(677f) Hydraulic Fracture Propagation in Unconventional Reservoirs Under the Influence of Natural Fracture Heterogeneities

Authors: 
Fu, W., University of Pittsburgh
Bunger, A. P., University of Pittsburgh
Damjanac, B., Itasca Consulting Group
Savitski, A. A., Shell International Exploration and Production
Determination of the hydraulic fracture propagation patterns in fractured unconventional reservoirs is important for the reservoir stimulation design and production estimation/enhancement. Past studies on hydraulic fracture-natural fracture interaction typically carry the assumptions that 1) natural fracture height coinciding with the reservoir/hydraulic fracture height, and 2) uniform properties of the natural fracture, which lead to 2D views. However, recent field studies and experimental observations demonstrate that natural fracture heterogeneities can strongly influence the hydraulic fracture propagation, which calls for further understandings. In this study, we consider the impact of natural fractures with varying mechanical and geometrical properties on hydraulic fracture propagation. A 3D analytical criterion is developed to estimate the dependence of hydraulic fracture propagation on spatially-varied natural fracture properties, characterized by the proportion of cemented region(s), cementation strength, and natural fracture height. It is compared with experimental results from analogue hydraulic fracturing tests and observed to provide good predictions. A lattice simulator is then employed to realize the fully-coupled simulation of hydraulic fracture growth in fractured media. Consistent with laboratory observations, the numerical simulation captures the 3D interaction behaviors between hydraulic fractures and natural fractures with non-uniform properties. It also matches the analytical criterion well for cases with different natural fracture cohesion, friction coefficient, tensile strength, location of cemented regions, cemented proportions, and/or host rock materials.