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.

This paper discusses the Oberbeck-Boussinesq approximation for heat and solute transport in porous media. In this commonly used approximation all density variations are neglected except for the gravity term in Darcy's law. However, in the limit of vanishing density differences this gravity term disappears as well. The main purpose of this paper is to give the correct limits in which the gravity term is retained, while other density effects can be neglected. We show that for isothermal brine transport, fluid volume changes can be neglected when a condition is fulfilled for a dimensionless number, which is independent of the density difference and specific discharge. For heat transfer an additional condition is required. One-dimensional examples of simultaneous heat and brine transport are given for which similarity solutions are constructed. These examples are included to elucidate the volume effects and the corresponding induced specific discharge variations. Finally, a two-dimensional example illustrates the relative effects of volume changes and gravity.

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