OIL SHALE 



501 



tent, and as a result 10-gallon-per-ton shale, when 

 treated by alternative methods such as hydrogena- 

 tion or synthetic gas in a retort, can be made to yield 

 15-20 gallons of light oil per ton, or alternatively 

 1,700-2,600 cubic feet of high-quality synthetic gas. 

 A minimum thickness and grade of 5 feet of shale 

 yielding an average of 10 gallons of oil per ton by 

 conventional retort was adopted by Duncan and 

 Swanson (1965, p. 13) for computing oil shale re- 

 sources. The identified resources of 200 billion bar- 

 rels of oil (table 95) are in formations of Devonian 

 and Mississippian age in the Central and Eastern 

 United States. (See Duncan and Swanson, 1965, fig. 

 2.) They include resources in the central part of the 

 eastern Highland Rim of Tennessee, where the Gas- 

 saway Member of the Chattanooga Shale averages 

 15 feet in thickness, yields an average of 10 gallons 

 of oil per ton, and contains an average of 0.006 per- 

 cent uranium (Conant and Stansfield, 1968). Areas 

 of New Albany Shale in Indiana and Kentucky in- 

 clude black shale zones 20-100 feet thick that yield 

 an average of 10-12 gallons per ton and contain the 

 major part of the resources. 



The hypothetical resources in the unexplored or 

 little-sampled parts of this very widespread unit are 

 estimated to total about 800 billion barrels of oil 

 (Duncan and Swanson, 1965, p. 14). 



OTHER SHALE DEPOSITS 



In Alaska, oil shales are contained in rocks of 

 mostly marine origin which underlie large areas in 

 the north. These sequences range in age from Miss- 

 issippian through Early Cretaceous, and consist 

 dominantly of black shale, chert, and black organic 

 limestone, except for the Cretaceous rocks which are 

 dominantly sandstone and conglomerate (Donnell, 

 Tailleur, and Tourtelot, 1967 ; Duncan and Swanson, 

 1965, p. 14) . Most of the area is complexly faulted 

 and folded, and good exposures are rare in the 

 tundra-covered slopes. Near the Nation River in 

 eastern Alaska, outcropping Upper Triassic oil shale 

 that is locally 200 feet thick is reported to yield 

 about 30 gallons of oil per ton. On the north slope of 

 the Brooks Range, exposures of Upper Triassic 

 through Lower Cretaceous shale contain thin zones, 

 less than 5 feet thick, of oil shale that yields as much 

 as 160 gallons of oil per ton. Other zones, 20 feet or 

 more thick, are known to yield an average of 15 

 gallons of oil per ton. These shales also contain un- 

 usually high concentrations of trace elements such as 

 silver, gold, and merucry. Because of the lack of 

 data, identified resources of oil shale are extremely 

 small, but Duncan and Swanson (1965, p. 14) esti- 

 mated that hypothetical resources total about 450 



billion barrels of oil, of which about 250 billion bar- 

 rels would be in high-grade oil shale. 



Beds of oil shale associated with coal are numer- 

 ous in the United States, but they are generally thin 

 and lean, or of small extent. Identified resources — 

 those in carefully appraised deposits — are small. Hy- 

 pothetical resources may be large. 



FOREIGN OIL SHALE DEPOSITS 



Oil-shale deposits of Cambrian to Cenozoic age 

 are abundant throughout the world in all types of 

 depositional environments. The identified resources 

 of shale oil in areas outside the United States total 

 about 1.1 trillion barrels of oil (table 96). Most of 

 the resources are in a few large groups of marine 

 platform shale deposits, such as the Irati Formation 

 of Permian age in Brazil, the Cambrian and Ordo- 

 vician marine shale deposits in northern Europe and 

 northern Asia, and the Jurassic deposits of western 

 Europe and the Russian Platform, and in one large 

 lacustrine deposit, the Triassic oil shales of central 

 Africa (Duncan and Swanson, 1965; Duncan, 1967). 

 Hypothetical resources total about 7.3 trillion barrels 

 of oil, principally in the Irati Formation of Brazil, 

 and in the Cambrian marine shale of northern Asia. 



Reviews of world occurrences are summarized by 

 Duncan and Swanson (1965), Duncan (1967), and 

 Smith, Smith, and Kommes (1959) ; deposits in the 

 U.S.S.R. are described by Kotlukov (1968), and 

 those in Brazil by Padula (1969) . 



Table 96. — Shale-oil resources of the world (excluding the 

 United States) in billions of barrels, by grade (oil yield) 

 of oil shale 



[All numbers 



nded; Ne, not estimated: from Duncan 

 1965, table 3] 



Identified ^ Hypothetical ^ Speculative ^ 



25-100 10-26 25-100 10-25 25-100 10-25 



gal gal gal gal gal gal 



per per per per per per 



ton ton ton ton ton ton 



Africa 100 



Asia 90' 



Australia and New Zealand Small 



Europe 70 



North America (excluding 



United States) Small 



South America _Small 



Total 260 



4,000 

 5,400 

 1,000 

 1,200 



80.000 

 110,000 

 20,000 

 26,000 



14,600 296,000 



^ Identified resources: Specific, identified mineral deposits that may or 

 may not be evaluated as to extent and grade, and whose contained 

 minerals may or may not be profitably recoverable with existing tech- 

 nology and economic conditions. 



^Hypothetical resources: Undiscovered mineral deposits, whether of 

 recoverable or subeconomic grade, that are geologically predictable as 

 existing in known districts. 



■' Speculative resources : Undiscovered mineral deposits, whether of re- 

 coverable or subeconomic grade, that may exist in unknown districts 

 or in unrecognized or -unconventional form. 



SPECULATIVE RESOURCES 



Speculative resources of shale oil in undiscovered 

 deposits of shale were calculated by Duncan and 

 Swanson (1965, p. 7) as follows: 



