Fundamental processes related to CO2:CH4 exchange rates, mineral volume changes, organic mobility, and mineral stability occurring in fractured shale gas formations during exposure to supercritical CO2 (scCO2) are not well understood. In addition, experimental data used to distinguish differences between physico-chemical processes, e.g. adsorption, desorption, vs. intercalation or carbonation, are difficult to obtain and interpret. Atomistic simulations can be extremely valuable in the examination of interactions occurring between important clay minerals and scCO2 equilibrated with water or brines to identify dominate parameters controlling adsorption and desorption of acid gases. Density functional based molecular simulations are used to probe the reactivity, mechanisms, transport and structural implication in these systems and their impact on their potential use for natural resource recovery. Integrated with the simulations are results derived from a set of newly developed experimental techniques designed to characterize physico-chemical reactions at reservoir conditions. The variable expansion in clays is rationalized in thermodynamic terms and semi-quantitative concentrations of interlayer H2O and CO2 are established. These findings support the concept for utilizing CO2 as a working fluid to extract methane during secondary or tertiary recovery operations. Key finding indicate the hydration state of the clay are important and CO2 surface adsorption is driven by the evolution of the supercritical medium.

Adsorption, reactivity, and transport in clays under sequestration conditions: A density fucntional perspective

247th National Meeting (2014)

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