Abstract

The ability to detect oil spills reliably, as well as to carry out fast and effective recovery operations, is the onus of any extraction company working in the field. Unfortunately, detecting and tracking oil spills is no easy task. By employing a combination of radar, optical and infrared (IR) sensors, operators are empowered to not only detect, characterise and track spills, but also to locate "combatable oil", i.e. where oil is at its thickest, and therefore, where recovery efforts should be mobilised.

Radar-based oil spill detection (OSD) systems can be supported to great effect by the addition of optical and IR sensors. Real-time evaluation of oil spill thickness using such a combination of sensors is achieved thanks to the exploitation of some of oil's natural properties.

The first of these properties is that oil will interact with the surface of the sea, affecting radar backscatter imagery. When oil is present on the sea surface it impacts the surface tension of the water and, as a result, wind does not create the same short-wave patterns on the surface as in areas free of oil. This means that areas covered with oil will not exhibit backscatter in the same way as areas free of oil.

The second of these properties is that when oil and water are at the same temperature, oil emits less infrared energy than water, meaning that oil will appear cooler than water when observed using an infrared sensor. Additionally, unlike water, oil absorbs almost all light in the visible part of the electromagnetic spectrum, meaning that thick oil (where the upper layers of oil are insulated from the water below) will heat up in the daytime and become hotter than water. At night, the inverse will be observed, with the upper layer of thick oil cooling to below the temperature of the surrounding water.

As a result of these properties, areas of the sea that are polluted with oil will appear differently on the various sensor displays based on the thickness of the spill, the wind and current conditions, and whether it is day or night. By harnessing the combination of radar, optical and infrared sensors, operators can determine the location of spills in daylight or darkness. They can also determine the leading edge of the spill, allowing for an understanding of its trajectory, and where recovery efforts should focus their attention.

Furthermore, automatic tracking and historical insights can add much-needed information to user interface displays, giving operators comprehensive situational awareness.

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