Kinematic Features and Magnitudes of Fluid Induced Seismicity – Case Studies and Their Interpretation

Sometimes fluid injections are characterized by a risk to induce a seismic event of a significant magnitude. Here we address magnitude distribution of seismicity induced by borehole fluid injections. However, firstly we give a short introductory review of microseismicity interpretation in geothermic reservoirs and by hydraulic fracturing. Then, we introduce a simple theoretical model, which predicts the earthquake magnitude distributions for fluid injection experiments. The temporal distribution of microearthquake magnitudes depends on the injection pressure, the size of the borehole injection section, the hydraulic diffusivity of rocks, and is also inherited from the statistics of pre-existing crack/fracture systems controlling the local seismicity. We consider different case studies and show how our model can be used to optimise the design of fluid injection experiments and reduce their seismic risk.