Hydro-mechanical modeling of hydraulic fracture propagation and its interactions with frictional natural fractures

摘要

Hydraulic fracturing is a key technique to activate natural fracture networks aiming at increasing permeability of non-conventional reservoirs. In order to design effective stimulations, it is necessary a good understanding of the hydraulic fracture propagation and its interaction with natural fractures. A robust methodology was developed using the finite element method to study the mechanisms that influence the activation of natural fractures and the subsequent process of hydraulic fracture propagation. An innovated mesh fragmentation technic is developed to simulate hydraulic fracture propagation with arbitrary paths. The behavior of the hydraulic fracture is modeled using hydromechanical cohesive interface elements with progressive damage model. The Mohr Coulomb criterion with tension cutoff is incorporated to represent the frictional behavior of natural fractures. The developed methodology is validated through literature data on experimental test results. The three main possibilities of interaction events (opening, crossing and arrest) are predicted accurately. Subsequently, the effect of some primary parameters such as the angle of approach between hydraulic and natural fracture, the stress ratio between minimum and maximum horizontal stresses and the internal friction angle of the natural fracture were studied to provide a better insight of the propagation processes of the hydraulic fracture. An interaction response diagram is proposed combining the effects of those parameters to provide a good estimative of fracture interaction.