The feasibility or otherwise of responding effectively to an oil spill in ice-infested waters has for several years been one of the core questions in the often contentious debate about whether or not oil and gas development should take place in the Arctic offshore.
And, working on the basis that knowledge and data are the keys to addressing Arctic oil spill concerns, a joint industry program coordinated by Norwegian research company SINTEF and begun in early 2006 has completed a series of research projects, establishing facts about the properties of spilled oil in icy water and the effectiveness of potential response techniques.
Oil on waterThe researchers were able to obtain permission from the Norwegian government to put actual crude oil into the sea in carefully controlled conditions, thus enabling the testing of oil behavior and cleanup effectiveness in ice conditions closely similar to those that might be encountered in an Arctic oil spill emergency. So, in addition to carrying out a variety of laboratory tests, the researchers were able to run some experiments in fjord ice at SINTEF’s research facility at Svea in Svalbard, as well as carry out larger scale tests in sea ice in the Barents Sea.
The end results of the research include a dataset for the development of oil spill contingency plans; a web-based oil spill response guide for Arctic and ice-covered waters; and some new technologies for offshore Arctic cleanup.
And on March 14 in Anchorage, Alaska, members of the program team presented their findings to an audience of oil industry personnel, government officials and people from environmental organizations.
The Norwegian Research Council and oil companies Statoil, Shell, ConocoPhillips, Chevron, Agip KCO and Total sponsored the research, with numerous other entities contributing to the program, including the U.S. Minerals Management Service, Alaska Clean Seas, the Cordova-based Oil Spill Recovery Institute and the University of Alaska Fairbanks.
Weathers slowlyA key finding from the research was that, although different types of crude oil would behave in different ways following an oil spill, in general oil breaks up and mixes with water much more slowly in Arctic conditions than would spilled oil in, say, temperate latitudes. At the same time, the presence of pack ice can provide a natural barrier to oil movement, thus acting as a system of natural booms that can prevent the oil from spreading over an excessively wide area.
The slow-weathering phenomenon, a consequence of relatively low water temperatures and low levels of wave action, would extend the time window during which some oil recovery techniques could be applied, thus giving responders more time to plan their actions and move any necessary equipment to the response site. Weathering effects include the mixing of oil with seawater, the release of some oil components into the water column, and the general degradation of the oil.
A field test on one type of crude oil found that in heavy broken ice conditions the water content of the oil slowly grew to around 40 percent after more than three days on the water, while in open water the same crude attains a water content in excess of 70 percent within a just a few hours.
But the tests also showed wide variations in weathering rates, depending on the type of crude oil involved.
In-situ burningThe slow weathering of spilled oil in icy water would aid in the in-situ burning of oil, a technique thought to be particularly appropriate for oil spill response in the Arctic, Steve Potter, from oil spill consulting firm St. Ross Environmental Research and a member of the research team, told the Anchorage audience.
“For a lot of the spills that we might be concerned about in Arctic regions, we really think that in-situ burning is going to be a primary countermeasure,” Potter said. “… It offers some significant advantages over mechanical containment and recovery in terms of the overall effectiveness of the technique, and also in terms of the logistics involved to mobilize an effective response.”
And much work has already been done to determine the effectiveness of in-situ burning in Arctic conditions, Potter said.
As water mixes with oil during the weathering of the oil, the oil becomes increasingly difficult to burn. But field tests on one type of crude oil showed that although the degree of weathering did not markedly change the effectiveness of a burn once the burn had started, the time period during which it was feasible to ignite the oil increased from less than a day in open water to more than three days in the slow weathering environment of a 90 percent ice cover. However, the weathering characteristics specific to each particular oil are also critical in determining the time window for a burn, Potter said.
Thickness of the slickThe presence of sea ice also tends to limit the spreading of an oil slick on the water surface, thus increasing the slick thickness and reducing evaporation rates, further extending the time period during which the oil can be ignited, Potter said.
“The key parameter for an effective burn is developing a good initial slick thickness,” he said.
In a test conducted in the Barents Sea, oil was ignited after weathering on the water for five days and the resulting burn proved 90 percent effective, he said.
To find a way of burning oil in situations where the sea-ice cover was insufficient to constrain the oil slick and maintain slick thickness, the research team tried the use of herding agents, chemicals that cause a slick to contract when added in small quantities.
In fact, by increasing the thickness and concentration of an oil slick, the use of chemical herders might prove beneficial in conjunction with other spill response techniques, such as the mechanical removal of the oil, Potter said.
Tests at Svalbard demonstrated that the application of a herding agent to oil that was spreading unconstrained near an ice floe enabled an estimated 90 percent of the oil to be burned from the water surface, with herders continuing to concentrate the oil while the burn progressed, Potter said.
