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Published in:
2013 | OriginalPaper | Chapter
8. Reservoir Fluid Characterization of the Weber Sandstone and Madison Limestone on the Rock Springs Uplift in Southwest Wyoming
Authors : Scott A. Quillinan, J.Fred McLaughlin
Published in: Geological CO2 Storage Characterization
Publisher: Springer New York
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Abstract
Formation brine characterization provided the data for analytical permitting requirements, evaluating reservoir confinement, and reaction path modeling. The brines of the Weber Sandstone and Madison Limestone of the Rock Springs Uplift are sodium-chloride type with total dissolved solid concentrations in excess of 75,000 mg/L. Due to the high TDS the Wyoming Department of Environmental Quality has classified these as Class VI groundwater.
Solutes of the brines are enriched above the seawater evaporation trend line, indicating that the brines have been heavily influenced by additional mineral dissolution, specifically halite. The composition of dissolved gases were measured and found to be unique to each formation. Dissimilarities in the brine chemistries and associated dissolved gases indicate that the target formations are isolated from each other.
Both the Weber and Madison fluids are supersaturated with respect to dolomite and calcite. With respect to anhydrite, the Weber is saturated or slightly undersaturated and the Madison is undersaturated. Simulations of CO2 injection into the formation brines suggest a decrease in pH and an increase in the partial pressure of CO2, calcite dissolution and anhydrite precipitation. These reactions will likely cause an increase in porosity of 1–3 %.
Hydrogen sulfide concentrations in the reservoir increased between the first and second sampling set (0.04 to 127 mg/L in the Weber and from 29 to 87 mg/L in the Madison). Although the cause of this increase is unknown, it is recommended that careful consideration be given to reservoir management during CO2 injection. Additionally, H2S monitoring should be an element of water production scenarios for CCUS.