The Big Piney–La Barge complex, with cumulative gas production of 1.2 Tcf, has been the leading gas-producing area in Wyoming since 1956. It also contributes significant oil production, which has amounted to about 65 million bbl. Ultimate reserves are estimated to be 2.5 Tcf of gas and 75 million bbl of oil. In addition, condensate production averages about 3 bbl/MMcf of gas.
Production is from rocks as young as Paleocene and as old as Triassic. The major gas reservoir in the area is the Cretaceous Frontier Formation. Structural, stratigraphic, and combination traps are all common in the Big Piney—La Barge area. Probably significant to trapping the hydrocarbons in the Paleocene strata was the transgression of Paleocene units onto the Big Piney—La Barge platform or anticline. The area was anticlinally folded during Late Cretaceous and early Paleocene times, and Mesaverde units reflect the influence of the Moxa arch to the south and the Monument Buttes–Blue Rim arch to the southeast. Accumulations in the Frontier are essentially structurally controlled west of the La Barge thrust; however, east of that thrust, production is mainly from stratigraphic traps.
Figures & Tables
With three previous volumes published by AAPG on structure of American oil fields, this publication takes 17 of these oil fields and describes them in detail. The reservoirs described in these 17 papers range in age from Devonian to Pleistocene; their litholgies are standstone, limestone, or dolomite; and the trapping mechanisms are structural or stratigraphic or a combination of the two. The North American oil fields described are distributed from Alaska and the McKenzie Delta area of Canada on the northwest, to the Gulf of Mexico and Southern Floriday on the southeast. This publication also includes an index to those North American oil and gas fields which have been described in previous AAPG publications.