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The Rangely oil field is in northwestern Colorado in the central Rocky Mountain region and on the northeastern edge of the Uinta basin. The structure is an asymmetrical fold trending northwest and southeast, with 1,900 feet of surface closure. Dips range from 15º to 35º on the southwest flank and from 4º to 6° on the northeast side. Major production in the field is from the Weber sandstone of Permian-Pennsylvanian age. Some shale oil is produced from the Mancos of Upper Cretaceous age. One well produces from the Triassic Shinarump conglomerate. Prior to the completion of a pipe line from Rangely to Wamsutter, Wyoming, in September, 1945, oil was hauled by truck to Salt Lake City, Utah, and Craig, Colorado. By December 26, 1946, the pipe line had moved 8,867,014 barrels of oil.

Weber sand production at Rangely was discovered in 1932 by The California Company’s Raven A-1. Subsequently the discovery well was shut in until the war-time drilling program began in 1943. At the height of the drilling campaign in the summer of 1946, 52 rigs were active in the field. By January 1, 1947,185 Weber wells had been completed, 17 were pumping, and one well was producing from the Shinarump conglomerate.

The Weber formation, a dense cross-bedded sandstone, produces commercially from the upper 550 feet of section, of which 30 per cent is estimated as being effective. Throughout the field the sand’s permeability ranges from 0 to 330 millidarcys and may average about 20 millidarcys. Its porosity ranges from 9 to 16 per cent. Despite the dense characteristics of the sand, some wells have produced as high as 1,000 barrels per day on initial production tests through ¼-inch choke. The oil column embraces a total of 830 feet. A gas cap is present with the gas-oil contact placed 330 feet subsea and the oil-water contact tentatively established at 1,160 feet subsea. Surface and subsurface structure maps of the Rangely field are marked by simplicity. No faults of major importance have yet been found.

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