FEASIBILITY OF IN SITU RETORTING OF GREEN RIVER OIL SHALE, UTILIZING NUCLEAR EXPLOSIVES FOR FRACTURING.

Although hydraulic fracturing and chemical high explosives may be used to fracture shallow and thin beds, nuclear explosives may be required for adequate fracturing of the Green River oil shale in the center of the Piceance Basin of Colorado, where there are deposits as thick as 2000 ft (610 m) under as much as 1000 ft (305 m) of overburden. Experiments were conducted at the Bureau of Mines Laramie Energy Research Center in batch-type retorts accommodating particle-size ranges expected to be present in a nuclear-explosive created chimney. In seven tests with the large retort, recoveries were 39% to 62% of Fischer assay, with shale charges assaying 8. 0 to 10. 1 wt% of oil. In tests of lean shale (5. 75 wt%) in the small retort, the highest yield was 51% of Fischer assay. Results of these tests have been encouraging and indicate that the creation of adequate permeability through carefully designed and controlled fracturing techniques is a critical factor.