<<Oil recovery and oil-on-water exercises in high seas,
offshore Norway>>by
Jan Allers, Vice Chairman
NOSCA - Norwegian Oil Spill Control Association
Oslo, Norway

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CONTENTS:
1. Introduction

p.

3-4

2. Status - after the EKOFISK BRAVO blowout in 1977

p. 4

3. Oil recovery and oil-on-water exercises in high seasp. 5 - 6

4. Significant oil-on-water exercises and real life incidents:

p. 6 - 9

4.1 PFO's full scale testing of V-shaped boom systems, in -hull andover the side skimming systems in 1980.
4.2 NOFO's oil-on-water exercise in June 1985

p. 10-16

4.3 The Occidental Pipeline rupture in the British sector of the p. 17-19
North Sea in November 1986
4.4 NOFO's oil-on-water exercise in Sept. 1990

p. 19-22

4.5 NOFO's oil-on-water exercise in August 1995

p. 22-25

5. Advances in the Norwegian oil spill preparedness since p. 25
EKOFISK BRAVO in 1977 until today

21. INTRODUCTION:
Norway is exposed to nearly all kinds of oil spill threats as a result of an increased oil
exploration and exploitation (E&E) which by 1997 covers well over half of the 21.465
km long coastline.
The threats may come from:-offshore (meaning high seas) oil exploration and exploitation-tanker accidents inshore as well as nearshore-pipeline ruptures-ships' groundings or collisions
Further it should be emphasized that in winter time Norway has very harsh weather
conditions that may be the main cause for some of the above incidents. In a very similarmanner the winter weather may also be very detrimental to efficient oil recovery
operations.
The two main incidents that triggered government action in the seventies were the<<Torrey Canyon>> disaster and the EKOFISK BRAVO blowout.
The Ministry of Environment through SET, its Pollution Control Authority, issued aset of very demanding rules requiring the oil companies drilling on the Norwegiancontinental shelf to build up a mechanical oil spill response capability with thefollowing requirements:- there must be available a total oil spill response capability which can contain, recoverand store an acute oil spill of 8.000m3 emulsion per 24 hours- 25 % of this capability must be operative inside 24 hours- the balance of the response equipment must be operative inside 48 hours- the oil recovery equipment must be dimensioned for efficient operations in at least
2,5m significant (Hs) wave height and in currents up to 1,5 knots
At the time neither the infrastructure nor the equipment existed to meet theserequirements. The oil companies invited the industry to develop the mechanical oil spill
response equipment - for a new and very promising market.

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The government through SFT had given permission to the oil companies to join forces
in meeting the capital demanding requirements and it was in 1978 that they founded
NOFO, Norwegian Offshore Clean Seas Association for Operating Companies.
NOFO soon took an active lead in the general R&D as well as a practical developmentof what over a 10 to 15 years period became a very efficient, large scale offshore oil spill
contingency.
While NOFO was mainly responsible for the offshore E&E activities SFT through its
Oil Spill Control Dept. in Horten was responsible for coastal spills caused by traditional
ship groundings and collisions or third party mystery spills. Later this role has changed
and SFT plays a more active role in developing and building up oil spill contingencies
for coastal as well as inshore response operations.

2. Status for the Norwegian oil spill response capability after the
EKOFISK BRAVO blow-out in 1977.
Phillips Petroleum, the owner of the EKOFISK field, was nearly unprepared for a longweek's blow-out in March 1977. Only prototype mechanical oil spill response equipment
was available for oil containment in high seas offshore.
The booms were operated in U-configuration requiring three vessels i.e. two vessels forboom towing and the third one, the OILREC vessel, to operate the disc skimmer
attached to a hydraulic suspended crane. A total of 24.000 tonns blew out from the
BRAVO platform (no fire), 40 % evaporated rather quickly. The weather was moderate
and the waves never exceeded 2 - 2,5 m Hs in max. 12m/sec. winds. One may say thiswas a good lesson learnt and a good kick-off point for NOFO to develop oil recovery
systems- for two boat operations- with dynamic, freefloating high capacity skimming systems- with booms operated in improved configurations to feed more oil to the skimmers- with booms that could contain oil above the classic limitation of 0,7 to 0,9 knot towing
speed.

