|Hydraulic fracturing optimization for unconventional reservoirs - The critical role of the mechanical properties of the natural fracture network
|Year of Publication
|Nagel NB, Garcia X, Lee B, Sanchez-Nagel M
|Society of Petroleum Engineers - SPE Canadian Unconventional Resources Conference 2012, CURC 2012
|The success of many shale plays depends on the optimal stimulation of natural fractures, and the characterization of the natural fracture systems is a key issue often leading to the construction of a discrete fracture network (DFN). The DFN chiefly consists of fracture spacing, fracture dip, and dip direction from numerous sources, and, in some cases, is matched to well test data allowing for the determination of hydraulic properties. However, a commonly missing component of natural fracture characterization, and the component most important to evaluating the coupled hydro-mechanical behavior of the fractures during a hydraulic fracture stimulation, is the evaluation of the mechanical behavior of the fractures. The important mechanical parameters of the fractures include: a) elastic properties such as shear and normal stiffness, which relate changes in pore pressure to changes in aperture; b) strength parameters such as cohesion and friction angle, which define when a fracture may shear and open; c) dilational properties, which relate fracture opening to shear slippage; d) fracture toughness, which determines the pressure required to extend a fracture; and e) initial aperture. In this paper, using a new, state-of-the-art, fully-coupled, 3D distinct element hydraulic fracturing simulator, mechanical fracture parameters were evaluated in a parametric study in order to determine their impact on the effectiveness of hydraulic fracture stimulations. Copyright 2012, Society of Petroleum Engineers.