Evaluation of Fracture Toughness and Its Impact on Hydraulic Fracturing

The inherent anisotropy in shales due to the presence of fine laminations makes the process of fracture prediction complex. An optimized Hydraulic Fracture design requires a better understanding of anisotropy in rock strength and its impact on fracture propagation. This paper presents a workflow to generate continuous fracture toughness (KIC) profiles (parallel to bedding and perpendicular to bedding) using laboratory generated correlations between fracture toughness and other rock properties like UCS, Young’s Modulus and Tensile Strength. Anisotropic nature of fracture toughness has not been studied in detail previously which this paper seeks to address. A Boundary Element Method model was used to study the effect of anisotropy in fracture toughness and the magnitude on fracture geometry for a field in North America. Fracture simulations show anisotropy in KIC does impact hydraulic fracture propagation especially in cases where stress barriers are absent and neglecting it would lead to inaccurate predictions of fracture geometry.