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3. Oil recovery and oil-on-water exercises in high seas.
Backed by abundant economic resources made available by the parent companies in thelate seventies/early eighties NOFO set out to develop the new offshore oil spill
contingency such as- equipment- vessels (on a standby basis)- crews (not permanently employed)- onshore equipment bases (hired)- relevant exercise and training programs
And NOFO was met with an additional challenge when offshore drilling for oil was
opened up in northern Norway in 1982. The operational requirement for themechanical equipment was then increased to 3 m Hs wave height.
From 1980 until 1996 NOFO has carried out a total of appr. 23 full scale, realistic oilon-water exercises offshore Norway. During the same period Norway experienced ahigh number of oil spill incidents from ships that to a large extent supplemented theknow-how that NOFO had built up.
It ought to be added that SFT participated with their own vessels and resources in mostof the oil-on-water exercises. Sometimes SFT served as back-up and more recently inthe frontline with their new vessels and equipment that needed real life testing andtraining.

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Typically a NOFO oil-on-water exercise in the mid eighties included the following
resources:- one J-shaped 500 m long high seas boom with a high capacity freefloating skimmer
operated by one supply vessel (60 m) and one fishing vessel (40m)- three back-up systems (one with a V-shaped boom system and two with a U-shaped
boom system, all operated by three vessels each)- a significant amount of measuring instruments and over flight surveillance.
In the first years of testing volumes of up to 500m3 emulsion were discharged. Morerecently the volumes have been reduced to 250/125m3 emulsion. NOFO intentionally
mixed from exercise to exercise various crude oils from the Norwegian offshore fields
with sea water. Thus the discharges consisted of typically 65% seawater and 35% crude
oil. This was done in order to simulate the situation of a blow-out where the crude
would mix with the seawater before NOFO's response fleet would be on site to begin oil
recovery operations.

4. Significant oil-on-water exercises and real life oil spill incidents - whichhave contributed to the improvement of the Norwegian oil spill response capability inhigh seas offshore from 1980 to 1995.

4.1 PFO's full scale testing of V-shaped boom systems, in-hull and over theside skimming systems in 1980.
PFO- Oil Pollution Control Research and Development - was initiated by the Ministryof Environment in 1978. It is fair to say that it was the state's follow up of thedefficiencies detected after the EKOFISK BRAVO blowout. The program lasted for 4
years. 22 mill. NOK were allocated to development projects and 25 mill. NOK to R&D
projects. The Norwegian Industry Association funded parts of these means.
The Norwegian maritime industry had responded actively to the BRAVO blowout,
eager to develop new equipment capable of containing and recovering oil in high seas,
offshore conditions.
PFO therefore supported a large scale three week oil-on-water test in June 1980. The
equipment tested by four different makers were:6

1. a 35 m long V-shaped boom system with a built-in overflow skimmer pump
2. a 40 m long V-shaped boom system with a purpose built recovery section
including a centrifugal pump
3. a single ship, onboard skimming/settling system supplemented by a side sweep
boom
4. a single ship, over the side skimming system supplemented by a side sweep
boom
See drwgs. 1 - 4
All four systems included pumps which theoretically could recover from 400m3 to
700m3 water per hour.
The first week of the test program covered physical endurance tests in high seas. In
wind forces of 10 - 12 m/sec. and up to 2 m Hs several weaknesses were detected andmost of them corrected. - But vortex motions in front of the V-shaped booms at theconnection point between the guiding booms and the V-shaped boom could not be
adjusted.
The oil emulsion used had the following basic characteristics:

A lube oil, SAE 30, was chosen as basis oil. While this was a none Newton liquid it waschosen because it was close to the characteristics of a crude oil that had been drifting in
the ocean for 1/2 to 3 days. The mixing with seawater into an emulsion was done as pera formula developed by SINTEF.
The wave and wind conditions during the oil-on-water tests were:This means that during the first week there was mostly ocean swells and during thesecond mostly wind driven waves. - The oil emulsion was discharged from a vessel infront of the systems through a 100 m long 6 inch dia. hose kept floating by buoys. At theend of the hose was a polystyren box 2 x 2 x 0,5 in. The emulsion simply poured out on
top of the box and into the ocean. The discharge rates were kept at 60 m3/hour.

78Observations and discussions:
When evaluating the results obtained from this very comprehensive oil-on-water test
program it is useful to remember that this was the very first time that such an
ambitious (and costly) program had been launched in high seas, offshore conditions in
Norway. - While PFO would have preferred the seastate to have been fully developed
into 2,5 m Hs waves and 12 - 13 m/sec winds they were not very far from this goal. The
biggest challenge faced was the number of accurate measurements to be taken. That is
why the above tables refer to <<Efficiency variations>> x. It shows the Test Director's
overall reservations with regard to potential errors. He deserves credit for that!
The recovery rates of emulsion are by today's North Sea standards not very high, i.e. 40- 50 m3 per hour. The towing speed exceeded 1,0 knot most of the time for the V-shaped
booms. This must be considered a success in view of the classic limitation for booms
towed in a U-shape and where the oil will escape under the boom at 0,7 to 0,9 knot.
The usefulness of this kind of real life testing was also proven. Example:
During the physical endurance testing the bark (simulated for oil) appeared not to becapable of concentrating around the no 4 <<over the side skimmer>> whereas the oil
testing demonstrated no such deficiency.
The entire test program left the 4 makers with promising challenges and opportunities
for improvements that seemed achievable. The two makers of the V-booms (no 1 and no2) since <<merged>> what they considered the best features of the two designs. They
subsequently built a unit with a freeboard of 1,5m which became a very important oil
containment tool in the Norwegian oil spill contingency of the 1980'es. And it supported
the development of a unique high capacity, free floating overflow skimmer that needed
a good concentration of oil to operate at its maximum capacity. Ref. the following
chapters on NOFO' s oil-on-water tests.

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4.2 NOFO's oil on water exercise in June 1985.
While NOFO began their regular oil-on-water exercises in 1980 with essentially thesame type of mechanical oil recovery equipment that was used during the BRAVO
blowout in 1977 it was not until 1984 - 1985 that the first major improvements in
new equipment were made and put to test. In this section the major and very
comprehensive oil on water exercise carried out in June 1985 is described anddiscussed in some detail.
The June 1985 oil-on-water exercise was a joint venture between NOFO and SFT. A
total of 13 large vessels were mustered:- 11 oil spill response vessels of which 4 acted as OILREC vessels and 7 as towing
vessels.
- 1 tanker- 1 observation vessel
Further a total of 4 (1 primary and 3 back-up) mechanical oil recovery systems were in
operation as shown on drwg. no 5:

NOFO's primary:
A two-boat system operating with:a new fully integrated oil containment system consisting of 500 m guide boom with 85
cm freeboard (fence type) supported by a Cross Bridle and a V-shaped boom of 1,3 m
freeboard and with a submerged, horisontal net bottom.
And
a new freefloating overflow skimmer with a built-in screw as well as centrifugal pumps
and a cutting device against debris. Surrounding the overflow skimmer was a flexible
skirt w/floaters designed to maintain a near constant overflow level in high seas. The
skimmer was connected to a 100m long floating hose with a built-in set of discharge andhydraulic hoses plus an emulsion breaker hose. The floating hose was stored on anddeployed from a hose drum with a crane that would feed the hose with the skimmer atthe end down into the apex area of the V-shaped boom.

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NOFO's 1st back-up:
A three-boat system operating with:
A 2 x 200m 85 cm freeboard guide booms on each side of a V-shaped boom of 1,3m
freeboard and with a submerged, horisontal net bottom.
An overflow pump station with a combined discharge and hydraulic hose assembly in a
net stocking - running over the side of the V-shaped boom and onto the nearby OILREC
vessel.

SFT's 2nd and 3rd back-up:
Three-boat systems operating with:
400m inflatable oil booms towed in a U-configuration. The boom had 80cm freeboard
and a draft of 1m skirt and 50cm feather net to give the boom improved dynamic(heave) response in high seas.
For oil recovery in the 2nd back-up system a crane operated, vertical rope mop skimmer
was used.
For oil recovery in the 3rd back-up system there was a crane operated overflow
skimmer w/seawater injector to ease off the friction in the discharge hose. Thus it was
expected that the recovery capacity would be increased with less hose friction.

Measurements and recordings:
For optimal and correct measurements and recordings of oil thicknesses, oil recovery
rates and the overall exercise performance NOFO had included a series of hardware
and software such as:

For visual observations and recordings:
Film and video cameras in the air (including an IR-camera for night recordings) and on
the bridge of the OSC/OILREC vessel.

For underwater observations:
An ROV with video camera that operated inside the primary boom system.

For recordings and measurements:
A 40 ft. lab container on the deck of the OSC/OILREC vessel in which continuous
registrations through bypass lines were made first of all of pump rates from the new
overflow skimmer, amount of free water and emulsion and sampling equipment for the11emulsion's water content and emulsion. Moreover the skimmer's hydraulic pressure,hydraulic flow rate and temperatures in the power packs and hydraulic pumps were
measured. The monitors also took in the continuous incoming weather reports from theoceanographic buoy such as wind speed and direction, wave heights, current and its
drift direction plus air and ocean temperature.
Finally, the oil thicknesses around the freefloating skimmer head were measured
manually from a small workboat!
The emulsion used during the exercise was an evaporated crude oil from the
STATFJORD offshore oil field premixed with seawater to simulate a 12 hours crude oil
slick. The viscosity varied from 7.800 to 10.000cp. The emulsion was pumped into theocean by a tanker in front of the Primary System after the Back-up Systems had been
towed in position behind. A total of 550m3 were discharged while the single discharges
were maximum 100m3 - for the less significant tests the volumes were reduced to 30m3
and used in testing of the Back-up Systems.

Weather:Over the entire test period a strong breeze blowed out of the southwest resulting in asignificant wave height of 1,5 m (Hs). These were fair test conditions for first time trialsof new equipment.

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1. More emulsion was recovered than discharged. This was due the increased
percentage of seawater in the emulsion - and there were some leftovers from Test no 1.
The negative figure (-11) means that more oil was recovered than discharged for the
Test no 2.
2. System loss refers to the loss from this test only, i.e. what was recovered by the
Back-up systems has not been included.
3. Efficient Skimming Time means the time the hydraulic motor on the recovery pumphas been operating.
4. The system capacity is a result of the average recovery capacity for the entire
Efficient Skimming Time.
5. Real Skimmer Capacity expresses the average plateau value over 15 ins, during
which the emulsion flow into the skimmer has not restricted the capacity.
6. Max. Emulsion Capacity is the highest emulsion flow rate maintained during a 3
mins. period.
7. Max. Total Capacity is the highest emulsion plus water flow rate during a 3 mins.
period.

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From other sources than the Lab Container the following was recorded:- oil thicknesses up to 50cm in towing speeds at 1 knot.
- when the towing speed was increased up towards 1,5 knot the oil thickness increased
significantly in the Apex area of the V-shaped boom. Thus an improved flow into theoverflow skimmer was noted.
- The photos taken from the air with an ordinary camera showed small leakages of
emulsion in the form of blue shine which spread over a wide area and some long
streaks of emulsion strectching longitudinally behind the Apex.
- the underwater video from the ROV showed:．a pump-like movement from the boom's skirt likely caused by the wave actions.
．the boom skirt's outward inclination (caused by the shorter bottom tension line.
．a leakage of very small particles (droplets) of emulsion and small water droplets
covered with a thin oil film.

Discussions:This discussion focuses around the two most promising oil recovery systems tested i.e.:- the two-boat Primary System, and- the three-boat 1st Back-up System.
It was the first time ever that the max recovery capacity (seawater + emulsion) had
approached 300m3/hr., and correspondingly the emulsion capacity had passed
200m3/hr.by a good margin. These breakthrough results were achieved only with thePrimary System tested.
The Primary System's freefloating skimmer deployed by means of a 100m crane
operated floating hose was very easy to manoeuver (only 1 person). This was also thecase in positioning of the skimmer head inside the V-shaped boom at the Apex area
where the oil emulsion showed best concentrations. And the interim recovery of theskimmer head (for declogging of debris and possible repairs) was equally simple. The
Skimming System's independence from the Boom System was thus demonstrated to bea major benefit - and with only two vessels!

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While the skimmer head was not subjected to marginal weather conditions the skirt
fitted with floats provided a fully adjustable overflow in relation to the wave
movements. - While the exercise revealed that minor technical adjustments had to bedone the results had been so promising that NOFO decided to go for a full series of
new skimmers of this kind.

