Recovery of High-Viscosity Petroleum by Steam from Geothermal Heat

Steam stimulation is an efficient means of increasing recovery of petroleum from high-viscosity tar-sands deposits. Large amounts of steam are required with costs averaging about 50¢ per barrel. The economic development of many deposits depends on the availability of low cost steam. Geothermal heat has been considered as a source for producing steam. The feasibility of using a nuclear explosion in a geologic formation with normal temperature gradient for steam production near tar-sands deposits has been explored. A rubble chimney can be created at a depth of burial such that the temperature difference between the formation and the tar sands would be sufficient to reduce the viscosity of the oil for commercial recovery. Calculations indicate that a large tar-sands deposit in Venezuela could be steam stimulated to produce about 18 million barrels of oil. A 1 Mt nuclear explosion at a depth of burial of 3340 m might allow steam extraction of more than 1012 Btu at an estimated cost of <50¢ per barrel of steam produced.