Porosity change in heterogeneous and isotropic limestone coastal aquifer during mixing of seawater and freshwater
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ORIGINAL ARTICLE
Porosity change in heterogeneous and isotropic limestone coastal aquifer during mixing of seawater and freshwater Ezzeddine Laabidi1 · Marwen Ben Refifa1 · Rachida Bouhlila1 Accepted: 20 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Calcite dissolution, porosity development are strongly influenced by mixing phenomenon, fluid density and heterogeneity (variability of the hydraulic proprieties). This study presents an approach for calculating porosity change in a heterogeneous porous media during mixing of seawater and freshwater. The proposed approach is based on the Phillip’s analytical solution and is determined by five main steps: (1) Generate a random K-field, (2) Calculate the flow and transport of the heterogeneous porous media, (3) Evaluate the dispersivity coefficient results of the heterogeneity aspect, (4) Evaluate the dissolution capacity of calcite during mixing of two solutions and (5) calculate the porosity change. This approach takes into account the effect of the aquifer heterogeneity on the dispersivity and is applied to simulate the effect of calcite dissolution on the porosity development in a heterogeneous idealized aquifer during seawater intrusion. Results presented in this work are preliminary to assess the effect of heterogeneity on the geochemical reaction during mixing. Keywords Heterogeneous aquifer · Mixing · Dispersivity · Calcite dissolution · Porosity change
Introduction Carbonate rocks have attracted greater attention of hydrogeologists in the past few decades, both from the point of view of water supply as well as potential sites for waste disposal. Carbonate rocks are also of great economic value having large deposits of oil, gas, and minerals. Carbonate reservoirs often represent a source of water of high quality and containing more than 60% of the word’s oil reserves and 40% of the word’s gas reserves (Nurmi and Standen 1997). Dissolution of carbonates has been commonly predicted by geochemical models to occur at the seawater-freshwater mixing zone of coastal aquifers along a geological time scale (Price and Herman 1991; Pulido-Leboeuf 2004). Due to the * Ezzeddine Laabidi [email protected] Marwen Ben Refifa [email protected] Rachida Bouhlila [email protected] 1
Laboratory of Modeling in Hydraulics and Environment (LMHE), National Engineering School of Tunis (ENIT), University of Tunis El Manar (UTM), Bp 37, Le Belvédère, 1002 Tunis, Tunisia
high reactivity of these rocks, a significant change in their structure is identified. This structure change is in relation to the development of dissolution zones during seawater and freshwater mixing that may affect the water resources in the case of an aquifer (Purser 1980). Numerical modeling and laboratory results can be applied to characterize these complex systems (Corbella et al. 2004, 2006; Sanz et al. 2011). In the last few decades many work have been developed and are as follow: Singurindy et al. (2004) performed a laboratory experiment to measure the
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