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Barents Sea field test of herder to thicken oil for i n situ burning in drift ice. In: Proceedings of 33rd Arctic and Marine Oilspill Program Technical Seminar (AMOP) Technical Seminar, June 7-9, Halifax, Nova Scotia

Authors:
Barents Sea Field Test of Herder to Thicken Oil for In situ Burning in Drift Ice
Ian Buist and Steve Potter
SL Ross Environmental Research Ltd
Ottawa, Canada
Stein Erik Sørstrøm
SINTEF
Trondheim, Norway
Abstract
A 2-day field research program was conducted off Svalbard in late May 2008
to test the efficacy of a chemical herding agent in thickening oil slicks on water
among very open drift ice for subsequent in situ burning. The objective of this study
was to continue research on the use of chemical herding agents to thicken oil spills in
broken ice to allow them to be effectively ignited and burned in situ. More
specifically, the goal of the work was to conduct two meso-scale field burn
experiments with crude oil slicks of approximately 0.1 and 0.7 m3 in open drift ice.
Prior to carrying out the field experiments, two series of small laboratory tests were
carried out with candidate crudes (Heidrun and Statfjord) for the field experiments to
determine the ability of the USN herder to contract slicks of the oils.
The first field experiment involved 102 L of fresh Heidrun crude released into
a monolayer of USN herding agent that had just been placed on the water. This slick
was unexpectedly carried by currents to a nearby ice edge where the oil was ignited
and burned. Approximately 80% of the oil was consumed in the ensuing burns.
The second experiment involving the release of 630 L of fresh Heidrun crude
onto water in a large lead. The free-drifting oil was allowed to spread for 15 minutes
until it was far too thin to ignite (0.4 mm), and then USN herder was applied around
the slick periphery. The slick contracted and thickened for approximately 10 minutes
at which time the upwind end was ignited using a gelled gas igniter. A 9-minute long
burn ensued that consumed an estimated 90% of the oil.
1 Introduction
The key to effective in situ burning is thick oil slicks. Pack ice (7 to 9+ tenths)
can enable in situ burning by keeping slicks thick. In drift ice conditions (less than 7
tenths) oil spills can rapidly spread to become too thin to ignite. Fire booms can
collect and keep slicks thick in open water; however, field deployment tests of booms
and skimmers in open drift ice conditions in the Alaskan Beaufort Sea highlighted the
severe limitations of containment booms in even trace concentrations of ice (Bronson
et al., 2002): they rapidly accumulate large amounts of brash and slush ice. If slicks
could be thickened to the 2- to 5-mm range in drift ice, even with no possibility of
physical booming, effective burns could be carried out (SL Ross 2003). For
application in drift ice, the intention is to herd freely-drifting oil slicks to a burnable
thickness, then ignite them with a Helitorch. The herders will work in conjunction
with the limited containment provided by the ice to allow a longer window of
opportunity for burning.
The use of specific chemical surface-active agents, sometimes called oil
herders or oil collecting agents, to clear and contain oil slicks on an open water
surface is well known (Garrett and Barger, 1972; Rijkwaterstaat, 1974; Pope et al.,
1985; MSRC, 1995). These agents have the ability to spread rapidly over a water
surface into a monomolecular layer, as a result of their high spreading coefficients, or
spreading pressures. The best herding agents have spreading pressures in the mid-40
mN/m range, whereas most crude oils have spreading pressures in the 10 to 20-mN/m
ranges. Consequently, small quantities of these surfactants (about 5 L per linear
kilometre or 50 mg/m2) will quickly clear thin films of oil from large areas of water
surface, contracting the oil into thicker slicks.
Herders sprayed onto water surrounding an oil slick result in formation of a
monolayer of surfactants on the water surface. These surfactants reduce the surface
tension of the surrounding water significantly (from about 70 mN/m to 25-30 mN/m).
