Seismic Moment Evolution During Hydraulic Stimulations
Stephan Bentz, Grzegorz Kwiatek, Patricia Martínez‐Garzón, Marco Bohnhoff, Georg Dresen
Abstract
Abstract Analysis of past and present stimulation projects reveals that the temporal evolution and growth of maximum observed moment magnitudes may be linked directly to the injected fluid volume and hydraulic energy. Overall evolution of seismic moment seems independent of the tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. Data suggest that magnitudes can grow either in a stable way, indicating the constant propagation of self‐arrested ruptures, or unbound, for which the maximum magnitude is only limited by the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection or not at all. Monitoring and traffic light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near‐real time and at high resolution for an immediate reaction in injection strategy.