A method for treating lean and rich zones of a hydrocarbon containing formation is provided. In one embodiment, heat from one or more heaters may be provided to at least a portion of the formation. Heat may be allowed to transfer from the one or more heaters to a first part of the formation. In certain...http://www.google.de/patents/US7066257?utm_source=gb-gplus-sharePatent US7066257 - In situ recovery from lean and rich zones in a hydrocarbon containing formation
