Natural CO2 accumulations in the western Williston Basin: A mineralogical analog for CO2 injection at the Weyburn site

► The Duperow Formation in the Williston Basin contains natural accumulations of CO2. ► The Duperow Formation is a mineralogical analog for CO2 injection at Weyburn–Midale site. ► Mineral assemblages in the Duperow are identical to Weyburn–Midale site. ► CO2-bearing Duperow carbonate horizons show n...

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Bibliographic Details
Published in:International journal of greenhouse gas control 2013-06, Vol.16 (S1), p.S25-S34
Main Authors: Ryerson, F.J., Lake, John, Whittaker, Steven, Johnson, James W.
Format: Article
Language:English
Subjects:
Geologic carbon sequestration
GEOSCIENCES
Natural analog
Natural carbon dioxide accumulations
Supercritical carbon dioxide
Water–rock interaction
Weyburn carbon dioxide injection
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Summary:► The Duperow Formation in the Williston Basin contains natural accumulations of CO2. ► The Duperow Formation is a mineralogical analog for CO2 injection at Weyburn–Midale site. ► Mineral assemblages in the Duperow are identical to Weyburn–Midale site. ► CO2-bearing Duperow carbonate horizons show no evidence of secondary dawsonite. ► Physical and solution trapping alone enable long-term geologic storage of CO2 in carbonate-evaporite sequences. The Devonian carbonates of the Duperow Formation on the western flank of the Williston Basin in southwest Saskatchewan contain natural accumulations of CO2, and may have done so for as long as 50 million years. These carbonate sediments are characterized by a succession of carbonate cycles capped by anhydrite-rich evaporites that are thought to act as seals to fluid migration. The Weyburn CO2 injection site lies 400km to the east in a series of Mississippian carbonates that were deposited in a similar depositional environment. That long-term isolation of natural CO2 can be accomplished within carbonate strata has motivated the investigation of the Duperow rocks as a potential natural analog for storage of anthropogenic CO2 in carbonate lithologies. For the Duperow strata to represent a legitimate analog for Midale injection and storage, the similarity in lithofacies, whole rock compositions, mineral compositions and porosity with the Midale Beds must be established. Here we compare lithofacies, whole rock compositions, mineralogy and mineral compositions from both locales. The major mineral phases at both locales are calcite, dolomite and anhydrite. In addition, accessory pyrite, fluorite, quartz and celestine (strontium sulfate) are also observed. Dawsonite, a potential CO2-trapping mineral, is not observed within the CO2-bearing horizons of the Duperow Formation, however. The distribution of porosity in the Midale Vuggy units is similar to that of the Duperow Formation, but the Marly units of the Midale have significantly higher porosity. The Duperow Formation is topped by the Dinesmore evaporite that is rich in anhydrite, and often contains authigenic K-feldspar. The chemistry of dolomite and calcite from the two localities also overlaps. Silicate minerals are in low abundance (
ISSN:1750-5836
1878-0148
DOI:10.1016/j.ijggc.2012.12.015