Intricate unconventional fracture networks provide fluid diffusion pathways to reactivate pre-existing faults in unconventional reservoirs

Abstract

Hydraulic fracturing-induced earthquakes are typically triggered via a hydraulic connection between stimulated wells and pre-existing faults. Despite this, relatively little modeling has focused on fluid migration along fractures and faults in shale reservoirs. The experimental measurements and logging data were collected first to create a high-resolution 3D petrophysical and geomechanical model of a Duvernay reservoir. To simulate the real-time growth of complex hydraulic-natural fracture networks, an unconventional fracture model (UFM) is constructed that considers fluid flow, interactions between hydraulic and natural fractures, reservoir petrophysics, and geomechanics. Coupled poroelastic modeling quantifies the well-fault hydraulic connection in terms of spatiotemporal stress and pressure changes, assessing the fault stability during hydraulic fracturing. The UFM model is applied to three field case studies, and the findings are evaluated against those of induced earthquake clusters. The non-uniform intricate fracture networks are discovered to provide fluid diffusion pathways for hydraulic fracturing-induced earthquakes. To reduce possible seismic risks, fault stability must be assessed prior to hydraulic fracturing in unconventional reservoirs.