Method of recovery of bitumen from tar sand formations

patentA competent permeable communication zone connecting injection and production wells completed in a tar sand which communication zone will be rigid and will not tend to slump or heal may be developed by injecting a fluid in the injection well under such pressure so as to fracture the tar sand formation between the injection well and the production well and circulating a fluid between the injection and production wells which is at a temperature sufficiently low to freeze the water in tar sands. The fluid may contain propping agents to hold the fracture surfaces apart. This procedure will rigidify the hydrocarbon portion of the tar sand formation in the vicinity of the fracture zone as well as freeze the water in the tar sand formation. Once the fracture is established a solvent for the hydrocarbon in the tar sands may be circulated preferably at a temperature below the freezing point of the water in the tar sands to extract the bitumen therefrom