Die Methode der Reaktiven Abscheidung wurde benutzt, um zu untersuchen ob und in welcher Weise das Silicidwachstum mittels einer Monolage aus Sb, d.h. mittels eines surfactant (surface active agent), gesteuert werden kann. Hierzu wurden unter UHV-Bedingungen die Metalle Mn, Ti und Ni auf geheizte Si(001) bzw. Si(001)-Sb Substrate abgeschieden. Die Probenanalyse erfolgte durch LEED, RBS, XRD, SEM, TEM und AFM. Die Theorie zum surfactant-gesteuerten Wachstum wird vorgestellt und auf das System des reaktiven Silicidwachstums übertragen. Die Probenanalysen zeigen, dass eine Monolage von Sb in der Lage ist das Wachstum der drei untersuchten Silicide zu beeinflussen. Für das System der Höheren Mangansilicide kommt es zu einer Erhöhung der Inseldichte um bis zu zwei Größenordnungen und zu Änderungen in den Orientierungsbeziehungen der Silicidinseln. Beim Wachstum der Titansilicidschichten konnte durch das surfactant die pinhole-Bildung unterdrückt werden. Das dritte untersuchte Silicid ist das Nickeldisilicid. In diesem Fall wird der Ort der Keimbildung von der Si-Oberfläche in das Volumen des Si-Substrates verschoben, d.h. die Oberfläche wird vollständig passiviert, zusätzlich treten neue Orientierungsbeziehungen auf.

Thèse doctorat : Sciences pharmaceutiques : Strasbourg 1 : 2006. / Titre provenant de l'écran-titre. Notes bibliogr. Index.

A limited number of laboratory studies and pilot programs have been reported in chemical Enhanced Oil Recovery (EOR) flooding of carbonate reservoirs (Adams & Schievelbein, 1987). Fewer still have involved surfactants in limestone reservoirs. No surfactant/polymer flood on a field wide basis of a carbonate reservoir has ever been documented in the literature (Manrique, Muci, & Gurfinkel, 2010). This void represents a colossal opportunity given that nearly a third of the 32 billion barrels of oil consumed in the world each year come from carbonate reservoirs (Sheng, 2011, pp. 1, 254). This thesis is based on experiments with a high hardness (~5,000 ppm divalent ions) carbonate field. Phase behavior, aqueous stability, and core flood experiments were performed using polymer and various surfactants and co-solvents. Both commercially available and laboratory synthesized surfactants were tested. The objective was to optimize the chemical injection design in order to lower interfacial tension between water and oil in the reservoir. Research was also done with alkali intended for use with hard brines. The main challenges when working with hard brine were poor solubilization and low aqueous stability limits. However, highly propoxylated and ethoxylated surfactants mixed with internal olefin sulfonates, hydrophilic sulfates, and sec-butanol were observed to have very high solubilization ratios, fast phase behavior equilibration times, negligible viscous macroemulsion effects, and excellent aqueous stability. Spinning drop interfacial tensiometer tests confirmed low IFT values were obtained for a range of acceptable salinities with hard brine. Three core floods were performed using one of the surfactant formulations developed. One flood was done with field core, brine, and crude oil and failed to meet expectations because of high levels of heterogeneity (vugs) within the core that lead to an elongated oil bank and low and slow oil recovery. The other floods were done with Estillades Limestone. The first Estillades flood used hard synthetic field brine and had better mobility but poor oil recovery. The last core flood had good mobility and recovered 90% of the residual oil to water flooding, but only after a total of 1.1 pore volumes of 1.0 wt% surfactant solution were injected. The results provided in this thesis constitute proof of concept that S/P flooding can be done in high salinity and hardness reservoirs. / text

