Colloidal gas aphrons (CGAs) recently used as part of water-based drilling fluids have been found effective in controlling the filtration rate by bridging the pores of the reservoir rock and therefore, reducing the formation damage. This research aims to generate colloidal gas aphrons (CGA) in oil based drilling fluids; to study stability, rheology and the filtration loss characteristics of CGAs and to investigate formation damage properties of CGAs as a drilling fluid. Aphrons were generated in mineral oil using a polymer-surfactant mix. Based on how changing the polymer and surfactant concentration affects the physico-chemical characteristics of the fluid, an optimum formulation for the aphron drilling fluid was suggested. The stability of microbubbles was investigated by looking at the effects of time, temperature and pressure on the aphron yield and bubble size distribution. Effects of temperature and pressure on the density of the oil-based aphron fluids have been investigated. Based on the PVT analysis results, an equation of state was proposed. Finally, the performance of the oil-based aphron fluid in porous media was investigated. The effects of changing the CGA fluid injection rate, the type of saturating fluid and the wettability of the porous media on the pressure drop were examined. An assessment of the formation damage following the oil-based CGA fluid injection was also made. / Petroleum Engineering

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A microbubble dispersion (MBD) was used to supply oxygen for an aerobic fermentation of Baker's yeast. The 1-liter microbubble dispersion generator supplied bubbles for 20-liter and 50-liter working volume fermentations in a 72-liter pilot scale fermenter. The microbubbles were stabilized by the surfactants naturally present in the culturing broth medium. The growth patterns of yeast Saccharomyces cerevisiae, cultured at agitation speeds of 150 rpm and 500 rpm, were compared for oxygen supplied by ordinary air sparging and by MBD sparging. Both air sparged and MBD systems were supplied air at equivalent volumetric flow rates. The volumetric oxygen transfer coefficients (KLa) were estimated by the yield coefficient method. The KLa values increased from 142.5 to 458.3 h-1 and from 136.1 to 473.3 h-1 for 20- and 50- liter runs, respectively, as the agitation speed was increased from 150 to 500 rpm in the ordinary air sparged fermentations. The oxygen transfer coefficients in the MBD sparged fermentations were found to be independent of the fermenter agitation speed at approximately 480 h-1 for 20-liter runs and 340 h-1 for 50-liter runs. The growth rates for MBD at 150 rpm were essentially equivalent with air sparged fermentations at 500 rpm. The total power consumption per unit volume of broth for the 150 rpm, MBD fermentation was 68% lower than the 500 rpm, air sparged run for the 20-liter fermentations and was 55% lower for the 50-liter fermentations. / Master of Science

La tesi di dottorato è stata sviluppata all'interno del progetto nazionale Valorvitis ed è suddivisa in due parti. La prima riguarda la caratterizzazione chimica di sei estratti di vinacce d’uva ottenute diverse varietà di uva: tre a bacca rossa( Pinot Noir, Barbera e Nebbiolo) e tre a bacca bianca (Moscato, Muller Thurgau e Chardonnay). Ogni estratto è stato caratterizzato per contenuto e composizione in composti fenolici. La seconda attività consiste nello studio di un metodo alternativo di estrazione-purificazione basato sull'impiego di Gas Aphron Colloidali (CGAs) con la finalità di ridurre i costi di processo, la quantità di solvente da utilizzare durante la fase di estrazione e, allo stesso tempo, aumentare il grado di purezza dell’estratto in termini di contenuto polifenolico. / The present PhD thesis work was carried out under the framework of the Valorvitis.Extracts have been obtained from different red (Pinot Noir, Barbera and Nebbiolo) and white (Moscato, Muller Thurgau and Chardonnay) grape marcs and quantitatively analysed for the content of total phenolics, tannins, anthocyanins, cinnamic acids, flavonoids, flavonols, sugars (glucose and fructose) and for the anti-oxidant power (AOP). A new extraction-purification process based on CGAs application has been investigated. CGAs were first reported by Sebba (1987) as micro bubbles, with dimension among 10–100 μm, composed of a gaseous inner core surrounded by a thin surfactant film, which are created by intense stirring of a surfactant solution above its critical micellar concentration. Surfactants are able to catch phenolics thanks to both electrostatic and hydrophobic interactions depending on the surfactant (ionic or non-ionic) and on the phenolic compound. In this project the low-cost non-ionic food grade surfactant Tween 20 was used.