When the surfactant monolayer reaches the edge of a thin oil slick it changes the
balance of interfacial forces acting on the slick edge and allows the interfacial
tensions to contract the oil into thicker layers. Herders do not require a boundary to
“push against” and work well even in open water. A conceptual drawing of the
herding process is shown in Figure 1.
Figure 1. Conceptual drawing depicting the herding process in drift ice.
A comprehensive, multi-year, multi-partner research program to study the use
of chemical herding agents to thicken oil slicks in order to ignite and burn the oil in
situ in loose pack ice was completed in 2007 (SL Ross 2007). The program included:
1. A very small scale (1 m2) preliminary assessment of a shoreline-cleaning
agent with oil herding properties to assess its ability to herd oil on cold
water and among ice (SL Ross 2004).
2. Small-scale (1 m2) experiments to explore the relative effectiveness of
three oil-herding agents in simulated ice conditions; larger scale (10 m2)
quiescent pan experiments to explore scaling effects; smaller-scale (2 to 6
Herders
sprayed on
water around
perimeter of
slick
Herders rapidly
spread to form
monolayer
Herders change
surface chemistry of
water forcing slick
into smaller area
m2) tank testing to investigate wind and wave effects on herding efficiency;
and, small (300 mL) ignition and burn tests (SL Ross 2005).
3. Experiments at the scale of 100 m2 in the indoor Ice Engineering Research
Facility Test Basin at the US Army Cold Regions Research and
Engineering Laboratory (CRREL) in November 2005 (SL Ross 2007).
4. Experiments at the scale of 1000 m2 at Ohmsett in artificial drift ice in
February 2006 (SL Ross 2007).
5. A series of 20 burn experiments at the scale of 30 m2 with herders and
crude oil in a specially prepared test basin containing broken sea ice in
November 2006 at the Fire Training Grounds in Prudhoe Bay, AK (SL
Ross 2007).
The U.S. Navy cold-water herder formulation (65% Span-20 and 35% 2-ethyl
butanol) used in these experiments proved effective in significantly contracting fluid
crude and refined oil slicks in brash and slush ice concentrations of up to 70% ice
coverage. Slick thicknesses in excess of 3 mm, the minimum required for ignition of
weathered oil in situ, were routinely achieved. The presence of frazil ice restricted the
spreading of the oil and the effectiveness of the herder. Short, choppy waves in the
test ice caused a herded slick to break up into small slicklets, although this may be an
artifact of the relatively small volumes of oil used in the experiments. Longer, non-
breaking waves, simulating a swell in drift ice, did not appear to cause a herded slick
to break up, and in fact may have assisted the process by promoting spreading of the
herder over water to the slick’s edge.
Application of the herder to the water prior to the oil being spilled resulted in
thicker slicks than post-spill application. This approach might be used in the event of
a chronic spill event in pack ice conditions, such as a blowout or a pipeline leak.
Otherwise unignitable crude oil slicks that were contracted by the USN herder
could be ignited and burned in situ in both brash and slush ice conditions at air
temperatures as low as 17°C. Measured oil removal efficiencies for herded slicks
averaged 50% for 7.5-L slicks and 70% for 15-L slicks. The efficiencies measured for
the herded slicks were only slightly less than the theoretical maximums achievable
for equivalent-sized, mechanically contained slicks on open water. The type of ice
(brash or slush) did not significantly affect the burn efficiency.
When ignited, the herded slicks did spread slightly, but once the flames began
to die down, the residue was re-herded by the agent remaining on the water
surrounding the slick. Generally, it was not possible to reignite re-herded residue.
Steeper, cresting waves detracted from the burn efficiency while longer, non-breaking
waves did not. The oil removal rate for the slicks was in the range expected for
equivalent-sized, mechanically contained slicks on open water.
2 Objective and Goal
The objective of this study was to continue research on the use of chemical
herding agents to thicken oil spills in broken ice to allow them to be effectively
ignited and burned in situ.
More specifically, the goal of the work described here was to conduct two
medium-scale field burn tests with crude oil slicks of approximately 0.1 and 0.7 m3 in
open drift ice off Svalbard in May 2008.
