Central Utah Thrust Belt Exploratioin Is in Its Infancy
Michael Pinnell, Spiro Vassilopoulos, and Floyd Moulton
8171 Old Coventry Circle, Sandy, UT
Recent worldwide research has demonstrated that each salient of major thrust belt hydrocarbon entrapment can be unique in source rock, reservoir rock, trapping mechanism, time of hydrocarbon migration and sealing properties. Central Utah's Thrust Belt (CUTB) follows this pattern. To date, only Navajo Sandstone reservoir rocks in hanging wall, thin skinned, thrust bend folds have been extensively tested in this promising trend. By way of comparison, the Peruvian thrust salient of the Andean Thrust Belt has at least five unique structural trapping mechanisms as well as several ages of source beds and reservoir rocks. Insufficient exploration in Central Utah precludes us from even knowing if such a variety of entrapment exists. It is known that very thick sequences of Mississippian age source rocks, immediately west of, and in part within the CUTB, have yielded extremely large volumes of hydrocarbons. It is also known that hydrocarbons migrated into CUTB area structures both before and after Sevier age thrusting. Therefore, it can be inferred that hydrocarbons are trapped in the thousand-foot thick Mississippian carbonate reservoir rocks pervasive in the region in very large, simple, but deeper hanging and foot wall folds seen on seismic data. Giant fields from this same horizon in Wyoming and Canada have been known for decades. These structures have not yet been tested in Utah. Covenant Field is a large, gas-free oil seep having re-migrated from a pre-thrust, hydrocarbon filled foreland structure, possibly contained in Mississippian carbonates. It should be west of Covenant and contain oil, gas and condensate. Similar accumulations are known in Wyoming, Canada and Peru. This feature has not yet been drilled in the CUTB. Other similarly large anticlines appear on seismic data and are also untested. Additional non-commercial oil seeps are known on trend. Most likely, they are derived from untested, deeper, commercial accumulations. The transitional trend between Mississippian carbonate platform facies to the east and foreslope facies, and the Deseret-Chainman starved basinal facies on the west, run through the Central Utah Thrust Belt. Strato-structural traps and reefs may be present. Other basins with a similar lithologic sequence are prolific oil and gas producers like the Permian Basin of West Texas. This transition in Central Utah, masked below complex thrusting and Tertiary fill, has never been explored.
AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013