Investigation of carbon sequestration via induced calcite formation in natural gas well brine

The permanent storage of carbon in mineral form using natural brines found in geologic formations is at the forefront of carbon sequestration research. A complex chemistry describes the ultimate fixation of carbon in stable minerals, such as calcite. However, the parameters that govern carbonate formation are not well understood. Accordingly, the purpose of this study is to induce and characterize calcite formation by reacting natural gas brine with CO2. Brine pH has a significant effect on this conversion and can thus be adjusted to induce calcite precipitation using a laboratory scale reactor operated at temperatures of 75 and 150 degrees C and pressures of 600 and 1500 psi. Initial pH conditions of at least 9.0 are optimal for carbonate precipitation in reactions of 18 It. Although the reaction duration is not long enough to successfully correlate brine compositional changes with precipitation and pH evolution, X-ray diffraction analysis clearly confirms the presence of calcite. Scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis provides an introductory look at the microscale production of these minerals.