Mechanism of Calcium Carbonate Whisker Enhancing Cement's Resistance to Contraction and Its Application

Perforation, acidizing and fracturing operations often cause damage to the integrity of cement sheath. Volumetric contraction of cement during hydration process always produces micro fissures and micro annulus, forming channeling path for channeling between formations, which in some cases may cause oil and gas to channel to the surface. These problems are brought about by the lack of toughness of set cement and the volumetric contraction of cement slurry during hydration. In laboratory studies, calcium carbonate whisker was added to cement slurry at 0, 1%, 2%, 3% and 4%, respectively, and the flexural strengths, compressive strengths, rate of volumetric contraction, and the overall properties of the set cement at 1, 3, 7, 14 and 28 days, respectively, were measured. Compared with cement slurry without treatment of calcium carbonate whisker, cement slurries treated with 3% calcium carbonate whisker, after aging for 28 days, had compressive strength increased by 36%, flexural strength increased by 33.67%, and volumetric contraction reduced by 82.97%. The overall properties of the cement slurry also satisfied the need for well cementing.