Grain scale modelling of deformation bands formation in porous reservoir rocks

Title : Grain scale modelling of deformation bands formation in porous reservoir rocks

Abstract:

Deformation bands in porous reservoir rocks can significantly reduce porosity and permeability, influencing fluid flow and reservoir performance. Understanding the grain-scale mechanisms responsible for their formation remains an important challenge. We present a new intergranular bonding model for polyhedral particles in the open-source Discrete Element Method (DEM) application Yade, and investigate its ability to reproduce deformation-band development under compactional-shear conditions. The model incorporates a mixed-mode tensile–shear bond failure formulation, allowing grain-scale cohesion loss to develop during deformation.

Cohesion between neighboring polyhedral grains is introduced through bonded contacts that apply equal and opposite forces between interacting particles. The bonds can fail in tension, shear, or a combination of both according to an elliptical failure criterion. Polyhedral particles were chosen to better represent the geometry of natural grains. Each grain is represented by a single numerical body. This avoids the need to construct grains from multiple bonded spheres and eliminates the additional internal contacts and bonds required by such approaches.

Simulations are performed in a 2D compactional shear setup. Samples with different initial porosities and sorting characteristics are considered. During deformation, bond failure localizes into narrow shear zones that resemble natural deformation bands. Strain and cohesion loss become concentrated within these localized regions, while the surrounding material experiences less deformation.

The results suggest that intergranular bonding is an important component of DEM models aimed at reproducing strain localization in porous rocks. The polyhedral model also allows future implementation of grain fracturing without discretizing grains into smaller elements. The proposed model provides a basis for investigating how grain-scale cohesion loss influences the macroscopic mechanical response of porous reservoir rocks.

Biography:

Bakul Mathur is a PhD researcher at Friedrich-Alexander University Erlangen-Nürnberg (FAU), Germany, specializing in computational geomechanics and the Discrete Element Method (DEM). Her research focuses on grain-scale modeling of deformation bands, grain breakage, and strain localization in porous rocks. She holds master’s degrees in Computational Science in Engineering from TU Braunschweig, Germany, and Petroleum Engineering from the University of Alaska Fairbanks, USA, following a B.Tech. in Petroleum Engineering from PDPU, India. After completing her bachelor’s degree, she gained field experience in coal-bed methane operations in Durgapur, India.