Investigation of the linear elastic fracture mechanics and its applicability in hydraulic fracturing modeling and design

Although the application of linear elastic fracture mechanics (LEFM) is one of the most prevalent theories used in hydraulic fracturing, when the damaged area around the fracture tip exceeds the limit, LEFM is not applicable. In this paper, the singularity-dominated and fracture process zones are defined to examine the applicability of using LEFM under constant fracture pressure in simulations of hydraulic fracturing. The sizes of the singularity-dominated and fracture process zones are evaluated at the hydraulic fracture tip under different faulting conditions. Furthermore, this study indicated that the fracture process zone dominated the singularity-dominated zone around the fracture tip under the various conditions investigated. However, when there is tensile failure in rocks the use of the LEFM is not appropriate. The sensitive analyses demonstrated that fracture pressure and minimal principal stress are the dictating factors regarding the relevance and applicability of LEFM. The results presented in this investigation can be used to define the damage process around the fracture tip under specific conditions while modeling hydraulic fracture treatment. The primary outcome of this study was to improve the understanding of LEFM and its impact on modeling of hydraulic fracture treatments. In addition, the results of this study also demonstrated the capacity of the model in relation to capturing the essential characteristics of the crack tip, including the onset of unconfined compressive strength, tensile strength, reservoir pressure, and various stress conditions. Moreover, the results of this study can also contribute to the understanding of the damage mechanism around a fracture tip under similar conditions, which can lead to improved modeling of hydraulic fracturing.