Surfactant related recovery processes are of increasing interest and importance because of high oil prices and the urge to meet energy demand. High oil prices and the accompanying revival of EOR operations have provided academia and industry with great opportunities to test alkaline surfactant polymer (ASP) methods on a field scale and to develop novel surfactant systems that can improve the performance of such EOR processes. This dissertation intends to discuss both opportunities through two unique projects, the development of novel surfactants for EOR applications and the design for an alkaline/surfactant/polymer (ASP) field pilot. In Section I of this dissertation, a novel series of anionic Gemini surfactants are carefully synthesized and systematically investigated. The remarkable abilities of Gemini surfactants to influence oil-water interfaces and aqueous solution properties are fully demonstrated. These surfactants are shown to have great potential for application in EOR processes. A wide range of Gemini structures (C₁₄ to C₂₄ chain length, -C2- and -C4- spacers, sulfate and carboxylate head groups) was synthesized and shown to have high aqueous solubility, with Krafft points below 20°C. The critical micelle concentrations (CMC) for these new molecules are measured to be orders of magnitude lower than their conventional counterparts. The significantly more negative Gibbs free energy for Gemini surfactant drives the micellization process and results in ultralow CMC. An adsorption study of Gemini surfactants at air-water and solid-water interfaces shows their superior surface activity from tighter molecular packing, and attractive characteristics of low adsorption loss at the solid surface. All anionic Gemini surfactants synthesized have an extraordinary tolerance to salinity and/or hardness. No phase separation or precipitation occurs in the aqueous stability tests, even in the presence of extremely high concentrations of mono- and/or di-valent ions. Moreover, ultra-low IFT values are reached under these conditions for Type I microemulsion systems, at very low surfactant concentrations. The stronger molecular interaction between the Gemini and conventional surfactants offers synergy that promotes aqueous stability and interfacial activity. Gemini molecules with short spacers are capable of giving rise to high viscosities at fairly low concentrations. The rheological behavior can be explained by changes in the micellar structure. A molecular thermodynamic model is developed to study anionic Gemini surfactants aggregation behavior in solution. The model takes into account of the head group-counter-ion binding effect and utilizes two simplified solutions to the Poisson-Boltzmann equation. It properly predicts the CMC of the surfactants synthesized and can be easily expanded to investigate other factors of interest in the micellization process. Section II of this dissertation studies chemical formulation design and implementation for an oilfield where an alkaline/surfactant/polymer (ASP) pilot is being carried out. A four-step systematic design approach, composed of a) process and material selection; b) formulation optimization; c) coreflood validation; 4) lab-scale simulation, was successfully implemented and could be easily transferred to other EOR projects. The optimal chemical formulation recovered over 90% residual oil from Berea coreflood. Lab-scale simulation model accurately history matches the coreflood experiment and sets the foundation for pilot-scale numerical study. Different operating strategies are investigated using a pilot-scale model, as well as the sensitivities of project economics to various design parameters. A field execution plan is proposed based on the results of the simulation study. A surface facility conceptual design is put together based on the practical needs and conditions in the field. Key lessons learned throughout the project are summarized and are invaluable for planning and designing future pilot floods. / text

This work addresses fundamental aspects of designing templates and curing conditions for the synthesis of mesoporous metal oxide thin films. The first section addresses selection of cationic-carbohydrate surfactant mixtures to synthesize templated silica thin films for selective adsorption of simple carbohydrates based on molecular imprinting. Nuclear magnetic resonance and fluorescence spectroscopy results suggest a novel structure for mixtures of alkyl glucopyranosides or xylopyranosides with cationic (trimethylammonium) surfactants. Despite thermodynamically favorable mixing, the carbohydrate headgroups in the mixed micelle adopt an inverted configuration with their headgroups in the micelle core, and therefore are inaccessible for molecular imprinting. This orientation occurs even when the alkyl tail length of the carbohydrate surfactant is greater than that of the cationic surfactant, but this limitation can be overcome by introducing a triazole linker to the carbohydrate surfactant. The next section addresses the effects of aging conditions on the structural and chemical evolution of surfactant templated silica thin films. The third section describes the synthesis of carbohydrate/cationic surfactant imprinted silica thin films with orthogonally oriented cylindrical pores by modifying the glass surface with a random copolymer. The last part of the dissertation addresses the effect of pore orientation on the transformation mechanism of block copolymer templated titania thin films during high temperature curing. Mesoporous titania thin films can be used for photochemical and solar cell applications, but doing so requires addressing the tradeoff between loss of mesostructural order and growth of crystallinity during thermal treatment. By using advanced x-ray scattering techniques it has been shown that the titania films with vertically oriented pores can better withstand the anisotropic stress that develops during thermal treatment compare to titania films with mixed pore orientation. For instance, films with parallel or mixed pores can only be heated at 400 °C for a brief time (~10 min) without loss of order, while orthogonally oriented films can be heated at 550 °C or greater for extended time periods (on the order of hours) without significant loss of long-range mesopore structure. Detailed kinetic modeling was applied to enable the comparison of activation energy for mesostructure loss in films as a function of pore orientation and thickness.

