or mixtures of injection fluids including without limitation steam although a variety of fluids or mixture of fluids may be used in the practice of this invention in all cases such fluids should be injected through the horizontal section 4a of the well bore at a point located at or near the toe 6 of the well bore where recoverable fluids are used as the injection fluid such fluids may be separated and recovered at the surface from the mixture 13 of fluids produced from a well through means known in the art regardless of the fluid used as the injection fluid simultaneous injection of the injection fluid 11 and production of the mixture 13 of diluted and upgraded oil and injection fluid from the reservoir 1 is preferred the present invention will operate with greatest efficiency in reservoirs characterized by high permeability 1 darcy or greater as typically found in heavy oil bearing reservoirs composed of unconsolidated material however where reservoir conditions are less than ideal means e g fracturing acidizing the reservoir etc known in the art can be used to improve reservoir permeability and to facilitate the efficient performance of the process of the invention where initial conditions within the reservoir 1 initially do not provide sufficient 34 injectivity 34 to allow for the commencement of simultaneous production and injection of fluids other processes known in the art such as cyclic injection and production of fluids primary production or fracturing of the reservoir may be applied using such well until such injectivity is created upon sufficient.