Abstract
This paper describes recently observed problems of cement sheath deposition on the inside circumference of a casing string. Actual job parameters and several proposed causes of the cement sheath are reviewed. The probable hypothesis for the cement sheath deposition is a combination of temperature, cement retardation, large cement volumes, and the surfactant contained in the slurry. This hypothesis was explored through the use of large-scale, physical models to duplicate the actual well problem in the laboratory.
Based on test results, the principal cause of cement sheath development is surfactant in the cement slurry. Once the surfactant is removed or retarding agent is added to the slurry, the cement slurry can be successfully placed. This paper also includes a laboratory procedure that provides for timely screening of potential cement slurries to determine sheathing tendencies.
