X-ray Core-Flooding Experiments to Study H2 and Cushion Gas Residues in Highly Permeable Sandstone Formations

This work mainly aims to evaluate gas flow behavior in sandstone for different gas types and enhance the understanding of the role of capillary pressure and gas displacement efficiency during underground storage. With this motive, we conducted a series of gas core-flooding experiments into brine-saturated sandstone core samples using three different gases (CO2, CH4, and H2), at ambient temperature. We integrated an X-ray scanning technique to detect the gas residual after the core-flooding experiment. We mainly report that: 1- Gas core-flooding experiments showed that CO2 exhibited slightly the highest average gas saturation by ≈ 40%, while the average gas saturation for H2 and CH4 were almost similar ranging between 25-30%. However, the gas residuals in the sample were zero for all gases. These outcomes suggest that the gas residuals in this sandstone sample are unaffected by the gas type, indicating the high potential for gas recovery (especially for hydrogen during withdrawal cycles), and the high displacement efficiency in sandstone rocks. 2- The calculated capillary numbers at constant flowrate (2 cc/min) were in very low values (×10-8), suggesting that all gases entered the pores immediately during the injection, and acted as a non-wetting phase.