Oil Shale Reserves - Definition of Reserves

Definition of Reserves

See also: Shale oil extraction and Oil shale economics

Estimating shale oil reserves is complicated by several factors. Firstly, the amount of kerogen contained in oil shale deposits varies considerably. Secondly, some nations report as reserves the total amount of kerogen in place, including all kerogen regardless of technical or economic constraints; these estimates do not consider the amount of kerogen that may be extracted from identified and assayed oil shale rock using available technology and under given economic conditions. By most definitions, "reserves" refers only to the amount of resource which is technically exploitable and economically feasible under current economic conditions. The term "resources", on the other hand, may refer to all deposits containing kerogen. Thirdly, shale oil extraction technologies are still developing, so the amount of recoverable kerogen can only be estimated.

There are a wide variety of extraction methods, which yield significantly different quantities of useful oil. As a result, the estimated amounts of resources and reserves display wide variance. The kerogen content of oil shale formations differs widely, and the economic feasibility of its extraction is highly dependent on international and local costs of oil. Several methods are used to determine the quantity and quality of the products extracted from shale oil. At their best, these methods give an approximate value to its energy potential. One standard method is the Fischer Assay, which yields a heating value, that is, a measure of caloric output. This is generally considered a good overall measure of usefulness. The Fischer Assay has been modified, standardized, and adapted by the American Petroleum Institute. It does not, however, indicate how much oil could be extracted from the sample. Some processing methods yield considerably more useful product than the Fischer Assay would indicate. The Tosco II method yields over 100% more oil, and the Hytort process yields between 300% to 400% more oil.

Largest oil shale deposits (over 1 billion metric tons)

Deposit	Country	Period	In-place shale oil resources (million barrels)	In-place oil shale resources (million metric tons)
Piceance Basin	United States	Cretaceous	1,525,157
Green River Formation	United States	Paleogene	1,444,992	213,000
Uinta Basin	United States	Paleogene	1,318,964
Phosphoria Formation	United States	Permian	250,000	35,775
Eastern Devonian	United States	Devonian	189,000	27,000
Heath Formation	United States	Early Carboniferous	180,000	25,578
Olenyok Basin	Russia	Cambrian	167,715	24,000
Congo	Democratic Republic of Congo	?	100,000	14,310
Irati Formation	Brazil	Permian	80,000	11,448
Sicily	Italy	?	63,000	9,015
Tarfaya	Morocco	Cretaceous	42,145	6,448
Volga Basin	Russia	?	31,447	4,500
St. Petersburg, Baltic Oil Shale Basin	Russia	Ordovician	25,157	3,600
Vychegodsk Basin	Russia	Jurassic	19,580	2,800
Wadi Maghar	Jordan	Cretaceous	14,009	2,149
Dictyonema shale	Estonia	Ordovician	12,386	1,900
Timahdit	Morocco	Cretaceous	11,236	1,719
Collingwood Shale	Canada	Ordovician	12,300	1,717
Italy	Italy	Triassic	10,000	1,431