Laboratory evaluations on the mechanical impact of nanoparticle additives in a heavy wellbore cement

Abstract

Ever since its inception, the oil and gas industry has taken a short term approach to maintaining zonal isolation and permeant plugging using wellbore cements. Continuous changes to their environment over the life of a well plague the cement with shifting pressures and temperatures that exploit its brittle nature, as well as its weak bond with steel casing. As a result, failure occurs and allows communication between previously isolated formations. Concern over migratory fluids along the wellbore has given rise to a fresh desire to perfect wellbore and P&A cements by making use of nanoparticle additives. The purpose of this study and the thesis it frames is to evaluate the mechanical impact small concentrations of nanoparticle barite and magnetite have on a heavy wellbore cement. Compressive and tensile strengths of the cement body have been determined and experimental apparatuses and procedures have been established and used to evaluate the bond strength of cement to a steel substrate from both pure tensile as well as shear loadings. Results show that while a significant improvement to the bond strength is seen as the nanoparticle concentration increases, the compressive strength is only marginally improved and a negative impact is seen in the tensile strength of the cement body. Additionally, an increase in stiffness was seen as nanoparticle concentrations increased; and their interactions in a fully hydrated cement were visually observed using scanning electron microscopy (SEM).