Many producing volatile oil reservoirs experience a significant decrease in well deliverability when the bottom-hole pressure of the well falls below the bubble point pressure. This is due to the liberation of a gas phase which resides in the pore space and blocks the flow of the oil phase. This situation is known as "gas blocking". This occurs because the presence of two or three immiscible phases (gas, oil and water) results in a reduction of the oil saturation and a decrease in the oil relative permeability. The main objective of this research was to develop an effective and durable chemical treatment method to improve and/or restore the productivity of volatile oil wells undergoing "gas blocking". The treatment method is based on the use of fluorinated surfactants in tailored solvents to increase the oil relative permeability by changing the wettability of the rock’s surface. High-temperature high-pressure (HTHP) core flood experiments were used to evaluate the uses of fluorinated surfactants under reservoir conditions. Analytical tools such as X-ray photoelectron spectroscopy (XPS), high-performance liquid chromatography (HPLC) and computerized axial tomography (CT Scan) were also used to interpret the experimental results. High-pressure high-temperature (HPHT) coreflood tests showed that the treatments improved the oil and gas relative permeability in both sandstone and limestone cores. This was observed for synthetic volatile oil mixtures with gas-oil ratios (GOR) in the range of 4000 to 13,000 scf/STB at low capillary numbers (Nc) on the order of 1x10-5 to 1x10-6 and for PVT ratios greater than 0.5. The fluorinated chemical treatments were effective in the presence of connate water over the temperature range of 155°F to 275°F. Wettability alteration was measured using contact angle and imbibition rate tests. Results from analytical tools showed that fluorinated surfactants were uniformly adsorbed along the core and the surfactant desorption after treatment was low (10 ppm or less). The gas saturation decreased following treatment and both the oil and gas relative permeability increased. Numerical simulations using the measured relative permeability data were used to estimate the gain in productivity for treated wells. The proposed fluorinated chemical treatments could be used as a preventive treatment or for a damaged well that has already been producing below the bubble point to increase oil production rates and recoverable reserves. / text

The use of compressed CO2 processing to alter the pore size, structure and timescale of silica condensation in surfactant templated silica thin films and powders is investigated by systematically varying the template structure and CO2 processing conditions. Tailoring the mesoporous materials increases its potential applications, as demonstrated in catalysis, drug delivery, chromatographic and electrode applications. This work demonstrates for the first time the applicability of fluorinated surfactants as templates for the synthesis of mesoporous silica thin films by dip coating. Well-ordered films with 2D hexagonal close-packed pore structure are synthesized in an acid-catalyzed medium using three cationic fluorinated templates of varied tail length and branching (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and (CF3)2CFC5F9C2H4NC5H5Cl). CO2 processing of the fluorinated templated silica results in a significant and controlled increase in pore diameter relative to the unprocessed films. The pore expansion is significantly greater compared to the negligible expansion observed in hydrocarbon (C16H23NC5H5Br) templated silica. The greater swelling of the fluorinated templates is attributed to the favorable penetration of CO2 in the CO2-philic fluorinated tail and the relative solvation of each template is interpreted from their interfacial behavior at the CO2-water interface. The CO2 based pore expansion observed in fluorinated surfactant templated films is extended successfully to base-catalyzed silica powders templated with a fluorinated surfactant (C6F13C2H4NC5H5Cl). Pore expansion in silica powders is significantly less than in acid catalyzed films and demonstrates the effects of pH on surfactant selfassembly in CO2 and increased silica condensation at basic conditions, which inhibits pore expansion. Finally, the use of fluorescence probe molecules is demonstrated for in-situ monitoring of the of CO2 processing of surfactant templated silica films to provide time dependent data on the local environment and dynamics of CO2 penetration. CO2 uptake occurs in surfactant tails even for hydrocarbon templates (C16H23N(CH3)3Br and C16H23NC5H5Br), which display negligible CO2 based swelling of the resulting pores. The timescale of silica condensation increases significantly in the presence of CO2 suggesting opportunities for structure alteration through application of external forces, such as magnetic fields and change in substrate chemistry and system humidity

