EVALUATING UPPER ORDOVICIAN STRATA IN THE LUCK POT FIELD, BORDEN COUNTY, TEXAS FOR CARBON DIOXIDE STORAGE

The Permian Basin of West Texas and Southeastern New Mexico has produced over 30 billion barrels of oil (BBO) over the past 100 years. Most of this production has come from conventional carbonate reservoirs under primary, secondary (waterflood) or tertiary recovery (Enhanced Oil Recovery utilizing CO₂). EOR projects in the Permian Basin have been injecting CO₂ for more than 50 years. Recently, United States tax legislation (45Q) has renewed interest in older oil and gas fields in the Permian Basin as potential CO₂ storage reservoirs. One possible target is the Late Ordovician carbonates of the Montoya Group, Sylvan Formation, and Fusselman Formation. In the eastern Midland Basin, the Luck Pot Field produces from a stratigraphic trap formed along the Fusselman Formation’s eroded margin. Four cores spanning portions of the Montoya, Sylvan, and Fusselman formations were evaluated petrographically and with a portable x-ray fluorescence spectrometer (pXRF) to evaluate sedimentary facies and reservoir properties. The Montoya is comprised of shallow subtidal, bioturbated skeletal dolopackstones that grade into deeper water dolowackestones. Vertical karsting beneath an exposure surface at the top of the Montoya marks the transition to the Sylvan, which has previously been described as conformable. This change is also observed in the pXRF data with a stepwise shift consistent with the observed lithology change. The Sylvan Formation is a green to gray planar laminated dolomitic mudstone with increasing carbonate content toward the top of the formation. The contact between the Sylvan and overlying Fusselman formation is transitional from dolomitic mudstone to dolowackestone. This transition is also identified geochemically with a decrease in detrital signatures (Si, Al, Zr, etc.) and an increase in carbonate signatures (Ca and Mg) between the Sylvan and the Fusselman. The gradational boundary between the Sylvan and the Fusselman noted here contrasts with previous reports of an unconformity between these formations. When combined with traditional petrophysical log interpretations the sedimentary facies relationships and geochemical data from these cores will aid in assessing the potential for Upper Ordovician strata to serve as viable targets for CO₂ sequestration on the Northeast Shelf of the Permian Basin.