Boom towing configurations:This exercise demonstrated the V-shaped boom's good capability to concentrate thicker
layers of oil around skimmer head - better than the U-or J-configured boom systems.
．The configuration with a short <<Inside>> guide boom from the OIREC vessel to theV-shaped boom permits the freefloating skimmer head attached to the end of the
100m hose to drift into the Apex area.
．The <<outside>> guide boom gives the system an optimal sweep width (area coverage)
while the Cross Bridle adjusts the angle of the guide boom to max. 25 degrees as per
NOFO's own findings.
．The submerged horisontal net bottom - apart from maintaining the shape of the Vshaped boom - also tends to even out or spread the vertical currents of at the back of
the V over a larger area. Thus the towing speed may be increased to a higher level
than for the U- or J-configured boom systems. before oil escapes under the boom.
To operate such a fully integrated oil containment system requires two vessels withgood manoeuvering capabilities and well trained personell in the wheelhouse. Ideally
the OJLREC vessel should have both a bow thruster and two variable pitch propellers.
The two persons at the helm (OILREC and towing vessels) must communicate very
closely in order to make course adjustments. This is important in order to avoid
deformation of the V-shaped boom.
During the tests it was found that the freefloating skimmer head tended to getentangled in the net protection around the freeboard of the V-shaped boom. This net
protection as it turned out later could simply be removed. Improvement in the deck
handling of the fully integrated oil containment system seemed necessary - too many
deckhands were required during deployment and recovery and it was too time
consuming!
The three boat 1st Back-up System also benefitted from the V-shaped boom in thecentre giving equally good concentration of oil. But the system's pumping station wasvery exposed to debris clogging plus the towing of the combined discharge andhydraulic hose set by a third vessel was somewhat sensitive.

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The pumping station had to be hoisted out of the Apex area for declogging. This was atime consuming and somewhat risky operation because the OILREC vessel had to movevery closely to the boom and use its own crane to get the pumping station out of theocean. - The discharge and hydraulic hose set had to pass over the side of the boom
which also could be critical with a potential for mechanical damages.
In general the three boat 1st Back-up System had less pumping capacity and did not
perform as well as the two-boat Primary System.
This was the costliest and most comprehensive NOFO oil-on-water exercise carried out
since the first one in 1980. As it appears from the statistics and the discussions, it
proved, however, a very successful one.

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4.3 The Occidental Pipeline rupture in the British sector of the North Sea
in November 1986.
On 26 November Occidental Petroleum company's Piper/Claymore subsea pipeline in
the British sector of the North Sea spilled appr. 2.500 tonnes of crude oil. After one
day's drift in the ocean the spill appeared as 26km2 slick. While the British reported
that the oil slick had dissipated significantly by 29 November it appeared that what
remained was drifting into the Norwegian sector in heavy westerly winds.
On 4 December the flight surveillance carried out by SFT reported slicks containing
what appeared to be heavily weathered oil. The slicks were so near the coast just southof Bergen (where a large number of salmon farms would be threatened)that SFTordered one NOFO system and 2 SFT systems to be mobilized. - Occidental had
previously chartered a Norwegian vessel with a single ship, side sweep system thattogether with two tugs had followed the slick for a few days. These vessels had tried tobreak up the slicks in the heavy weather by hosing them down with water andsteaming through them.
The NOFO system was quickly mobilized and arrived on scene in the early morning
hours of 5 December: i.e. one OILREC vessel (S/V Gullbas) and one towing vessel (F/V
Knester). The single slick then consisted of a dominant part blue shine and thickemulsion cakes spread over an area of appr. 5 x 2km. SFT had indicated based on
overflights and observations from the on-scene commanding vessel that the slick
contained 2000 tonnes oil emulsion. Samples of the emulsion cakes were measured tocontain 45 to 47% seawater and the viscosity was appr. 28.000 cp.
NOFO's OJLREC vessel deployed its 500m long fence boom with 85cm freeboard in a
J-formation with a cross bridle inside 55 ins. The wind was blowing from NE at 10 - 11
m/sec and the waves were high due to the previous days' gale conditions. The towing
speed was 1,2 knots when the boom system approached the slick.

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The log record from Dec. 5, 1986 then shows:1240 hours: Oil begins to build up in thick layers and the towing speed is reduced to 1
knot.
1400 hours: Winds 7 m/sec. out of the NE. The freefloating skimmer with the crane
operated 100 m hose system was deployed.
1405 hours: The skimmer's pumps were started up.
1430 hours: 23rn3 recovered (average pump rate 55m3/hour)
1445 hours: 42m3 recovered (average pump rate 76m3/hour)
1500 hours: Winds increased to 13,5 m/sec.
1510 hours: The skimming was stopped, the boom was empty.
A total of 72m3 had been recovered - average pump rate was 96m3/hour.
1515 hours: Turning the 500m boom system towards the SW.
1540 hours: Turned to SW 250 degr. into another slick area spotted by the OSC vessel.
1600 hours: The Cross Bridle wire broke.
1610 hours: Began recovery of the 500m boom system.
1700 hours: Winds 24m/sec. out of WNW 300 degr.
1805 hours: The entire boom system back on deck - final recovery in full gale winds 27m/sec.
1 hr. 35 mins. towing and 1 hr. 5 mins. skimming with an average pumping rate of 66,5
m3/hour had been required. During this period the winds had increased from 9m/sec. to
13,5m/sec. in waves that probably approached 3m Hs. See drwg. no 6.
NOFO's system was deployed also the following day (Dec. 6, 1986). A full gale had been
blowing during the night breaking up the emulsion cakes even further. At mid day an
oil slick was detected from the SFT's aeroplane - the slick appeared to consist mostly of
blue shine. Until 1400 hours it was still blowing hard (18m/sec. out of the NW). While
the wind decreased the 500m J-shaped boom system was deployed at 1440 hours andtowed into the slick over a 4,5 hours period. Very little oil was built up inside the boom
and a SFT vessel was brought alongside the bottom of the J of the boom and used avertical rope mop skimmer to recover 2 m3 oil emulsion and very little free water.

