Abstract: The invention is a method of recovering hydrocarbons from an underground vertical hydrocarbon reservoir having a substantial vertical thickness, an oil saturation relatively near residual oil saturation to gas, and at least one injection well and one production well penetrating the reservoir. The method comprises injecting a surfactant slug into the bottom of the reservoir above any water zone or aquifer, and driving the surfactant slug upwards through the reservoir by the use of some driving force. The driving force may be supplied by one or more of a combination of methods comprising producing the gas cap of the reservoir, producing hydrocarbons banked above the surfactant slug, or injecting fluid below the surfactant slug. Hydrocarbons are recovered at one or more production wells.

Abstract: The invention is a method for recovering residual hydrocarbons from a reservoir which has been previously swept by gas. The invention steps comprise drilling and completing at least one horizontal injection well relatively near the top of the reservoir, injecting a miscible solvent through the horizontal injection well to create a curtain of solvent falling through the previously gas swept reservoir, and producing hydrocarbons and other fluids that have been banked below the falling solvent curtain through a vertical or horizontal production well.

Abstract: The invention is a method for recovering residual hydrocarbons from a reservoir which has been previously swept by gas. The invention steps comprise drilling and completing at least one horizontal injection well relatively near the top of the reservoir and relatively near a substantially vertically oriented boundary of the reservoir, drilling and completing at least one second injection well between the horizontal injection well and the vertical boundary of the reservoir, injecting a miscible solvent through the horizontal injection well to create a curtain of solvent falling through the previously gas swept reservoir, and injecting a drive fluid into the reservoir through the second injection well to drive the curtain of falling solvent horizontally through the reservoir. A production well is employed to produce hydrocarbons and other fluids that have been banked in front of the horizontally driven falling solvent curtain.

Abstract: The disclosed invention is a method of conducting a miscible carbon dioxide and hydrocarbon solvent flood in a steeply dipping reservoir. A mixture of carbon dioxide and light hydrocarbon solvent is injected in the updip end of the reservoir in such a ratio as to achieve at least multiple contact miscibility between the mixture and the formation hydrocarbons. As the flood front moves downdip with increasing formation pressure, the amount of injected enriching hydrocarbon solvent is decreased while multiple contact miscibility is maintained in the flood front. Hydrocarbons and carbon dioxide are recovered from at least one production well downdip of the injection well.