A dehydrogen is an ‘under-wrapped’ hydrogen bond in a protein that is purported to be a hot spot for binding due to the favorable replacement of water with hydrocarbon upon binding of another protein. A model at the level of dielectric constants is used to test the validity of the claim that moving a hydrogen bond from high dielectric (i.e. a dehydron) to low dielectric (i.e. after binding of another protein) is actually a thermodynamically favorable process. In simulation, several proteins have been shown to undergo a dewetting transition when fixed components are separated a small distance. A new atomic-level hydrophobicity scale is combined with topographical information to characterize protein interfaces. The relationship between hydrophobicity and topography for protein surfaces known to be involved in binding is examined. This framework is then applied to identify surface characteristics likely to have an affect on the occurrence of a dewetting transition. Cadmium selenide (CdSe) nanoparticles form nanospheres or nanorods when grown in solutions of varying concentrations of the surfactants hexylphosphonic acid (HPA) and trioctylphosphine oxide (TOPO). Relative binding free energies are calculated for HPA and TOPO to the solvent-accessible faces of CdSe crystals. Binding free energies calculated with a Molecular Mechanics-Generalized Born model are used to identify a set of low free energy structures for which the solvation free energy is refined with the solution to the Poisson equation. These relative binding free energies provide information about the relative growth rates of these crystal faces in the presence of surfactants. Relative growth rates are then used to help understand why nanoparticles form certain shapes in the presence of specific surfactants. / text

Accurate simulation of chemical flooding requires a detailed understanding of numerous complex mechanisms and model parameters where grid size has a substantial impact upon results. In this research we show the effect of grid size on parameters such as phase behavior, interfacial tension, surfactant dilution and salinity gradient for chemical flooding of a very heterogeneous oil reservoir. The effective propagation of the surfactant slug in the reservoir is of paramount importance and the salinity gradient is a key factor in ensuring the process effectiveness. The larger the grid block size, the greater the surfactant dilution, which in turn erroneously reduces the effectiveness of the process indicated with low simulated oil recoveries. We show that the salinity gradient is not adequately captured by coarse grid simulations of heterogeneous reservoirs and this leads to performance predictions with lower recovery compared to fine grid simulations. Due to the highly coupled, nonlinear interactions of the many chemical and physical processes involved in chemical flooding, it is better to use fine-grid simulations rather than coarse grids with upscaled physical properties whenever feasible. However, the upscaling methodology for chemical flooding presented in this work accounts approximately for some of the more important effects, as demonstrated by comparison of fine grid and coarse grid results and is very different than the way other enhanced oil recovery methods are upscaled. This is a step towards making better performance predictions of chemical flooding for large field projects where it is not currently feasible to perform the large number of simulations required to properly consider different designs, optimization, risk and uncertainty using fine-grid simulations. / text

The ability to select low-cost, high-performance surfactants for a wide range of crude oils under a wide range of reservoir conditions has improved dramatically in recent years. Surfactant formulations (surfactant, co-surfactant, co-solvent, alkali, polymer, and electrolyte) were developed by using a refined phase behavior approach. Such formulations nearly always result in more than 90% oil recovery in core flood when good surfactants with good mobility control are used. The advances that have improved performance, reduced cost, increased robustness, and extended the range of reservoir conditions for these formulations are described in this work. There are thousands of possible combinations of the chemicals that could be tested for each oil and each chemical combination requires many observations over a long time period at reservoir temperature for proper evaluation. It would take too long, cost too much and in many cases not even be feasible to test all combinations. In practice the scientific understanding is used to match up the surfactant/co-surfactant/co-solvent characteristics with the oil characteristics, temperature, salinity, hardness and so forth. Synthesized and new surfactants with much larger hydrophobes and more branching than previously available were tested. New classes of co-solvents and co-surfactants with superior performance were test to improve aqueous solubility. These new developments resulted in improved ASP formulations for both oils that react with alkali to make soap and oils that do not. Many of these developments are synergistic and taken together represent a breakthrough in reducing the cost of chemical flooding and thus its commercial potential. / text