3 Laboratory Tests
Prior to carrying out the field experiments, two series of small laboratory tests
were carried out with two candidate crudes (Heidrun and Statfjord) for the field
experiments to determine the ability of the USN herder to contract slicks of the oils.
The tests involved herding the oils on shallow water at 0°C with two salinities (15
and 30‰), different ice types and two energy conditions in small (24cm x 33cm)
trays on a rocking shaker in an environmental chamber and static tests with ice in
larger (1m x 1m) pans. Full details may be found in Appendix B and C. Figure 2
shows the results obtained with the Statfjord crude and Figure 3 presents the results
for the Heidrun crude. The red line on the y-axis of the two graphs highlights 3 mm,
the generally accepted minimum ignitable thickness for weathered crude oil.
Comparison of the results shows that the Heidrun crude was much more effectively
herded than the Statfjord crude. This was likely because the Statfjord crude began to
gel as soon as it was poured on the cold water, due to its low pour point. The Heidrun
crude was selected for the field experiments. It’s physical properties at 0°C are given
in Table 1.
Figure 2. Laboratory test results with Statfjord crude.
Figure 3. Laboratory test results with Heidrun crude.
Tray-15 ppt-o/w-calm
Tray-30 ppt-o/w-calm
Tray-15 ppt-cubes-calm
Tray-30 ppt-cubes-calm
Pan-15 ppt-blocks-calm
Pan-30 ppt-blocks-calm
Time Zero
10 minutes
60 minutes
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Average Slick Thickness (mm)
Herding of JIP Field Experiment Statfjord Crude with USN Formulation
Small-scale laboratory tests at 0°C
Tray-15 ppt-o/w-calm
Tray-30 ppt-o/w-calm
Tray-15 ppt-o/w-rocking
Tray-30 ppt-o/w-rocking
Tray-15 ppt-cubes-calm
Tray-30 ppt-cubes-calm
Pan-15 ppt-blocks-calm
Pan-30 ppt-blocks-calm
Time Zero
10 minutes
60 minutes
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Average Slick Thickness (mm)
Herding of Heidrun Crude with USN Formulation
Small-scale laboratory tests at 0°C
Table 1: Physical properties of fresh Heidrun crude oil at 0°C
Oil
Density (g/mL)
@ 15°C
Density (g/mL)
@ 0°C
Viscosity @ 15°C
Heidrun Crude
0.908
0.919
126 mPas @ 10s-1
Figure 4. Map of general location for May 22 and 24, 2008 herder experiments.
4. Test Procedures
The experiments with the herder were part of a larger experiment that took
place off Svalbard from May 18 to 28, 2008. Figure 4 shows the general location of
the two herder and in situ burning experiments that took place on May 22 and May
24, 2008. The preparations for the field tests of herding and in situ burning included:
Obtaining fresh Heidrun crude (800 L) and recording actual liquid heights in
the discharge drums.
Preparing 10 L of USN herder (65% v/v Sorbitan Monolaurate [Span 20] and
35% 2-ethyl butanol).
Preparing two herder application systems loaded with 2 to 3 L of warmed
USN herder (8-L capacity, pressurized hand-held garden sprayers Figure 5
kept warm in insulated aluminum shipping boxes with hot water bottles).
Setting up weigh-scales for weighing burn residue.
Pre-weighing sorbent boom and pads used to recover residue.
Preparing igniters (Suregel, gasoline, tools, electronic balance and glassware
for measuring and mixing small batches of Heli-torch fuel, plastic baggies and
propane-soldering torch on a pole).
Loading and launching two small boats with equipment used to apply herder
and igniters. GPS receivers were placed on each boat.
Launching the helicopter to obtain aerial photos and video of herding. A GPS
receiver was used to record the helicopter’s position.
Figure 5. Pressurized garden sprayer used to apply herder to water.
