Depleted oil wells and deep saline aquifers may hold promise as repositories for atmospheric carbon dioxide, according to a team of researchers whose study is published in Geology. For their experiment, Yousif Kharaka of the U.S. Geological Survey, Dave Cole of ORNL's Chemical Sciences Division and colleagues injected 1,600 tons of carbon dioxide to a depth of 1,500 meters into a brine aquifer hosted by a sandstone formation in the Texas Gulf Coast. Researchers tracked the movement of the CO2 via chemical and stable isotope data, including pH, alkalinity, iron and gas compositions, and oxygen and hydrogen isotopes of the brine. They discovered that the CO2 caused rapid dissolution of minerals, especially calcite and iron oxyhdroxides, which could lead to the creation of pathways in the rock and leakage of CO2 and brine. Ultimately, additional research is needed to answer some key questions about whether this approach is viable for sequestering CO2. The research was funded by DOE's Office of Fossil Energy.
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