Effect of adding organo-modified montmorillonite nanoclay on the performance of oil-well cement paste in CO2-rich environments

Abstract

This work studies the influence of incorporating organo-modified montmorillonite (OMMT) nanoclay in class G cement pastes on chemical and mechanical resistance in CO2-rich environments. Cement paste specimens, with and without added nanoclay (0.5%, 1%, 2% in wt.), were submitted to degradation tests in CO2-saturated water and wet supercritical CO2, at 90 °C and 15 MPa. Scanning electron microscopy, X-ray diffraction, computed X-ray microtomography, pycnometry, Vickers microhardness measurements, and compressive strength tests were used to evaluate the effect of the OMMT nanoclay on the cement paste properties. The addition of 0.5% OMMT nanoclay increased the specific density and the compressive strength of hardened cement paste and decreased chemically modified layer as a result of CO2 attack. However, these effects became less evident with increasing OMMT nanoclay content. Additionally, the Vickers microhardness and compressive strength results suggest that OMMT nanoclay can prevent the high precipitation of carbonates that influences the diffusion of CO2 into cement paste.