| abstract |
Petroleum may be recovered from viscous petroleum containing formations including tar sand deposits by first creating a fluid communication path low in the formation, followed by injecting a heated fluid, aqueous or nonaqueous, into the fluid communication path, followed by injecting a volatile solvent such as carbon disulfide, benzene or toluene into the preheated flow path and continuing injecting the heating fluid. The low boiling point solvent is vaporized and moves upward into the formation where it dissolves petroleum, loses heat and condenses thereafter flowing down carrying dissolved bitumen with it into the preheated flow path. The low boiling point solvent effectively cycles or refluxes within the formation and is not produced to the surface of the earth. Bitumen is transferred from the volatile solvent to the heating fluid continually passing through the communication path, and bitumen and heating fluid are recovered together as a mixture or solution. |