A laboratory investigation was conducted on oil displacement from porous media by the use of either a slug of propane followed by gas or a slug of carbon dioxide followed by water. A comparison was made of the efficiencies of these two solvent flooding processes for petroleum reservoirs. The results of flooding experiments on cores and on scaled pattern models showed the effect, on oil recovery, of type of porous medium, pore geometry, length to width ratio of the flood pattern, fluid viscosities, and miscibility. Oil recoveries of from 60 to 80% of the original oil in place were obtained by these solvent flooding processes as compared with conventional waterflood recoveries of between 35 to 50% on the same cores and linear models. Furthermore these recoveries were obtained with solvent slug sizes of 10 to 30% of a hydrocarbon pore volume, with less solvent being required as the length of the flood path increased. Data showing the relations between mobility ratio and volumetric sweep efficiency for the propane-gas and carbon dioxide water flooding processes for two widely different types of porous medium are included in this paper.
It was concluded that in reservoirs where pressure, oil viscosity and composition, and flooding pattern are favorable, either of these solvent flooding processes would give oil recoveries considerably higher than conventional waterflood or gas drive. It was further concluded that this improved recovery would be realized earlier in the life of a flood with carbon dioxide-carbonated water than with propane followed by gas.