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Molecular dynamic simulations of montmorillonite-organic interactions under varying salinity : an insight into enhanced oil recovery.

Underwood, Thomas and Erastova, Valentina and Cubillas, Pablo and Greenwell, H.C. (2015) 'Molecular dynamic simulations of montmorillonite-organic interactions under varying salinity : an insight into enhanced oil recovery.', Journal of physical chemistry C., 119 (13). pp. 7282-7294.


Enhanced oil recovery is becoming commonplace in order to maximize recovery from oil fields. One of these methods, low-salinity enhanced oil recovery (EOR), has shown promise; however, the fundamental underlying chemistry requires elucidating. Here, three mechanisms proposed to account for low-salinity enhanced oil recovery in sandstone reservoirs are investigated using molecular dynamic simulations. The mechanisms probed are electric double layer expansion, multicomponent ionic exchange, and pH effects arising at clay mineral surfaces. Simulations of smectite basal planes interacting with uncharged nonpolar decane, uncharged polar decanoic acid, and charged Na decanoate model compounds are used to this end. Various salt concentrations of NaCl are modeled: 0‰, 1‰, 5‰, and 35‰ to determine the role of salinity upon the three separate mechanisms. Furthermore, the initial oil/water-wetness of the clay surface is modeled. Results show that electric double layer expansion is not able to fully explain the effects of low-salinity enhanced oil recovery. The pH surrounding a clay’s basal plane, and hence the protonation and charge of acid molecules, is determined to be one of the dominant effects driving low-salinity EOR. Further, results indicate that the presence of calcium cations can drastically alter the oil wettability of a clay mineral surface. Replacing all divalent cations with monovalent cations through multicomponent cation exchange dramatically increases the water wettability of a clay surface and will increase EOR.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Publisher statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of physical chemistry C, copyright © 2015 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Date accepted:05 March 2015
Date deposited:15 May 2015
Date of first online publication:09 March 2015
Date first made open access:09 March 2016

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