Abstract
Hydraulic fracturing re-distributes pore pressure and stresses inside rock and causing failure by fracture initiation and/or activation of discontinuities such as natural fractures or layering boundaries. The clear result of this process would be enhancement of the formation permeability. In this paper, poroelastic numerical method is employed to investigate interactions of hydraulic fractures and porous rock. Besides, evolution of potential failure (microseismic events) during hydraulic stimulation is studied. The model uses indirect boundary element method. Temporal variations and pressure-dependent leak-off, hydro mechanical response of porous matrix, fluid flow in matrix, couplings of matrix volumetric deformation and pore fluid dissipation, and hydraulic fractures interaction are taken into account. Results clearly show the modification/redirection of principal stresses around pressurized hydraulic fracture. It also shows that modified stresses cause failure around the fracture tip which generally covers a bigger area than the fracture itself and could results in an overestimation of the stimulated reservoir volume. Then, pressurization of multiple parallel fractures studied. As expected, it is found that fracture geometry and the distance between hydraulic fractures are the most important factors in modifying the stress state and pore pressure and consequently extent of failure region. It was also observed that the opening of a fracture induces shear stresses on adjacent fractures. The SIF for pressurized cracks was calculated for Mode I and Mode II, and it was shown that when the distance between hydraulic fractures increases, the Mode I SIF also increases and the Mode II SIF decreases.'ép.
