Reactive flow channelization in fractured cement-Implications for wellbore integrity

Successful long-term geological storage of carbon dioxide (CO2) to reduce increasing atmospheric levels is dependent on seal integrity. If wellbores that penetrate a sealing caprock have permeable fractures in or along a cemented annulus, the fractures provide a potentially fast path for leakage. Because the leaking fluids are reactive toward cement, understanding how reaction, transport, and flow are coupled along a cement fracture is critical to predicting leakage evolution over time. Core flow experiments conducted in our laboratory show channelized flow of acidic brine in fractured cement cores. By staining the initial flow path of an unreactive fluid along the core and comparing it with the final flow path after the acid is introduced we can show that reactive flow is localized to a fraction (16-40%) of the original flow path. This provides experimental evidence that reactive feedbacks can significantly alter the flow along the fracture and needs to be better understood to ensure safety of long-term geological CO2 storage. (C) 2013 The Authors. Published by Elsevier Ltd.