Local Stress Redistribution Controls Interactions between Hydraulic Fractures and Pre-existing Fractures
2026-06-10 • Computational Engineering, Finance, and Science
Computational Engineering, Finance, and Science
AI summaryⓘ
The authors studied how pre-existing natural fractures in rock affect the path of new hydraulic fractures used in processes like underground fluid injection. By combining lab tests and computer simulations on special plastic samples, they found that the way these natural fractures cause local changes in stress and shear forces determines whether the hydraulic fracture bends away or connects to them. Their work shows that fractures can change from simply opening up to moving in a more complex way because of these stress changes. This helps better predict fracture growth in subsurface engineering.
Hydraulic fractureNatural fracturesShear deformationStress redistributionPoroelasticityExtended finite element methodMode I-II fractureDigital image correlationTensile openingMixed-mode fracture propagation
Authors
S. Shandilaya, M. Alaleeli, S. H. Kim, M. Mobasher, S. Roshankhah
Abstract
Hydraulic fracture (HF) propagation in naturally fractured formations is strongly influenced by local stress states near pre-existing natural fractures (NFs). The role of NF-induced shear deformation and stress redistribution in controlling HF trajectories remains poorly characterized. This study investigates how NF-induced stress redistribution governs HF-NF interactions through coupled laboratory experiments and poroelastic extended finite element simulations on intact and pre-fractured PMMA specimens under plane-strain conditions. Digital image correlation provides full-field measurements of displacement and strain evolution during mechanical loading and hydraulic fracturing. Under fixed-base, lateral confinement, and vertical compression boundary conditions, inclined NFs induce asymmetric stress redistribution and shear deformation, generating distinct local stress states prior to fluid injection. The results demonstrate that the HF trajectory is governed by the sign and spatial distribution of shear stress and shear strain components generated by NF orientation relative to the far-field maximum principal stress. Shear deformation that promotes compressive stress development adjacent to the NF causes the HF to deflect away, whereas shear deformation that reduces the effective normal stress along the NF promotes fracture attraction and linkage. Corresponding numerical reproduction of HF curvature in pre-fractured specimens requires mixed-mode (Mode I-II) fracture energy release criteria, while the intact specimen propagates in pure Mode I. Overall, the findings reveal a transition from tensile opening to shear-assisted mixed-mode propagation as local stress states evolve due to the presence of NFs, providing a mechanistic basis for predicting and controlling fracture trajectories in subsurface stimulation and storage applications.