Initial 0.1 m3 Test The first test on May 22 involved releasing an accurately
measured 0.1 m3 of the fresh Heidrun crude oil into a monolayer of USN herding
agent that had already been applied to the water surface. This was done because the
winds at the time of the test (5 to 5.5 m/s measured at the surface) were marginal, and
the possibility existed that the slick would quickly break up into many small slicklets
before the herder could be applied. The oil was released by opening the large bung on
a drum tipped on its side at the edge of a large floe once the RV Lance had moved off
crosswind several hundred metres and any disturbances to the ice field created by the
ship had attenuated (Figure 6).
Once the slick had finished spreading (based on aerial observations of the
slick from the helicopter) oblique aerial digital photographs were taken at an altitude
of about 100 m to record the size of the herded slick.Next, attempts were made to
ignite the slick. This was attempted initially by hand from a small boat positioned at
the upwind edge of the free-floating herded slicks. Baggies containing about 120 mL
(4 oz.) of gelled gasoline were placed in the slick near the edge and ignited with a
propane-fuelled soldering torch (Figure 7). Eventually, this technique was used to
ignite slicks herded against ice edges.
Digital video of the ignition and burn was taken from the helicopter in order
to document burn times and areas. Once the slicks had extinguished, aerial
photographs were taken to document the residue area, and samples were taken from
one of the boats to estimate the reside thickness. Then, personnel in small boats
recovered as much of the residue as possible with the pre-weighed sorbent materials
in order to obtain an estimate of the oil removal efficiency. The recovered burn
residue was placed in plastic garbage bags and returned to the research vessel for
water decanting, drying, re-weighing and disposal.
Figure 6. Releasing Heidrun crude from drum from side of floe on May 22, 2008.
Figure 7. Ignited baggie containing gelled gasoline with propane soldering torch.
Using Adobe Photoshop®, the known dimensions of the two boats in the
photographs were used to correct the perspective of the photographs of the slicks
taken from the helicopter (Note: The GPS positions of the boats and helicopter could
not be used to correct the vertical angle of the photos because their times had not
been synchronized). Next, the oil slick was colorized to make it stand out better from
the background. Then, the colored oil slick in the image was defined as black and
everything else as white. Figure 8 illustrates the transformation of the images.
Finally, image analysis software called Scion Image© was used to count the number
of black pixels in each image. The pixel count was converted to area using scaling
factors obtained from images of the two boats with known dimensions. The slick area
was converted to average thickness using the initial spill volume. The error in slick
thickness determined using this method is likely on the order of ± 10%.
Figure 8. Digital transformation of aerial photographs to determine slick area.
0.7 m3 Test The second test on May 24 involved releasing an accurately
measured 0.63 m3 of the fresh Heidrun crude oil from four drums tipped over on the
side of a large floe among very open drift ice (Figure 9). The wind speed was 4,4 m/s
measured at the surface. The crude was allowed to spread until the thick portion has
reached an equilibrium area (as judged from the helicopter) and the thick portion was
still a relatively contiguous slick. The RV Lance had moved off crosswind several
hundred metres to prevent any disturbances to the slick created by the ship.
Figure 9. Releasing 0.63 m3 of Heidrun crude oil on May 24.
Once the slick had finished spreading (based on aerial observations of the
slick from the helicopter) oblique aerial digital photographs were taken at an altitude
of about 100 m to record the size of the herded slick and samples of the slick were
taken to determine slick thickness. Then herder was applied around its periphery and
the contraction of the slick was monitored from the helicopter.
Next, the slick was ignited. This was done by hand from a small boat
positioned at the upwind edge of the free-floating herded slick. One baggie of gelled
gasoline containing about 1 L of gelled gasoline was placed in the slick near the
upwind edge and ignited with a propane-fuelled soldering torch.
Digital video of the ignition and burn was taken from the helicopter in order
to document burn times and areas. Once the slicks had extinguished, aerial
photographs were taken to document the residue area, and samples were taken from
one of the boats to estimate the reside thickness. Then, personnel in small boats
recovered as much of the residue as possible with the pre-weighed sorbent materials
in order to obtain an estimate of the oil removal efficiency. The recovered burn
residue was placed in plastic garbage bags and returned to the RV Lance for water
decanting, drying, re-weighing and disposal.
