Hydraulic Fracture Interaction with Cemented Natural Fracture: A Three Dimensional Discrete Element Method Analysis

Abstract

AbstractThe propagation path of hydraulic fracture is significantly affected by the properties of cemented natural fractures (i.e., veins), such as, stiffness, tensile and shear strength, and flow characteristics. Moreover, the magnitude of stress anisotropy can control the results of hydraulic fracture crossing or diverting into the vein. To study the effect of vein properties and the differential stress on the interaction of hydraulic fractures with mineral-filled veins, we employed a three-dimensional (3D) Discrete Element Method (DEM) model which couples the fluid flow and the bonded-particle assembly. The hydraulic fracture interaction with the vein was investigated by monitoring the bond breakages and measuring the fracture diversion distance along the vein before kinking back into the rock matrix. Numerical results are in good agreement with the fracture diversion results from the published experimental and numerical SCB tests of Marcellus shale with calcite-filled veins. The propagating hydraulic fracture is more likely to divert into the veins with smaller approach angle. Increasing the differential stress leads to fracture crossing than diversion into the vein. For veins with greater stiffness than the host rock, microcracks were generated in the vein before the hydraulic fracture intersected it. For tight formations with stiffer veins, the vein permeability did not have much influence on the fracture diversion result since the damage induced by the stress concentration ahead of the hydraulic fracture tip dominated the fluid flow in the vein.