Intensity and volumetric characterizations of hydraulically driven fractures by hydro-mechanical simulations

A fully coupled hydro-mechanical model based on the discrete element method has been built up to characterize the properties of fluid driven fractures. The rock mass is represented by a set of discrete elements interacting through elastic-brittle bonds that can break to form cracks which can coalesce to form fractures. The fluid flow between the elements is computed as a function of the dual pore space deformation in the intact medium and of the cracks' aperture in the fractures through a finite volume scheme. A series of hydraulic fracturing simulations were performed on intact specimens subjected to different loading conditions. The respective contributions of the matrix permeability, fluid compressibility, injection flow rate and state of stress are investigated while the effect of the distance between the perforation clusters, the wellbore-deviation from the minimum principal stress direction and the orientation of the injection slots for multiple injection treatments along a wellbore segment. For the analysis the evolutions of the P33 (fracture volume) and P32 (fracture intensity) indices are followed. The results show how, for a single injection treatment, P33 and P32 values can be affected by the state of stress inside the medium. Also, they show that aligning the perforation slots with the maximum horizontal stress direction might be a straightforward solution to optimize the opening of the induced fractures.