Browsing by Author "Wang, Le"

Now showing 1 - 5 of 5
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    Insights on Foam Transport from a Texture-Implicit Local-Equilibrium Model with an Improved Parameter Estimation Algorithm
    (American Chemical Society, 2016) Zeng, Yongchao; Muthuswamy, Aarthi; Ma, Kun; Wang, Le; Farajzadeh, Rouhi; Puerto, Maura; Vincent-Bonnieu, Sebastien; Akbar Eftekhari, Ali; Wang, Ying; Da, Chang; Joyce, Jeffrey C.; Biswal, Sibani L.; Hirasaki, George J.
    We present an insightful discussion on the implications of foam transport inside porous media based on an improved algorithm for the estimation of model parameters. A widely used texture-implicit local-equilibrium foam model, STARS, is used to describe the reduction of gas mobility in the state of foam with respect to free gas. Both the dry-out effect and shear-dependent rheology are considered in foam simulations. We estimate the limiting capillary pressure Pc* from fmdryvalues in the STARS model to characterize foam film stability in a dynamic flowing system. We find that Pc* is a good indicator of foam strength in porous media and varies with different gas types. We also calculate Pc* for different foaming surfactants and find that foam stability is correlated with the Gibbs surface excess concentration. We compare our improved parameter estimation algorithm with others reported in literature. The robustness of the algorithm is validated for various foam systems.
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    Modeling micelle formation and interfacial properties with iSAFT classical density functional theory
    (AIP Publishing, 2017) Wang, Le; Haghmoradi, Amin; Liu, Jinlu; Xi, Shun; Hirasaki, George J.; Miller, Clarence A.; Chapman, Walter G.
    Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactant properties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.
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    Segregation of Amphiphilic Polymer-Coated Nanoparticles to Bicontinuous Oil/Water Microemulsion Phases
    (American Chemical Society, 2017) Qi, Luqing; ShamsiJazeyi, Hadi; Ruan, Gedeng; Mann, Jason A.; Lin, Yen-Hao; Song, Chen; Ma, Yichuan; Wang, Le; Tour, James M.; Hirasaki, George J.; Verduzco, Rafael
    Polymer-coated nanoparticles are interfacially active and have been shown to stabilize macroscopic emulsions of oil and water, also known as Pickering emulsions. However, prior work has not explored the phase behavior of amphiphilic nanoparticles in the presence of bicontinuous microemulsions. Here, we show that properly designed amphiphilic polymer-coated nanoparticles spontaneously and preferentially segregate to the bicontinuous microemulsion phases of oil, water, and surfactant. Mixtures of hydrophilic and hydrophobic chains are covalently grafted onto the surface of oxidized carbon black nanoparticles. By sulfating hydrophilic chains, the polymer-coated nanoparticles are stable in the aqueous phase at salinities up to 15 wt % NaCl. These amphiphilic, negatively charged polymer-coated nanoparticles segregate to the bicontinuous microemulsion phases. We analyzed the equilibrium phase behavior of the nanoparticles, measured the interfacial tension, and quantified the domain spacing in the presence of nanoparticles. This work shows a novel route to the design of polymer-coated nanoparticles which are stable at high salinities and preferentially segregate to bicontinuous microemulsion phases.
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    Surface Complexation Modeling of Calcite Zeta Potential Measurements in Brines with Mixed Potential Determining Ions (Ca2+, CO32-, Mg2+, SO42-) for Characterizing Carbonate Wettability
    (Elsevier, 2017) Song, Jin; Zeng, Yongchao; Wang, Le; Duan, Xindi; Puerto, Maura; Chapman, Walter G.; Biswal, Sibani L.; Hirasaki, George J.
    This study presents experiment and surface complexation modeling (SCM) of synthetic calcite zeta potential in brine with mixed potential determining ions (PDI) under various CO2 partial pressures. Such SCM, based on systematic zeta potential measurement in mixed brines (Mg2+, SO42−, Ca2+ and CO32−), is currently not available in the literature and is expected to facilitate understanding of the role of electrostatic forces in calcite wettability alteration. We first use a double layer SCM to model experimental zeta potential measurements and then systematically analyze the contribution of charged surface species. Calcite surface charge is investigated as a function of four PDIs and CO2 partial pressure. We show that our model can accurately predict calcite zeta potential in brine containing a combination of four PDIs and apply it to predict zeta potential in ultra-low and pressurized CO2 environments for potential application in enhanced oil recovery in carbonate reservoirs. Model prediction reveals that calcite surface will be positively charged in all considered brines in pressurized CO2 environment (>1 atm). The calcite zeta potential is sensitive to CO2 partial pressure in the various brine in the order of Na2CO3 > Na2SO4 > NaCl > MgCl2 > CaCl2 (Ionic strength = 0.1 M).
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    Thermodynamic Modeling and Molecular Simulation of Amphiphilic Systems
    (2017-02-16) Wang, Le; Chapman, Walter G.
    Interfacial phenomena are of vital importance to industrial and commercial applications from enhanced oil recovery to personal care products. To optimize interfacial processes, amphiphiles are usually involved, and, unlike simple molecules, amphiphiles possess both hydrophilic(water-loving) and hydrophobic(oil-loving) properties. Compared to the knowledge gained regarding the properties of simple fluids in the bulk region, our knowledge of modeling and prediction of the phase behavior and interfacial properties of amphiphiles is relatively less abundant. The goal of this thesis is to enhance our understanding of the phase behavior and interfacial phenomena of the systems containing amphiphiles using molecular simulation and statistical mechanics based theories. In particular, we have studied fundamental aspects related to enhanced oil recovery, i.e. interfacial tension, micelle formation, middle-phase microemulsion, foam stability and wettability alteration of reservoir rock surfaces. In this thesis, the interfacial Statistical Associating Fluid Theory that relies on fundamental measure theory, mean field treatment of van der Waals interaction, and Wertheim's thermodynamic perturbation theory for association and chain connectivity along with molecular dynamics simulation have been used to study the molecular structure and interfacial properties of surfactant containing systems. Key contributions of this thesis include: First, an approach inside iSAFT framework based on the Method of Moments that predicts the formation of middle-phase microemulsions of surfactant/oil/water systems has been presented. Second, the iSAFT approach has been extended to model surfactant micelle formation. Complete interfacial tension isotherm can be predicted. The effects of surfactant architecture have been studied. Third, the role of lauryl betaine as a foam booster was investigated. Insight was gained on the interaction between lauryl betaine and alpha olefin sulfonate. Fourth, the adsorption of deprotonated naphthenic acid on Calcite surface was studied, which is important in understanding the wettability alteration of carbonate reservoirs.