Browsing by Subject "Emulsions"
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Item Breaking and curing rates in asphalt emulsions(2012-12) Banerjee, Ambarish; Prozzi, Jorge Alberto; Bhasin, Amit; Korgel, Brian; Folliard, Kevin J.; Zhang, ZhanminThis PhD dissertation addresses a number of issues pertaining to the use and application of surface treatments using asphalt emulsions. The work conducted as part of this research study shows in detail the problems associated with the state-of-practice and how these issues can be addressed using a scientific and rational approach as opposed to the experience-based approach which is prevailing currently. The first objective of this research study focuses on developing a methodology to determine the total amount of evaporative water loss of an emulsion before the aggregates are placed. An algorithm is presented that can be used by field inspectors and practitioners for the optimal timing of chip placement. The second objective focuses on another key aspect associated with the constructability of surface treatments, i.e., the optimal time to open a new surface treatment to traffic. Laboratory tests were conducted on the emulsion and aggregates to measure the rate of moisture loss and the evolution of the rheological properties as function of time. This was related to the field measured evaporation rates to determine the minimum stiffness required for optimal performance of the chip seal towards adequate resistance to raveling. The final objective of this dissertation focuses on developing a theoretical understanding of the current flowing through a circuit when an emulsion separates into its constituent phases when placed in an electric field. The measured current depends on a set of material properties that include the emulsion’s viscosity, surface potential, and dielectric of the medium and the strength of the electric field. A theoretical formulation was developed that relates the current flowing through the circuit with the mobility of the charged particles and the bulk charge density. The proposed theory was further utilized in developing a test procedure to quantify the breaking characteristics of asphalt emulsions. Results demonstrated that the parameters obtained from these tests were repeatable and different for different types of asphalt emulsions. It was also noticed that for a given type of emulsion the test method is sensitive to factors such as water content and partial breaking due to mechanical agitation.Item Carbon dioxide and water emulsion stability and rheology with nonionic hydrocarbon surfactants or particles(2009-05) Adkins, Stephanie Sue; Johnston, Keith P., 1955-For the first time the interfacial properties of nonionic hydrocarbon surfactants at both the air-water and CO₂-water interfaces are investigated in terms of surfactant structure to determine the changes in surfactant efficiency (negative of the logarithm of the surfactant concentration to create a surface pressure of 20 mN/m). At the air-water interface, linear surfactant tails are more efficient due to the higher packing ability of the straight chains in the dense surfactant monolayer. However, at the CO₂-water interface, surfactant adsorption is small and tails can be solvated. Thus, branching which increases both tail solvation and tail hydrophobicity also enlarges the hard disk area of the surfactant to ultimately increase the efficiency of the surfactant at the CO₂-water interface. CO₂-in-water concentrated emulsions (foams) are studied over short and long times to evaluate the foam stability as a function of both surfactant structure and foam conditions using in-situ optical microscopy. The surface pressure measured at the CO₂- water interface is correlated with the short time stability of coalescing foams with very small cell sizes (under 0.4 [mu]m in diameter). Long time stability of bubbles to coalescence is shown under a variety of conditions. The rheology of these bulk CO₂-in-water foams under high-pressure conditions are also evaluated through measurements of the pressure drop over a capillary tube. Viscosities in excess of 200 cP are measured, an increase of over 1000 time that of pure CO₂ (0.09 cP at 24 °C and 2000 psia). The viscosity of the C/W foams are found to correlate with bubble size, continuous phase viscosity, shear rate, and interfacial tension. Hydrophobic silica particles adsorbed at the interface are also used to stabilize water-in-CO₂ emulsions as an alternative to surfactant stabilizers. The difficulties of tail solvation associated with many hydrocarbon surfactants in CO₂ can be removed by using particles instead of surfactant. A porous cross-linked shell is formed about the hydrophilic (colloidal and fumed) silica to render the particles CO₂-philic and the crosslinking removes ligand tails from the particle surface.Item Design and synthesis of surfactants and nanoparticles for mechanistic studies of foams, emulsions and wettability alteration(2019-08) Alzobaidi, Shehab; Johnston, Keith P. 1955-; Bonnecaze, Roger; DiCarlo, David; Lynd, Nathaniel; Prodanovic, MasaSurfactants or nanoparticles are shown to stabilize carbon dioxide (CO₂)-in-water (C/W) foams, nitrogen (N₂)-in-water (N/W) foams and CO₂-in-oil (C/O) emulsions and to alter the wettability of oil-wet calcite surfaces to water-wet. Chapter 2 