Abstract: Steam is injected into the reservoir, heats the reservoir to mobilize and recover at least a fraction of reservoir hydrocarbons, forming a steam chamber in the reservoir. The steam is continuously injected into the reservoir to mobilize and recover reservoir hydrocarbons therefrom until at least one of (i) an upper surface of the chamber has progressed vertically to a position that is approximately 25 percent to 75 percent the distance from the bottom of the injection well to the top of the reservoir, and (ii) the recovery rate of the hydrocarbons is approximately 25 percent to 75 percent of the peak predicted recovery rate using steam-assisted gravity drainage. A viscosity-reducing hydrocarbon solvent is injected into the reservoir, the solvent being capable of existing in vapor form in the chamber and being just below the solvent's saturation pressure in the chamber, mobilizing and recovering additional hydrocarbons from the reservoir.

Abstract: A process for recovery of hydrocarbons from an underground reservoir penetrated by an injection well and a production well spaced from the injection well, the process comprising: