Measurement of Interfacial Tension in Hydrocarbon/Water/Dispersant Systems at Deepwater Conditions

Document Type

Article

Publication Date

4-28-2014

Abstract

This chapter reports on an experimental study conducted to measure hydrocarbon/water/dispersant interfacial tension (IFT) at simulated conditions of pressure and temperature pertaining to the Deepwater Horizon oil spill. The remedial subsea application of chemical dispersants draws interest to evaluate the interfacial interactions between oil and water at such great water depths. Most importantly, a quantification of the IFT between spilled oil and seawater at deepwater conditions can provide insight into the effectiveness of the chemical dispersion of spilled oil. An optical cell apparatus capable of withstanding such extreme conditions was designed, fabricated, and utilized to make the IFT measurements at deepwater conditions of high pressure and low temperature. Accurate fluid density measurements, which are essential for precise IFT determination, were made using a high-quality density meter and were used to calculate the IFT by the computerized pendant drop method. The influence of pressure, temperature, water salinity, and dispersant concentration on the IFT was each investigated independently. The effect of water depth was also studied by simulating the conditions of pressure and temperature simultaneously. The effectiveness of Corexit® 9500 in dispersing Macondo crude oil was quantified through the reduction in the oil-water IFT. The dispersion of the crude oil was also compared to that of n-octane at similar deepwater 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 10,000ppm dispersant-in-oil concentration, the oil adopted the shape of a continuous stream instead of breaking up into small droplets. Accordingly, ultralow oil-water IFT was not achieved despite such a high dispersant concentration, indicating ineffective chemical dispersion at seafloor conditions.

Publication Source (Journal or Book title)

Oil Spill Remediation: Colloid Chemistry-Based Principles and Solutions

First Page

295

Last Page

315

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