Hydromechanical modeling of unrestricted crack propagation in fractured formations using intrinsic cohesive zone model

Abstract Production from unconventional reservoirs has revolutionized the oil and gas industry strongly through the development of innovative applications, such as horizontal drilling and shale stimulation by hydraulic fracturing. However, the presence of geological discontinuities such as natural fractures (NFs) complicates the hydraulic fracturing treatment and affects the general geometry of the hydraulic fracture (HF). For that reason, it is essential to develop and implement robust numerical methods capable of simulating the phenomena present during hydraulic fracturing in a naturally fractured formation. This paper presents a novel mesh fragmentation technique to simulate unrestricted hydraulic fracture propagation in fractured media. This method is based on the hydromechanical zero thickness interface element combined with the cohesive zone model (CZM). An algorithm for inserting the especial triple-noded interface elements into conventional 2D finite element meshes is described. We introduce a simple but effective topological data structure that considers each finite element independent of others. The proposed topological structure ensures the generation of new nodes and faces which are necessary for the insertion of interface elements. The implementation is validated by simulating some cases of fracturing experiments in laboratory. The numerical procedure provides very good agreement with the laboratory tests and shows the robustness of the proposed computational approach. Some advantages and limitations of the proposed methodology are discussed.