Empirical and numerical investigation into the influence of fluid injection volume and rate on induced seismicity in the Montney Formation, northeastern British Columbia

Abstract

Hydraulic fracturing operations to support production from unconventional oil and gas reservoirs have been subject to public concerns and regulatory oversight regarding the generation of induced seismicity. These concerns have been shaped by experiences such as those for the Montney Formation in northeastern British Columbia that have seen an increase in seismic activity in response to hydraulic fracturing activities. Although the geological conditions present play a central role in the susceptibility of a well to induced seismicity, operational factors such as fluid injection volume and rate are of special interest as these can be engineered and controlled to mitigate the induced seismicity hazard. Results are presented in this paper from an empirical investigation analyzing data from the Montney that explore the influence of injection volumes and rates to the triggering of induced seismicity. The results from the empirical analysis indicate that injection volume correlates more strongly with induced seismicity for wells that target the Middle Montney formation, whereas injection rate was seen to be a more significant influencing factor for wells targeting the Upper Montney formation. Our hypothesis is that this difference is due to the presence of a more dense and interconnected natural fracture network in the Middle Montney that influences the likelihood of fluid-flow diffusion and connectivity with a critically stressed fault. Results are provided from a series of advanced 3-D numerical models used to support this hypothesis and provide mechanistic understanding.