Another technique for constraining and thickening an oil slick for burning is the use of fire boom, a special type of floating boom constructed from fire-proof material and sometimes water cooled. A fire-boom test involved towing a length of boom in a U configuration between two vessels, to gather some floating ice. About 1,000 gallons of oil was then discharged into the water around the gathered ice. A subsequent burn resulted in the removal of an estimated 98 percent of the oil, Potter said.
Dispersant applicationThe research team also found that the relatively slow weathering of oil in icy conditions expands the time window during which it would be possible to apply dispersant chemicals, as an alternative to removing or burning the oil.
Dispersants work somewhat like dish soap, enhancing the natural action of waves in the sea in breaking the oil into tiny droplets that drift into the upper 30 feet or so of the water column, with the size of the droplets making them especially susceptible to biological degradation, said SINTEF researcher Per Daling.
“The aim of using dispersant is to remove the spilled oil from the surface by transferring it and diluting it into the water column,” Daling said.
To tackle the issue of spraying dispersant onto oil in water around ice floes, the researchers successfully tested the use of maneuverable spray arms, deployed from a vessel and somewhat similar to the devices used to spray de-icing fluid onto aircraft wings. And, since in heavy ice conditions there is relatively little wave action to drive the dispersal of the oil, the testers used the prop wash or jet motors of response boats to agitate the water and hence thoroughly mix the water with the potion of oil and dispersant.
The result turned out to be a higher level of oil dispersion than would typically be achieved in open water using wave action rather than boat thrusters to break up the oil.
“The results from this JIP verified the potential for using dispersant in ice-covered areas and the results here form a good basis for further development of technology and also operational response strategies for using dispersants in high ice coverage,” Daling said.
Mechanical removalThe mechanical removal of oil from the water’s surface using devices known as skimmers is a very common oil spill response technique in open sea water. However, although the presence of sea ice could assist this technique by blocking oil movement and corralling the oil slick, the presence of ice in the water presents some significant challenges. In particular, the ice can obstruct or clog the skimmer mechanism.
People have evaluated skimmer designs for the segregation or deflection of ice during skimming operations. And conventional thinking, following a Canadian report in 1992, is that skimmers in which brushes lift oil from the water show the highest potential for successful use in sea-ice conditions, said Ivar Singsaas, a member of the SINTEF research team. Skimmers that mop up oil using a form of absorbent rope are also effective in sea ice, he said.
For field testing in actual sea ice, the SINTEF researchers decided to try two existing skimmer models, each involving a brush skimmer design with rotating cylindrical drum brushes. Both skimmers proved quite effective in removing oil from ice-laden water, with one skimmer achieving higher recovery rates that the other. Overall skimming effectiveness is sensitive to the precise ice conditions and the type of oil being recovered, Singsaas said.
The research team also tested an early prototype of a floating, self-propelled skimmer, designed to operate in undisturbed water at some distance from a support vessel. This skimmer showed good ice handling capabilities but is still under development.
“The mechanical recovery of oil spills in ice is possible,” Singsaas said, in summarizing the research results. In the absence of small ice fragments or slush ice in the water, oil recovery rates may be similar to those achievable in open water, he said.
Oil detectionIn addition to testing techniques for cleaning up spilled oil, the researchers in the SINTEF program tried the use of a wide variety of techniques to detect the oil that had been discharged into the environment for the testing. Oil detection will likely prove a critical component of any oil spill response in conditions where snow and ice are prevalent.
The team found that ground penetrating radar, using a small radar system slung below a helicopter, was particularly effective in locating oil trapped below ice and snow. Vessel-based marine radar systems would also appear to have some potential in detecting oil slicks in open drift ice.
Vessel-based, aircraft-based or hand-held infrared detection equipment seems to offer much promise for locating oil on water between ice floes, with infrared detection from aircraft overflying a spill area seeming to have the greatest potential.
However, trained dogs also proved remarkably adept at finding even quite small volumes of oil in snow and ice.
“The dogs proved very capable in being able to not only operate in pretty extreme conditions for quite a few days at a time, but also to really successfully define borders of oil spills and to actually pinpoint in many cases the boundaries of the hydrocarbon plume that they were smelling from a large distance,” said David Dickins of DF Dickins Associates.
The team also tested some satellite-based surveillance techniques, including synthetic aperture radar. These techniques would seem to have particular value in monitoring ice conditions, to provide information helpful in planning and managing a spill response project.
And a key lesson from the tests was that people need a variety of different oil detection techniques for use in a flexible way determined by the particular oil spill situation, Dickins said.