Microseismic monitoring and interpretation of injection data from the In Salah CO2 storage site (Krechba), Algeria

-Microseismic data analysis together with interpretation of injection data at the In Salah CO2 storage site provides a valuable tool for improved understanding of the subsurface injection and storage processes. More than 1500 microseismic events have been detected semi-automatically between August 2009 and May 2012 and the occurrence of the events correlates clearly with increased injection rates and well-head pressures. Most likely the fracture pressure has been exceeded temporarily, resulting in a sudden increase of microseismicity. Waveform cross- correlation of the events demonstrates that most events occur in three distinct clusters. Clusters with shorter S-P wave differential travel times clearly correlate with the CO2 injection at KB502, whereas events with larger S-P wave times do not. An uncertainty analysis and a network design study conclude that a more extensive microseismic network would be needed to resolve locations and potential correlations with injection data