Geological Sequestration of CO2: Is Leakage Unavoidable and Acceptable?

Publisher Summary Large-scale injection of CO 2 captured from major point sources into geological formations in sedimentary basins offers a potential solution to the atmospheric carbon problem. For this concept to succeed, potentially negative consequences associated with CO 2 injection must be identified, and their impacts must be shown to be acceptably small. Most negative impacts identified to date are associated with unintended leakage of CO 2 from the formation into which it is injected. Geological sequestration of CO 2 requires careful risk analysis to avoid unintended consequences of the subsurface injection. One potentially serious problem associated with injection into mature sedimentary basins is the possible leakage of injected CO 2 through or along existing wells. Over long time scales, these wells may serve as short-circuit pathways for leakage, with possible contamination of shallow subsurface zones, and ultimate leakage back into the atmosphere. Transport models for leakage analysis and overall risk assessment must include proper representation of the effects of existing wells. A multi-scale framework offers a guide for inclusion of existing wells into practical simulators.