Innovative applications of carbon dioxide foam in geothermal energy recovery: Challenges and perspectives - A review

Geothermal energy recovery from deep rock formations could significantly contribute to world energy demand by enabling sustainable and renewable energy resources. However, traditional reservoir development methods such as large-scale hydraulic stimulation have faced significant environmental and technical challenges, including reservoir damage, groundwater and surface pollution, high water consumption, and induced seismicity. Carbon dioxide foam is an attractive novel alternative for reservoir stimulation for oil/gas and geothermal energy recovery, while also offering the additional benefit of CO₂ sequestration. However, the applicability of CO₂ foam under deep underground conditions presents a significant challenge that requires comprehensive understanding. The study aims to explore the critical scientific potentials and challenges of CO₂ foam for reservoir stimulation, particularly in high-temperature and high-pressure environments. The foam decay process is critically assessed, encompassing critical mechanisms such as liquid drainage, coarsening and coalescence, which are influenced by temporal, pressure, and temperature variables. Recent studies report that the addition of optimal small quantities of different additives, including surfactant, polymer, and nanoparticles, enhances the physio-chemical properties of the foam and reduces foam decay at high temperatures. Surfactants like C22-tailed tertiary amine, N-erucamidopropyl-N,N-dimethylamine (UC₂₂AMPM), Oleylamidopropyldimethyl Betaine (OAPB) and Alpha-Olefin Sulphonates (AOS) with Cocamidopropyl Betaine (TEGO) have shown promising stability at 100 °C, while polymers like Partially Hydrolyzed Polyacrylamide (HPAM) and Guar gum improve stability but may degrade at high temperatures. Nanoparticle (NP) stabilised foam offers superior stability, though it is also affected by time and temperature. Previous studies have shown contradictory results on the influence of pressure on CO₂ foam highlighting the need for further comprehensive research. This paper also reviews pilot studies that have reported the successful implementation of CO₂ foam at natural gas recovery, offering insights that could be applied to geothermal energy recovery. Overall, the paper offers a systematic review of the recent innovations aimed at enhancing CO₂ foam performance under high-temperature high-pressure deep reservoir conditions and proposes future research directions and recommendations for novel additive combinations.