Foam-assisted low interfacial tension and foam-improved sweep efficiency are attractive enhanced oil recovery (EOR) methods with numerous studies and researches have been conducted in the past few decades. For example, CO₂-Enhanced Oil Recovery (CO₂-EOR) is very efficient in terms of oil displacement. However, due to the low viscosity of super critical CO₂, the process usually suffers from poor sweep efficiency. One method of increasing sweep efficiency in CO₂-EOR has been identified through the use of surfactants to create "foams" or more correctly CO₂-in-water (C/W) macroemulsions. Polymer flooding techniques such as Alkali -- Polymer (AP), Surfactant -- Polymer (SP), and Alkali -- Surfactant -- Polymer (ASP) have been the only proven chemical EOR method in sandstone reservoirs with many successful pilot tests and field projects. However, the use of polymer is limited in carbonates due to unfavorable conditions related to natural characteristics of this type of lithology. In this case, foam-assisted EOR, specifically Alkali -- Surfactant -- Gas (ASG) process, can be an alternative for polymer flooding. It is a fact that large amount of the world's oil reserves resides in carbonate reservoirs. Therefore, an increase in oil recovery from carbonates would help meet the world's increasing energy demand. This study consists of two parts: (1) the development of new surfactant for creating CO₂ -- in -- water macroemulsions for improving sweep efficiency in CO₂ -- EOR processes; (2) systematic study of ASG method as a novel EOR technique and an alternative for polymer flooding in carbonate reservoirs. Both studies are related to the use of foam as a mobility control agent. In the first part, the design and synthesis of twin tailed surfactants for use at the CO₂/water interface is discussed. The hydrohobes for these surfactants are synthesized from epichlorohydrin and an excess alcohol. Subsequent ethoxylation of the resulting symmetrical dialkyl glycerin yields the water soluble dual tailed surfactants. The general characteristics of these surfactants in water are described. A comparison is carried out between twin-tailed dioctylglycerine surfactants and linear secondary alcohol surfactant based on results from a core flood. The results show that even above the cloud point of the surfactants, the twin tailed surfactants create a significant mobility reduction, likely due to favorable partitioning into the CO₂ phase. The data covers surfactant structures designed specifically for the CO₂-water interface and can be used by producers and service companies in designing new CO₂-floods, especially in areas that might not have been considered due to problems with reservoir heterogeneity. Second part contains a systematic study of ASG process on carbonate rocks through a series of experiments. The purpose is to demonstrate the performance as well as the potential of ASG as a new EOR technique. In this study, basic concepts in chemical EOR are presented, while the design of chemical formulation, phase behavior, and the role of foam are discussed in details. Experimental results showed relatively good recovery, low surfactant retention. However, pressure drop during chemical injections were high, which indicates the formation of both strong foam and viscous microemulsion at the displacement front when surfactant starts solubilizing oil. Overall, ASG showed good performance on carbonate rocks. Optimization can be made on surfactant formula to form less viscous microemulsion and therefore improve efficiency of the process. / text

Highly fractured carbonate reservoirs are a class of reservoirs characterized by high conductivity fractures surrounding low permeability matrix blocks. In these reservoirs, wettability alteration is a key method for recovering oil. Water imbibes into the matrix blocks upon water flooding if the reservoir rock is water-wet. However, many carbonate reservoirs are oil-wet. Surfactant solution was used to enhance spontaneous imbibition between the fractures and the matrix by both wettability alteration and ultra-low interfacial tensions. The first part of this study was devoted to determining the wettability of reservoir rocks using Amott-Harvey Index method, and also evaluating the performance of surfactants on wettability alteration, based on the contact angle measurement and spontaneous imbibition rate and ultimate oil recovery on oil-wet reservoir cores. The reservoir rocks have been found to be slightly oil-wet. One cationic surfactant BTC8358, one anionic surfactant and one ultra-low IFT surfactant formulation AKL-207 are all found to alter the wettability towards more water-wet and promote oil recovery through spontaneous imbibition. The second part of the study focused on the parameters that affect wettability alteration by surfactants. Some factors such as core dimension, permeability and heterogeneity of porous medium are evaluated in the spontaneous imbibition tests. Higher permeability leads to higher imbibition rate and higher ultimate oil recovery. Heterogeneity of core samples slows down the imbibition process if other properties are similar. Core dimension is critical in upscaling from laboratory conditions to field matrix blocks. The imbibition rate is slower in larger dimension of core. Further, we investigated the effects of EDTA in surfactant-mediated spontaneous imbibition. Since high concentration of cationic divalent ions in the aqueous solution markedly suppresses the surfactant-mediated wettability alteration, EDTA improved the performance of surfactant in the spontaneous imbibition tests. It is proposed in the thesis that surfactant/EDTA-enhanced imbibition may involve the dissolution mechanism. More experiments should be conducted to verify this mechanism. The benefits of using EDTA in the surfactant solution include but not limited to: altering the surface charge of carbonate to negative, producing the in-situ soap, reducing the brine hardness, decreasing the surfactant adsorption, and creating the water-wet area by dissolving the dolomite mineral. / text