Whitney Canyon-Carter Creek Field: Gas Production from Carbonate Reservoirs in a Thrust Belt Structural Setting, Western Wyoming, U.S.A.

SIEVERDING, J. L., Chevron USA, Inc., Houston, TX, and F. ROYSE, JR., Chevron USA, Inc. (retired), Arvada, CO

Located in the Fossil basin area of the Wyoming thrust belt, giant Whitney Canyon-Carter Creek field has in place reserves of approximately 4.5 tcf of gas, 125 MMBO (condensate), and 24 million long tons sulfur. It is the largest gas field in the U.S. Rocky Mountains.

Hydrocarbons are trapped in large, reverse faulted anticlinal closures that formed completely within the Absaroka thrust plate during Laramide deformation. These structures are ramp anticlines that developed when the Absaroka plate was thrust eastward over ramps in the underlying fault plane.

Production is sour natural gas and condensate mainly from Paloezoic reservoirs. The most significant are dolomitized carbonate reservoirs of the Mississippian Mission Canyon and Lodgepole formations and the Ordovician Big Horn Dolomite. The Pennsylvanian Weber Sandstone and the Triassic Thaynes Formation have minor production. Source rocks are subthrust Cretaceous shales that were placed in the oil generation window after thrusting and subsidence.

The economically most important reservoir is the Mission Canyon Formation with 79% of the total gas in place. Intercrystalline and moldic porosity was created by dolomitization and subsequent partial solution of mud-supported sediments during early diagenesis. Structural deformation fractured the reservoir, but also created a diagenetic environment that allowed calcite, anhydrite, and dolomite cements to sporadically plug all porosity types.

Discovery of Whitney Canyon-Carter Creek field began by identifying a large, potentially productive area within the Fossil basin. Initial concepts were based on regional structural cross sections from surface geology and sparse well control, aeromagnetic data, geochemical and palynological work, and a regional 100% seismic line. Individual prospects were identified from CDP stacked seismic data and structural models developed from other thrust belts.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)