R-3 Repository :: Browsing by Author "Miller, Clarence A."

Browsing by Author "Miller, Clarence A."

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A microvisual study of viscosity and mass transfer effects on two-phase flow in porous media
(1989) Cline, John Gilbert; Miller, Clarence A.
A microvisual flow cell was used to observe the effects of fluid viscosity ratio and of pore size distribution on the mechanisms of steady cocurrent two-phase flow in porous media. The transition in flow mechanisms was found to have the same dependence on capillary number, N$\sb{\rm ca}$, for all viscosity ratios provided N$\sb{\rm ca}$ was defined in terms of the interstitial velocity of the wetting phase. A simple theoretical model of ganglia flow through an idealized pore constriction was developed. Although velocity varied greatly during ganglion passage, the average volumetric flow rate of the nonwetting phase agreed well with relative permeability theory. A series of displacement experiments were performed with several oil-water-alcohol systems where diffusion occurred between oil and water phases. The amount of spontaneous emulsification observed was found to be greatest in systems where both Marangoni flow and local super saturation due to diffusion were expected.
A new simplified compositional simulator
(1994) Buchwalter, James Lee; Miller, Clarence A.
A new simplified fully implicit compositional simulator has been developed. This simulator is different from existing models because it combines the conventional black oil equations with a compositional injection component equation. Sets of two dimensional pvt and injection component K value tables at constant pressure and variable mole fraction injection component are generated using a cubic equation of state used in the compositional simulator. The data are generated from a series of cells loaded with the initial composition of the reservoir. Pore volume increments of injection gas are cycled through the cells in sequence, with oil and gas volumes passing downstream in proportions calculated by the relative permeability curves. This pvt test replicates a one dimensional compositional cycling process at fixed pressure. The resulting data describes a unique compositional path through the phase diagram for constant pressure and variable mole fraction injection gas, and this path is independent of cell position in the simulator. The simulator runs at speeds that far exceed the speeds in current compositional simulators, primarily because the speed is independent of the number of components. Small problems with several hundred cells typically run about 10 times faster, and larger speed increases are realized for bigger problems. The simulator has been tested successfully for gas cycling projects including the Third SPE Comparative Solution Project and CO2 flooding projects. Results for constant and variable pressure cycling, with and without vertical crossflow were in good agreement with a compositional model.
Activity coefficient prediction by hard sphere expansion corresponding states theory
(1985) Quock, Deborah Eileen Reeder; Estle, Thomas L.; Miller, Clarence A.; Robert, Mark A.
A new method has been developed for predicting liquid activity coefficients in ternary mixtures from group contributions. In this method, activity coefficients are obtained by applying the Gibbs-Duhem equation to the excess Gibbs free energy of mixing. Gibbs free energies of the mixture and pure component fluids are calculated from an expansion about a reference fluid in powers of ratios of hard sphere diameters and molecular potentials. When the pure component differs from the reference by one additional structural group, these ratios represent the size contribution and the attraction contribution respectively of this group to the thermodynamic property of the pure fluid. Deviations of the reference hard sphere property to that of the fluid being modeled are corrected for by use of hard sphere equations of state. Results indicate that this method is useful for predieting activity coefficients of ternary mixtures from binary activity coefficient data.
Analysis and modelling of the effects of micellar solubilization on the degradation rates of n-alkanes
(1996) Bury, Scott Joseph; Miller, Clarence A.
The transport, uptake and degradation of hydrocarbons by microorganisms has been a subject of interest for many years. The inherent low solubility of most hydrocarbons has been thought to be one of the limiting factors in the overall rate of degradation of hydrocarbons. The ability of surfactants to form micelles and increase the solubility of hydrocarbons to many times their normal solubility may overcome this limitation. Designed experiments with well defined surfactant systems of known phase behavior were done to investigate the effects of micellar solubilization by nonionic, ionic, and mixed nonionic and ionic surfactants on the degradation of n-alkanes by pure cultures of three strains of Gram-negative bacteria. It was found that solubilization by nonionic surfactants greatly increased the growth rates and accompanying oxidation of alkanes for two of the three bacterial strains. It also appeared, from initial experiments, that the inhibitory effect of the ionic micelles could be mediated by the addition of nonionic surfactants to form mixed micelles. A mathematical model that treated the solubilized alkanes as soluble substrates via a Monod expression with competitive enzyme interaction successfully described the experimental data. Nonlinear parameter estimation using a maximum likelihood method indicated that $\rm\mu\sb{max}$ was constant for a particular bacterial strain, and independent of surfactant concentration and alkane. The variation in observed growth rates was reflected in the variation of the $\rm K\sb{s}$ parameter which was found to be a function of surfactant type and alkane. The variation appears to represent differences in the rates of transport of the alkanes through the cell membranes.
