Adsorption behaviour and thermodynamics of water on deep reservoir and its influence on CO2 sequestration

Abstract

In this study, the adsorption experiments of water vapour on deep reservoir were conducted. The thermodynamics for water vapour adsorption were analysed. Results illustrate that primary binding centres have stronger affinity than secondary binding centres. Water molecule will be preferentially trapped at primary binding centres in low-pressure region. In high-pressure region, secondary adsorption predominates. Primary adsorption spontaneity increases with pressure. At secondary binding centres and total binding centres, the spontaneity degree quickly improves and then slowly decreases as pressure increases. The transfer of water molecules from the more energetic binding centres to the less binding centres leads to the initial reduction in entropy loss (ΔS) and isosteric heat of adsorption (Q st). The late enhancement in ΔS and Q st is caused by the growing water clusters. Water vapour adsorption can promote CH4 desorption. By occupying adsorption sites and reducing pore connectivity, water vapour adsorption causes an unfavourable effect on CO2 sequestration.