Numerical Modeling of Fluid-Driven Fractures in Permeable Media Using Symmetric Cohesive Elements

ABSTRACT: Hydraulic fracturing is one of the most widely used techniques adopted in the oil industry to enhance reservoir permeability. In traditional hydraulic fracture modeling, the numerical model simulates half of the fracture geometry by taking advantage of model symmetry. However, hydraulic fracture modeling in heterogeneous rock formations considering a fully coupled formulation can require significant computational effort, especially in 3D models. This work proposes a symmetric cohesive element to simulate fluid-driven fractures in permeable porous media. In this approach, the hydraulic fracture path coincides with the plane of symmetry of the fracture, allowing the simulation of only a quarter of the fracture geometry. The symmetric cohesive element is obtained by imposing suitable constraints on the displacement degrees of freedom. In addition, the hydromechanical properties are updated to induce symmetric hydraulic fracture propagation. The proposed technique is successfully compared against the traditional full model, demonstrating simulation accuracy with substantially reduced computational cost. The numerical results demonstrate the capability of the proposed approach to successfully simulate hydraulic fracturing under under K and propagation regimes. Finally, this approach is an attractive alternative to simulate field scale models considering heterogeneous permeable rock formations. 1. INTRODUCTION The oil and gas industry employs the hydraulic fracturing technique to enhance unconventional reservoir permeability. The fracturing process involves the high-pressure injection of fracturing fluid to create cracks inside the rock formation, facilitating the migration of trapped hydrocarbon. However, it can lead to geomechanical problems such as seismicity (Rutqvist et al., 2013). Therefore, a better understanding of the hydraulic fracturing behavior is essential to reduce the associated environmental risks. However, the numerical modeling of hydraulic fracturing requires a better understanding of the physical mechanisms and also the ability to build field-scale models (Searles et al., 2016). In the last decades, numerical models have been developed to simulate hydraulic fracturing problems with complex fracture geometry (J. Adachi et al., 2007). Recently, several authors developed fully coupled HM zero-thickness interface elements, which modeled longitudinal and transversal fluid flow inside the fracture (Ng Segura Zielonka et al., 2014). The capability of this approach was verified through comparison with available analytical solutions (Carrier & Granet, 2012) and laboratory fracturing tests (Searles et al., 2016). However, accurate modeling of hydraulic fracturing requires refined mesh close to the fracture plane, which is computationally expensive for 3D field-scale models.