Central Utah Thrust Belt Tectonics: Sevier Plus Salt May Lead to Very Large Reserves

Pinnell, Michael L. ¹, Floyd Moulton² (1) Pioneer Oil and Gas, South Jordan, UT (2) Consultant, Salt Lake City,

Covenant Oil Field is the first of a plethora of petroleum producing prospects of similar geology in the Central Utah Thrust Belt. Wolverine made this 100 million bbl oil discovery in 2004. Paleozoic age oil is produced from the 1,200 foot thick Jurassic Navajo Sandstone. Evaporitic and mudstone deposits of the Arapien Shale form the seal. Originally 5,000 feet thick, the salty section may now exceed 12,000 feet. The down (west) side of the Ancient Ephraim Fault half-grabben is the obvious salty source, where over 6,000 feet of evaporative related sediments were originally deposited. How this thick section was mobilized then transported ten to fifteen miles to the west is the question. We anticipate definitive evidence of either an extensive, syntectonic bachthrust or our preferred interpretation of a post-compressional subsurface salt glacier. The answers will come from seismic and well data derived from exploration and development of the yet to be discovered oil and gas fields along this almost undrilled trend. We identify ten to twelve structural anomalies similar to the Covenant Field as a “string of pearls” ready to be harvested from along this Gunnison Thrust. Twenty additional drillable structures are present on older thrusts west of the Gunnison Thrust. Wolverine and other companies plan at least ten wildcat wells this year.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana