Hybrid effect of basalt fiber and carbon fiber on the mechanical properties and microstructure of oil well cement

Abstract

In order to study the hybrid effect of basalt fiber and carbon fiber on the mechanical properties of oil well cement, the response surface design method was adopted to optimize the mixed content of basalt fiber and carbon fiber in oil well cement. With the help of X-ray diffraction (XRD) and scanning electron microscope (SEM) characterization, the crushed samples of oil well cement mixed basalt fiber and carbon fiber was micro-analyzed, and the enhancement mechanism of basalt fiber and carbon fiber on the compressive strength and splitting tensile strength of oil well cement was explored. The research results showed that basalt fiber and carbon fiber mixed can significantly increase the compressive strength and splitting tensile strength of oil well cement. Compared with oil well cement without fiber, the maximum compressive strength of oil well cement with mixed fiber for the curing time of 3 days, 7 days and 28 days was increased by 48.94%, 24.05% and 25.68%, respectively. The maximum splitting tensile strength of oil well cement with mixed fiber for curing time of 3 days, 7 days and 28 days was increased by 151.14%, 68.01% and 46.28%, respectively. Moreover, addition of 0.55 wt% basalt fibers and 0.09 wt% carbon fibers in oil well cement leads to more ductile behavior with higher peak compressive strength after 3 days curing time. Addition of 0.29 wt% basalt fibers and 0.32 wt% carbon fibers in oil well cement leads to more ductile behavior with higher peak splitting tensile strength after 3 days curing time. The addition of carbon fiber and basalt fiber does not change the hydrates of oil well cement after oil well cement hydration. The improvement of the mechanical properties of fiber-reinforced oil well cement mainly depends on the fiber bridging, crack deflection and fiber pulling out or breaking. Based on the theory of linear elastic fracture mechanics, a fiber oil well cement crack resistance model was constructed. The results of this study provide a certain reference for the application of fiber-reinforced oil well cement with requirements for tensile and crack resistance in oil and gas well cementing projects.