| abstract |
Powdered and liquid fluid loss additives are disclosed for use in cementing wellbores, particularly oil and gas wellbores. Excellent fluid loss control is achieved over a wide range of conditions using various cements systems. The invention utilizes polyvinyl acetate polymers as a fluid loss additive. The polyvinyl acetate polymer is used in conjunction with a dispersing sulfonated polymer and surfactant. This highly effective combination is then adjusted to individual well conditions with chelating agent, cross-linking agent, biocides, antifoams, or combinations of these. The dispersants are novel dispersing agent polymers such as melamine sulfonate polymer, vinyl sulfonate polymer and styrene sulfonate polymer and mixtures of these. These dispersant materials are usually prepared at low pH and can be used in the acid form, or neutralized to form salts of the polymers, wherein the salt can be a Group I or Group II metal salt, or ammonium salts (common salts). |