Effect of Sugar on Thickening Time of Cement Slurries
Sugar is widely recognized as a cement retarder by the drilling industry and has been used in cementing operations where cement returns are expected on surface. Experts disagree about the effect that sugar has on cement slurries, a few believe that it acts as both an accelerator and a retarder depending on the concentration, but the majority believe that the sugar acts as a retarder only.
Preliminary lab tests performed at Louisiana State University showed that sugar could be both, a retarder or accelerator, depending on the concentration of sugar used. The effect appeared to be quite controversial and the issue deserved further study.
The objectives of this research project were to verify these unexpected results, perform more testing, and try to find an ambient concentration of sugar that has no effect on the thickening time of the slurry. The cement and sugar systems studied in this project where all tested in the Halliburton Fluids Center in Lafayette, Louisiana. For these tests, cement Lafarge Type I and common granulated table sugar were used.
Lab tests of thickening time and compressive strength were conducted using different concentrations of sugar. The results indicated that the sugar acts as a retarder of cement slurries when added in small concentrations and as an accelerator when added in high concentration. The compressive strength tests showed that the accelerated slurries developed very little or no compressive strength, indicating that no hydration of the cement grains occurred. The retarding mechanism of the sugar is well documented, but the acceleration effect is not widely known. An attempt was made to explain the mechanisms involved in the shorter thickening time and lack of compressive strength observed at high sugar concentrations.
These project findings are of great practical importance to the drilling industry. Sugar is currently used in the field with the idea that it will always retard the slurry.
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Marta Susana Bermudez works for Chevron as a production engineer. She graduated with a BS degree in chemical engineering from the Universidad Metropolitana in Caracas, Venezuela, and a masters’ degree in petroleum engineering from Louisiana State University. Before going to graduate school, Bermudez worked for Schlumberger in Venezuela for 8½ years in cementing and drilling fluids. While working for Schlumberger, she was assigned to East Venezuela, Mexico, West Venezuela, Oklahoma, and New Orleans.