Scaling of seismicity induced after injection stop to better understand hydraulic fracturing processes

Abstract

Fluid injections into unconventional reservoirs, performed for fluid-mobility enhancement, are accompanied by microseismic activity which frequently continues after the injection stop. Previous studies reveal that the triggering of seismic events can be described by non-linear diffusion of pore-fluid pressure where the diffusivity becomes pressure-dependent. The spatio-temporal distribution of postinjection-induced microseismicity has two important features: the triggering front, corresponding to early and distant events, and the back front, enveloping the growing aseismic zone around the well bore-hole. To describe the temporal behavior of postinjection-induced seismicity, we introduce a scaling law for the back front. We show that it is sensitive to the degree of non-linearity of the fluid-rock interaction and to the Euclidean dimension of the space of seismicity. To validate the theory, we numerically model non-linear pore-fluid pressure diffusion and generate catalogs of synthetic seismicity. We demonstrate that back fronts of synthetic seismicity and of observed fluid-induced seismicity can be well described by the proposed asymptotic scaling. Therefore, this theoretical understanding is of particular importance for future reservoir characterization and hazard assessment.

Presentation Date: Wednesday, October 19, 2016

Start Time: 11:35:00 AM

Location: 144/145

Presentation Type: ORAL