Rheology, curing temperature and mechanical performance of oil well cement: Combined effect of cellulose nanofibers and graphene nano-platelets

Abstract

Cellulose nanofibers (CNFs) were prepared through acid hydrolysis and used in combination with graphene nano-platelets (GNPs) as modifiers for oil well cement (OWC). The rheology behavior of CNF/GNP-OWC slurries at three temperatures (i.e., 20, 40, and 60°C) was measured and modeled using four different rheological models. Thermal properties, surface functional groups, morphology, and mechanical performance of the composites were characterized. CNF/GNP-OWC slurry exhibited a typical shear-thinning behavior with reduced shear viscosity at higher shear rates. The use of CNFs and GNPs led to increased yield stresses of fresh CNF/GNP-OWC slurry and temperature significantly influenced the yield stress values. Among these rheology models, the Vom Berg model exhibits the best fitting result of the slurry rheology data (R2=0.999). The addition of CNFs and GNPs increased degree of hydration (DOH) value of CNF/GNP-OWC composites. Both flexural and compressive strengths of the CNF/GNP-OWC composites were enhanced with added CNFs and GNPs. The reinforcing mechanism was attributed to the increased DOH, reduced pores, and bridging effect of CNFs and GNPs in the composites.