Efeito da adição de cargas minerais leves na resistência mecânica de grautes para cimentação de poços offshore

摘要

The preparation of cement slurries for offshore well cementing involves mixing all solidcomponents to be added to the mixing water on the platform. The aim of this work was tostudy the formulation of pre-prepared dry mixtures, or grouts, for offshore oilwellcementing. The addition of mineral fillers in the strength of lightweight grouts applied fordepths down to 400 m under water depths of 500 m was investigated. Lightweight materialsand fine aggregates were selected. For the choice of starting materials, a study of thepozzolanic activity of low-cost fillers such as porcelain tile residue, microsilica anddiatomaceous earth was carried out by X-ray diffraction and mechanical strengthtests. Hardened grouts containing porcelain tile residue and microsilica depicted high strengthat early ages. Based on such preliminary investigation, a study of the mechanical strength ofgrouts with density 1.74 g/cm3 (14.5 lb/gal) cured initially at 27 °C was performed usingcement, microsilica, porcelain tile residue and an anti-foaming agent. The results showed thatthe mixture containing 7% of porcelain tile residue and 7% of microsilica was the one withthe highest compressive strength after curing for 24 hours. This composition was chosen to bestudied and adapted for offshore conditions based on testes performed at 4 °C. The groutcontaining cement, 7% of porcelain tile residue, 7% of active silica and admixtures (CaCl2),anti-foaming and dispersant resulted satisfactory rheology and mechanical strength aftercuring for 24 hours of curing