Maps of Natural Fracture Reactivation Likelihood: a Comparison Between Homogeneous and Heterogeneous Stress Fields

Abstract

Previous methods (e.g.: Zoback, 2007) for fracture reactivation assumed a uniform stress field to apply on either fault or fracture. However, local stress is often perturbed by different mechanisms such as faulting, folding, mechanical contrast between layers, salt body effect or even subsidence caused by reservoir production. Ignoring local perturbation on the stress field can lead to unrealistic reactivation map and dramatically fail to assess fracture seal integrity. In the present work, we propose to compare fracture reactivation maps based on a uniform stress field (classic method) and a more realistic heterogeneous stress-field using a Mohr-Coulomb failure criterion. To do so, we introduce a geomechanically-based stress inversion method iBem3D that generates stress-field controlled by faulting and regional tectonic stress (Maerten F., 2010; Maerten et al, 2016a, 2016b; Maerten F. and Maerten L., 2016c), which are the mechanisms considered in this present work. The resulting maps show that reactivation can be dramatically different in places where seal integrity can be breached in places for uniform stress-field while likely intact for the heterogeneous stress field.