Hydraulic Fracture Propagation in Unconventional Reservoirs: The Role of Bedding Plane

Abstract

Hydraulic fracturing is a widely used technology in stimulation of un- conventional reservoirs to obtain commercial production. Meanwhile, the bedding plane between sandstone and mudstone is a key challenge in unconventional reser- voirs especially. During hydraulic fracture propagation, any diversion or abrupt change in hydraulic fracture path caused by bedding plane, leads to job failure. In this paper, presents a numerical simulation method for a growth of hydraulic fracture interacting with a geological discontinuity in bedding plane. A 3-D hy- draulic fracture model has been developed that can consider the elastic-plastic rock deformation coupled to fluid flow. The fracture growth is modeled by the damaged plasticity model of the continuum medium. The injection fluid flow rate value is given by the subroutines. This paper gives out a engineering example using the method to computer. The numerical calculation results coincide with test results which are microseismic data of a fracture propagation. The bedding plane between sandstone and mudstone can result in fracture blunting, crossing or entering the interface. The numerical results indicate that hydraulic fracture diversion is con- trolled strongly by the shear strength of the discontinuity, as well as the mechanical property. It is clearly observed that the larger differences of the mechanical prop- erty is more easily to deflection, due to the interfacial shear deformation increases. Once the shear stress is larger than the shear strength of the interface, the fracture tip become blunting and failure along the interface. So the fracture growth pattern depends on the shear strength of the interface and the stress contrasts. The hydraulic fracturing methods that include interfacial properties can be used to better simulate fracturing in bedding plane, and it is important to improve fracture design and evaluation in unconventional reservoirs.