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Discussion:
This real life oil spill demonstrated clearly that the high seas 500m J-shaped boom
system together with the freefloating skimmer with the 100m crane operated floating
hose worked well in strong winds and waves that in all likelihood exceeded 2,5 m Hs.
While the tension on the Cross Bridle wire that broke during the recovery of the boom
must have been extremely high (in excess of 10 tonnes) the physical strength of theboom had proven to be very satisfactory. The freefloating skimmer system also stood up
to the rough weather without any technical or physical damages.
In total NOFO's longterm development of a high seas, offshore oil containment andrecovery system had satisfied the requirements of the Norwegian environmental
authorities from 1976.

4.4 NOFO's oil-on-water exercise in Sept. 1990.
As usual this exercise took place in offshore conditions appr. 120 n. miles from theNorwegian west coast, this time in the vicinity of BP's Ula-field. This was a NOFO
exercise where SFT's only system served as back-up except for a smaller 20m3
discharge where SFT's vertical rope mop skimmer was tested with an excellent result.
A total of 3 complete NOFO systems (of which one included a brand new automatic
inflated oil boom), 1 SFT system and one BP single ship, side sweep system with an inhull skimming device were in operation.
The UK participated with a surveillance plane and a dispersant plane, Norway with ahelicopter and a surveillance plane while Denmark, the Netherlands, Sweden andFrance each participated with part time surveillance planes. An observer vessel carrieda large number of national as well as international observers.
This chapter describes the equipment, vessel and airborne input during the mostimportant discharge i.e. discharge no 6 being a 250 m3 oil emulsion (appr. 70%
seawater content) from the Gullfaks field. On the one hand this was by far the biggest
discharge during the exercise and on the other hand it was of special importancebecause for the first time it was a large night discharge. A helicopter surveyed the drift
pattern from the tanker's discharge position 1000m in front of the boom systems andthen gave instructions to the OSC/OILREC vessel how to attack the slick, based on the
FLIR system's (Forward Looking Infrared camera) observations

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NOFO's Primary two-boat System consisted of:- A fully integrated oil containment system being a divided 420m long guide boom with
100cm freeboard (cylindrical) supported by a cross bridle, and a V-shaped boom of 1,5m freeboard and with a submerged, horistontal net bottom.
- NOFO's free floating 350m3/hr. skimming system which had become their standard
since 1985/6.
This equipment was operated by the OSC/OILREC vessel <<Far Turbot>>.

NOFO's 1st Back-up two-boat System consisted of:- Identical equipment as per above.

SFT's 2nd Back-up three-boat System consisted of:- 200m long 80cm freeboard boom (cylindrical) towed in a U-configuration- A crane operated 85m3/hr. vertical rope mop skimmer (the system was deployed fromthe third vessel alongside the wide apex of the U)

NOFO's 2nd Back-up System was deployed but never came in operation due to a
failure in the new boom's inflation hoses.
In addition to the FLIR and the other air surveillance receiving equipment <<Far
Turbot>>carriedNOFO's40'

Lab

Containerwithimprovedmeasurement

intstrumentation compared with the 1985 package. Other means to aid and observe theexercise were:- current and drift prognosis radioed in from an oceanographic buoy
- night glasses and night binoculars- SLAR (side looking airborne radar) and IR installations in the planes.

The discharge no 6.
The tanker discharged appr. 250m3 emulsion at an hourly rate of 120m3/hour between
1935 hours and 2230 hours (in complete darkness).