focuses on developing an understanding of the aqueous and interfacial properties of single viscoelastic surfactants to stabilize C/W foams for extended time with highly viscous aqueous phases. Surface modified amphiphilic silica nanoparticles are then investigated as alternatives to surfactants to increase the stability of C/W and N/W foams. Here, the first examples of nanoparticles with known surface modification that stabilize foams in high salinity brines at elevated temperature are presented. The fundamental understanding gained from surfactant design for C/W foam studies is used to design stabilizers for C/O emulsions. Here, polymeric surfactants with polydimethylsiloxane backbones and pendant linear alkyl chains are designed to stabilize novel C/O emulsions despite the low interfacial adsorption driving force, given the low interfacial tension. Finally, silica nanoparticles with various modifications (anionic, cationic and nonionic) are used to mechanistically study wettability alteration of oil-wet calcite surface to water-wet, especially in high salinity environments.Item Emulsions and microemulsions of water and carbon dioxide: novel surfactants and stabilization mechanisms(2005) Ryoo, Won Sun; Johnston, Keith P., 1955-During the last two decades colloid and interface science in the field of supercritical fluid technology has brought enormous potentials in the utilization of supercritical carbon dioxide as an environmentally benign solvent. Liquid or supercritical CO2 exhibits solvent properties that are tunable with pressure, and is essentially nontoxic and nonflammable. Emulsions and microemulsions of water and CO2, whether in the form of water-in-CO2 (w/c) or CO2-in-water (c/w), offer new possibilities for separations on the basis of polarity, and as media for reactions between polar and nonpolar molecules. For the first time, formation of thermodynamically stable c/w microemulsions was characterized by dynamic light scattering (DLS) technique. High-pressure carbon dioxide swells potassium carboxylate perfluoropolyether (PFPE-K) cylindrical micelles in water, elongating the micelles significantly from 20 up to 80 nm. As the micelles swell to form microemulsions, the solubility of pyrene increases by a factor of ca. 10. It was demonstrated w/c microemulsions may be formed with nonionic hydrocarbon surfactant. Methylated branched tail of the surfactant enhances formation of stable w/c microemulsions as it raises surfactant solubility in CO2, shifts the curvature towards bending about water, and weakens interdroplet interactions by reducing overlap between surfactant tails. As a novel medium for reactions, w/c microemulsions with low water content are utilized for the synthesis of TiO2 nanoparticles via the controlled hydrolysis of titanium tetraisopropoxide. The size of particles could be controlled by adjusting the water-to-surfactant ratio (wo). Based on DLS measurements, the size of TiO2 particles was comparable to that of the microemulsion droplets indicating steric stabilization was sufficient during the rapid hydrolysis. Finally, electrostatic repulsion between water droplets of w/c emulsion was explored as an alternative to the steric stabilization mechanism. Negative zeta-potentials as high as 70 mV are measured for emulsion droplets by microelectrophoresis. Unprecedented crystalline structure of the droplet array with a spacing of several droplet-diameters is identified by microscopy, and investigated in terms of a balance between long-range electrostatic repulsions acting through the low dielectric medium (εr = 1.5 for high pressure CO2) and the gravitational force which tends to decrease inter-droplet distances.Item Multifunctional foams and emulsions for subsurface applications(2017-12) Singh, Robin, Ph. D.; Mohanty, Kishore Kumar; DiCarlo, David; Huh, Chun; Saleh, Navid; Sepehrnoori, KamyFoams and emulsions hold immense potential in assisting in the different stages of oil recovery processes such as enhanced oil recovery, drilling, and completion. This work is focused on developing robust, multifunctional foams or emulsions for subsurface applications, which offer unique advantages over conventional methods. The first half of the dissertation is focused on investigating novel foams stabilized using nanoparticles and/or surfactants to improve the gas enhanced oil recovery process. Gas flooding often has poor volumetric sweep efficiency due to viscous fingering, channeling, and gravity override. Foam is a promising tool to improve sweep efficiency in gas floods. It can reduce the mobility of gas by several orders of magnitude by increasing its apparent viscosity while keeping the liquid phase mobility unchanged. For sandstone reservoirs, which are typically water-wet in nature, two different approaches of foam stabilization using nanoparticles were developed. In the first approach, synergistic stabilization of foams with a mixture of hydrophilic nanoparticles and an anionic surfactant was investigated. Foam stability experiments in bulk and porous media tests showed that adding hydrophilic nanoparticles to surfactant formulations increases the foam stability. Microscopy revealed that nanoparticles are trapped in lamellae as well as at the Gibbs-Plateau borders. These nanoparticles act as physical barriers and retard the liquid drainage and