Covenant Oil Field, Central Utah Thrust Belt:
Possible Harbinger of Future Discoveries

Authors: Thomas C. Chidsey, Jr. and Michael D. Laine, Utah Geological Survey (UGS), Salt Lake City, UT; and John R. Vrona and Doug Strickland, Wolverine Gas & Oil Corporation, Grand Rapids, MI.

Venue: American Association of Petroleum Geologists annual convention, Long Beach, CA, April 1–4, 2007 (http://www.aapg.org/ [external site]).

Abstract: After over 50 years of exploration in the central Utah thrust belt, or “Hingeline,” the 2004 discovery of Covenant oilfield proved that this region contains the right components (trap, reservoir, seal, source, and migration history) for large accumulations of oil. To date, 10 producing wells and 1 dry hole have been drilled from two surface pads. Covenant has produced over 2 million barrels of oil and no gas; the field averages 6,400 barrels of oil per day. The Covenant trap is an elongate, symmetric, northeast-trending anticline, with nearly 800 feet of structural closure and bounded on the east by a series of splay thrusts in a passive roof duplex. The eolian Jurassic Navajo Sandstone reservoir is effectively sealed by mudstone and evaporites in the overlying Jurassic Twin Creek Limestone and Arapien Shale. Oil analysis indicates a probable Mississippian source oil derived and migrated from rocks within the Hingeline region. Cores from the Navajo Sandstone display a variety of eolian facies (dune, interdune, lake/playa, fluvial/wadi), fracturing, and minor faults which, in combination, create reservoir heterogeneity. Reservoir sandstone is 97% frosted quartz grains (bimodal grain size), with some quartz overgrowths and illite. The net reservoir thickness is 424 feet over a 1,600-acre area. Porosity averages 12%; permeability is less than or equal to 100 millidarcies. The drive mechanism is a strong water drive; water saturation is 38%. A thorough understanding of all the components that created Covenant field will determine whether it is a harbinger of additional, large oil discoveries in this vast, underexplored region.

Related NETL Project: The goal of the related NETL project entitled “Major Oil Plays in Utah and Vicinity/PUMP 2” (DE-FC26-02NT15133) is to increase recovery of oil reserves from existing reservoirs and from new discoveries by providing play portfolios for the major oil-producing provinces (Paradox Basin, Uinta Basin, and thrust belt) in Utah and adjacent areas in Colorado and Wyoming.

NETL Project Contacts:
NETL – Virginia Weyland (virginia.weyland@netl.doe.gov or 918-699-2041)
UGS – Thomas Chidsey, Jr. (tomchidsey@utah.gov or 801-537-3364)