Weather.
The weather was not as strong as one might have preferred:- mean wind speed 6 m/sec. out of NW- waves 1,5m Hs with 2,7m H max.
- wave periods 5 secs.
- mean current 0,1 knot

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Oil recovery and oil recovery results:
The oil recovery began nearly two hours after the tanker had begun its discharge andlasted for 85mins. - from 2128 hours until 2253 hours.
The oil recovery results into the Primary System as measured in the Lab Container
onboard <<Far Turbot>> were:- Total volume (incl. seawater) acc. to the flowmeter:

322 m3- Of this the emulsion (with 76% seawater) amounted to:

162 m3- Recovery percentage calculated back to crude oil

61,1 %- Max. pump rates over a 3 min. period

310 m3/hr.

- Max. pump rate over a 15 min. mean period

300 m3/hr.

- Max. emulsion rate over a 3 min. period

263,6 m3/hr.

- Max. emulsion rate over a 15 min. mean period

235,2 m3/hr.

Nothing was recovered by the 1st Back-up System due to a shut pump valve. SFT's
2nd Back-up System recovered 4m3 emulsion with 81% seawater.
See drwg. no 7 as an illustration of pump rates, both totals and emulsions.

Discussions:This was a success for NOFO's first FUR directed oil-on-water exercise in full darkness.
The helicopter's video from the FUR clearly showed that some oil emulsion escaped
under the towing line before entering the boom system. The slick spread significantly
in width - most likely due to the relatively calm weather and weak current. Therfore oil
also escaped on the port side of the OILREC vessel <<Far Turbot>>. The FLIR video
did not show any significant leakages under the Primary System's boom (neither theguide booms, nor the V-shaped boom).
While the helicopter operated FLIR did assist in the good performance there is no doubtthat the darkness alone with oil emulsion escaping unnoticed caused more losses thanwould have been the case in broad daylight.
When including some more details from this night operation it is worthwhile
mentioning that the first overflights should be made at 1000 ft. to 1500 ft. level without
zooming the FLIR camera. Thus one gets a good overview. Later flights should include
flying at lower altitudes and with zooming of the camera. - The emulsion thicknesses
were measured at sea surface level and in the light brownish areas the thicknesses
varied between 1,3 and 2,1mm. However, inside the slick the variation in thickness is
significant. For estimation of the emulsion during the night discharge (no 6) 1mm
thickness may be considered an average for small, freefloating slicks. Calculations of
the thickness in the main slick indicated an average thickness of appr. 3mm. These
calculations

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were based on a slick measured by IR at 36.000m3 and the amount of discharged
emulsion of 110m3. A lot of reservations should be taken into account because theseestimations refer to the first experiences gained by NOFO from an oil recovery
operation in full darkness.
Finally a comment on a different subject. It was found that the drift prognosis for the
slicks were very useful. But they were presented in tables during the exercise. The
operators would have preferred map presentations of the slick.

4.5 NOFO's oil-on-water exercise in 1995.
Background:This exercise took place at the Frigg field in August and the weather was a pleasantwesterly wind at 2,7m/sec. with a 1m Hs wave condition. The current was a very
moderate 0,1 knot.
NOFO's fleet consisted of two systems each with one OILREC vessel and one towing
vessel. SFT joined the exercise with the Coastguard vessel <<Nordsjobas>> that
operated as OILREC vessel and F/V <<Smaragd>> that operated both as a towing
vessel and an OILREC vessel.
On NOFO's OSC vessel the contingency comprised:- a 400 m long heavy duty boom system (1,3m freeboard) towed in J-configuration
supported by a Cross Bridle- a 350m3/hr freefloating skimming system- a 40 ft. Lab Container- an Aerostat for on site surveillance (the Aerostat was deployed from the deck andpermanently moored at a 300 ft. level)- Receiving station for helicopter down link transmissions- Equipment for measuring environmental data (transmitted from a buoy)- Oil drift model program
Air support was also given from a surveillance plane (w/SLAR/IR/UV) and a helicopter
with FLIR camera.
This paper concentrates on Discharge 3 in the exercise plan. (The two first discharges
covered dispersant tests and Discharge no 4 in darkness was reduced significantly due
to problems with an unstable emulsion).

