Experimental and visual analysis of diffusive mass transfer between matrix and fracture under static conditions

This study investigates miscible interaction between oil saturated porous rock and solvent filled fractures driven by diffusion and natural convection. This type of mass transfer interaction is commonly encountered during enhanced oil recovery applications, groundwater contamination, underground waste disposal, and greenhouse (mainly CO2) sequestration. The first part of the study focuses on the visual analysis of the transfer of a hydrocarbon solvent into oil saturated rock to clarify the physics of the interaction process. The second part consists of a series of core experiments to compare the oil recovery performances of the mass transfer process. iameter and 5 cm long cylindrical Berea sandstone samples were coated with epoxy to create co- and counter-current type interactions. Mineral oil and kerosene were used as oleic phases and n-heptane was used as a solvent. Aged samples were also included in the experiments. The effects of interaction type (co- or counter-current) and direction (horizontal, vertical, and inclined), aging, gravity, and oil viscosity on the rate of oil recovery by diffusion and ultimate oil recovery were clarified. The core experiments were compared to the equivalent 2-D visualization experiments conducted on 5 × 5 × 0.03 cm sand pack models to account for the dynamics of the process. y, a quantitative analysis was performed and the effective diffusion coefficients obtained from the slope of the log–log plot of the recovery-time plots were correlated to the rock and fluid properties.