Study Reveals How Pre-existing Fractures Control Hydraulic Fracture Propagation Through Stress Redistribution
Researchers have identified that shear-induced stress redistribution around pre-existing natural fractures controls whether hydraulic fractures deflect away from or link up with those fractures. The study combined laboratory experiments on PMMA specimens with poroelastic extended finite element simulations, using digital image correlation to track full-field strain evolution. The findings provide a mechanistic framework for predicting fracture trajectories in subsurface applications such as oil and gas stimulation and underground energy storage.
A new preprint submitted to the International Journal of Rock Mechanics and Mining Sciences investigates how naturally occurring fractures (NFs) alter the local stress environment encountered by propagating hydraulic fractures (HFs). Using coupled laboratory experiments on intact and pre-fractured PMMA specimens under plane-strain conditions, alongside poroelastic extended finite element method (XFEM) simulations, the team found that the orientation of a natural fracture relative to the far-field maximum principal stress determines the sign and spatial distribution of shear stresses that develop before fluid injection even begins. Where shear deformation increases compressive stress adjacent to the NF, the hydraulic fracture deflects away; where it reduces effective normal stress along the NF, the hydraulic fracture is attracted and links with it. Accurately reproducing the observed HF curvature in pre-fractured specimens required mixed-mode (Mode I–II) fracture energy release criteria, whereas intact specimens propagated under pure Mode I tension. The results mark a mechanistic transition from simple tensile opening to shear-assisted mixed-mode propagation driven by NF-induced stress redistribution, offering improved predictive tools for subsurface fracture engineering.
What's missing
The study uses PMMA (a transparent polymer) as a proxy for rock, and the degree to which these results scale to heterogeneous natural rock formations with multiple interacting fractures, in-situ pore pressures, and three-dimensional geometries remains unvalidated. The work is a preprint and has not yet completed peer review.
What different sources said
- arXiv physicsCenter
Local Stress Redistribution Controls Interactions between Hydraulic Fractures and Pre-existing Fractures
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