Geopolymers for integrity of geothermal and CO₂ sequestration wells: A state-of-the-art review

Geopolymers, despite their limitations, have the potential to reduce carbon footprints in the energy sector as an environmentally friendly cement alternative, especially in geothermal applications. While geothermal wells are increasingly being recognized as a sustainable energy source, maintaining well integrity poses significant challenges due to extreme conditions such as high temperatures, pressures, and corrosive environments. These conditions often lead to the degradation of conventional cementitious and Class G Cement materials, which can lead to unwanted atmospheric emissions and groundwater contamination. Advanced nano-geopolymers (i.e., aluminosilicate-based materials known for their high thermal and chemical resistance and developed to address geopolymer limitations), are emerging as promising alternatives for geothermal well cementation. Studies have shown that the use of geopolymers in drilling operations can provide superior borehole stability while reducing environmental impact. The potential for carbon storage in geothermal wells adds significant value to these applications, contributing to climate change mitigation efforts. Current experimental studies evaluate the mechanical, thermal, and chemical stability of geopolymer formulations under simulated geothermal conditions, investigating critical parameters such as bond strength, permeability, and durability when exposed to high temperatures, pressures, and corrosive gases such as CO₂ and H₂S. This research also explores the unique challenges of geothermal well construction compared to conventional oil and gas wells, focusing on thermal stresses and material degradation in aggressive chemical environments. While challenges remain, advances in geopolymer technology continue to improve their applicability for combined geothermal well integrity and Carbon Capture, Utilization, and Storage (CCUS) applications.