"The drilling and casing of an 8-ft (2. 4 m) diameter shaft to a depth of 2,371 ft (723 m) in the Piceance Creek Basin of Colorado is described. This pioneer shaft allows access, for the first time, to the deep oil shales of the Saline Zone. Environmental research studies are planned from the shaft and bulk samples of the minerals nahcolite and dawsonite will be obtained for metallurgical testing. The shaft was spudded in on March 25 , 1977 , and drilled to a total depth of 2,371 ft (723 m) on October 2. Installation and cementing of the steel casing from surface to total depth were completed on December 27. Actual rig time was 237 days. Fishing operations took 59 days when the drill bit was lost in the shaft at a depth of 1 ,245 ft (379 m) . Results showed that a large-diameter shaft could be safely drilled through the Leached Zone in the Piceance Creek Basin. Problems encountered with the drilling assembly, drilling mud, and casing welding can be solved with improved design."