How Long Should We Observe Microseismicity after Finishing a Borehole Fluid Stimulation?

Microseismic monitoring of fluid injections from boreholes can be expensive. Thus, it is important to know how long a significant microseismicity can be observed after a stop of the injection. Here we present results of theoretical and numerical modelling of the seismicity rate induced by a fluid injection into a poroelastic medium with pre-existing fractures. We obtain an analytical solution for the post-stimulational seismicity rate and show that the Omori law, which is well known in global Seismology, can be applied as a good approximation. We show how parameters of the Omori law depends on the time elapsed after the injection termination. Our analytical results are in a very well agreement with the numerical modelling.