Dissolution and Precipitation Reactions between the Madison Limestone and Supercritical CO2: Implications for Carbon Capture and Storage in Southwest Wyoming

Levesque, Steven
As part of an ongoing research program to address anthropogenic emissions of CO2, the University of Wyoming has identified the Rock Springs Uplift (RSU) of southwest Wyoming as a suitable CO2 storage reservoir. The focus of this study is to investigate mineral dissolution/precipitation reactions between the Madison Limestone and saline formation water after injection of supercritical CO2. The stratigraphic section of interest is a dolomite packstone composed of fine-grained Mg-dolomite rhombohedrals. Experiments reacted samples of Madison Limestone from a well drilled on the RSU (12,350 foot interval) with formation water (ionic strength = 1.644 M) under reservoir conditions (100 ˚C, 345 bars) for 14 days. Analysis of minerals using optical microscopy and X-Ray Diffraction (XRD) determined the extent of mineral precipitation and dissolution. XRD results show no distinct change in mineralogy. However, observations through optical microscopy reveal rounded dolomite edges, an observation not seen on the unreacted limestone. Reacted brine samples were withdrawn from the ongoing experiment and are being analyzed for changes in cation and anion concentrations using an ICP-OES and ion chromatograph. The results of the experiment conclude that minor dolomite dissolution does take place in the Madison Limestone storage reservoir with the injection of supercritical CO2.
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