Preprints
https://doi.org/10.31223/X53D27
https://doi.org/10.31223/X53D27
19 Dec 2023
 | 19 Dec 2023

Impact of stress regime change on the permeability of a naturally fractured carbonate buildup (Latemar, The Dolomites, Northern Italy)

Onyedika Anthony Igbokwe, Jithender J. Timothy, Ashwani Kumar, Xiao Yan, Mathias Mueller, Alessandro Verdecchia, Günther Meschke, and Adrian Immenhauser

Abstract. Changing stress regimes control fracture network geometry and influence porosity and permeability in carbonate reservoirs. Using outcrop data analysis and a displacement-based linear elastic finite element method, we investigate the impact of stress-regime change on fracture network permeability. The model is based on fracture networks, specifically fracture sub-structures. The Latemar, predominantly affected by subsidence deformation and Alpine compression, is taken as an outcrop analogue for an isolated (Mesozoic) carbonate buildup 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 from the NW-SE and (ii) Alpine deformation from 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 increased by the density and connectedness of the fracture network and affected by shear dilation. 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 affect the overall aperture and permeability distributions and the flow patterns. These effects—potentially ignored in simpler stress-dependent permeability—can result in significant inaccuracies in permeability estimation.

Onyedika Anthony Igbokwe, Jithender J. Timothy, Ashwani Kumar, Xiao Yan, Mathias Mueller, Alessandro Verdecchia, Günther Meschke, and Adrian Immenhauser

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2713', Frederic Amour, 30 Jan 2024
    • AC2: 'Reply on RC1', Onyedika Anthony Igbokwe, 21 Feb 2024
  • RC2: 'Comment on egusphere-2023-2713', Anonymous Referee #2, 16 Feb 2024
    • AC1: 'Reply on RC2', Onyedika Anthony Igbokwe, 20 Feb 2024
Onyedika Anthony Igbokwe, Jithender J. Timothy, Ashwani Kumar, Xiao Yan, Mathias Mueller, Alessandro Verdecchia, Günther Meschke, and Adrian Immenhauser
Onyedika Anthony Igbokwe, Jithender J. Timothy, Ashwani Kumar, Xiao Yan, Mathias Mueller, Alessandro Verdecchia, Günther Meschke, and Adrian Immenhauser

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Short summary
We present a workflow that models the impact of stress regime change on the Latemar carbonate buildup using displacement-based linear elastic FEM and outcrop analysis. Stress-dependent heterogeneous apertures and effective permeability were calculated from boundary conditions constrained by the study area's stress directions. Our results show that simulated far-field stresses at NW-SE subsidence deformation and N-S Alpine deformation increased the overall fracture aperture and permeability.