CO2 is produced massively during multiple industrial activities, which contributes to environmental issues like the greenhouse effect. A common technique for carbon sequestration is to store liquefied waste CO2 in deep underground reservoirs of depleted oil and gas wells. The integrity of the well formation is thus of vital importance for the proper function of the storage well. In this study, a nanoparticle injection technology is proposed and studied to reduce porosity and block micro-cracks in a cemented well, which can remediate leakage pathways for the CO2. This technique uses an electrical field to drive the movement of charged nanoparticles through the cement sheath, while simultaneously driving out chloride ions which encourage corrosion. A desktop testing device is first adopted to verify the effectiveness of the method and for nanoparticle selection. Then, a full-size pressure vessel that can test well-cementing systems under elevated temperature and pressures is designed and built. Further experiments use cracked well cement samples made through the pressure vessel cured under high temperature and pressures. Various experimental results, including the conductivity profile, and permeability by water adsorption test show that the nanoparticle injection technique can help to reduce the permeability and seal micro-cracks of the well cement sheath to a certain extent. Some strategies to effectively remediate the leaked well are also proposed.
