Microscopic CO₂ Injection in Tight Formations: A Powerhouse Technology for Green Energy Transition

Advancing towards a green transition necessitates rely in renewable energies and the mitigation of Carbon Dioxide (CO₂) emissions through Carbon Capture, Usage, and Storage (CCUS) highlighting the substantial need to store greenhouse gases into geological formations, specifically tight formations. The subsurface storage and the consequent formation fluids displacement is challenging due to the rock’s pore network complexity. This work involved comprehensive laboratory work was performed on Bandera, Kentucky and Scioto sandstones including Routine Core Analyses, Mercury Injection Capillary Pressure (MICP), and Nuclear Magnetic Resonance (NMR)in order to determine novel criterion for optimal tight sand selection for safe and efficient CO₂ storage. Accordingly, Scioto sandstone is elected as the most appropriate candidate for CO₂–EOR among the tested sandstones due to its high micropore system capacity to store and confine injected CO₂. Coreflooding runs were conducted on Scioto sandstone composite coresto assess the storage efficiency under different injection schemes and NMR technology was employed to evaluate fluid distribution pre- and post-flooding, providing insights into fluids distribution in various pore sizes of the pore network. Results indicate that continuous miscible CO₂ was able to invade micropores providing the highest microscopic displacement compared to the other tested injection schemes. Such microscopic displacement can lead to permanent CO₂ storage in invaded tight pores due to capillarity mechanism. Our results demonstrate the effectiveness of NMR measurements in assessing pore fluids distribution and the potential for long term microscopic CO₂ storage and trapping in tight formations. Therefore, borehole NMR technology can be utilized to assess the near wellbore performance of CO₂ injection for EOR and geo-storage purposes.