The known GPS positions of the two boats in the photographs and the
helicopter (including its altitude at the time of a photograph) were used to calculate
the vertical angle of the photographs in order to correct the perspective of the pictures
of the slicks using Adobe Photoshop®. Next, the oil slick was colorized to make it
stand out better from the background. Then, the colored oil slick in the image was
defined as black and everything else as white. Finally, image analysis software called
Scion Image© was used to count the number of black pixels in each image. The pixel
count was converted to area using scaling factors obtained from images of the two
boats with known dimensions. The slick area was converted to average thickness
using the initial spill volume. The error in slick thickness determined using this
method is likely on the order of ± 10%.
Burn Calculations Burn efficiency and burn rate were calculated for each
experiment using equations (1) and (2), respectively. Burn efficiency is the ratio of
the mass of oil burned to the initial oil mass. Oil burn rate is a measure of the
decrease in the oil thickness over the period of the burn, from the time when 50% of
the slick area is aflame (ignition half-time) to the time when the flame area has
decreased to 50% of the slick area (extinction half-time). If 100% flame coverage was
not achieved, the rate is corrected by employing the maximum percent flame
coverage observed.
Burn Efficiency (mass %) = ((Initial Oil Volume x Oil Density) - Residue Mass) x 100% (1)
Initial Oil Mass
Oil Burn Rate (mm/min) =
(% Burn Efficiency) x (Initial Oil Volume) (2)
(Slick Area) x (Max. % Flame Cover) x (Extinction Half-Time - Ignition Half-Time)
The residue was assumed to be water free.
5 Results
The following summarizes the results of the field tests of herding and burning
oil slicks in open drift ice. Full details and calculations may be found in the report.
Initial 0.1 m3 Test The first field test, on May 22, involved 102 L of fresh
Heidrun crude released onto the water from the edge of a floe at approximately 1330
CEST. Approximately one litre of USN herder had already been sprayed onto the
water beside the floe, because there were concerns about the marginal wind speeds
rapidly breaking up the small slick (winds were 5 to 5.5 m/s measured with a
handheld anemometer on the floe). The oil did not spread significantly when released
into the herder monolayer; however, before it could be ignited, the oil unexpectedly
moved 90° to the left of the wind direction into a small pocket between two large
floes and collected against an ice edge. Figures 9 through 17 document the
chronology of the experiment. Three successful burns of the oil in the pocket and
against the edge of the adjacent floe were initiated over a 13-minute period. As much
as possible of the residue and unburned oil was recovered using the small boats with
pre-weighed sorbent pads and short sections of sorbent boom.
Table 2 lists the data collected for the burns. The estimate of burn efficiency
is 81%. Burn rate estimates were not possible because there were several individual
burns, but the residue from each was not kept separate.
Table 3 lists the estimated slick areas calculated from the aerial photographs.
Figure 19 shows the computer processed B&W images derived from the photographs
taken from the helicopter for the five slicks analyzed side-by-side at the same scale.
Figure 10. Just after oil release. Figure 11. First ignition attempts. Figure 12. Slick contacts floe.
Figure 13. Oil trapped in pocket. Figure 14. Ignition in pocket Figure 15. Oil burning in pocket.
Figure 16. Oil burning along floe. Figure 17. Burning complete. Figure 18. View downwind after burn.
Table 2: Burn data collected on May 22.
Burn #
Ignition
(min:sec)
Time to Flame Coverage
(min:sec)
Extinction
(min:sec)
Comments
50%
100%
50%
1
0:00
3:05
3:25
6:16
8:02
Burn travels
along back edge of
floe at end
2
7:40
8:10
8:27
-
10:43
Video off for 50%
extinction
3
9:55
-
10:49
12:29
13:04
Video off for 50%
ignition
Reside Collection
Weight of Oily
Sorbent After 24
hours Decant (kg)
Weight of Clean
Sorbent
(kg)
Residue
Weight
(kg)
Burn Efficiency
(mass %)
All Burns
Combined
33.4
15.3
18.1
81
Table 3: Estimated May 22 slick areas from aerial photo analysis.