Application of Foam for Mobility Control in Enhanced Oil Recovery (EOR) Process
(2014-04-24) Cui, Leyu; Hirasaki, George J.; Miller, Clarence A.; Biswal, Sibani Lisa; Alvarez, Pedro J.
This thesis focuses on the application of foam for mobility control in enhanced oil recovery (EOR) process. The performance of foam and surfactants was evaluated by systematic laboratory study. This includes the screening and evaluation of surfactant formulations for foam EOR process and the investigation of foam for mobility control at reservoir conditions. The adsorption of cationic surfactants on natural minerals was discussed in a separate chapter, although it is one aspect for evaluating surfactant formulations. A numerical model was used to fit the foam strength for foam flooding at reservoir conditions. The solubility, thermal and chemical stability and foaming ability of surfactant formulations were investigated in the screening and evaluation step. A qualified surfactant formulation for foam EOR should be soluble and stable from injection to reservoir conditions. The foaming ability of surfactant formulations needs to be verified in a porous media with crude oil. The bulk foam tests, i.e., foam height, equilibrium foam volume and foam half-life, are not suggested to be used for evaluating foaming ability of surfactant formulations, because of the poor correlation with foam tests in porous media. The detrimental effect of oil, especially for light crude oil, for foam stability was demonstrated. Foam boosters, e.g., betaine surfactants, can be used to stabilize the foam in the presence of crude oil. The mobility control ability of foam was evaluated in Silurian dolomite cores at reservoir conditions after screening and evaluation step. The apparent viscosity of foam was used to describe the mobility control ability. The higher apparent viscosity indicates the stronger foam and better mobility control ability. The strength of foam depends on foam quality, salinity and temperature. The influence of each parameter was investigated and illustrated by controlled experiments. Ethomeen C12 in formation brine and CO2 can generate strong foam at 120 °C and 3400 psi in a wide range of foam quality after the pressure gradient exceeded the minimum pressure gradient. The adsorption of cationic surfactant on the pure carbonate minerals is low owing to the repulsion of the electrostatic force. However, the natural carbonate minerals contain negatively charged impurities, e.g., silica and clays. The adsorption of cationic surfactants on these impurities was significant. Multivalent cations, i.e., Mg2+, Ca2+ and Al3+, can compete with cationic surfactants on the negatively charged binding sites to reduce the adsorption. The adsorption of Ethomeen C12 on silica was reduced from 5.33 mg/m2 in DI water to 3.31 mg/m2 in synthetic brine with 1.51×10-3 mol/L Al3+. The adsorption of Ethomeen C12 was measured at 2 atm CO2 to keep the solution clear. The method of methylene blue (MB) two-phase titration was improved to determine the cationic surfactant concentrations in high salinity brine. In summary, this study demonstrates the methodology to screen the surfactant formulations for the foam EOR process, elucidates the application of the foam for mobility control at reservoir conditions, improves the MB two-phase titration for cationic surfactant in high salinity brine and illuminates the reducing of the adsorption for cationic surfactants on natural carbonate minerals.
Developing stable foams from polymeric surfactants for water production control
(2005) Bhide, Vikram V.; Miller, Clarence A.; Hirasaki, George J.
This research explores a new method using foams for water production control in an oilfield. Reducing water production during oil production is an important objective impacting the profitability of a mature oilfield. Currently practiced methods using gel or polymer based systems either offer inadequate water flow reduction or suffer problems of proper placement in the field. Because of its properties, foam has the potential for use in water control. In this study, foams stable in presence of flowing water (washout stability) were developed using polymeric surfactants. A screening test was developed to measure the washout resistance of various conventional and polymeric surfactants. Foam from several polymeric surfactants such as triblock F108 and hydrophobically modified HMPA1 exhibited remarkable improvement in washout stability over conventional surfactants. Strong foam that offered a large resistance to flow of water was generated in a two-foot long sand pack with some of these polymeric surfactants. Again, the polymeric surfactants exhibited higher foam washout resistance than the conventional surfactants as predicted by the screening tests. Investigation of surfactant desorption from an air-water interface using bubble shape analysis showed that this improved foam washout resistance was due to almost irreversible adsorption of polymeric surfactants. Collapse of foam from polymeric surfactants at long times in the screening test was determined to be due to hydrodynamic effects and not desorption. Also, foam washout stability with polymeric surfactants in sand pack was found to be limited by air dissolution into flowing water. Scale-up calculations for oilfield geometries showed that foam from F108 can be stable for a long enough time, even with gas dissolution, for the process to be practicable. Foam stable to residual oil, expected in the water producing zones, was created by mixing an anionic surfactant CS-330 with nonionic F108. This is because ionic surfactants produce an electrostatic barrier that prevents entry of oil droplets into the air water interface. Flowing oil, however, produced a stable emulsion with this surfactant combination which offered a large resistance to flow. This was undesirable and was minimized by a brine flush to remove surfactant from the aqueous phase of the foam region before contact with flowing oil.
