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Belore R.,Sl Ross Environmental Research
Proceedings of the 38th AMOP Technical Seminar on Environmental Contamination and Response | Year: 2015

A study was conducted by SL Ross for the U.S. Bureau of Safety and Environmental Enforcement (BSEE) to provide information to support dispersant use decision-making with respect to oil spill chemical dispersant effectiveness under the environmental conditions likely to be encountered in the U.S. Beaufort and Chukchi Seas. This paper discusses the dispersant effectiveness testing conducted in the study. Interested readers can acquire the full research report from BSEE (SL Ross 2014). A suite of dispersant effectiveness tests using the SL Ross meso-scale wind-wave tank on four Alaskan crude oils with four water salinities were conducted to shed more light on the effectiveness of a marine dispersant over a range of water salinities under high energy breaking wave conditions. Alaska North Slope, Endicott, Northstar and Kuparuk crude oil were used in the testing. Tests were conducted on fresh, evaporated and evaporated plus emulsified crude oils. Tests were conducted in water with salinities of 5, 10, 20 and 30 ppt. All tests were conducted with a water temperature of 10 °C. Corexit 9500 was applied at a dispersant to oil ratio of 1:20 in all tests. The fresh oils were more effectively dispersed than the weathered oils that were more effectively dispersed than the weathered and emulsified oils. The most complete data sets collected (due to limitations of the LISST in measuring large oil drops) were for the fresh oil tests. The results for the fresh oils indicate that the final dispersant effectiveness values are highest for the 30 ppt water and in all cases drop linearly as the test water salinity decreased to 5 ppt.


Buist I.,Sl Ross Environmental Research | Meyer P.,MAR Inc.
Proceedings of the 35th AMOP Technical Seminar on Environmental Contamination and Response | Year: 2012

As a result of the experimental success to date thickening slicks for in situ burning in drift ice a research program has been undertaken to explore the use of herding agents for in situ burning in open water conditions as a rapid-response technique for oil spills offshore. The research involved two areas: 1. A series of comparative experiments was undertaken at the SL Ross lab with hydrocarbon-based and silicone-based herding agents in 1-m2 pans, a 10-m2 pan, small pans mounted on a rocking shaker and the SL Ross wind/wave tank to determine the best of several candidate herders for use on warmer water. Overhead digital photographs were taken and analyzed by computer to determine the herder effectiveness in the pan tests. The wind/wave tank tests were videotaped. 2. Surfactant film persistence (i.e., how long the monolayer generated by a specific herding agent will last as a function of sea state) and to what degree periodically replenishing the film can counteract this was investigated in an 8-day test program at Ohmsett from May 13 through 20, 2011. The experiments took advantage of the facility's newly upgraded wave making capabilities. Overhead digital video and photographs were taken to qualitatively compare and determine the persistence of three herding agents in calm conditions, a swell and breaking waves. A total of 11 experiments were completed with three herding agents (USN, Silsurf A108 and Silsurf A004-D) in the three wave conditions: 9 tests as per the test protocol plus an additional duplicate test and a control (no herder). Based on visual observations of the tests the following conclusions can be drawn: • The monolayer of each of the herders will survive for more than 45 minutes in a calm sea. • The presence of breaking or cresting waves rapidly disrupts the herder monolayer and the oil slick resulting in many small slicklets. • The monolayer survives for considerable periods of time in a swell condition, but the constant stretching and contracting of the herded slick results in elongating the oil slick and slowly breaking the slick into smaller segments. • The Silsurf A108 herder performed noticeably better than the other two herders in all test conditions.


Marty J.,WSP Canada | Potter S.,Sl Ross Environmental Research
Proceedings of the 37th AMOP Technical Seminar on Environmental Contamination and Response | Year: 2014

A risk assessment was completed concerning marine oil spills in Canadian waters south of the 60th parallel. The study was commissioned by Transport Canada following the 2010 recommendations of the Commissioner of the Environment and Sustainable Development. The objective of the study was to provide an overall risk estimate to aid in a broader review of Canada's preparedness and response arrangements for ship-source spills. For this study, risk was defined as the product of the probability of a spill occurring and the potential consequences should a spill occur. These two elements were estimated for 77 geographical areas and the results used to provide a relative measure of risk across the country.


