Disclosed is a method and apparatus for generating high pressure steam within a well bore for facilitating recovery of hydrocarbon deposits. The steam vapor generator is constructed for receiving high pressure water, fuel and oxidant in a downhole position for select mixing and combustion. High pressure water is received around a combustion chamber in an annular configuration and heated through a thermal wall region forming a lower portion thereof. The combustion chamber utilizes the heat energy of radiation to heat the water in the annular sleeve to the point of steam. The water sleeve further includes orifices for egress of the steam and a plurality of vent tubes within the water sleeve. The vent tubes extend substantially the length of the sleeve for receiving excess water vapor and/or undissolved gases created from the heat of vaporization and out-gassing. A collection chamber is provided beneath the combustion chamber in communication with the vent tubes and water sleeve for the mixing of the high pressure vapor and the exhaust thereof into the adjacent well formation.