Chidsey, Thomas C.1, Craig D. Morgan1, Kevin McClure1
(1) Utah Geological Survey, Salt Lake City, UT
ABSTRACT: Outcrop Analogs in Utah: Templates for Reservoir Characterization and Modeling
Utah is unique in that representative outcrop analogs are present for the thrust belt,
Uinta Basin, and Paradox Basin for each major oil play. Production-scale outcrop analogs
serve as “templates,” often in 3D, of reservoir-facies characteristics and
boundaries that determine the overall reservoir rock heterogeneity, and can be applied to
reservoirs worldwide. Examples include the Pennyslvanian Paradox Formation, Jurassic
Navajo Sandstone, and Tertiary Green River Formation for carbonate bioherm, eolian, and
fluvial-deltaic lacustrine reservoirs, respectively.
In the Paradox Basin, hydrocarbons are stratigraphically trapped in heterogeneous bioherms (mounds) of the Paradox Formation. Exposures of the Paradox along the San Juan River of southeastern Utah display mounds and intermound troughs to off-mound detrital wedges or fans bounded by flooding surfaces. These facies also show flow conduits for secondary/tertiary recovery projects, and various horizontal drilling targets.
The most prolific oil reservoir in the thrust belt is the eolian Jurassic Nugget Sandstone. Outcrop analogs in the stratigraphically equivalent Navajo Sandstone of southern Utah display large-scale dunal cross-strata and interdunal lithofacies such as oases and playas. These outcrops illustrate how eolian facies might effect petroleum movement and production rates.
The Green River Formation is the primary oil reservoir in the Uinta Basin. Outcrop analogs in Nine Mile Canyon, just 15 mi south of producing fields, display distributary-channel and interdistributary mud-flat deposits. These outcrops show that potential reservoirs can form laterally continuous flow units or pinch out to form flow barriers, all within 40 acres, a common well spacing interval in the basin.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.