Fiber-reinforced cement slurries for subsurface energy applications: A review of rheology, flow behavior, and mechanical performance

Fiber-reinforced cement slurries are complex non-Newtonian suspensions whose fresh-state and hardened properties depend on fiber type, dosage, aspect ratio, surface chemistry, density contrast, and dispersion quality. This review critically examines fiber-reinforced cement systems for subsurface energy applications, with emphasis on oil-well cementing, slurry rheology, pumpability, displacement behavior, and mechanical performance. The reviewed literature shows that small fiber dosages may have limited influence on bulk rheology in some systems, whereas nanofibers or higher fiber contents can substantially increase yield stress, apparent viscosity, thixotropy, and shear-thinning behavior through fiber–fiber interactions, network formation, and enhanced frictional contacts. For example, reported data show that 0.2 wt% cellulose nanofibers can increase the yield stress of oil-well cement paste from approximately 2 Pa to 10–18 Pa, illustrating the trade-off between improved suspension stability and reduced pumpability. Conversely, low fiber dosages can improve early mechanical performance; for instance, pre-dispersed alumina nanofibers at 0.1 wt% have been reported to increase the compressive strength of Class H oil-well cement by about 30%–50%, depending on curing time. The reviewed studies indicate that fiber reinforcement can enhance crack resistance, toughness, and durability through bridging, pull-out, crack deflection, pore refinement, and improved fiber–matrix bonding. However, most available studies focus on static rheology or hardened mechanical properties, while the dynamic displacement of fiber-reinforced cement slurries in narrow, inclined, and eccentric annuli remains poorly understood. Future research should integrate rheological characterization, annular displacement experiments, fiber-transport modeling, and mechanical validation to design cement slurries that are both pumpable during placement and durable after setting.