Numerical Simulation of Reactive Transport on Micro-CT Images
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Numerical Simulation of Reactive Transport on Micro-CT Images Peyman Mostaghimi1 · Min Liu1 · Christoph H. Arns1
Received: 27 September 2015 / Accepted: 30 May 2016 © International Association for Mathematical Geosciences 2016
Abstract Reactive transport is a key issue in hydrocarbon reservoirs, hydrogeological and environmental applications. A numerical model is presented to predict alteration of porous medium structure due to the dissolution mechanisms. The model includes the coupling of mass transport, chemical reactions and solid modification. It is validated by comparing reactive flow in a fracture geometry with previously published results and analytical expressions. Flow, transport, and chemical reaction are simulated directly on three-dimensional micro computed tomography images of rocks with increasing degree of heterogeneity: a sand pack, Berea sandstone, and limestone carbonate. Different regimes of transport and reaction are characterised by the dimensionless Péclet and Damköhler numbers. Dissolution patterns and geometrical evolutions of the solid phases obtained from imaging are investigated for different Péclet and Damköhler numbers and the effects of heterogeneity are included. The porosity profiles are presented in different classes of porous media after reaction. The results demonstrate different mechanisms such as uniform and face dissolution at transport- and reactive-limited regimes. The relationships between permeability and porosity are also explored. At high Péclet and Damköhler numbers, high-permeability channels are uniformly dissolved leading to significant increases in permeability. The largest changes in permeability are observed for the most heterogeneous sample, the carbonate, in all Péclet and Damköhler regimes. For low Damköhler but high Péclet numbers, a uniform dissolution occurs over the entire porous medium. The complex correlation for permeability in different porous structures is explained based on connectivity and morphological properties of the porous media obtained from porosity profiles and dissolution patterns. The exponent n in the power-law correlation between permeability and porosity is measured in different samples and our findings are con-
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Peyman Mostaghimi [email protected] School of Petroleum Engineering, The University of New South Wales, Sydney, Australia
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Math Geosci
sistent with experimental observations. This study helps improve the understanding of reactive flow at pore scale in porous media highlighting the interplay of Péclet and Damköhler numbers as well as the rock heterogeneity. Keywords Reactive transport · Dissolution · Micro-CT imaging · Pore-scale modelling · Lattice Boltzmann
1 Introduction Numerical studies of reaction in porous media have important applications in petroleum engineering as well as environmental and hydrogeological fields. For example, in geological storage of carbon dioxide in carbonate reservoirs, an acid solution is generated due to solubility of carbon dioxide in water. The acid dissolves the host rocks and aff
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