Exploration for potential oil and gas traps in subthrust zones along the thrusted forelands of a number of Rocky Mountain uplifts has gained renewed interest by the oil industry. In the past, two drawbacks to identifying and drilling these traps were: (1) they are obscured by burial beneath overthrust Precambrian crystalline or metasedimentary rocks, and (2) drilling through an appreciable thickness of these Precambrian rocks is expensive, time-consuming, but necessary to reach younger rocks in the subthrust zone.

The Willow Creek thrust is an example of this type of foreland subthrust exploration play. It is about 7 mi (11.3 km) north of the giant Rangely oil field (production from the Permian-Pennsylvanian Weber Sandstone), and forms the south flank of the Blue Mountain anticline, south of the Uinta Mountains, in northwestern Colorado. This foreland subthrust play was drilled in 1960 by Tennessee Gas and Oil Co. (now Tenneco), and was also studied through a combination of surface and photogeologic mapping, minimum subsurface well control and pre-multichannel seismic data. Structural closure was mapped on subthrust Weber Sandstone in fault contact with overthrust Precambrian rocks. Drilling of more than 2,000 ft (600 m) of Precambrian was required to penetrate the Weber Sandstone. Although the test had good oil shows in Triassic and Permian rocks, it was a dry hole. However, it confirmed the overall original structural interpretation, identified the presence and angle of the main thrust fault, and successfully penetrated an appreciable thickness of Precambrian rocks to reach the Weber.

The Willow Creek thrust may well be a type model of a foreland thrust play, and some of the geologic concepts involved in this study could be used as additional exploration tools to help find these elusive, prospective subthrust traps.

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