Depleted shale gas formations as naturally-occurring storage compartments for hydrogen: A molecular-level assessment

Abstract

The interaction of hydrogen with porous media is of great interest when assessing the potential of subsurface hydrogen storage. Shale gas formations resemble naturally-occurring storage compartments owed to their unique sealing features. Upon abandonment, these depleted formations can be utilized for long-term storage of hydrogen. The study begins with recreating realistic organic matter on a computational molecular simulation platform filled with methane at some assumed abandonment pressure for the assessment of depleted shale formations adsorption capacity for hydrogen. This study seeks to elucidate the adsorption behavior of hydrogen in the presence of organic matter and methane at the molecular level over a wide range of pressures and temperatures. The suitability of the Langmuir model for the prediction of hydrogen adsorption is evaluated. The results obtained indicate that hydrogen adsorption correlates with pressure, temperature, kerogen types, and maturity. In the presence of methane, hydrogen adsorption is predicted to be directly correlated with pressure. The difference in the adsorption of hydrogen is more pronounced at low temperature. Similarly, the difference in the adsorption is less at low pressure (e.g., 400 psi) and starts to increase with pressure up to 6000 psi. The adsorption capacity of hydrogen in the presence of methane is also lower than the case without methane for all kerogens. Isosteric heat also appears to be high at high temperature in the absence of methane. The Langmuir model appears to be a suitable theoretical framework to predict the hydrogen adsorption under varying pressure and temperature conditions.