Central Utah Thurst Belt: East Vergent Sevier Thrusts and a Laramide Back Thrust Combine to Create Very Large Reserves

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

Several seismically defined structures similar to but much larger than Covenant Oil Field (100 million barrels of oil) are in the process of being tested in the Central Utah Thrust Belt province. In this area, Paleozoic age oil and gas has migrated east in a manner similar to Canada's prolific 41 TCFGE thrust belt province. Strong evidence suggests other source rocks in addition to Mississippian shale may also yield hydrocarbons. Utah's Thrust Belt reservoir rocks are presently Jurassic age Navajo Sandstone and Twin Creek Limestone. Perhaps even more oil and gas has been trapped in deeper Paleozoic reservoirs than presently fill those of Jurassic age. Subsequent to most compressional tectonism, Jurassic salt deposits, thickest along the Ancient Ephraim fault, began to be mobilized. Transportation was westerly as much as ten to fifteen miles, perhaps along an extensive Laramide age, basement involved backthrust. Additionally, this bachthrust helped create and at the same time partially ensconce several large structures east of the main Sevier age thrust trends. The allochthonous (mobilized) salt, on the other hand, will continue to complicate seismic definition of prospect structures while, at the same time, provide a seal for the world class, 1,200 foot thick windblown Navajo Sandstone. This virtually unexplored province has the potential to provide many on shore giant oil and gas accumulations.