Fluorinated systems are defined by unique properties that offer advantages in drug delivery, material synthesis and industrial applications. In comparison to their hydrocarbon counterparts, the design of fluorinated solutes for tailored applications is limited by the inability to predict the effect of fluorination on phase behavior. This work examines and interprets the influence of fluorination on the phase behavior of fluorinated solutes and surfactants, with emphasis on their impact on vesicle bilayers. Thermodynamic partitioning of functionalized series of fluorinated and hydrocarbon nicotinate prodrugs fashioned to promote solubility in a fluorocarbon solvent (perfluorooctyl bromide; PFOB) is measured. Predictive approaches are also employed to describe partitioning of these nicotinates between immiscible phases relevant to drug delivery. The findings reveal no strong correlation of the partitioning trends with biological markers of cytotoxicity and prodrug uptake for PFOB mediated delivery. However, partitioning in model membranes (liposomes), which, increases with the hydrophobicity of the perhydrocarbon nicotinates, suggests incorporation in a cellular matrix is chain length dependent. The impact of incorporating fluorinated surfactants in catanionic vesicles, which form spontaneously in dilute aqueous solutions and serve as potential substitutes to conventional meta-stable liposome-based vesicles, is studied. Much larger isotropic vesicle regions are observed in the phase map of the partially fluorinated catanionic surfactant pair, cetylpyridinium bromide/ sodium perfluorooctanoate (CPB/SPFO) than in fully fluorinated HFDPC (1,1,2,2,-tetrahydroperfluorododecyl pyridinium chloride )/SPFO. Fluorescence probing of the vesicle bilayers suggest more fluid bilayers in CPB/SPFO than in HFDPC/SPFO due to better chain packing in the fully fluorinated bilayer. However, the vesicle region is expanded in more asymmetric fluorinated bilayers of HFDPC/SPFH (sodium perfluorohexanoate). The increased chain asymmetry in HFDPC/SPFH results in reduced packing density and more fluid bilayers than in HFDPC/SPFO. The robustness of CPB/SPFO and HFDPC/SPFO vesicles is demonstrated in the synthesis of silica hollow spheres by templating and the retention of encapsulated solutes. Higher colloidal stability of the silica spheres is achieved in HFDPC/SPFO relative to CPB/SPFO due to the barrier effect of the fluorinated bilayer. Similarly, higher solute retention in HFDPC/SPFO is observed. The modulation of phase behavior with fluorination offers opportunities in tunable applications of fluorinated bilayers.

Perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs)are anthropogenic fluorinated surfactants that have been detected in almost every environmental compartment studied, yet their production and applications are far outweighed by those of other higher molecular weight fluorinated surfactants used in commerce. These fluorinated surfactants are widely incorporated in commercial products, yet their post-application fate has not been extensively studied. This thesis examines various biological and environmental processes involved in the fate of these surfactants upon consumer disposal. Specific focus was directed towards the environmental chemistry of polyfluoroalkyl phosphate esters (PAPs), perfluoroalkyl phosphonates (PFPAs), and perfluoroalkyl phosphinates (PFPiAs), and their potential roles as sources of perfluoroalkyl acids (PFAAs) in the environment. PAPs are established biological precursors of PFCAs, while PFPAs and PFPiAs are newly discovered PFAAs in the environment. Incubation with wastewater treatment plant (WWTP) microbes demonstrated the ability of PAPs to yield both fluorotelomer alcohols (FTOHs), which are established precursors of PFCAs, and the corresponding PFCAs themselves. WWTP biosolids-applied soil-plant microcosms revealed that PAPs can significantly accumulate in plants along with their degradation metabolites. This has implications for potential wildlife and human exposure through the consumption of plants grown and/or livestock raised on farmlands that have been amended with contaminated biosolids. A number of compound-and environmental-specific factors were observed to significantly influence the partitioning of PFPAs and PFPiAs between aqueous media and soil, as well as, aquatic biota during sorption and bioaccumulation experiments respectively. In both processes, PFPAs were primarily observed in the aqueous phase, while PFPiAs predominated in soil and biological tissues, consistent with the few environmental observations of these chemicals made to date. Detection of the PAP diesters (diPAPs), PFPiAs, and fluorotelomer sulfonates (FTSAs),all of which are used commercially, in human sera is evidence of human exposure to commercial fluorinated products, but the pathways by which this exposure occurs remain widely debated. Overall, this work presents novel findings on the environmental fate of commercial fluorinated surfactants and each of the process studied shows a clear link between the use of commercial products and the fluorochemical burden currently observed in the environment.

Perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs)are anthropogenic fluorinated surfactants that have been detected in almost every environmental compartment studied, yet their production and applications are far outweighed by those of other higher molecular weight fluorinated surfactants used in commerce. These fluorinated surfactants are widely incorporated in commercial products, yet their post-application fate has not been extensively studied. This thesis examines various biological and environmental processes involved in the fate of these surfactants upon consumer disposal. Specific focus was directed towards the environmental chemistry of polyfluoroalkyl phosphate esters (PAPs), perfluoroalkyl phosphonates (PFPAs), and perfluoroalkyl phosphinates (PFPiAs), and their potential roles as sources of perfluoroalkyl acids (PFAAs) in the environment. PAPs are established biological precursors of PFCAs, while PFPAs and PFPiAs are newly discovered PFAAs in the environment. Incubation with wastewater treatment plant (WWTP) microbes demonstrated the ability of PAPs to yield both fluorotelomer alcohols (FTOHs), which are established precursors of PFCAs, and the corresponding PFCAs themselves. WWTP biosolids-applied soil-plant microcosms revealed that PAPs can significantly accumulate in plants along with their degradation metabolites. This has implications for potential wildlife and human exposure through the consumption of plants grown and/or livestock raised on farmlands that have been amended with contaminated biosolids. A number of compound-and environmental-specific factors were observed to significantly influence the partitioning of PFPAs and PFPiAs between aqueous media and soil, as well as, aquatic biota during sorption and bioaccumulation experiments respectively. In both processes, PFPAs were primarily observed in the aqueous phase, while PFPiAs predominated in soil and biological tissues, consistent with the few environmental observations of these chemicals made to date. Detection of the PAP diesters (diPAPs), PFPiAs, and fluorotelomer sulfonates (FTSAs),all of which are used commercially, in human sera is evidence of human exposure to commercial fluorinated products, but the pathways by which this exposure occurs remain widely debated. Overall, this work presents novel findings on the environmental fate of commercial fluorinated surfactants and each of the process studied shows a clear link between the use of commercial products and the fluorochemical burden currently observed in the environment.

This Thesis presents studies of molecular association in aqueous solution and at the liquid/solid interface. The investigated molecular systems range from self-aggregating surfactants to hydration water in contact with micelles or individual molecules. In most studies, combinations of various NMR methods were applied. These vary from simple chemical shift and intensity measurements to more elaborate self-diffusion and intermolecular cross-relaxation experiments. Non-ideal mixed micelles of fluorinated and hydrogenated surfactants were studied by an experimental procedure that allows an analysis in terms of micellar structure, using a minimal number of initial assumptions. Quantitative conclusions about micro-phase separation within mixed micelles were obtained within the framework of the regular solution theory. Additionally, NMR was introduced and developed as a powerful method for studying adsorption of surfactants at solid interfaces. Adsorption isotherms for pure and mixed surfactant systems and non-ideal mixing behavior of fluorinated and hydrogenated surfactants at solid surfaces were quantified. Fluorosurfactant-protein association was investigated using the methods described. Intermolecular cross-relaxation rates between solute and solvent molecules were recorded at several different magnetic fields. The results reveal strong frequency dependence for both small molecules and micelles. This finding demonstrates that intermolecular cross-relaxation is not solely controlled by fast local motions, but also by long-range translational dynamics. Data analysis in terms of recently developed relaxation models provides information about the hydrophobic hydration and micellar structure. / QC 20100914