Photo Time
Description
Slick Area (m2)
Average Slick Thickness (mm)
13:32:14
84
30.89
3.3
13:32:54
85
30.05
3.4
13:39:02
86
57.44
1.8
13:39:10
87
59.78
1.7
13:40:18
88
38.41
2.7
Figure 19. Comparison of all five processed photos from May 22 at same scale.
0.7 m3 Test The second field experiment took place on May 24 and involved
631 L of fresh Heidrun crude released onto the water from the edge of a floe. The oil
was released from 17:11:00 to 17:13:26 (all times are CEST). The oil was allowed to
spread on the water for approximately 15 minutes. Herder application (3L in total
were applied) commenced at 17:27 between the edge of the floe and the slick. This
was followed by herder application along two sides of the slick by personnel in one
boat and along the third side of the slick by the second boat. Winds measured with a
handheld anemometer on the floe were 4.4 m/s at 17:05. Figures 20 through 31
document the chronology of the experiment. The first igniter was placed on the
upwind edge of the herded slick at 17:36:25 and the burn finally extinguished at
17:45:33 after a large, intense burn traveling the length of the herded slick. As much
as possible of the residue and unburned oil was recovered using the small boats with
pre-weighed sorbent pads, short sections of sorbent boom and a full section of sorbent
boom; however, it was obvious from the helicopter that the entire residue was not
recovered. Figure 32 shows the amount of residue and unburned oil on the water after
the burn. Table 4 gives the data collected for the burn. The estimate of burn
efficiency based on the amount of oil released and residue recovered is 94%, but this
is likely high, based on Figure 32. A very rough estimate of the amount burned based
on burn times, burn areas estimates and a nominal 3.5 mm/min burn rate is near
100%.
Figure 20. Oil release begins. Figure 21. Oil release ends Figure 22. Max. oil area.
Figure 23. Herder applied from floe. Figure 24. Herder applied from 1st boat. Figure 25. Herder from 2nd boat.
Figure 26. Slick before ignition. Figure 27. Ignition at upwind end. Figure 28. Burn of upwind slick.
Figure 29. Extinction of upwind. Figure 30. Burn of downwind portion. Figure 31. Burn extinguished.
Table 4: Burn data collected on May 24.
Burn #
Ignition
(min:sec)
Time to Flame Coverage
(min:sec)
Extinction
(min:sec)
Comments
50%
100%
50%
Upwind
0:00
(17:36:40)
1:50
2:07
3:48
4:02
Upwind area ≈ ½ of
total; upwind
extinguished as
downwind ignited
Downwind
-
4:07
5:23
7:05
8:56
Formed long,
narrow fire
Reside Collection
Weight of Oily
Sorbent After 24
hours Decant (kg)
Weight of Clean
Sorbent
(kg)
Residue
Weight
(kg)
Burn Efficiency
(mass %)
Both
Burns
Combined
79.0
46.2
32.8
941
1 Review of aerial photos and video indicates that not all the unburnt oil and burn residue was collected therefore this
burn efficiency estimate is high.
Figure 32. Residue remaining after large burn.
Table 5 gives the slick areas (and slick thicknesses) calculated for the large
experiment. Figure 33 shows the computer processed B&W images derived from the
photographs taken from the helicopter for the three slicks analyzed to obtain the data
in Table 5 side-by-side at the same scale. These images were obtained by correcting
the aerial photo (or still from the video) for perspective and scale, based on the
relative positions of the helicopter and small boats in each photo, then selecting on
the corrected picture only the thick areas of the slick (visually estimated for each
image by distinguishing sheen areas from thicker oil areas by colour). Figure 34
shows the GPS positions of the boats in each photograph, and the GPS position of the
helicopter that were used (along with the helicopter’s altitude) to calculate the
perspective correction for the three. The “rules of thumb” for in situ burning state that
the minimum ignitable thickness for fresh crude is 1 mm and the minimum ignitable
thickness for weathered crude is 2 to 3 mm. It is thus clear that the slick, prior to the
application of the herder, was too thin to ignite, and that the slick, at the point that the
burning gelled gas was applied, was certainly thick enough to ignite.
