Improving Caprock Sealing Capacity through Surfactant and Polymer Treatments: Implications for CCS in Poland

Carbon capture and storage (CCS) is a vital technology for mitigating climate change by reducing anthropogenic CO2 emissions. Depleted hydrocarbon reservoirs are promising storage sites due to their proven containment history, existing infrastructure, and well-characterized geology. This study evaluates the sealing capacity and wettability behavior of caprocks from abandoned gas wells in Poland through a comprehensive mineralogical characterization using X-ray diffraction. High-pressure CO2 wettability tests revealed that mineralogical composition strongly influences wettability: carbonate and samples maintained hydrophilic behavior under elevated pressure, while quartz-rich samples transitioned rapidly to CO2-wet states, compromising seal integrity and increasing leakage risk. To address unfavorable wettability, two mitigation strategies were assessed: adsorption of the anionic surfactant sodium dodecylbenzenesulfonate (SDBS) and novel application of a hydrophilic polymer coating (P100). Both treatments effectively reduced contact angles and enhanced water-wet behavior with the polymer coating demonstrating superior durability and stability under simulated reservoir conditions. These findings improve the understanding of CO2-induced wettability alterations in heterogeneous caprock lithologies and provide practical methods to enhance capillary trapping and storage security. The study’s outcomes contribute valuable insights for site selection, operational approaches, and long-term risk mitigation strategies in geological CO2 storage projects.