The recovery of heavy crude oils and tars from subterranean oil bearing formations is enhanced by the injection of pressurized and heated hydrocarbon vapor into a single well drilled into the formation. Condensation of the hydrocarbon vapor heats the heavy oil and tars entrapped in the formation and...http://www.google.de/patents/US4407367?utm_source=gb-gplus-sharePatent US4407367 - Method for in situ recovery of heavy crude oils and tars by hydrocarbon vapor injection
