The Role of Parallel Fracture Networks for Induced Seismicity in the Duvernay Formation

Fluid injection and hydraulic fracturing can cause induced seismicity. Two commonly proposed causative mechanisms are pore pressure and stress perturbations, or a combination of the two. Since most studies of induced seismicity due to hydraulic fracturing to date have been recorded on a regional scale, they lack the resolution to shed light on some of the key questions currently in the field. Using a high-quality dataset obtained during hydraulic fracturing in the Fox Creek, Alberta area, the detailed mechanisms of fault activation were examined. This experiment, dubbed the Tony Creek dual Microseismic Experiment (ToC2ME), contains several events over MW 2.0, and shows high-resolution fault activation. Seismic anisotropy derived from induced events was used to determine the direction of a pre-existing fracture network, which is attributed to be the main conduit by which fault activation was triggered. Pore pressure modelling was carried out to show that the delay times between injection and activation are consistent with the time necessary for a sufficiently significant pore pressure perturbation to reach the main fault features.