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Discharge 3 aimed at a full system test for SFT's Coast Guard vessel<<Nordsjobas>>:- tow tests of the 800mm dia. 235m long fuily integrated oil containment system with aV-shaped boom section (0,5 -1,0-1,5 knots)- testing of a new high frequency transducer for continuous measurements of the oil
thickness in the Apex area of the V-shaped boom section- testing of the 250m3/hr. freefloating skimmer system- pumping of the recovered oil through an onboard manifold onto a towed temporary oil
storage bladder- discharging the towed temporary oil storage bladder at sea into a trailing OILREC
vessel.
It was the first time that SFT carried out this kind of complete system test where apotential shortage of tank capacity on the OILREC vessel would require offloading into
an ocean going temporary oil storage bladder.
One of NOFO's vessels discharged the oil emulsion at a distance of appr. 400m ahead of
CG/V Nordsjobas. The log recorded the following:
Start up:1605 hours

Stop:1626 hours (total discharge time 21 ins.)

Total discharge :50m3 (at a rate of 143m3/hr.)
Oil emulsion:29 m3 with a seawater content of 52%*

Viscosity:900 cst

Net oil volume:14 m3

Free seawater:21 m3* The emulsion had destabilized from the previous 67,5 %.

Boom towing:
The boom system was deployed at 1230 hours and according to the log data the boom
was towed in the oil emulsion as follows.
Tow tests in oil:1626 - 1640 hours (14 mins.)

Oil recovery fromthe boom's apex :1640 - 1739 hours (59 mins.) w/ the 250m3/hour skimmer
Last oil recovery
from the boom

:1830 hours** when the 250m3/hr skimmer was stopped there was still some oil emulsion left inside
the apex and this was recovered by the other SFT vessel with the vertical rope mopskimmer nearly one hour later.

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Volumes pumped into the temporary oil storage bladder from the boom:
The measurements were made at the manifold aboard the CG/V Nordsjobas.

Volumes pumped from the temporary oil storage bladder into the OILREC
vessel:The differences between what was recovered aboard CG/V Nordsjobas and pumped into
the bladder and then pumped aboard NOFO's OILREC vessel is explained by two
incidents.
The temporary storage bladder got a small cut caused by CG/V Nordsjobas unfortunate
manoeuvering and the aft end overload links burst due to incorrect handling during
emptying of the bladder.

Towing speeds and oil thickness measurements:
The new transducer had been connected to the skimmer head and measured the oil
thickness in the apex area. Enclosed is drwg. no 8 showing the relationship between thevessel's towing speed through the ocean and oil thicknesses measured in the apex areaof the V-shaped boom.

24Data were recorded every 3rd minute. And the most interesting period is the peak
period between 1701 hours and 1724 hours when the towing speed increased from 1
knot to 1,3 knot. Prior to this period the oil thickness was less than 11cm at 0,5 knot
while during the peak period the oil thickness increased to an average well over 30cm.
Higher towing speed pushed more oil into the apex area of the V-shaped boom and more
oil was fed to the skimmer. This can also be seen quite clearly form the records of theamount of free water pumped. Free water decreased significantly while the amount ofoil emulsion recovered during this 23 minutes' period was by far the highest.
Summary:First 24 minutes (1637 - 1701 hours):

11,2 m3 emulsion recovered

Next 23 minutes (1701 - 1724 hours):

19,4 m3 emulsion recovered

Final 15 minutes (1724 - 1739 hours):

10,0 m3 emulsion recovered

During the first period the boom system was still being filled and during the last period
it was being emptied. - The recovery rates averaged 100m3/hr from 1637 hours to 1701
hours, then decreased to 80 m3/hr. from 1701 hours to 1724 hours and subsequently
averaged 110m3/hour.

Final remarks:
While the entire exercise suffered somewhat from the difficulties with the unstableemulsion this part of the exercise was performed as planned but with a reduced amountof emulsion which might have given more conclusive results. And SFT had reason to besatisfied with the overall performance of their total oil containment, recovery andtemporary storage system.

5. Advances in the Norwegian oil spill preparedness since EKOFISKBRAVO in 1977 until today.
The Norwegian oil spill preparedness has progressed significantly over a 20 year period
and this is no doubt much thanks to NOFO's oil-on-water exercises. This kind of reallife experience has offered unique opportunities for understanding what goes on during
a spill. However, it may be a potential weakness that much of the Norwegian efforts
have focused around crude oil spills. This because no spill is alike and the heavy oil (f.ex.
Bunker oil) spills are much more costly and difficult to handle compared with crude oilspills. This is why SFT in recent years has taken a more active role in developing an oil
spill response strategy incorporating both an efficient high seas capability along thecoast and an inshore and onshore beach cleaning capability.

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