Coupled Hydro-Mechanical Analysis of Hydraulic Fracture in Naturally Fractured Reservoirs Using Finite Elements with Embedded Discontinuities
Aura Zuleta1; Leila Beserra1; Leonardo Guimarães1; Marcela Seixas1; Osvaldo Manzoli2; Kewin Passos Granados1
1 Federal University of Pernambuco; 2 universidade estadual paulista
doi:10.20906/CPS/CILAMCE2017-0275
Resumo
Hydraulic fracturing is a widely used method in the petroleum industry to recover as much oil as possible from the reservoir. In this method, artificial fractures are induced by fluid injection in order to increase rock permeability. In a naturally fractured reservoir, it is fundamental to know the influence of natural fractures on the geometry of the induced fracture because this is decisive for the mechanical properties of the rock, in-situ stresses and local heterogeneity. Due to the strong coupling between fluid flow and mechanical behaviour, the presence of plans of weakness induced by natural fractures makes modeling of hydraulic fracturing a challenging task. The choice of an appropriate constitutive model that predicts the mechanical behavior of fractures in a realistic way is a critical point. The hydraulic fracturing problem in naturally fractured reservoirs was simulated in a numerical code that adopts a strong discontinuity approach to embedding discontinuities in a finite element mesh and provides a numerical fluid flow analysis in a deformable reservoir. The resulting code is used to model hydraulic fracture propagation in naturally fractured reservoirs with relatively coarse meshes and reasonable computational time. The hydro-mechanical coupling has been determined by a law that relates the variation of permeability as a function of the displacement jump from the mechanical problem. In a homogeneous rock the preferential direction of hydraulic fracture propagation is perpendicular to maximum principal stress. On the other hand, in a naturally fractured reservoir a detailed knowledge of the natural fracture network is necessary to predict the propagation and aperture of induced fractures. The purpose of this prediction is to take decisions regarding the conditions under which the fracturing operation will be performed. To evaluate the effect of initial stress state in the direction of the induced fractures, the simulations were performed considering different scenarios for the initial stress stat
Palavras-chave: Hydraulic Fracturing; Natural Fractures; Finite Elements; Embedded Discontinuities