Stability analysis of the propagation of periodic parallel hydraulic fractures

When multiple fractures are propagating simultaneously, the fracture spacing may coarsen gradually resulting from loss of stability of the fracture system, which can also occur during the propagation of multiple hydraulic fractures (HFs). In this paper, the stability of the propagation of periodic parallel HFs in brittle solids is investigated based on a representative unit cell consisting two HFs. The fractures are driven to propagate by the inside fluid flow and fluid–solid coupling effect is involved. Both the stress interaction acting in the solid medium and the flow of fluid medium can influence the stability. Stability criterions are given based on the variations of the rates of change of the stress intensity factor with respect to facture velocities. Stability results are obtained by solving the system with fully coupled numerical method which considers the deformation of solid medium, fracture propagation, fluid flow in fractures, fluid partitioning into each fracture. Based on the numerical results, the influences of propagation regimes, fracture lengths and the fracture distance on the stability of HFs are investigated.