Epoxy resin‐cement paste composite for wellbores: Evaluation of chemical degradation fostered carbon dioxide

Excessive carbon dioxide (CO2) environmental emission can be partially solved using carbon geological storage technologies. Up‐to‐date materials in CO2 injection wells are strongly susceptible to acidic attacks causing their irreversible damage over a long time scale. This study investigates degradation by CO2 of epoxy resin‐cement paste composites at elevated pressure (50 bar) and temperature (70°C) to mimic wellbore conditions. The effect of epoxy resins on cement carbonation was evaluated by phenolphthalein test, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and numerical simulations. According to electronic‐structure‐based molecular dynamics simulations, the epoxy resin forms a separate phase that blocks potential reaction sites between the cement and CO2. Thanks to CO2‐phobic behavior, the resin repels CO2 and minimizes cement damage due to degradation process. The optimal content of epoxy resin in the cement paste was up to 30% w/w. The reported results provide clear guidelines for further evolution of reinforced cements for use in CO2 injection wellbores. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.