Assessment of undiscovered conventional oil and gas resources in the Paradox Basin, Utah, Colorado, New Mexico, and Arizona

Katherine Whidden, Krystal Pearson, Lawrence Anna, Paul Lillis, and Russell Dubiel

The U. S. Geological Survey (USGS) completed a quantitative assessment of the undiscovered, technically recoverable conventional oil and gas resources in the Paradox Basin, which extends into parts of Utah, Colorado, Arizona, and New Mexico. Conventional accumulations are defined as those that have well-defined boundaries and hydrocarbon-water contacts, and the reservoirs have adequate porosity and permeability for recovery of hydrocarbons. The Paradox Basin is asymmetric, deepest along the north margin adjacent to the Uncompahgre uplift in Utah and Colorado. In the Middle Pennsylvanian (Desmoinesian), interbedded salt and black shales of the Paradox Formation were deposited near the northern basin margin, along with clastics shed from the Uncompahgre uplift. Penesaline and normal marine carbonates were deposited along the gently dipping southwest basin margin and interfinger with the salt and black shales along the ramp margin. Thicker black shale intervals, such as the informally named Cane Creek, Gothic, Chimney Rock and Hatch intervals, were the source for much of the hydrocarbons in the Paradox Basin. A second distinct oil type in the basin is typed as representing either the Permian Phosphoria Formation or the Mississippian Delle Formation and equivalents, or both. Clastic deposition across the basin continued into the Permian and Mesozoic. The assessment was based on the geologic elements that define a total petroleum system (TPS), including petroleum source rocks, reservoirs and petroleum traps. Two TPSs were identified, the Paradox Formation TPS and the Permo-Carboniferous TPS. The Paradox Formation TPS includes three assessment units (AUs): the Leadville McCracken AU, the Pennsylvanian Carbonate Buildups and Fractured Limestone AU, and the Upper Paleozoic-Mesozoic Reservoirs AU. The Permo-Carboniferous TPS includes the Permian-Mesozoic Reservoirs AU.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012