Geochemistry of Geologic Carbon Sequestration: An Overview

Over the past two decades there has been heightened concern about, and an improving scientific description of, the impacts of increasing carbon dioxide concentrations in Earth’s atmosphere. Despite this concern, the global rate of addition of carbon dioxide to the atmosphere by the burning of fossil fuel, now approaching 10 Gton C/yr, continues to increase, and at an accelerating rate (Fig. 1a). Although many still hope and believe that carbon emissions can be arrested at near the current rates, and decreased over the remainder of the 21st century, there is as yet little evidence that this is going to occur. The driver for carbon emissions is a globally increasing demand for energy, and the fact that energy can be produced relatively inexpensively and with well-developed technology by burning coal, oil and natural gas. Given that the focus on fossil fuel energy is not lessening to an appreciable degree (Fig. 1b), it is not only prudent, but necessary to have the technology to reduce the carbon emissions associated with fossil fuel burning. This reduction can potentially be accomplished with large-scale carbon capture and storage, where carbon dioxide would be captured from the flue gases of electric power generation facilities, purified, compressed, and injected underground as a supercritical fluid into porous geologic rock formations (Oelkers and Cole 2008). To be effective in reducing carbon accumulation in the atmosphere, this injected or “stored” CO2 must remain underground for thousands of years with only insignificant amounts of leakage back to the surface (Benson and Cook 2005). To date, a significant number of large CO2 injection demonstrations and more modest pilot tests have been linked to either Enhanced Oil (EOR) or Gas Recovery (EGR) operations such as at the Weyburn EOR site in Canada, the In Salah site in Algeria and the …