Print this pageCentral Utah Thrust Belt: Covenant Field and the New Providence Field Discovery Portend Other, Exciting, New Structural Discoveries with Very Large Reserves of Both Oil and Natural Gas
Wolverine’s 2004 Covenant Field discovery initiated rapid lease acquisition but a fairly slow rate of wildcat drilling. Now that newly discovered Providence Field has dispelled the “One field wonder” concern, the rate of exploration has increased. There are several reasons. Providence Field appears to be larger, have more pay horizons, and more net feet of pay than was originally envisioned at Covenant. Gas is a confirmed commodity along with high gravity oil although deeper reserves may include sulfur. Covenant field, initially productive from an upper, back thrust block is now known to also be productive from a lower duplex structure, a circumstance unknown in 34 years of Wyoming overthrust exploration. At the northernmost Moxa Arch trend, Labarge Anticline ensconces approximately 21 TCF gas partly below the Darby Thrust in middle-Paleozoic-age carbonate rocks. An analog could established multiple TCF gas reserves in Utah’s already productive thrust province. Two new 3-D surveys and massive 2-D programs by aggressive independents suggest many large, undrilled anticlines are either in the process of being evaluated or will soon be drilled. Because hydrocarbons in Covenant and Providence Fields are source by down dip Paleozoic rocks, it is very possible that multiple thrust sheets of large, complex structures may be productive as is case in the Canadian overthrust belt.
We reaffirm the Ancient Ephraim Fault, initially a down-to-the west normal fault, may have been switched into a west-vergent reverse fault at the time of earliest compression (Moulton, 1982). The pre-existing Ephraim fault may have been forced into polarity-reversal, much like that seen in the early history of the Ventura Basin of California, where both the north and south down-to the-basin margins were soon converted to up-thrusts which are now overriding the basin and driving it downward by compressional closure. Any Sevier-age reverse movement on the Ephraim fault would have tended to create an early, subtle, regional arch, reversing the regional west dip and providing a broad antilcinal trap in the autochthonous Paleozoic section west of the fault.
The large umber of down to the east normal faults, seen along the Wasatch Plateau in central Utah, may be the consequence of backslip into the earlier Sevier-Laramide east-dipping, but west-vergent up-thrust fault zone. (No other mountain range, in or bordering the Basin and Range, has a comparable number of away-from-the basin faults.)
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009