Diffusion phenomena in oil-water-surfactant systems
(1983) Raney, Kirk H.; Miller, Clarence A.; Zygouakis, Kyriacos; Dyson, Derek; Hirasaki, George
The diffusional processes which occur when oil contacts an aqueous surfactant solution have been investigated. These are important in enhanced oil recovery by surfactant flooding, where the rate of phase equilibration can affect recovery efficiency. Also, they are pertinent to certain mechanisms of detergency. Experimentally, systems containing anionic surfactants and alcohol cosurfactants were studied by optical microscopy. A microscope which utilized a vertical sample orientation was specifically designed for this purpose. As a result, an Improved and detailed viewing of intermediate phase growth, interface velocities, and spontaneous emulsification was achieved. The conditions of interest ranged from low salinities at which the surfactant is water-soluble to high salinities at which it is oil-soluble. At low salinities, the initial aqueous solution was a dilute dispersion of liquid crystals in brine. After oil was gently brought into contact, an intermediate oil-in-water microemulsion began to form. Also, an increase in liquid crystal concentration was observed at the microemulsion interface. At intermediate salinities, where the surfactant solution was mostly liquid-crystalline, a brine phase and a middle-phase microemulsion were both formed. It was in this salinity range that spontaneous emulsification of brine drops in the oleic phase began to occur. At high salinities, only a brine phase formed between the initial phases. Myelinic projections slowly developed at the liquid crystal-brine interface and changed in size and shape as diffusion proceeded. These salinity conditions produced vigorous spontaneous emulsification of brine in oil. In some systems, the brine phase formed by diffusion was more dense than the liquid-crystalline phase below it. Brine would channel to low points and push liquid crystal up to the' oil interface. The points at which liquid crystal contacted the oil produced volcano-like instabilities where mass transfer was enhanced. Not unexpectedly, these systems equilibrated much more rapidly than those in which diffusion predominated. The theory of diffusion paths, extended to allow for diffusion in a dispersed-phase region, was used to solve the diffusion equations for a model, pseudo-ternary system. As a result, the calculated diffusion paths and interface velocities were used to qualitatively explain the various phenomena observed experimentally.
Diluted bitumen emulsion characterization and separation
(2010) Jiang, Tianmin; Miller, Clarence A.; Hirasaki, George J.
Stable water-in-oil emulsions persist in bitumen froth from surface mining process of Athabasca oil sands because of asphaltenes and clay solids. This dissertation focuses on the characterization and separation of water in diluted bitumen emulsions. A novel approach to process experimental data from classic NMR experiments for the characterization of water in diluted bitumen emulsions has been proposed and tested. NMR PGSE restricted diffusion measurement can characterize emulsion drop size distribution. Experiments show that drop size of emulsion does not change much with time, which indicates that water in diluted bitumen emulsion is very stable without demulsifier. Water fraction profile and water droplet sedimentation velocity can be obtained from MRI 1-D T1 weighted profile measurement. Emulsion flocculation can be deduced by comparing the sedimentation velocity from experiment data and Stokes Law prediction. PR5 (a polyoxyethylene (EO)/polyoxypropylene (PO) alkylphenol formaldehyde resin) is an appropriate demulsifier for water in diluted bitumen emulsion. Almost complete separation can be obtained in the absence of clay solids. For the sample with solids, a rag layer containing solids with moderate density forms between the clean oil and free water layers. Partially oil-wet clay solids prevent complete separation of the emulsion. Experiments reveal that wettability of clay solids has significant effect on emulsion stability. Kaolinite with 100 ppm sodium naphthenate in toluene-brine mixture is chosen as model system for wettability test. Wettability of kaolinite can be altered by pH control, silicate and surfactant. Adding 3x10 -3 M Na2SiO3 at pH 10 can get 80% of kaolinite water-wet. Over 90% of kaolinite becomes water-wet adding C8TAB, betaine 13 and amine oxide DO with optimal dosages. In diluted bitumen emulsion, about 10-4 M sodium meta-silicate can change the wettability of solids from partially oil-wet to more water-wet. Hereby the clay solids can settle down to the aqueous phase and the separation is almost complete. Wettability of kaolinite can be characterized via zeta potential measurement and modeling. Simplified Gouy-Stern-Grahame model and oxide site-binding model can be used to correlate zeta potential of kaolinite in brine with different additives. Sodium silicates have the greatest effect per unit addition on changing zeta potential of kaolinite and can be used to change the wettability of clay solids. Almost complete separation be obtained by the three-step procedure: (a) adding 10-4 M Na2SiO3 during initial emulsion formation to make the solids less oil wet; (b) removing the clean oil formed following subsequent treatment with demulsifier and adding NaOH or Na2SiO3 with shaking to destroy the rag layer and form a relatively concentrated oil-in-water emulsion nearly free of solids; and (c) adding hydrochloric acid to break the oil-in-water emulsion.
