Introduction
Last month, the 807ft tanker Eagle Otome collided with a barge at Port Arthur, Texas, USA, spilling over 450,000 gallons of crude oil. On 31st July 2009, the 167m bulk carrier Full City ran aground off southern Norway. Approximately 212 tonnes of oil emulsions were subsequently recovered from the waters. The damage from an oil spill can economically and environmentally devastate an area for many years. The cost of clean up can be equally horrifying. Statoil of Norway takes this issue seriously and has reviewed Oil Spill Detection (OSD) products from a number of suppliers. In December 2009, VisSim AS of Norway participated in trials conducted by Statoil, with the objective of assessing the longrange detection potential of radar-based OSD products. This article provides an overview of VisSim’s results in these tests.
Test conditions
The tests were conducted from the Troll C offshore platform, using Sea Hawk SHN-4000 radar. The radar provided four identical radar video outputs, enabling each suppliers’s system under evaluation to be separately, but simultaneously, connected to the same radar output signals. In addition, the radar was able to change between vertical and circular polarisation, and had three operator-selectable PRFs. Each supplier’s equipment was located in a separate room, so results could be individually viewed and assessed by Statoil
The VisSim OSD3000 System
Oil spill detection (OSD) is a valuable tool for minimising the impact of an oil spill; however, its benefits are significantly increased if it is integrated with other systems monitoring maritime activity. VisSim developed the OSD and VTMS technologies to be fully integrated. In fact, the radar video processing for spill detection is based upon the same VisSim technology used for tracking maritime vessels. This means a standard VTMS solution can easily be upgraded to provide automatic OSD and, with real-time tracking of both vessels and spills, the correlation between spill and polluter can be quickly determined. VisSim provided a PC with OSD3000 software, which was able to track both the oil spill and all vessel targets in the area.
Oil spill trial plan
Statoil set the plan for the oil spill trial: a slow-moving vessel would release an oil emulsion pollutant at a fixed rate, for a defined period of time. Halfway through the planned release, the vessel would change course. For trials conducted close to the offshore platform, the radar equipment would be set in short pulse mode. For tests further from the platform, the radar would be set to medium pulse.
First release of oil
After the vessel Normand Draupler had released the oil, there was a short delay while the oil began to spread. The first oil slick spread to cover an area of approximately 850m by 250m (area approximately 182,520m2; perimeter approximately 2,000m). The distance from the radar to the closest oil spot was measured at 2,100m. During the first oil release, the radar was operating on short pulse with circular polarization. VisSim’s OSD3000 successfully detected and plotted the oil spill on the traffic display automatically (no operator intervention was required). From the VTMS operational point of view, the traffic display (Figure 1: left) shows the track of the vessel and illustrates how this facility can identify the polluter. In this way, the integrated technology clearly provides benefits that will aid maritime authorities and VTMS operators to improve environmental protection.
