Hydration Products and Mechanical Properties Investigations of Nanofiber Additives in Cement Wellbore Environments

Abstract

Abstract Complete zonal isolation along with wellbore integrity is paramount to oil field development which ensures environmental safety and favorable well economics. However, the complexity of wells today increases the wellbore architecture's susceptibility to unavoidable stress events. This research focuses on utilizing aluminum oxide nanofibers (ANF's) in oil well cements. ANF's are a relatively new type of composite nanomaterial that has the potential to provide significant mechanical performance. A Scanning Electron Microscope (SEM) was used to study the morphology of ANF's. Nanofibers were ultrasonicated in water and characterized quantitatively by ultraviolet–visible spectrophotometry (UV-Vis) and qualitatively by transmission electron microscope (TEM) images. The results show ANF's have high dispersibility. Cement class "H" formulations containing different percentages of ANF's by weight of cement (BWOC) were mixed and cured with various additives for 24 hours at 76.7 °C with 24.13 MPa. Uniaxial compressive strength (UCS) tests were performed which suggested the inclusion of ANF's increases the UCS when compared to cement samples without ANF's. Although, high concentrations of ANF's results in nanofiber agglomeration which weakens the mechanical properties of the cement samples. The elastic properties of the cement samples were measured under cyclic confining pressures. All cement samples experienced low inelastic deformation during confining pressure cycling. Samples containing 0.1% ANF's BWOC possessed the lowest Modulus of Elasticity (MOE) and the highest Poisson's Ratio. This increases the cement sheath's chances of resisting deformation due to casing contraction/expansion. An X-ray diffraction (XRD) analysis was conducted to determine the hydration products. All cement formulation experienced the same XRD pattern with only variations in the diffraction peaks. Cement samples containing ANF's contained increased amounts of calcium silicate hydrate (C-S-H) gel due to the nucleation effect and the formation of tobermorite.