| abstract |
Many oil recovery techniques for viscous oil recovery including steam injection and in situ combustion require establishment of a high permeability fluid flow path in the formation. The method of the present invention comprises forming an initial entry zone into the formation by means such as hydraulic fracturing and propping, or utilizing high permeability streaks naturally occurring within the formation, and injecting into the propped fracture zone or high permeability streak a solvent for the petroleum contained in the formation, said solvent being saturated with a gas or containing appreciable quantities of gas dissolved therein. The solvent-gas solution is injected into the formation at a pressure up to a value equal in pounds per square inch to the overburden thickness in feet, until the formation in the exposed area has been pressurized to the desired pressure and thereafter terminating injection and producing the gas and solvent-bitumen mixture by solution gas pressure depletion. The operation may be repeated through several cycles in order to enlarge the flow channel, and in the instance of a multi-well throughput operation adjacent injection and production wells are both treated in a cyclical fashion until communication between injection wells and production wells is established. Suitable solvents include aromatic hydrocarbons such as benzene, toluene, and xylene as well as carbon disulfide. Suitable gases include carbon dioxide, methane, nitrogen and air. |