Abstract: The quality of steam downhole is determined by injecting into the steam first and second tracers, each tracer having an affinity to a single of the two phases, and then sensing the passage of the tracers over a pair of sensors spaced apart or known measured distance. Thus the velocity of the phases, the slip ratio between the phases and the steam quality can be determined.

Abstract: The vertical or both vertical and horizontal conformance of a stem drive process is improved by employing one or more infill wells between the injection well and production well, the infill well being in fluid communication with the bottom half or less of the formation. In the first step, petroleum is recovered from the infill well after oil production at the production well has proceeded to a predetermined point. After water cut of fluids being produced from the infill well reaches a predetermined value, the production well is converted from a production well to an injection well and steam is injected into the converted well while continuing recovering fluids from the infill well. When one infill well is employed in a more or less aligned arrangment between injection and production wells, the vertical conformance is improved. When one or more infill wells are utilized in a pattern comprising one or more injectors and one or more producers, both horizontal and vertical conformance is improved.