Dynamics and Wettability of Oil and Water in Oil Shales

It is critical to probe in situ the dynamics and wettability of oil, water, and gas trapped in the complex microstructure of oil-shale rocks. However, usual techniques cannot separate these fluids in shale rocks. Here, we use multifrequency and multidimensional nuclear magnetic relaxation (NMR) techniques for probing these dynamics. The frequency dispersion behaviors of the longitudinal relaxation rates 1/T-1 for oil and water confined in shales are interpreted through a relaxation model showing one-dimensional (oil) and two-dimensional (2D) (water) diffusing phases confined within the organic kerogen and mineral layers, respectively. We probe the average hopping and residence times of these fluids at pore surfaces and assign signals to water and oil at both organic and mineral pore surfaces for characterizing their local wettability. This allows interpreting our 2D T1T2 correlation spectra that could be made down-hole, thus giving an invaluable tool for investigating oil and gas recovery on these important porous rocks.