Rheological and mechanical properties of oil-well cement reinforced by hybrid inorganic fibers

The mechanical integrity of cement sheath during reservoir stimulation is critical for oil and gas wells. It is essential to optimize and design a cement slurry system that not only meets the primary cementing requirements but also has a good mechanical performance. In this study, effects of hybrid inorganic short-cut carbon fiber and basalt fiber on the rheological and mechanical performances of shale gas well cement were investigated. The rheological performance of prepared cement reinforced with hybrid inorganic fibers was researched by the viscometer, filtration loss meter, and consistometer. And the cement stone samples were tested by pressure testing machines. According to rheological behavior experimental results, the Power-law model was most suitable for describing the rheological behavior of slurries among the three models used in this study, and the rheological parameters, including consistency coefficient, yield point, and plastic viscosity of the studies cement slurries with fibers slightly increased in a suitable engineered addition. Combination of carbon fiber and basalt fiber can compromise the effect of the addition of a single fiber on the rheological properties of slurry and does not affect the workability and pumpability of slurry in terms of the fibers' additive amount of this study. Moreover, the fibers can also improve the sedimentation stability of cement slurry without significantly affecting its filtration loss and thickening time. In terms of mechanical properties of cement stone, no markedly difference in compressive strength was found between reference slurry and slurries with fibers, while the addition of carbon fiber and basalt fiber significantly improved the tensile strength and flexural strength, and also mitigated the brittleness of cement stone. The findings of this study can offer a key reference for the cement slurry design of oil and gas wells requiring reservoir stimulation.