Dissolution rates of surfactants and granules
(2003) Bai, Jinhua; Miller, Clarence A.
A quantitative penetration scan method was used to study rates of dissolution of pure, noncrystalline anionic surfactants in water. The displacement of phase boundaries from initial surface of contact was found to be proportional to the square root of time, indicating the importance of diffusion. For some surfactants studied such as Aerosol OT (AOT) and 7-phenyl tetradecane sulphonate, myelinic figures grew from the initial surface of contact between surfactant and water toward the aqueous phase. A simple model was developed which included both this swelling and diffusion in the rest of the surfactant-containing region. The usual penetration scan method involving semi-infinite phases was supplemented by a novel modified scan in which only a thin layer of surfactant was used. With the combined results it was possible to obtain effective diffusivities of the liquid crystalline phases of AOT and of the two lamellar phases of 7-phenyl tetradecane sulphonate. Values were of order 10-10 m2/s. Videomicroscopy was used to investigate the mechanisms and rates of dissolution for a system containing the pure nonionic surfactant C12E 4 and the soap sodium oleate. A microinjection technique was used to inject drops of surfactants or surfactant mixtures into water. Although C 12E4 itself does not dissolve in water, dissolution was observed when drops of its mixtures with sufficient oleic acid were injected into alkaline buffer solutions. Formation of sodium oleate during the dissolution process made the surfactant mixture more hydrophilic and hence soluble. A lamellar phase formed upon injection and dissolved by a shrinking core mechanism. A hanging drop slide technique was developed and used to study disintegration of single granules consisting of many zeolite particles bound together with liquid nonionic surfactant. For pure nonionic surfactants and their mixtures, granules disintegrated below the cloud point of the pure surfactant or mixture. Disintegration did not occur when the neat surfactant developed viscous myelinic figures upon contact with water. Nor was it observed when an aqueous phase coexisted with a surfactant-rich L1 phase or L3 (sponge) phase at equilibrium. Similar behavior was observed for commercial nonionic surfactants and their mixtures.
Dissolution, processing and fluid structure of graphene and carbon nanotube in superacids: The route toward high performance multifunctional materials.
(2012-09-05) Behabtu, Natnael; Pasquali, Matteo; Biswal, Sibani Lisa; Thomas, Edwin; Miller, Clarence A.; Adams, Wade
Carbon allotropes have taken central stage of nanotechnology in the last two decades. Today, fullerenes, carbon nanotubes (CNTs), and graphene are essential building blocks for nanotechnology. Their superlative electrical, thermal and mechanical properties make them desirable for a number of technological applications ranging from lightweight strong materials to electrical wires and support for catalysts. However, transferring the exceptional single molecule properties into macroscopic objects has presented major challenges. This thesis demonstrates that carbon nanotubes and graphite dissolve in superacids and these solution can processed into macroscopic objects. Chapter 2 reviews neat CNT fiber literature. Specifically, the two main processing methods —solid– state and solution spinning — are discussed. CNT aspect ratio and fibers structure are identified as the main variables affecting fiber properties. Chapter 3 shows that graphite can be exfoliated into single-layer graphene by spontaneous dissolution in chlorosulfonic acid. The dissolution is general and can be applied to various forms of graphite, including graphene nanoribbons. Dilute solutions of graphene can be used to form transparent conductive films. At high concentration, graphene and graphene nanoribbons in chlorosulfonic acid forms a liquid crystal and can be spun directly into continuous fibers. Chapter 4 describes a solution–based method to form a thin CNT network. This network is an ideal specimen support for electron microscopy. Imaging nanoparticles with atomic resolution and sample preparation from reactive fluids demonstrate the unique feature of solution–based CNT support compared to state–of–the–art TEM supports . Chapter 5 describes CNT liquid crystalline phase. Specifically, CNT nematic droplets shape and merging dynamics are analyzed. Despite nanotube liquid crystals having been reported in various CNT systems, a number of anomalies such as low order parameter and spaghetti–like, nematic droplets are reported. However, CNTs in chlorosulfonic acid show elongated, bipolar droplets typical of other rod–like molecules. Moreover, their large aspect ratio allows capturing the transition from homogeneous to bipolar transition expected from scaling arguments.The equilibrium shape and merging dynamics demonstrate the liquid nature of CNT liquid crystals. Chapter 6 describes the CNT/chlorosulfonic acid fiber spinning. The influence of starting material, spinning dope concentration, spin draw ratio and coagulation on fiber properties is discussed. The linear scaling of fiber strength with CNT aspect ratio is demonstrated experimentally, once the best properties from different batches are compared. Moreover, Successful multi–hole spinning demonstrates the intrinsic scalability of wet spinning to meet the typical production output of industrial–scale spinning. Chapter 7 compares acid–spun CNT fibers to other CNTs fibers as well as existing engineered materials. Acid–spun CNT fibers combine the typical specific strength of high–strength carbon fibers to the thermal and electrical conductivity of metals. These properties are obtained because of a highly aligned, dense structure. The combined strength and electrical conductivity allow acid-spun fibers to be used as structural as well as conducting wire while the combined electrical and thermal properties allow for exceptional field emission properties. In conclusion, we demonstrate that multifunctional properties of carbon nanotubes that have fuelled much of the research in the past 20 years, can be attained on a macroscopic level via rational design of fluid–phase processing.
