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

The performance of carbon disulfide ( CS 2 ) as a novel agent for enhanced oil recovery has been investigated by conducting a comprehensive series of core flooding experiments where in porous rock, CS 2 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 CS 2 , channeling in higher permeable layers and viscous fingering. Since CS 2 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 CS 2 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.