Drilling operations of all descriptions in the Rocky Mountain Region during 1938 reached a total of 483, divided as follows.

Table

Discovery of new oil fields includes Cole Creek, Natrona County, Wyoming; Wilson Creek, Rio Blanco County, Colorado; North Cut Bank, Glacier County, Montana; Big Hollow, Albany County, Wyoming; and Shoshone, Park County, Wyoming. The last is a black-oil discovery, and, coupled with the field extension at Hamilton Dome, Hot Springs County, Wyoming, promises to add materially to the black-oil reserves of Wyoming. The shallow discovery at Big Hollow is of low gravity, and of probable minor significance. The North Cut Bank discovery is the first Moulton sand (Kootanai--Lower Cretaceous) oil producer, although several gas wells have been completed in this zone.

Extensions of other proved fields were accomplished at West Kevin, Toole County, Montana, and at Lance Creek, Niobrara County, Wyoming. The eighteen Leo sand (Minnelusa) completions at Lance Creek during 1938 indicate that the ultimate productive area from this zone may reach 5,500 acres, with a gross recovery approaching 47,500,000 barrels.

Deepening or recompleting wells in proved fields resulted in a Tensleep discovery for Mahoney Dome, Carbon County, Wyoming, and in a small oil well from shallow Wasatch sands at Hiawatha, Moffat County, Colorado. Mahoney Dome had previously produced natural gas commercially from the Dakota and Sundance sands, and Hiawatha, gas from shallow Wasatch sands.

New gas fields resulted during 1938 from drilling the Beaver Creek, Fremont County, Wyoming; at Oil Springs, Carbon County, Wyoming; and in Sec. 30, T. 37 N., R. 4 W., Glacier County, Montana. The last discovery is 4 miles north of the main Cut Bank gas area, and produces from the Moulton sand. The gas at Beaver Creek was found in a sand of the Morrison formation; and, at Oil Springs, in the Lakota and First and Second Sundance sands. Extension of the Muskrat gas field, Fremont County, Wyoming, and of the Clay Basin gas field, Daggett County, Utah, was also accomplished by 1938 drilling.

The gross production of oil in the Rocky Mountain region (exclusive of southeastern New Mexico) for 1938, is estimated at 25,450,205 barrels, as compared with 27,397,660 barrels in 1937.