the Ostwald ripening process. To fundamentally understand the role of nanoparticles in altering the foam dynamics in porous media, a high-pressure visualization experiment was performed in a 2D layered, heterogeneous porous media. This experiment showed that immiscible foams can result in significant incremental oil recovery of 25% to 34% OOIP (over waterflood). In the second approach, foam stabilized using in-situ surface-activated nanoparticles without any surfactant was explored as an EOR agent. The surface chemistry of the hydrophilic nanoparticles was tailored by adsorption of a small amount of short-chain surface modifiers to obtain surface-modified nanoparticles (SM-NP). Foam stabilization using these SM-NP was compared with that using a conventional surfactant to evaluate the potential of these SM-NP to act as an effective foaming agent. Carbonate reservoirs, which are typically highly heterogeneous and oil-wet in nature, pose additional challenges for an effective foam EOR process. Crude oils are typically detrimental to foam stability. An oil-wet carbonate will have a thin oil film on the surface and thus foam lamellae stabilization is challenging. Therefore, wettability-alteration of rock matrix toward water-wet condition using a surfactant is required to favor the in-situ foam stability. This work demonstrated for the first time a synergistic approach of using foams with wettability-altering capabilities for oil-wet systems. It was shown that optimal surfactant formulations can not only alter the wettability of a carbonate core from oil-wet to water-wet conditions, but also can significantly increase the in-situ foam stability even in presence of crude oil. The second half of the dissertation is focused on developing novel microencapsulation techniques using the concept of water-in-air powders for subsurface applications. A facile, one-step method was reported to encapsulate micro- or nano-sized hydrophilic particles using silica nanoparticles. The encapsulated particles can be released based on an external stimulus, such as a change in pH of the external continuous phase. The use of this novel carrier system was demonstrated for the delayed release of PPG particles for conformance control. The application of this technology was then explored for microencapsulating highly concentrated acids (~10 wt.% HCl) for acid treatment of shales. The advantages of these novel acid-in-air powders over conventional acid-in-oil emulsions (which are typically used for shale acidization processes) were illustrated in terms of the thermal stability, corrosion inhibition efficiency, and shale surface reactivity.Item Nanoparticle-stabilized natural gas liquid emulsions for heavy oil recovery(2017-05) Griffith, Nicholas Daniel; Daigle, HughThe transport of nanoparticle-stabilized emulsions through porous media and its effects on enhanced oil recovery are only marginally understood. This thesis explores the characteristics of nanoparticle-stabilized emulsion flow in porous media, especially in respect to its residual oil recovery capabilities. Widely available, low-cost natural gas liquids were emulsified in brines using polyethylene glycol-coated silica nanoparticles. Emulsions with various aqueous nanoparticle phases and oil phases were generated via beadpack co-injection or sonication at varying salinities for observations of emulsion characteristics. In general it was found that high-salinity emulsions generated via sonication were more robust: statically and dynamically more stable than their lower salinity counterparts. Emulsions generated via beadpack co-injection displayed non-Newtonian shear-thinning rheology and larger droplet sizes. Emulsions generated via sonication displayed Newtonian rheology and much smaller droplet sizes. Coreflood experiments were conducted to assess the effects of different emulsion properties on residual oil recovery of heavy oils, effective permeability reduction capabilities (i.e. conformance control), and in-situ emulsion stability. During low salinity emulsion floods, no emulsion was produced in the effluent. However, by increasing the salinity, emulsion was produced in the effluent and up to 89% residual mineral oil was recovered at low injection rates (~16 ft/day). Increases in residual oil recovery during high salinity floods can be explained by DLVO and Filtration theory. By increasing the ionic concentration, the magnitude of repulsive electrostatic double layer forces are decreased, leading to increased droplet interception on grain surfaces. This results in more efficient droplet-pore throat blockage, therefore, redirecting displacing fluids into less permeable zones. Increasing the magnitude of the zeta-potential of injected emulsions resulted in marginal increases in oil recovery, significant reductions in effective permeability, and in-situ emulsion stability. It was concluded that at high zeta-potentials, emulsion droplets are likely repulsed via electrostatic repulsive forces rather than through mechanical bridging of aggregates between droplets, as observed in high salinity emulsions. The increase in permeability reduction in the high zeta-potential case occurs due to the droplets’ increased resistance to flow through a pore throat, a product of increased repulsive forces between droplets and grains encountered at tight