EGU23-9317, updated on 07 May 2024
https://doi.org/10.5194/egusphere-egu23-9317
EGU General Assembly 2023
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effect of stress regime change on fractured carbonate’s permeability: A case of Latemar carbonate buildup (The Dolomites, Northern Italy) 

Onyedika Anthony Igbokwe1,2, Jithender Timothy3, Ashwani Kumar4, Xiao Yan5,7, Mathias Mueller6, Alessandro Verdecchia6, Günther Meschke7, and Adrian Immenhauser6,8
Onyedika Anthony Igbokwe et al.
  • 1University of St Andrews, School of Earth and Environmental sciences , Earth Sciences, United Kingdom of Great Britain – England, Scotland, Wales (oai1@st-andrews.ac.uk)
  • 2Department of Physics, Geology and Geophysics, Alex Ekwueme Federal University Ndufu-Alike, Ikwo, P.M.B. 1010, Abakaliki, Ebonyi State, Nigeria
  • 3Centre for Building Materials, Technical University of Munich, Franz-Langinger-Straße 10, 81245, Munich, Germany
  • 4Advance Manufacturing Lab, ETH Zürich, Switzerland
  • 5Department of Geotechnical Engineering College of Civil Engineering, Tongji University, Shanghai 200092, China
  • 6Ruhr-University Bochum, Institute of Geology, Mineralogy and Geophysics, Universitätsstraße 150, 44801 Bochum, Germany
  • 7Ruhr University Bochum, Institute for Structural Mechanics, Universitätsstraße 150, 44801 Bochum, Germany
  • 8Fraunhofer IEG (Institution for Energy Infrastructures and Geothermal Systems), Lennershofstrasse 140, 44801 Bochum, Germany

Changes in stress regimes impact the geometry of fracture networks and affect the porosity and permeability of carbonate reservoirs. This is, predominantly, because of the complexity of the deformation phases, the poor understanding of the mechanical and diagenetic mechanisms that affect apertures, and the difficulty in precisely characterizing aperture distributions in the subsurface. Utilizing outcrop data analysis and displacement-based linear elastic finite element modelling, we study the effect of stress regime change on fracture network permeability. The model is based on fracture networks, specifically fracture sub-structures.

The Latemar, which is primarily affected by subsidence deformation and Alpine compression, is used as an outcrop analogue for isolated (Mesozoic) carbonate formations with fracture-dominated permeability. We apply a novel strategy involving two compressive boundary loading conditions constrained by the study area's NW-SE and N-S stress directions. Stress-dependent heterogeneous apertures and effective permeability were computed by: (i) using the local stress state within the fracture sub-structure and (ii) running a single-phase flow analysis considering the fracture apertures in each fracture sub-structure.

Our results show that the impact of the modelled far-field stresses at: (i) subsidence deformation (first stage loading) from the NW-SE, and (ii) Alpine deformation (second stage loading) from the N-S, increased the overall fracture aperture and permeability. In each case, increasing permeability is associated with open fractures parallel to the orientation of the loading stages and with fracture densities. The anisotropy of permeability is affected by shear dilation and is increased by the density and connectedness of the fracture network. The two far-field stresses simultaneously acting within the selected fracture sub-structure at a different magnitude and orientation do not necessarily cancel out each other in the mechanical deformation modelling. These stresses effect the overall aperture and permeability distributions. These effects, which may be ignored in simpler stress-dependent permeability, can result in significant inaccuracies in permeability estimation, especially in the subsurface carbonate reservoirs.

How to cite: Igbokwe, O. A., Timothy, J., Kumar, A., Yan, X., Mueller, M., Verdecchia, A., Meschke, G., and Immenhauser, A.: Effect of stress regime change on fractured carbonate’s permeability: A case of Latemar carbonate buildup (The Dolomites, Northern Italy) , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9317, https://doi.org/10.5194/egusphere-egu23-9317, 2023.