Numerical modeling and investigation of fracture propagation with arbitrary orientation through fluid injection in tight gas reservoirs with combined XFEM and FVM

Abstract

Hydraulic fracturing is widely used in the petroleum engineering to enhance the reservoir conductivity. The most 3D simulators for modeling hydraulic fracturing assume that the created fracture propagates perpendicular to the minimum horizontal stress. In the reality, the fracture orientation is more or less affected by many factors, e.g. the reservoir heterogeneity. If the fracture is strongly reoriented, then such 3D simulators could not be used. Therefore, it is essential to investigate the orientation problem. In this paper, a 2D numerical approach to model hydraulic-driven fractures with arbitrary orientation in tight gas reservoirs is presented. The approach is based on the elasticity and lubricant theory with consideration of fully hydro-mechanical coupling effects. It was solved using a combination of the extended finite element and the finite volume methods. The approach was verified by modeling the dynamical growth of a KGD fracture (a model developed by Kristnovitch-Geertsma-Daneshy). Three numerical examples are illustrated. The first example is hydraulic fracturing in a heterogeneous reservoir. The hydraulic fracture propagated asymmetrically with approx. 7 m or 1.5° deviation in the direction of maximum principal stress. In the second example, a two stage multiple hydraulic fracturing was modeled. The influences of the perforation and the first fracture on the second fracture were observed from the modeling results. In the third example, a re-fracturing operation after 1 year of production was modeled. Due to the irregular stress change, an almost 90° fracture reorientation was observed.