Drainage of static and translating foam films
(1997) Singh, Gurmeet; Miller, Clarence A.; Hirasaki, George J.
Drainage of a mobile, symmetric, plane-parallel thin liquid film between two gas bubbles (foam film) is studied. An analytical solution for the rate of thinning of such a liquid film with an insoluble surfactant and having both film elasticity and surface viscosity is presented for the first time. Analysis is extended to the more general case of a soluble surfactant and compared with previous analyses. Surfactant material parameters affecting the rate of thinning are identified and grouped into a single dimensionless parameter, the surfactant number which describes the transition from a mobile to an immobile film. Significant deviation from the Reynolds velocity is found when this dimensionless parameter is small. Since draining foam or emulsion films are generally of nonuniform thickness with a thick region or 'dimple' as the central part and separated from the Plateau border by a thinner 'barrier ring', an analytical solution is not possible. Hence a numerical model was developed. This model simulates the hydrodynamics associated with the drainage of an axisymmetric, dimpled, mobile foam film with an insoluble surfactant. This extends the work of Joye (1994) which was limited to immobile films. Results of the parametric study indicate that the rate of drainage of these films is dependent on surfactant properties viz. elasticity, surface dilatational viscosity, surface shear viscosity and surface diffusivity. These properties are grouped into a single dimensionless parameter which is the same as obtained by our analytical solution for a plane parallel film and which correlates with the rate of drainage of the foam film. This parameter describes the transition from a mobile film to an immobile film. The simulations indicate considerable motion of the interface for draining mobile foam films. Foam texture in a porous medium is governed by the hydrodynamics of individual foam films (lamellae) flowing through pores of varying size. The stability of foam in a particular application depends upon the stability of a lamella in the porous medium, especially as the lamella expands in translating from a small pore (pore throat) to a larger pore (pore body). The numerical simulator developed above is extended to translating foam films to model the effect of various parameters on foam stability. The model predicts that the travelling lamella is unstable only for certain ranges of surfactant properties, porous media geometry and flow conditions, for e.g. gas flow rate and capillary pressure. Simulations show that mobile foam films stretch in going from a pore throat to a pore body and may thin down to the critical thickness and break, under certain conditions. In contrast immobile foam films are very stable due to an entrainment effect which occurs as the film expands in going from a pore throat to a pore body. The critical capillary pressure at which a moving lamella will break is determined as a function of film and porous medium properties. Further the concept of asymmetric drainage of foam films in porous media has been explored.
Dynamic aspects of emulsion stability
(2004) Pena, Alejandro A.; Miller, Clarence A.; Hirasaki, George J.
This dissertation encompasses novel theoretical, experimental and computational advances in the understanding of the transient behavior of emulsions undergoing phase separation. Firstly, the kinetics of dissolution of single drops of pure hydrocarbons and their mixtures in aqueous solutions of a nonionic surfactant (C12E8) was studied theoretically and experimentally. At moderate surfactant concentrations, both interfacial resistance to mass transfer and diffusion of micelles carrying solubilized oil dictated the solubilization rates. At high surfactant concentrations, the onset of spontaneously generated convection in the aqueous phase was observed. In such cases, convection aided mass transport in the bulk phase and reduced the diffusional resistance, thus leaving interfacial resistance as rate-controlling. Data suggest that the adsorption/fusion of micelles at the interfaces was the elementary molecular step within the kinetic mechanism that dictated the interfacial resistance to mass transport. Experimental results for the solubilization of single droplets were correlated without adjustable parameters with a plausible mass transfer model in agreement with such mechanism. This model was extended to polydisperse emulsions of hydrocarbons in nonionic surfactant solutions, and it was successfully applied to correlate data from experiments on solubilization in emulsions, Ostwald ripening and compositional ripening. In addition, a new experimental technique based on nuclear magnetic resonance (NMR) was developed to characterize emulsions. The contributions of this work include a novel theory to interpret results from NMR restricted diffusion experiments and an original procedure that couples diffusion measurements with transverse relaxation rate experiments to determine drop size distributions with arbitrary shape, the water/oil ratio of the emulsion and the rate of decay of magnetization at the interfaces, i.e., the surface relaxivity. It is shown that the procedure also allows identification of whether the dispersion is oil-in-water (O/W) or water-in-oil (W/O) in a straightforward manner and is suitable to evaluate changes in drop size distributions in time steps of approximately five minutes without manipulation or destruction of the sample. Finally, the effect of chemicals of known structure and composition (alkylphenol polyalkoxylated resins and polyurethanes) on the stability and properties of brine-in-crude-oil emulsions was assessed experimentally. (Abstract shortened by UMI.)
