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' CHAPTERTHREE Affected Environment <br />with the following 14 ]eases; (COC10066, COC18423, COC48394, COC48887, COC52787, <br />COC53325, COC60122, COC60332, COC60402, COC60722, COC61712, COC61714, <br />COC61715, COC84892). With the exception of Duck Creek Fed 1603, which produces a high <br />pazaffin crude during the summer months only, no producing oil or gas wells exist on American <br />Soda's lease block. <br />3.1.3.2 Oil Shale <br />The Piceance Creek Basin contains rich deposits ofkerogen-bearing dolomitic mazlstone (oil <br />shale) of the Eocene Green River Formation. The estimated total reserves of the Piceance Creek <br />Basin amount to approximately 1,200 billion barrels of shale oil (Robson and Sauliner 1980). <br />The Parachute Creek Member contains most of the oil shale and ranges in thickness from 900 to <br />1,200 feet on the southern and western mazgins of the basin to neazly 1,900 feet in the <br />depositional center. The Upper Garden Gulch Member also contains some kerogen-bearing rock. <br />The Mahogany Zone, which is 100 to 200 feet thick, consists of kerogen-rich strata and is the <br />richest oil shale interval in the basin. These oil shale deposits represent a potential energy <br />resource which could supply the United States' oil demand for many decades (Weeks et al. <br />1974). The upper 40 to 60 feet of the Mahogany Zone could be suitable for conventional room <br />and pillaz mining. Estimated in place resources within this interval are approximately 94,000 <br />barrels per acre of shale oil. Estimated in place resources within the Saline Zone aze <br />approximately 1,500,000 barrels per acre of shale oil (BLM 1986a). <br />' 3.1.3.3 Nahcolite <br />The Piceance Creek Basin contains the world's lazgest and most economically significant <br />nahcolite resource. Conservative estimates of in-place nahcolite in the basin have been reported <br />at 29 billion tons (Dyni 1981). The nahcolitic oil shale has been estimated to cover some 257 <br />squaze miles of the Piceance Creek Basin (Smith et al. 1973). The thickest and richest nahcolite- <br />bearing stratigraphic intervals are known to occur in the depositional center of the basin in Tl S <br />and T2S, R97W and R98W. The Piceance Site encompasses approximately 4,954 acres <br />' overlying the depositional center of the basin. Current drill hole data taken from near monitoring <br />we1120-1 and the experimental test cavities indicate the presence of significant sodium resotuces, <br />with a total saline interval almost 770 feet thick at an average nahcolite content in excess of 26 <br />percent by weight (Dyni 1974). This equates to 333 million tons of nahcolite per squaze mile for <br />a total Piceance Site resource estimate of some 2.44 billion tons of nahcolite. <br />Studies of nahcolite-rich intervals in the Saline Zone have shown that 26 mappable horizons are <br />present within an 800-foot interval from about 1,400 to 2,200 feet bgs. Individual beds may be <br />all nahcolite or nahcolitic halite or grade into haute. Beneath the Piceance Site, there aze seven <br />' nahcolite beds greater than 6 feet thick that have in excess of 43 percent nahcolite by weight. <br />The Love Bed is a tan microcrystalline nahcolite interval present at 1,700 feet below ground <br />level at monitoring we1120-1. The Love Bed is 7.4 feet thick here and averages 53 percent <br />' nahcolite by weight. This horizon alone contains a total nahcolite resource of approximately 57 <br />million tons. The Greeno Bed is a honeycomb disseminated nahcolite-rich bed located at a depth <br />of 2,062 feet below grade at monitoring well 20-1. At that location, the Greeno Bed is 5.9 feet <br />' thick and averages 76.5 percent nahcolite by weight. The laterally continuous TI Bed is a little <br />deeper than the Greeno Bed, but neither of the Piceance Site drill holes was drilled deep enough <br />Geology 3-7 <br />1 <br />