Abstract: A thermal process for recovering heavy viscous petroleum from a subterranean hydrocarbon formation having low relative permeabilities to water and oil wherein a well bore penetrating the formation and surrounding subterranean strata are initially heated by injecting a heated fluid containing steam into the well and simultaneously venting a portion of the fluid at the surface to lift any condensed liquids forming in the well bore towards the surface to keep the well essentially free of condensed fluids. The well injection and venting are continued until the well and surrounding subterranean strata are heated sufficiently for the heated fluid to be injected into the formation without condensed liquids forming in the well at a rate greater than the formation can accept. The heated fluid is then injected directly into the formation at a high injection rate to raise the formation temperature to a desired level, followed by withdrawing the resulting heated petroleum therefrom through the well.

Abstract: A new and improved process for the recovery of heavy viscous petroleum from a subterranean formation is disclosed. A heated fluid comprising steam and a heated non-condensable gas is injected into the formation through a penetrating well at an initial predetermined injection rate until the injection rate diminishes to a predetermined level. The injection is then discontinued and a heated non-condensable gas is immediately injected into the formation through the well until the injection rate thereof reaches a desired level. The steam-gas mixture and heated non-condensable gas are then alternately injected in sequence until the steam-gas mixture can be injected into the formation continuously at a desired injection rate and the formation and petroleum have been heated to a predetermined extent. The heated, mobile petroleum is then recovered by withdrawal through the well in a conventional manner.