Master of Science in Petroleum Engineering (MSPE)
The events of the Deepwater Horizon oil spill in the Gulf of Mexico were associated with great water depths that made it difficult to understand the behavior of the spilled oil as it came in contact with the seawater. The remedial subsea application of chemical dispersants draws interest to evaluate the interfacial interactions between the oil and water at such great water depths. Most importantly, a quantification of the interfacial tension (IFT) between the spilled oil and seawater at deepwater conditions can provide insight into the effectiveness of the chemical dispersion of spilled oil. In this study, Macondo crude oil and synthetic seawater samples were used to measure the oil/water IFT by the Pendant Drop method at deepwater conditions of pressure and temperature. A laboratory apparatus capable of representing such conditions was designed and established to enable IFT and density measurements. Reagent grade n-octane was also used to compare its behavior to that of crude oil. The effectiveness of a commercial dispersant, Corexit® 9500, was assessed through the evaluation of the magnitude of the reduction in the hydrocarbon/water IFT. The influence of pressure, temperature, water salinity and dispersant concentration on the IFT was each studied independently as well. The measured oil/water IFT decreased from 25.69 to 22.55 mN/m as both pressure and temperature were changed from water surface to seafloor conditions. The dispersant was capable of reducing the IFT by 70 % from its original value at the water surface while only a 50 % reduction was observed at seafloor conditions. The low temperature associated with the seafloor was determined as the main factor responsible for deteriorating the dispersant effectiveness as pressure had a relatively smaller effect on the IFT. The dispersant was also observed to perform better when dissolved in the crude oil as compared to the time it was dissolved in the water. However, at 10,000 ppm dispersant-in-oil concentration, the oil adopted the shape of a continuous stream instead of breaking up into small droplets. Accordingly, ultra-low oil/water IFT was not achieved, despite such a high dispersant concentration, indicating ineffective chemical dispersion at seafloor conditions.
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Abdelrahim, Mohamed, "Measurement of interfacial tension in hydrocarbon/water/dispersant systems at deepwater conditions" (2012). LSU Master's Theses. 394.
Rao, Dandina N.