Hydromechanical simulation of Hydraulic Fracturing in naturally fractured reservoir using strong discontinuity approach

Abstract

Hydraulic Fracturing is a widely used method for enhancing oil exploitation in petroleum industry. In this method, some artificial fractures are induced in the reservoir by fluid injection and the overall rock permeability is increased. The geometry of the induced fracture is dominated by the rock's mechanical properties, in-situ stresses, and local heterogeneities such as natural fractures and weak bedding planes. In this paper, a strong discontinuity approach, to embed discontinuities into finite elements was implemented in a numerical code, which performs numerical analysis of fluid flow in a deformable reservoir. This technique is based on the decomposition of the displacement field, inside the element, into a component associated with the deformation of the continuum portion and a component related to the rigid-body relative motion between the two parts of the element. Moreover, the traction continuity condition must be imposed to ensure a correct relationship between the tractions on the internal interface and the stresses in the surrounding continuum portion. Hydromechanical coupling was determined by a law that relates the variation of transmissivity as a function of the fracture aperture. The resulting numerical code was used to model hydraulic fracture propagation through naturally fractured reservoirs in a very efficient manner.