constrictionsItem Relationship between interfacial properties and formation of microemulsions and emulsions of water and supercritical carbon dioxide(2001-08) Psathas, Petros; Johnson, Keith P.The utilization of supercritical (SC) CO2 as an alternative green solvent has attracted significant research devotion in the last decade. Its uniqueness lies on the fact that CO2 is a non-FDA regulated solvent mainly generated as the sideproduct of industrial process, is easily recyclable, readily available, non flammable and essentially non toxic. Dense CO2 is non-polar (unlike water), has weak van der Waals forces (unlike oils) and as such may be considered a third type of fluid phase in nature, somewhat similar to fluorocarbons. The use of SC CO2 has expanded into broad technological areas one of which is the stabilization of water-in-CO2 dispersions that offer new possibilities for separations on the basis of polarity, and as media for reactions between polar and nonpolar molecules. The formation of stable emulsions of water-in-CO2 (W/C) so far has been hampered by the lack of suitable surfactants. The synthesis of various molecularly engineered surfactants is demonstrated in this study, among which are polydimethylsiloxane (PDMS)-based block copolymer ionomers, ionic and nonionic perfluoropolyether (PFPE) and nonionic perfluorooctylmethacrylate (PFOMA)-based ones. The concentrated W/C emulsions are characterized with electrical conductivity, optical microscopy and multiwavelength turbidity technique. The emulsion stability is assessed as a function of formulation variables that influence the surfactant monolayer curvature, such as temperature, pH, salinity and pressure. The response of the interfacial activity of the surfactant to changes in the variables above is monitored with interfacial tension (γ) measurements and is correlated to emulsion stability. Moreover, salinity is used to tune the surfactant aggregation characteristics, resulting in spontaneous microemulsion formation upon crossing the critical microemulsion concentration (cµc). Based on guidelines provided by γ versus temperature, stable concentrated (50:50 by mass) C/W miniemulsions consisting of 200 nm droplets are formed with the phase inversion temperature (PIT) method. Finally, the formation of unflocculated and stable dilute W/C emulsions is studied with a homologous series of PFOMA-based nonionic surfactants, and mapping of γ with surfactant hydrophilicity provide useful pathways for the synthesis of the optimum structure.Item Stabilization of dispersions in carbon dioxide and in other low-permittivity media(2006) Smith, Peter Griffin; Johnston, Keith P., 1955-Electrostatic stabilization of emulsions and particle dispersions in liquid and supercritical carbon dioxide (CO2) reduces the limitations on steric stabilization imposed by the weak solvent strength of CO2. This research focuses on charging and electrostatic stabilization of particles dispersed in CO2 and other low-permittivity media. Despite ultralow dielectric constant (1.5–2.5), dispersal of counterions in reverse micelles can prevent pairing with particle surfaces, enabling the required particle charging. TiO2 particles were electrostatically stabilized in CO2 at spacing of several diameters. Dispersions in low-permittivity solvents require sensitive instrumentation to measure electrophoretic mobilities (zeta potentials), which are low relative to those in aqueous solvents, motivating electrophoresis with velocimetry by differential-phase optical coherence tomography (DP-OCT). DP-OCT with transparent electrodes enables close electrode spacing and thus high electric fields despite low applied electric potential, to avoid electrohydrodynamic instability and electrochemical interference. Further advantages include ability to analyze small volumes and turbid dispersions, avoidance of electro-osmosis, and potential for single-particle measurement. The effect of surface viii hydrophilicity on the charging of TiO2 particles in low-permittivity toluene was studied. Partitioning of ions between particle surfaces and micelle cores was analyzed according to differences in their hydrophilicities and extents. The strategic design of particle surfaces and counterion stabilizers and the continued use of phase-sensitive velocimetry for electrophoresis in low-permittivity solvents should further clarify these complex charging mechanisms. Another important stabilization mechanism in CO2 is steric stabilization with surfactants active at the CO2–water interface. The fractional free volume (FFV) available to CO2 was demonstrated to be important in the design of surfactants with stubby tails. An understanding of the role of FFV and the use of a weakly hydrophilic headgroup enabled design of tertiary amine esters, a new class of nonfluorinated surfactants with extremely low aspect ratio. The structures adapt easily for study of surfactant architecture. These low-molecular weight surfactants are attractive replacements for more widely used fluorinated surfactants for tunable CO2-inwater emulsions. A fundamental understanding of electrostatic stabilization in lowpermittivity media and further investigation of structure–property relationships for interfacial activity of surfactants will aid development of new classes of colloids in the unusual medium of CO2.