Molecular Dynamic Simulations of Montmorillonite–Organic Interactions under Varying Salinity: An Insight into Enhanced Oil Recovery

Abstract

Publisher's copyright statement:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Journal of physical chemistry C, copyright c 2015 American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/acs.jpcc.5b00555Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractEnhanced oil recovery is becoming commonplace in order to maximise recovery from oilfields. 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 non-polar decane, uncharged polar decanoic acid and charged Nadecanoate model compounds are used to this end. Various salt concentrations of NaCl are modelled: 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 clays 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 present that the presence of calcium cations can drastically alter the oil wettability of a clay ⇤To whom correspondence should be addressed 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.

Wetting Effects and Molecular Adsorption at Hydrated Kaolinite Clay Mineral Surfaces

“…21 The work presented that 8 it was the ionic composition of the brine, rather than the salinity itself, that played an important role upon the adsorption of organic matter to mineral surfaces.…”

“…21 The decanoates initially adjacent to the hydroxyl surface remain adsorbed throughout the 50 ns production run via an anion exchange mechanism. …”

A molecular dynamics investigation into the adsorption behavior inside {001} kaolinite and {1014} calcite nano-scale channels: the case with confined hydrocarbon liquid, acid gases, and water

“…An example of this kind is the study the interaction of carbon dioxide and clay minerals, a matter of potential usage for underground carbon sequestration purposes (Chen et al 2015a, b, c;Javanbakht et al 2015;Makaremi et al 2015;Tenney and Cygan 2014). Another example of the kind is the study of interactions between mineral surfaces (representative of reservoir rocks) and mixture of hydrocarbon/water/acid gases (representing typical reservoir fluids), to put petroleum production industry in target (Chun et al 2015;Fazelabdolabadi and Alizadeh-Mojarad 2016;Underwood et al 2015;Wu et al 2012) or analysis of mobilization and recovery of fluids/asphaltene from nanopores using MD Youssef et al 2015;Stukan et al 2012). More recently, Xie et al (2016) studied oil contamination removal process at microscales, using the molecular dynamics technique.…”

Insights into asphaltene aggregation in the Na-montmorillonite interlayer

“…The CHARMM36 force field, which is compatible with ClayFF (Wright and Walsh, 2012;Underwood et al, 2015), was used to model the asphaltene and humic substance. The simple-point-charge water model was used which was suitable for capturing the water interactions with asphaltenes and humic acids (Ahn et al, 2008;Kuznicki et al, 2009;Jian et al, 2013).…”