The total burn times (from 50% flame coverage after ignition to 50% flame
coverage prior to extinction) measured from the video for the two burns were 2
minutes and 3 minutes. For in situ crude oil fires on water greater than 3.5 m in
dimension, the nominal burn rate is 3.5 mm/min, indicating that further thickening of
the slick occurred after ignition. This could have been caused both by the continuing
chemical action of the herder (the lab tests showed the herder could thicken Heidrun
crude to more that 5 mm) and the effects of air being drawn into the fire by the hot,
rising combustion gases inducing a surface water current that herded the slick (SL
Ross 2007).
5 Summary
Two experimental burns of free-drifting oil slicks in pack ice were
successfully completed. The first experiment involved 102 L of fresh crude released
into a monolayer of USN herding agent that had just been placed on the water. This
slick was unexpectedly carried by currents to a nearby ice edge where the oil was
ignited and burned. Approximately 80% of the oil was consumed in the ensuing
burns. The second experiment involving the release of 630 L of fresh crude onto
water in a large lead. The free-drifting oil was allowed to spread for 15 minutes until
it was far too thin to ignite (0.4 mm), and then USN herder was applied from small
boats around the slick periphery. The slick contracted and thickened for
approximately 10 minutes at which time the upwind end was ignited using a gelled
gas igniter. A 9-minute long burn ensued that consumed an estimated 90% of the oil.
Table 5: Estimated May 24 slick areas from aerial photo analysis.
Figure 33. Comparison of all three processed photos from May 24 at the same scale.
Figure 34. UTM positions of boats and helicopter at times aerial photos taken on
May 24.
Photo Time
Description
Thick Slick Area
(m2)
Average Slick Thickness (mm)
17:24:50
Max. spread
(Figure 24)
1658
0.4
17:34:48
Herder applied to
3 sides of slick
(Figure 25)
403
1.6
17:37:41
Just after ignition
(Figure 26)
153
4.1
Positions - May 24th
8,603,600.0
8,603,700.0
8,603,800.0
8,603,900.0
606,900.0 607,000.0 607,100.0 607,200.0
MOB Boat 100 HP Outboard Boat Helicopter
Positions at 17:24:50 Positions at 17:34:50 Position at 17:37:31
6 Acknowledgments
This work was funded by a consortium of oil companies: Shell, Statoil,
ConocoPhillips, Chevron, Total, Agip KCO; and, the Norwegian Research Council.
The Field Exercise during which these experiments took place was organized and
co-ordinated by SINTEF. The contents of this paper do not necessarily reflect the
views and policies of the funders, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
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Article
Forty-seven chemicals were investigated to determine their usefulness as practical materials with which to form single-molecule-thick films that are capable of reducing the area covered by oil spilled on water. These chemicals are able to maintain the oil in a layer up to a maximum of approximately one-half inch thick by preventing it from spreading over the water surface. If the oil has spread before adding the chemical, the monomolecular film pushes the oil back into a thick layer. Such materials, classified as Collecting Agents by the National Contingency Plan, may be quite useful in increasing the efficiency of oil recovery devices, since all such devices perform better on thicker layers of oil. All materials investigated are commercially available in large quantities. The best five materials of those examined are reported with a summary of their properties.
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Bronson, M., E. Thompson, F. McAdams and J. McHale. 2002. Ice Effects on a Barge-Based Oil Spill Response Systems in the Alaskan Beaufort Sea. Proceedings of the Twenty-fifth Arctic and Marine Oilspill Program Technical Seminar, Environment Canada, Ottawa, pp 1253-1269
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