Failure Behavior Modeling of Unconsolidated Rock under Hydraulic Fracturing Operation

Hydraulic fracturing is an operation in which viscous fluid is injected through a well and by applying respective pressure rocks are fractured. The operationends with narrow channels having high permeability, which leads to more oil production. Adjacent rocks to the well face catastrophic failure while farther awayfrom the well fracture is expected to diminish as a consequence of pressure drop. In this paper, radius of fractured zone under different conditions of fluidviscosity and boundary load is modeled. Fluidis injected to a cylindrical sample, which is made of homogenous, high porous and high permeable Quartz sandstone witha special grain size. The modeling is implemented with finite element analysis software, the COMSOLMultiphysicsapplying Poroelasticity module. A failure expression defined by Suarez-Rivera et al.is used as fracture criterion and von Mises equivalent stress ischosen to be a representative of how rock is stressed while pressure was obtained from diffusivity equation. The results indicate that fracture initiation is a highfunction of boundary load and regardless of economic issues, optimum viscosity is required to be defined forhydraulic fracturing operation. In addition, fluid rheology can be more critical for unconsolidated (i.e. high porous andhigh permeable) rocks.

Keywords:

Hydraulic fracturing , Stress profile , Fractured zone , Unconsolidated rock