Effect of anionic and nonionic surfactants on the biodegradation of solubilized n-decane
(1997) Salma, Tauseef; Miller, Clarence A.
Developing an improved understanding of enhanced biodegradation is of great importance in remediation of contaminated soils and aquifers and in cleanup of oil spills. The effect of several nonionic and anionic surfactants and their mixtures on the biodegradation of n-decane was investigated. Microbial growth of Pseudomonas aeruginosa on the solubilized hydrocarbon was found to be stimulated by all of the non-ionic surfactants tested, with varying degrees of enhancements in the rate of biodegradation compared to that found in the absence of surfactant. Three anionic surfactants, Linear Alkyl benzene Sulfonate (LAS), Sodium Dodecyl Sulfate (SDS) and Neodol 25-3S, an alcohol ethoxysulfate, were investigated. Both SDS and N25-3S stimulated the degradation of n-decane. LAS did not support the growth of P. aeruginosa with or without decane but its mixtures with the nonionic surfactant Neodol 25-7 did enhance the overall degradation except at very high LAS contents. A novel aspect of this study was the simultaneous measurements of surfactant concentration, cell mass, and n-decane concentration as a function of time when the surfactant was SDS. A modified Monod model was developed to simulate bacterial growth rate and substrate and surfactant degradation. Predictions of the model were in good agreement with experimental data. With the assumption that the cell mass generated by degradation of a given quantity of n-decane was the same when other surfactants were used, it was possible to apply the model successfully in other systems where it was not feasible to measure surfactant degradation. The half saturation constant K$\sb{\rm S}$ for n-decane degradation was high both for highly degradable surfactants and for poorly degradable mixtures such as those with high contents of LAS. A minimum value of K$\sb{\rm S}$ is reached for surfactants and surfactant mixtures with intermediate degradation rates. The degradation rate of n-decane was maximized for this condition.
Effect of oils, soap and hardness on the stability of foams
(2004) Zhang, Hui; Miller, Clarence A.
A systematic study of foam stability in the presence of model nonpolar oils and their mixtures with oleic acid was conducted for two commonly used surfactants (anionic and nonionic) under neutral and alkaline conditions with different amounts of dissolved calcium. In some cases insoluble calcium soap or microemulsions formed in situ. Measurements of the rate of collapse of a foam column were supplemented by microscopic observations of individual foam and "pseudoemulsion" films and by measurement of equilibrium and dynamic surface and interfacial tensions. In the absence of calcium soap use of equilibrium values of conventional entry E, spreading S, and bridging B coefficients was adequate to explain the effect of oils on stability of foams containing the nonionic surfactant. For the anionic surfactant E must be modified to account for electrostatic repulsion in the pseudoemulsion film. Calcium soap particles at the oil-water interface facilitate entry of oil drops and the associated bridging of foam films or Plateau borders, producing a substantial antifoam effect. When this synergistic effect occurs, conventional values of E govern oil entry. In some cases for oils that were mixtures of triolein and oleic acid foam is unstable during foam formation and initial foam drainage but stable at later times, behavior which is explained by calculating transient values of E, S, and B. Addition of n-dodecanol produced significant stabilization of foams of the anionic surfactant containing dispersed oil drops both when calcium soap was present and when high levels of calcium had destabilized the foam at neutral pH. ESB theory proved useful in predicting this effect. An amine oxide surfactant was less effective as a foam booster. In the absence of oil, calcium soap particles can destabilize foams of both surfactants. A model for predicting the precipitation boundary including the enhancement of calcium content in the electrical double layers of surfactant micelles yielded results in agreement with experiment. Foam was less stable while precipitation was occurring (hours) than at equilibrium, perhaps because calcium oleate, which initially formed at the interfaces, was extracted as oleate concentration decreased to its equilibrium value.
Foam for mobility control in alkaline/surfactant enhanced oil recovery process
(2006) Yan, Wei; Miller, Clarence A.; Hirasaki, George J.
