Fault Triggering Mechanisms for Hydraulic Fracturing-Induced Seismicity From the Preston New Road, UK Case Study

We investigate the physical mechanisms governing activation of faults during hydraulic fracturing. Recent studies have debated varying importance different fault reactivation in settings. Pore pressure increase caused by injection is generally considered to be primary driver induced seismicity. However, very tight reservoir rocks, unless a fracture network exists act as conduit, rate diffusion may too low explain spatio-temporal evolution some microseismic sequences. Thus, elastic and poroelastic stress transfer aseismic slip been invoked observations events occurring beyond expected distance reasonable diffusive front. In this study we use high quality data acquired fracturing at Preston New Road (PNR) wells, Lancashire, UK, examine triggering mechanisms. Injection through both wells generated felt seismicity—an M L 1.6 PNR-1z 2018 an 2.9 PNR-2 2019—and show that each operation activated with orientations. Previous already shown seismicity was triggered combination direct effects opening. Here perform similar analysis seismicity, finding mostly likely dominated increased fluid secondary zone fractures. opening would also acted promote slip. It significant no microseismicity observed on previously operations. This dataset therefore provides unique opportunity estimate minimum perturbation required activate fault. As it appears there connection between them stimulation, any stimulation must or transfer. such, computing created onto fault, are able approximate bound for perturbation: excess 0.1 MPa, orders magnitude larger than stated estimates generalized threshold.