Patent ID: 7731793

Claim:
A method of making a hydraulic cement slurry exhibiting reduced fluid loss comprising the steps of slurrying a hydraulic cement composition with water and admixing a fluid loss additive therewith, the improvement comprising: i providing a polymeric fluid loss additive which consists essentially of a polyvinyl alcohol (PVOH) blend and a dispersant, wherein the PVOH blend includes a first polyvinyl alcohol polymer and a second polyvinyl alcohol polymer, wherein both the first polyvinyl alcohol polymer and the second polyvinyl alcohol polymer have a degree of hydrolysis of at least 99%; wherein the first polyvinyl alcohol polymer has a characteristic viscosity of about 10 to 50 cps; wherein the second polyvinyl alcohol polymer has a characteristic viscosity which is about 50% to 100% higher than the characteristic viscosity of the first polyvinyl alcohol polymer; and ii combining the polymeric fluid loss additive with the cement slurry.