A method to enhance steam flooding where at least two horizontal wellbores are utilized. Carbon dioxide is injected into a lower perforated horizontal wellbore. Once sufficient carbon dioxide has been injected into the formation, steam is injected through the lower horizontal wellbore. The steam displaces the carbon dioxide into the formation where it contacts and mixes with hydrocarbonaceous fluids. Steam causes the carbon dioxide to expand, thereby providing for a better sweep of the formation. Steam injection is ceased and liquid carbon dioxide injection again is commenced. Afterwards, steam is injected again into the formation. This sequence is continued until it becomes uneconomical to produce hydrocarbonaceous fluids from an upper horizontal wellbore. Hydrocarbon displacement efficiencies are enhanced when hydrocarbons are produced into the upper horizontal wellbore due to viscosity and density differences.