The Reinforcing Effect of Calcium-Based Whisker in High-Temperature Sand-Cement Mixtures

To satisfy the requirement of high temperature mechanical properties of oil well cement in heavy oil production,the application of calcium-based whisker in oil well cement as well as in cement with silica sand at high temperatures was investigated. First, the reinforcing and toughening effect of calcium sulfate whisker (CSW) and self-made whiskers (GZWS and GZWL) at 80℃ on oil well cement rock was tested, and then on the base of it, respectively. Compressive of cement with silica sand mixed with 5% GZWL in dry-heat curing at 600℃ was studied as well. The result showed that CSW had no reinforcing and toughening effect on oil well cemented rock, while GZWS and GZWL had obvious reinforcing and toughening effects, and GZWL with greater length diameter ratio was superior to GZWS. With the increased application of GZWL, the compressive strength and impact toughness of oil well cement stone increased, too. When 5% was added, the compressive strengths of cement rocks 1, 3, 7 and 28 d were increased by 18.7%, 42.4%, 20.6% and 20.7% respectively, compared with neat paste. Impact toughness was increased by 6.8%, 7.0%, 12.8% and 13.0% in the curing age. The result of the high temperature experiment showed the compressive strength of cement with silica sand with 5% GZWL was more than twice the contrast. It was demonstrated that GZWL efficiently acts as a high temperature resistance reinforcing admixture. Furthermore, a whisker with hydrophilicity had a good reinforcing effect, and the greater the long diameter ratio of whisker, the higher the reinforcing effect.