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Exploration History and Petroleum Geology of the Central Utah Thrust Belt

Douglas A. Sprinkel, Utah Geological Survey, 1594 W. North Temple, Suite 3110, Salt Lake City, UT 84116, phone: 801-537-3316, fax: 801-537-3400, [email protected] and Thomas C. Chidsey, Jr, Utah Geological Survey, P.O. Box 146100, Salt Lake City, UT 84114-6100.

Central Utah has seen cycles of petroleum exploration for the past 50 years because explorationists viewed the geology as a natural extension of successful plays elsewhere in Utah. Early efforts tested anticlines identified from surface mapping and seismic reflection data. During the late 1970s to early 1980s companies drilled thrust belt-style structures in the wake of the Pineview discovery in northern Utah. Although these efforts failed, companies confirmed the area was similar in structural style, reservoir types, and timing to the productive thrust belt to the north. The lack of a Cretaceous source seemingly was to blame for these failures; however, oil and gas shows were common in Mississippian, Permian, Triassic, and Jurassic rocks. The recent discovery of Covenant field by Wolverine Oil and Gas Company in the Jurassic Navajo Sandstone along the Sanpete-Sevier Valley antiform has rekindled thoughts of exploration in central Utah; however, this time exploration is based on local success.

Exploration in the central Utah thrust belt will focus on a thrust belt of Paleozoic-cored blind thrusts east of the exposed Charleston-Nebo and Pavant thrusts, which formed during the Cretaceous and early Tertiary Sevier orogeny. Likely targets include anticlines associated with thrust imbricates (or imbricate fans) and possible antiformal stacks of horses forming duplex structures in the Navajo and other reservoirs such as the Permian Park City-Kaibab Formations, Triassic Moenkopi Formation, and Jurassic Twin Creek Limestone. These features are obscured by complex surface geology, but may be closely related to regional antiforms in the Jurassic Arapien Shale.