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BSEE facility conducts response testing Tests technology for detection of oil in sea ice, technology for monitoring of dispersed oil and two new oil skimming systems Alan Bailey Petroleum News
With an offshore oil spill being a worst-case nightmare both for the oil industry and for anyone concerned about protecting the marine environment, research continues in how to most effectively deal with oil discharged into seawater. In its latest newsletter, Ohmsett, the Bureau of Safety and Environmental Enforcement’s New Jersey test facility, has reported some recent testing of new response technologies, including new methods for the monitoring of spilled oil and new oil skimming systems.
The Ohmsett facility consists of a long pond-like tank that can simulate a variety of ocean conditions, for the testing of oil spill response equipment and technologies.
Measuring droplet size One project conducted at Ohmsett this year involved the evaluation of a new acoustic technique for measuring oil droplet sizes, when crude oil released underwater is mixed with oil dispersant in the presence of methane gas, a situation which prevailed during the Gulf of Mexico Deepwater Horizon disaster. The testing formed part of a project funded by BSEE and conducted by Paul Panetta from Applied Research Associates Inc. and a team of researchers from Virginia Institute of Marine Science and College of William and Mary.
Laser-based optical systems which are used for measuring subsurface oil droplets run into problems when high concentrations of oil obstruct the passage of light through the fluids. The concept behind the new technology is, instead, to use a sonar system to generate an acoustic image of the oil plume, measuring the way in which the sound frequency responds to the scattering effect of the gas and oil.
“Acoustic measurements are needed because the current methods using the LISST (laser in-situ scattering transmissiometer) are not suitable for subsurface releases where the concentration of oil is too high for the LISST,” Panetta explained. “The LISST also ceases to operate when its optical window becomes coated with oil.”
Measuring the resonance The Ohmsett testing involved fitting oil and dispersant nozzles, and a gas bubbler, onto a submersible frame placed in the facility’s tank. Upon the subsurface release of oil, dispersant and methane, instruments used low-frequency sound to excite the acoustic resonance of gas bubbles and the acoustic response of both the oil and the gas, with high frequency sound also being used to measure the response of oil and gas to the acoustic signals.
LISST equipment was also used for measuring oil droplet and gas bubble volume and size distributions, presumably to verify and calibrate the results of using the acoustic technique.
Oil and ice coverage Another project at Ohmsett this year involved improvements to the way in which the facility measures oil and ice coverage when testing spill response techniques in simulated sea-ice conditions - the facility has particular value in this type of testing, which can be difficult or impossible to conduct in the ocean itself.
Ohmsett uses photographic imagery for measuring the ice and oil, through a very time consuming process involving a pixel-by-pixel analysis of the imagery. A project funded by BSEE and conducted by MAR Inc. and Ocean Imaging of California involved the development of imaging technology that enables measurement at near real-time speeds, thus presumably improving the efficiency with which spill response tests can be conducted in ice-laden water.
The project employed existing technology to collect camera images and thermal data from the Ohmsett tank, using engineered saltwater ice. The researchers then used the collected data to calibrate and refine computer software used for image and data processing. The team returned to Ohmsett to test the results. The consequence was the construction of a compact device that can be deployed to map the extent of a simulated oil spill, differentiating between oil, ice and open water, and providing data about the thickness of oil between and around ice blocks.
Skimming systems Also this year, Ohmsett has provided the venue for the testing of two new oil skimming systems.
One of these, developed by French company Ecoceane and called the Workglop 128, consists of a 40-foot, self-propelled skimming vessel, with integrated boom arms and an integrated skimming system that sucks oil from the water surface. The vessel was tested at speeds ranging from one to three knots in both calm and wave conditions, using a medium oil and then a heavy oil.
“We have worked for seven years on the research and development using advanced software simulations and prototypes to achieve the technology represented by the Workglop 128,” said Benjamin Lerondeau, technical manager for Ecoceane. The system can collect oil in wave conditions and follow the movement of the oil, while also creating less emulsion when collecting fluids than other systems, Lerondeau said.
Potential future developments include fitting the technology to larger vessels, not specifically intended for oil spill response, and the development of a system for the recovery of oil in icy water, he said.
Oil shaving Another skimming system tested at Ohmsett, the OilShaver system, developed by Norwegian company Husen AS, consists of a boom-like structure which is towed through the water and which shaves oil from the water surface. The recovered oil is directed into a containment area, from where it flows into a chamber with an oil skimmer and a hydraulic offload pump. Apparently, the system had been tested previously at Ohmsett but required some redesign following trials of the system during a Norwegian oil-on-water exercise.
Ingvar Huse, the system designer, said that the latest testing at Ohmsett demonstrated that system is now ready for the marketplace.
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