HIGH TEMPERATURE VISCOSIFYING AND FLUID LOSS CONTROLLING ADDITIVES FOR WELL CEMENTS, WELL CEMENT COMPOSITIONS AND METHODS

摘要

A high temperature viscosifying and fluid loss controlling additive for use in well cements, well cement compositions including the additive and methods of usin g the compositions are provided. The well cement compositions of this invention ar e comprised of a hydraulic cement, water and a viscosifying and fluid loss controlling additive comprising a mixture of a polymer comprised of at least one monomer which is calcium tolerant, anionic and disperses basic cement slurries, at least one monomer which hydrolyzes i n basic cement slurries to generate anionic carboxylate groups that bind with calcium and viscosify the slurries and at least one monomer which generates non-ionic pendant groups o n the polymer upon hydrolyzing in basic cement slurries to prevent polymer precipitation a nd a homopolymer of a monomer which hydrolyzes in basic cement slurries to genera te anionic carboxylate groups that bind with calcium, viscosify the slurries and preven t settling in the slurries.