This thesis addresses several key issues in the design of foam for mobility control in alkaline-surfactant enhanced oil recovery processes. First, foam flow in fracture systems was studied. A theory for foam flow in a uniform fracture was developed and verified by experiment. The apparent viscosity was found to be the sum of contributions arising from liquid between bubbles and the resistance to deformation of the interfaces of bubbles passing through the fracture. Apparent viscosity increases with gas fractional flow and is greater for thicker fractures (for a given bubble size), indicating that foam can divert flow from thicker to thinner fractures. The diversion effect was confirmed experimentally and modeled using the above theory for individual fractures. The amount of surfactant solution required to sweep a heterogeneous fracture system decreases greatly with increasing gas fractional flow owing to the diversion effect and to the need for less liquid to occupy a given volume when foam is used. The sweep efficiency's sensitivity to bubble size was investigated theoretically in a heterogeneous fracture system with log-normal distributed apertures. Second, the foam application in forced convection of alkaline-surfactant enhanced oil recovery processes was studied. From sand pack experiments for the alkaline-surfactant-polymer process, a 0.3 PV slug of the surfactant blend studied can recover almost all the waterflood residual crude oil when followed by a polymer solution as mobility control agent. But this blend is a weak foamer near its optimum salinity while one of its components, IOS, is a good foamer. Two types of processes were tested in sand packs to study possible process improvements and cost savings from replacing some polymer by foam for mobility control. The first used IOS foam as drive after the surfactant slug, while the second, which is preferred, involved injecting gas with the surfactant slug containing polymer followed by IOS foam. It was found that foam has higher apparent viscosity in high than in low permeability region. Thus, use of foam should be more attractive in heterogeneous system to get better sweep efficiency.
Foam generation and propagation in heterogeneous porous media
(2001) Tanzil, Dicksen; Miller, Clarence A.; Hirasaki, George J.
This thesis addresses several key issues in the design of foam processes in porous media. Laboratory experiments were performed to identify the conditions for the generation of strong foam. They demonstrated that strong foam in homogeneous porous media is obtained above a critical dimensionless number that represents the point when there are sufficient lamellae to create discontinuity in all flowing gas paths. The critical number corresponds to a critical pressure drop that scales inversely with the square root of permeability. The results imply that mobilization and division is the primary mechanism for the generation of strong foam in homogeneous media. Effects of heterogeneity on foam generation and propagation are studied. Steady-state analysis suggests snap-off occurring near permeability increase due to the drop in capillary pressure. Experiments in homogeneous and heterogeneous sand-packed columns revealed that the foam mobility in the two cases could indeed differ by two orders of magnitude, due to snap-off for flow across an abrupt increase in permeability. This mechanism of foam generation is dependent on the degree of permeability contrast and the gas fractional flow. At low gas fractional flow, a permeability contrast of at least about 4 is necessary. Snap-off also occurs when the increase in permeability is gradual. In this case, small capillary number (e.g. low flow rate) is required. A simple foam model was developed and incorporated into an existing reservoir simulation package. In addition to a fixed increase in foam effective viscosity---a feature that is common in many previous models, the increase in trapped gas saturation during imbibition is included. The latter is critical to model diversion in surfactant-alternating-gas processes. Observations from a field-scale foam application for aquifer remediation were reviewed. The reservoir simulator that included the foam model was successfully utilized to simulate the process and interpret its results. The field results are consistent with the conditions for strong foam and the effects of heterogeneity identified in the laboratory. Simulations indicated that foam mobility in the vertical direction, which is generally perpendicular to stratification, was about 1 to 2 orders of magnitude less than its horizontal mobility. The reduction in vertical mobility due to snap-off in stratified media implies that foam in field-scale processes should propagate farther than previously thought.
Intermediate phase formation and spontaneous emulsification of hydrocarbon/alcohol/surfactant/water systems
(1998) Rang, Moon Jeong; Miller, Clarence A.
Spontaneous emulsification, intermediate phase formation, and other dynamic behavior were studied for various ternary and quaternary systems containing hydrocarbon, alcohol, surfactant and water, using several experimental techniques such as oil drop and vertical cell contacting experiments using a videomicroscopy system, and macro-scale emulsification experiments in some systems. Experiments were conducted when surfactant was initially located in the aqueous phase and when it was initially in the oil phase. An extended quasi-steady-state approximation theory for the diffusion process was developed to describe the dynamic behavior, especially intermediate phase formation, which occurred when a drop of a polar oil having an appreciable water solubility contacted a dilute surfactant solution. Extensive experimental results for heptanol drops contacting dilute amine oxide solutions showed a consistency with the theory. It was found that spontaneous emulsification in hydrocarbon/hydrophilic nonionic or zwitterionic surfactant/hydrophobic alcohol/water systems was caused by the local supersaturation mechanism wherever the surfactant was initially located. In order to produce complete spontaneous emulsification of an oil drop in water, the oil phase should contain initially an optimum content of alcohol, which is near the oil composition at the phase inversion temperature (PIT) condition for water-insoluble alcohols and somewhat higher for slightly water-soluble alcohols. In either case the equilibrium phase behavior and diffusion must combine in such a way that the drop is completely converted to a microemulsion or the lamellar liquid crystalline phase which subsequently becomes supersaturated in oil, causing nucleation of small oil droplets. This sequence of events stems from the drop being made more hydrophilic by some combination of alcohol diffusion into the aqueous phase, surfactant diffusion into the drop (when it is initially in the aqueous phase), and hydration of the ethylene oxide groups of a nonionic surfactant (when it is initially in the oil). The results show that a proper combination of a hydrophilic nonionic surfactant and a hydrophobic alcohol dissolved in oil can induce its complete spontaneous emulsification in water. However, addition of a single, pure surfactant near its PIT to an oil does not produce complete spontaneous emulsification because the phase behavior does not permit the above sequence of events to occur.
