid for form a filter cake on the subterranean surface. Also provided is a method of degrading a filter cake with an aqueous fluid or aqueous acidic fluid, wherein the filter cake is produced from the drill-in fluid. Further provided is a specific order of addition of constituents of the drill-in fluid, which results in improved filter cake performance and/or filter cake removal.