A Coupled Three-Dimensional Hydraulic Fracture Propagation Model Accounting for the Effect of Bedding Layers

Unconventional shale reservoirs have been the most recent production frontier in the United States. Optimization of the production of shale reservoirs depends greatly on hydraulic fracture treatment. In recent studies, strongly contrasting properties of multi-layered rocks and pervasively distributed weak interfaces become the primary factors in determining the propagation pathway of fractures, which further influences the fracture height growth and fracture geometry. Few of hydraulic fracture propagation models enable us to quantitatively estimate the fracture height containment or predict fracture geometry under the influence of multiple bedding planes. Therefore, development of a reliable and practical simulator for modeling fracture propagation that enables accurate prediction of the fracture height growth in multiple-layered shale formation is critical to efficient resource development. In this dissertation, I have developed a coupled three-dimensional hydraulic fracture propagation model considering the effects of bedding planes. In this model, a fully three-dimensional displacement discontinuity method is used to model the rock deformation. The advantage of this approach is that it addresses both the mechanical interaction between hydraulic fractures and weak bedding planes in three-dimensional space and the physical mechanism of slippage along weak bedding planes. Fluid flow governed by finite difference methodology considers the flow in both vertical fractures and opening bedding planes. An iterative algorithm is used to couple fluid flow and rock deformation. Comparison between the developed model and the PKN model showed good agreement. Analysis of different fracture geometry and sensitivity analysis of different parameters are conducted to investigate their impacts on the opening of vertical fractures and bedding planes, and also the shear sliding along the bedding planes. A width jump, created along the vertical fracture when the vertical fracture penetrates the bedding plane, is regarded as a primary mechanism of fracture height containment. Both widths of fracture segments and shear sliding along the bedding plane are positively related with the distance between the injection source and the bedding plane segment. Higher formation Young’s modulus can restrict the opening of bedding plane and retard the fluid percolation into the bedding plane. Smaller fracture spacing gives rise of the opening reduction of the fracture segments. Our model enables us to provide a critical insight for the selection of the proppant grain size range and assessment of the required pumping rate to obtain the required width at both junction and intersected bedding plane