Weighted fluid loss control pill for completion and workover operations

A method of plugging an opening in a reservoir comprising:

• a) injecting into a subterranean formation, a treatment fluid comprising:
• i) a weighted brine carrier fluid;
• ii) a biopolymer suspension agent for increasing the viscosity of said weighted brine carrier fluid;
• iii) a particulate polymetaphosphate composition, wherein the particulate polymetaphosphate composition is present in an amount ranging from 10 to 200 pounds per barrel of carrier fluid, and wherein the polymetaphosphate composition is selected from the group consisting of sodium polymetaphosphate ((NaPO3)6), sodium trimetaphosphate ((NaPO3)3), potassium polymetaphosphate ((KPO3)6), potassium trimetaphosphate ((KPO3)3), magnesium polymetaphosphate (Mg(PO3)2) and calcium polymetaphosphate (Ca(PO3)2);
• and,
• iv) a fluid loss control additive;
• b) blocking at least one opening in said subterranean formation with the particulate polymetaphosphate composition;
• c) blocking at least one gap between particles of the particulate polymetaphosphate composition or a gap between the particulate polymetaphosphate composition and said opening with the fluid loss control additive;
• d) performing one or more additional operations that uses a fluid in said subterranean formation, wherein the fluid is not lost through the blocked openings;
• e) circulating an aqueous acidic fluid through said wellbore to remove the particulate polymetaphosphate composition and the fluid loss control additive;
• and,
• f) flowing fluids through the unblocked opening.