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The Big Piney gas and oil field, located in T. 26-30 N., R. 112-114 W., Lincoln and Sublette counties, Wyoming, lies within the Green River Basin, east of the north-south trend of the Wyoming Range. Oil and gas are contained in lenticular and blanket sands ranging in ages from Tertiary to Jurassic, namely, Wasatch, Mesaverde, Baxter, Frontier, Muddy, and Nugget formations.
Drilling in this area began with the discovery of oil by the Wyoming Reserve Petroleum Corporation, from the Wasatch (Almy) sediments at the La Barge oil field in 1924. Promotional drilling ventures continued off and on until oil was discovered in the Mesaverde formation at North La Barge field by Circle Oil Company in 1930. Wyoming Petroleum Corporation's Budd No. 1, after a blow-out in 1938, stimulated an unpredicted lease play in the immediate area. With the advent of a pipeline for natural gas, development drilling programs were initiated by major and independent oil companies in 1954.
Variations in sedimentation, offshore bars, and thickness changes to the northeast, and south, provide updip gas and oil reservoirs in Wasatch sediments. Alphabetic nomenclature has been ascribed to various sands within this Wasatch section. Mesaverde sediments, although widespread, are not only influenced by an unconformity and faulting, but also by facies changes not unlike the overlying Wasatch sediments.
Consistent with the overlying Mesaverde and Wasatch sediments, the Baxter formation contains varying shaly sand conditions which, coupled with imbricate thrust faulting, further complicate subsurface studies adjacent to the Darby-La Barge thrust complex. Commercial gas zones have been defined at and adjacent to La Barge oil field. The Frontier formation is delineated into subthrust and overthrust members by the steep attitude of the La Barge thrust fault. Five benches are defined in the Second Frontier, four of which are lenticular in outline. The Second Bench of the Second Frontier provides the only true blanket sand in this entire interval.
Muddy production appears to be controlled by variable sand conditions and permeability barriers. To date only two isolated productive areas have been defined.
Nugget sediments are undoubtedly widespread through the Big Piney-La Barge area. Oil accumulation at Tip Top and Hogsback is structurally controlled but complicated in part by minor thrust faults.
Deeper Phosphoria, Tensleep, and Madison horizons have not been penetrated east of the Darby-La Barge thrust complex.
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