Miscible displacement of oils by carbon disulfide in porous media: Experiments and analysis

Abstract

The performance of carbon disulfide (CS2) as a novel agent for enhanced oil recovery has been investigated by conducting a comprehensive series of core flooding experiments where in porous rock, CS2 miscibly displaces “oil” (model fluids such as n-Decane, mineral oils, and crude oils) with a large range of viscosities and field-relevant flow rates. The recovery of oil and the three-dimensional spatial distribution of injected and displaced fluids were obtained from x-ray computed tomography. In all experiments, the displacement was unstable. The dominating displacement patterns were gravity under-run of the more dense CS2, channeling in higher permeable layers and viscous fingering. Since CS2 was fully miscible with all considered fluids, no difference in behavior between model fluids and crude oils was found. The recovery after injection of one pore volume of CS2 was parametrized using the dimensionless scaling groups Péclet number, gravity to viscous forces ratio G, and the logarithmic viscosity ratio R. At small viscosity ratios and large flow velocities (viscous dominated flow, small values of G), recoveries over 90% were observed. Slower flow and more viscous oils reduce the oil recovery.