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The Cordilleran orogenic belt is generally considered to be a single tectonic element extending from northern Alaska to Central America. Two segments of the North American part of this element are oil and gas producers--the Canadian foothills thrust belt and the Wyoming-Utah-Idaho Overthrust belt.
Turner Valley was the first field discovered in the Canadian foothills. In the 55 years since that discovery, 32 fields have been found containing 9.3 Tcf of initially recoverable gas, 143 million bbl of natural gas liquids and 132 million bbl of oil. The first significant field discovery in the U.S. Overthrust belt was made in 1975 at Pineview. By the end of 1979 eleven new fields had been found, containing an estimated 500 million bbl of recoverable oil and 5.5 Tcf of recoverable gas, plus natural gas liquids.
The Canadian province is considered to be an appropriate geologic analog to the U.S. Overthrust belt, based on a number of characteristics common to both provinces. These include general structural configuration, trap types, reservoirs, stratigraphy, timing of migration of hydrocarbons, depth of burial, and age of tectonic movement. However, significant differences include age of major source rocks and paleothermal histories.
The future potential of the immaturely explored Wyoming-Utah-Idaho Overthrust belt is assessed by using a volumetric method, wherein hydrocarbon yields in barrels of oil and cubic feet of gas per cubic mi of sediments are established for the more densely explored Canadian foothills. These yields are applied to the less densely explored U.S. Overthrust belt. The usefulness of this method lies in the correct interpretation and analysis of similar, as well as dissimilar, geologic characteristics of the analog province. In addition, the assessment of the U.S. Overthrust belt is further refined by using the southerly productive part of this province as an "internal" analog which is applied to the remaining area of the province.
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