Stress/strain variability in fractured media: a fracture geometric study

Abstract

The presence of natural fractures in fractured media plays a vital role in the in-situ stress state, which is predominantly influenced by tectonic stresses and local perturbations. Fracture orientation, wellbore stability/orientation, and permeability anisotropy are strongly dependent on local stress variations. In this study, a discrete fracture network (DFN) was generated using the stochastic approach to investigate the correlation between geometrical properties of the fracture network (fracture density and length) and local stress variability. Afterward, the FLAC2D software was employed to propagate the stress redistribution in the simulation process. Considering the tensorial nature of stress, a stress field was calculated under orthogonal static boundary conditions. A tensor-based mathematical formulation was applied to compute total stress variability, shear strain distribution, and total displacement in different fracture network realizations. The results demonstrated that the mean local stress perturbation, effective variance (as an indicator of total stress variability), shear strain distribution, and total displacement increased with the rise of stress ratio and fracture density. The aforementioned parameters decreased as the power-law length exponent of the DFN generator increased. Overall, it is concluded that the stress/strain variability and total displacement in a dense fracture network and large length fractures have their maximum values.