Abstract: In a viscous oil reservoir in which the stratification of the rock permeability is insufficient to confine steam within the most permeable strata, oil can be produced by forming and expanding a steam channel through which steam is flowed and oil is produced. Steam is injected and fluid is produced at rates causing a steam channel to be extended between locations that are horizontally separated. A foam-forming mixture of steam, noncondensable gas and surfactant is then injected into the steam channel to provide foam and a relatively high pressure gradient within the channel, without plugging the channel. A flow of steam-containing fluid through the steam channel is continued in a manner such that the magnitudes of the pressure gradient, the rate of oil production, and the rate of steam channel expansion exceed those which could be provided by steam alone.