Geologic carbon sequestration (GCS) is considered by the Intergovernmental Panel on Climate Change (IPCC) to be a critical approach to reduce the accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere during the transition to a low-carbon energy economy. Subsurface rocks can trap the supercritical CO2 phase within pores on timescales sufficiently long to allow dissolution and mineralization reactions. Capillary trapping in porous reservoir rocks is governed by pore throat dimensions and the interfacial free energy (IFE) of fluid/fluid and fluid/mineral pairs. All IFE values contain contributions from long- and short-range interactions that are seldom measured or predicted individually, limiting our ability to predict changes in wetting with conditions such as pressure or solution chemistry. However, all phases interact through long-range van der Waals (vdW) forces that are rigorously determined by the full optical properties of the relevant phases. We show a consistent experimental and computational method to determine these contributions to IFE for relevant GCS fluids and minerals. We used in situ inelastic X-ray scattering at approximately 10 keV to measure the low-energy electronic excitation spectra of GCS relevant fluids and minerals at up to 100 bar and 65C. These data were processed using the Krämers-Kronig transform to generate the full complex dielectric properties and Lifshitz theory to calculate the London dispersion functions for vdW calculations. We predict the contribution of vdW interactions to the IFE of fluid/fluid and fluid/mineral pairs including water, brine, supercritical CO2 and CO2-saturated water as a function of pressure. This work clarifies the roles of vdW interactions in subsurface systems including the stabilization of nanoscale brine wetting films in CO2/H2O/mineral systems and the excess sorption of CO2 in nanoscale pores.

van der Waals wetting forces relevant to geologic carbon sequestration from inelastic x-ray scattering

253rd National Meeting (2017)

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