| Flow through experiments were conducted with intact glauconite-bearing sandstone cores from the Tunnel City Group to determine the effectiveness of iron carbonate precipitation as a trapping mechanism for CO2. Mossbauer spectroscopy indicated that the ferrous/ferric ratio of iron in the glauconite-bearing sandstone was 0.24. The experimental design entailed the use of a fluid delivery system that permitted control of flow rate (0.01 ml/min), as well as confining and pore fluid pressure (200 and 150 bar, respectively). The source fluid was a 1 molal NaCl brine charged with approximately 0.58 mol CO2/kg solution held constant at 150 °C. A second experiment was conducted to test the effect of reducing conditions on the formation of iron carbonate minerals. The dissolved chemistry of outlet fluid provided evidence of fluid saturation with dolomite and siderite, and revealed a decrease in alkalinity. This suggests that glauconitic sandstones may be a favorable host rock for carbon sequestration. |
