In Situ Measurement of Oil Slick Thickness

During an oil spill response, one of the main challenges is the ability to measure, in situ and in real time, the oil slick thickness at different locations throughout the slick. This paper presents an instrument that can respond to this need by employing a capacitive-based sensor designed for oils of different viscosities. There are three main advantages to our proposed instrument over the prior art: first, it can operate in dynamic environments, measuring oil thicknesses under wavy sea conditions and while dragged. Second, our proposed design requires only initial factory calibration; once a baseline capacitance is recorded in the air, the instrument can measure the thickness of oils under varying environmental conditions and for both light and crude oils. Third, using solutions in both software and hardware, our instrument mitigates the effect of oil fouling, an issue long considered problematic in the community of oil thickness measurement. The proposed instrument was tested extensively at the Ohmsett Facility, first in a laboratory, then inside a large outdoor tank, by dragging the sensor at different velocities, through waves of varying amplitude and frequency. Results demonstrated the accuracy, repeatability, and robustness of the proposed instrument using multiple oil types and thicknesses under static and dynamic conditions.