Buist I.,Sl Ross Environmental Research | Canevari G.,GP Canevari Associates | Nedwed T.,ExxonMobil
Proceedings of the 33rd AMOP Technical Seminar on Environmental Contamination and Response | Year: 2010

Buist et al. (2007) found that herding agents will allow thickening of oil slicks and in situ burning in drift ice and close a gap for this response option in ice. The herding agents studied were developed in the 1970's and used hydrocarbon-based surfactants as the active ingredient. The best herding agent found was a formula developed by the US Navy. There have been significant advances in surfactant technology since the 1970's with the development of two classes of "superwetter" surfactants - fluorosurfactants and silicone-based surfactants. This paper describes research that evaluated the use of these next-generation surfactants as the active ingredient in herding agents. In 2007 and 2008, tests were carried out comparing the efficacy of herding agents formulated with silicone-based surfactants, formulated with fluorosurfactants, and the US Navy herder. The fluorosurfactant-based herders did not perform significantly better than the US Navy herder. In static tests, a silicone-surfactant based herder initially produced significantly higher herded slick thicknesses but declined back to the thickness of the US Navy herder over the one-hour test period. In 2009, experiments were conducted with three new silicone-based surfactant herder formulations: first, in the SL Ross lab at small-scale (1-m2 pans); and second, at much larger scale using the US Army Corp of Engineers Cold Regions Research and Engineering Laboratory (CRREL). These tests and comparisons with prior work found that one of the new silicone surfactant formulations significantly outperformed the USN herder.


Belore R.,Sl Ross Environmental Research
Proceedings of the 37th AMOP Technical Seminar on Environmental Contamination and Response | Year: 2014

The primary objective of this work was to determine if the presence of natnral gas or methane in a subsea oil and gas discharge would reduce the effectiveness of a dispersant injected into the gas-oil mixture. The underlying concern is that some of the dispersant might be attracted to the hydrocarbon gas bubble-water interface and not be available to attach to the oil-water interface and thus reduce the effectiveness of the applied dispersant. Tests were conducted with air (non-hydrocarbon) or methane (hydrocarbon) with all other parameters kept constant and the resulting oil drop size distributions compared. The significance of dispersant to oil ratio (DOR), gas to oil ratio (GOR). oil type and orifice diameter were also evaluated in the test program. The size of the oil drops generated in the subsea release, specifically the volume medium drop diameter (VMD) metric of the oil drop size distribution, was used as the criteria for comparison of dispersant effectiveness. Tests were conducted both at the SL Ross laboratory facilities in Ottawa and at the BSEE operated National Oil Spill Response Research & Renewable Energy Test Facility (Ohmsett) in Leonardo, New Jersey. The tests utilized a horizontal jet release to segregate the rising oil drops and gas bubbles to allow direct measurement of the oil drops using a laser in-situ particle size analyzer (LISST). Air pressurized supply tanks and precision needle valves for flow control were implemented for the oil and dispersant delivery systems. Gas flow was controlled using a rotameter flow meter. The effect of methane in the flow stream on dispersant effectiveness was not consistent throughout all tests. For two of the oils tested a slight reduction in dispersant effectiveness was identified, as measured by an increase in the oil drop size distribution VMD by about 20 to 30 microns, when methane as opposed to air was present in the flow stream. Terra Nova crude oil, in the small orifice tests conducted at SL Ross, and Endicott crude oil in the large orifice tests conducted at Ohmsett exhibited a slight reduction in effectiveness. For the Dorado oil tested at Ohmsett there was no apparent loss in effectiveness when methane was present in the discharge in either the small or large orifice tests conducted. The dispersant to oil ratio (DOR) had a significant effect on dispersant effectiveness in all of the tests conducted, as would be expected. DOR s of at least 1:100 were needed to achieve dispersions with oil drop VMDs of less than about 100 microns for the various conditions tested. The orifice size used in the testing appeared to have an effect on the dispersant effectiveness with better dispersant efficiency generally achieved in the larger orifice tests. The effect of gas to oil ratio (GOR) on the dispersant effectiveness was inconclusive. This study did not address the issue of deep water releases, gas properties under high pressure, complex natural gas mixtures, or hydrate formation under high pressure conditions and is applicable only to shallow well blowout situations.

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