In situ recovery from a hydrocarbon containing formation

A method of in situ treating a relatively permeable formation that contains heavy hydrocarbons, comprising:

• providing heat from one or more heat sources to at least one portion of the formation;
• allowing the heat to transfer from the one or more heat sources to a selected mobilization section of the formation such that the heat from the one or more heat sources mobilizes at least some of the hydrocarbons in the selected mobilization section of the formation;
• controlling the heat from the one or more heat sources such that an average temperature in at least a majority of the selected mobilization section of the formation is at most about 150° C.;
• controlling a pressure in at least a majority of the formation, wherein the controlled pressure is at least about 2 bar absolute;
• providing a gas to the formation at a controlled pressure to controllably increase a flow of the mobilized hydrocarbons within the formation;
• and
• producing a mixture from the formation.