Efeito anti-regressão de sílicas alternativas na cimentação de poços de petróleo a alta temperatura e alta pressão

Abstract

Well cementing in high-temperature scenarios is a critical process in well construction. In high-temperature and high-pressure environments, challenges increase significantly because the cement must withstand elevated temperatures without compromising its stability and mechanical properties. This study aimed to evaluate the contribution of different replacement percentages in the combined use of two silica-rich (SiO2) waste materials: Quartz-Aluminous Sand (QAS) and Biomass Thermal Treatment Residue (BTTR), in comparison to a reference paste with Crystalline Silica, a typical mineral additive used in cementing operations in hightemperature environments. Specimens were cast according to international standards and cured directly in a curing chamber at 180 °C and 3000 Psi (20 MPa) for 7, 14, and 28 days. After these curing periods, the specimens underwent uniaxial compressive strength testing to evaluate their mechanical strength. Samples were collected for microstructural analyses, including Xray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), as well as qualitative analyses by energy dispersive spectroscopy (EDS). The results showed that the reference paste with 35% Crystalline Silica replacement preferentially formed the Xonotlite phase at all three curing ages. The ternary pastes, with 50% combined replacement of residues from industrial mortar production and biomass thermal treatment, preferentially formed the Tobermorite phase at all curing ages; the presence of the Tobermorite phase is a positive indicator for the long-term stabilization of ternary cementitious systems. Systems using the combined waste materials rich in silica (SiO2), with an AQAAQA/RTTB ratio below one, achieved 87% of the compressive strength when compared to the Crystalline Silica system. These aspects can provide a solid basis for optimizing formulations used in wells.