Laboratory development of the surfactant/foam process for aquifer remediation
(1998) Szafranski, Robert Crawford; Miller, Clarence A.; Hirasaki, George J.
The research presented was used to develop the surfactant/foam process for aquifer remediation. The surfactant/foam method was designed to address the problem of removing dense non-aqueous phase liquids (DNAPLs) spread throughout a somewhat heterogeneous aquifer. The developmental research included demonstrating the effectiveness of the surfactant/foam process and determining the effects that various parameters had on the technique. Parameters tested included the effects of different contaminants on foam, the effects of varying surfactant solution formulation, the effects of flow rate and slug size, and the effect of temperature on the process. The final design utilized a 4% surfactant solution at its optimal salinity, 11,500 ppm NaCl with trichloroethylene at room temperature and 10,250 ppm NaCl with field DNAPL at 12$\sp\circ$C. Trichloroethylene was used as a representative DNAPL for the laboratory work. Foam was generated with pressure regulated air injection rather than a rate constrained gas injection. This method allowed a high gas flow rate when little foam was present, and a lower, more maintainable, flow rate as foam was generated. The process was tested in several experiments in layered sandpacks in a two-dimensional model. The permeability ratios of the sand layers ranged from 7:1 to 20:1. Packings included both a high permeability sand overlying a low permeability sand and the opposite configuration. The experiments resulted in complete removal of TCE from the sandpacks after one to two pore volumes (PV) of surfactant injection. In contrast, surfactant floods without foam in the same packs required between 13 PV and 28 PV, depending on the sands' arrangement and permeability ratio. The surfactant/foam process was also tested in a larger scale two-dimensional model. Foam was successfully propagated across the eight foot length of the layered sandpack. A field demonstration was then carried out in a fifteen by twenty foot well pattern. The preliminary field results indicate that the surfactant/foam process recovered more DNAPL from the site than had been present initially due to contaminant migration into the well pattern. The final DNAPL saturation at the field site was approximately 0.0003 in the volume swept.
Mechanisms of symmetric and asymmetric drainage of foam films
(1994) Joye, Jean-Luc Lucien; Miller, Clarence A.
The drainage of horizontal thin liquid films produced from aqueous solutions of ionic surfactants was studied experimentally, using videomicroscopy and interference techniques, for several surfactants in a wide range of concentrations. Two types of drainage were observed: asymmetric and symmetric. The film drainage was found to be much faster in the asymmetric case. First, axisymmetric drainage was investigated. In this case, a numerical model was developed to simulate the entire drainage process, including the film formation. The condition for the transition from a nearly "plane-parallel" film to a dimpled film in the absence of disjoining pressure was determined. The ratio of the minimum to maximum thickness in the film and a dimensionless rate of drainage was correlated with the ratio of the maximum possible curvature in the dimple to the curvature in the meniscus. The presence of disjoining pressure makes a qualitative difference in film drainage. Low electrolyte concentrations in a film containing ionic surfactants produce a repulsive disjoining pressure that inhibits formation of the thin barrier ring and thus of the dimple itself. The film drains rapidly to its equilibrium thickness. For high electrolyte concentrations, disjoining pressure is dominated by van der Waals attraction. As a result a thin annular film forms that forces the dimple into a lens with a finite contact angle. These types of behaviors were observed experimentally. Then, the mechanisms of asymmetric thin film drainage were investigated. A simple linear stability analysis and a two dimensional numerical model were developed and showed that asymmetric drainage is caused by a hydrodynamic instability that is produced by a surface-tension-driven flow and stabilized by surface viscosity, surface diffusivity and system length scale. A criterion for the onset of instability causing asymmetric drainage was determined. Experiments performed on aqueous solutions of SDS and SDS:1-dodecanol showed the strong dependence of the drainage type on the surface shear viscosity. Experimental results were found to be in good agreement with the stability predictions.
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.

Browsing by Author "Miller, Clarence A."

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