Improved oil recovery sensor

Abstract

A new type of sensor was developed to measure oil content in seawater or other highly saline waters for offshore oil spill recovery operations. Currently responders do not have a quantitative method for knowing in real time how much water they are collecting with their oil. The sensor combines two measurement principles: a dielectric measurement and an eddy current loss measurement. The dielectric measurement is used for high oil content mixtures and emulsions that are of water-in-oil type, leading to a relatively low electrical conductivity. The eddy current measurement is used for low oil content mixtures and emulsions, that are of oil-in-water type, and have high electrical conductivity. Both measurements are carried out at high frequencies, in the 10–50 MHz range, which makes the measurement insensitive to the type of oil and its dispersion, as well as polarization effects, while maintaining sufficiently large skin penetration depths. The sensor was demonstrated in laboratory tests as well as at the Bureau of Safety and Environmental Enforcement’s (BSEE’s) Ohmsett testing facility using mixtures of several crude and refined oils with water salinities in the 1–5% range. In all cases, the sensor provided a reliable oil content measurement with average errors of about 3% in a laboratory setting and about 7% during Ohmsett testing, which is sufficient for offshore oil recovery operations. Having this information will allow a responder to make on-the-spot adjustments to maximize recovery efficiency. In addition, the sensor will provide data on overall oil/water collection during a response. Other uses include oil and gas industry applications, where oil-water mixtures need to be evaluated for oil content or, equivalently, for water cut, and where high-water salinity prevents use of traditional sensors based on the dielectric principle alone.