Numerical computations of rock dissolution and geomechanical effects for CO 2 geological storage

Kajetan Wojtacki (1) , Jolanta Lewandowska (2) , Philippe Gouze (3) , Artur Lipkowski (4)

1 M3 - Mathématiques et Modélisations en Mécanique
2 PMMD - Physique et Mécanique des Milieux Divisés
3 Géosciences Montpellier
4 GUT - Gdańsk University of Technology

The paper is motivated by the long term safety analysis of the CO 2 geological storage. We present a methodology for the assessment of the ge-omechanical impact of progressive rock dissolution. The method is based on the use of X-ray tomography and the numerical dissolution technique. The influence of evolution of the microstructure on the macroscopic properties of the rock is analysed by using periodic homogenization method. The numerical computations show progressive degradation of all components of the stiffness (orthotropic) tensor. Moreover, the evolution of associated mass transfer properties (as tortuosity and conductivity tensors), by using the periodic homogenization method, is also calculated. The correlation between the mechanical parameters and the transfer properties during the dissolution pro-cess is presented. The results show that the highest increase of the hydraulic conductivity (in direction Y) is not associated with the highest decrease of Young modulus in this direction. Moreover, the highest decrease of Young modulus (in the direction X) is not associated with percolation in this direction. Finally, an incremental law to calculate settlement, in case of a rock with evolving microstructure, is proposed. The solution of the macroscopic settlement problem under constant stress and drained conditions showed that the geomechanical effects of the rock dissolution are rather limited.

Mots clés: numerical computations; X-ray tomography; CO2 storage; homogenization; chemo-mechanical coupling; mi- crostructure

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Mécanique des solides [physics.class-ph]

Kajetan Wojtacki, Jolanta Lewandowska, Philippe Gouze, Artur Lipkowski. Numerical computations of rock dissolution and geomechanical effects for CO 2 geological storage. International Journal for Numerical and Analytical Methods in Geomechanics, 2015, 39, pp.482-506. ⟨10.1002/nag.2316⟩. ⟨hal-01104204⟩