The physical properties of pure and mixed geofluids confined in the narrow pores of earth materials play important roles in the uptake, mixing, storage, extraction, and transport of these fluids. Fluid-pore interactions play out at the molecular to microscopic levels, and include sorption, wetting, diffusion, and flow, all impacted by confinement effects. Neutron scattering experiments probe the pore structure and dynamics of pore fluids and provide detailed information about density and volume of fluid phases, sorption properties, as well as species mobility and self diffusion characteristics [1]. We will discuss excess sorption, neutron diffraction, quasi-elastic neutron scattering (QENS), and molecular studies which provide detailed insight into mineral associations of light hydrocarbons, water, and CO2 with shale components. This work aims at obtaining a basic understanding of the sorption capacity and fluid recovery amounts and rates of shales, and their dependence on shale composition, structure, and pore size distribution. Of great interest are the accessibilities of clay interlayer pore spaces, which contain large fractions of the clay and shale internal surfaces, to different fluids. Neutron diffraction (ND) measurements of the clay interlayer d001 Bragg peak intensities and and positions of clays in contact with these fluids can provide detailed insights into sorption mechanisms. ND and excess sorption data are interpreted to yield the mean fluid densities in the interlayer spaces, and possible coordinations with the interlayer cations and their hydration shells. Small-angle neutron scattering in combination with excess sorption measurements yields the density and volume of fluid sorption phases in nanopores and information about preferential sorption loci in rocks with multiscale porosities. Using Monte Carlo and MD modeling techniques, the underlying forces and mechanisms of fluid sorption processes in minerals and rocks can be determined.

Gas and supercritical fluid adsorption at mineral surfaces, in narrow pores, and to swelling clays: Impacts of hydration and fluid identity

255th National Meeting (2018)

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