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17. Arctic Offshore Technology and Its Relevance to the Antarctic K. R. Croasdale INTRODUCTION In considering the issue of potential antarctic oil and gas resources, especially offshore, it is perhaps relevant to look to the Arctic for an analog of what might be possible. This chapter will provide a briefing on the technology being used and/or developed for Arctic offshore oil and gas operations. For our purposes, the Arctic will be defined as northern offshore areas subject to major ice coverage. Therefore, the Canadian east coast, with its iceberg problems, is also included. My major focus will be on operations in Canada, where most oil and gas activity has taken place. Other nations bordering on the Arctic, however, also have interests in Arctic off-shore resources and are developing technology similar to that which I will describe. Where appropriate, reference will be made to the similarities and contrasts between the Arctic and the Antarctic. The chapter will conclude with some specific comments on the possible adaptation of Arctic offshore technology to the Antarctic. GEOGRAPHY AND OIL AND GAS RESOURCES The Arctic consists mainly of a large ocean surrounded by land that is divided here and there by straits, channels, and small seas. The Arctic Ocean can be considered a polar Mediterranean--an inland sea with very little com- munication, except through the Fram Strait, with the other oceans of the world. It is a hostile region, but because of the populated, surrounding land masses, human presence around the 245

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246 fringes of the Arctic Ocean has existed for at least 40,000 years. Only during the past three centuries, however, have Europeans endeavored to explore and exploit the region. Early ventures used wooden sailing ships and were conducted either for whaling or for exploration, especially in the search for a northwest passage to Asia. Arctic technology used before about 1900 was not really adequate; many expeditions spent years at a time trapped by ice in the Arctic, and many of the explorers perished. Today, the major incentive for Arctic operations is the exploitation of minerals, primarily oil and gas. During the past 15 years or so, the Canadian oil industry, encouraged by government incentives and the prospect of large discoveries, has been very active in exploring Canada's Arctic and offshore areas. Although no produc- tion has yet occurred from Canada's offshore Arctic, several promising discoveries have been made: . · gas and oil in the Beaufort; · gas and some oil in the High Arctic (Arctic Islands); · gas off Labrador;'and oil off Newfoundland. Furthermore, there is the promise of large oil and gas reserves yet undiscovered. Canadian government sources predict mean potential recoverable reserves of oil for the Canadian Beaufort of about 8.5 billion barrels; for the Arctic Islands, about 4.3 billion barrels; and for the Canadian east coast, about 12 billion barrels. On the Alaskan continental shelf, a mean value for potential recoverable reserves is about 818 billion. This, plus the desirability of North American self-sufficiency in energy, is the incentive that has led the major oil companies and governments actively to pursue the exploitation of Arctic oil and gas (despite its high cost relative to oil and gas operations in more temperate regions). Of course, the high cost of Arctic oil and gas operations is mainly a function of the climate, the remoteness, and especially the presence of offshore ice THE ARCTIC OFFSHORE ENVIRONMENT . The Arctic Ocean is covered with drifting ice. Only in the more southerly coastal zones does the ice clear every summer. The major drift patterns of the Arctic ice are

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247 shown in Figure 17-1. The Pacific or Beaufort gyral dominates the ice drift in the North American sector of the Arctic Ocean, rotating clockwise, completing one revolution in about 10 years at a rate of several kilometers per day. It consists mostly of multiyear ice with an average thickness of about 5 m. Around the edges of the Arctic Ocean, the ice melts and reforms every year, creating first-year ice with a maximum thickness of about 2 m. Close to shore, out to about 20 m water depth and between islands, the ice becomes landfast each winter. The approximate demarcations among the various ice zones in the winter in the Beaufort Sea are shown in Figure 17-2; this is typical of most of the coastal regions of the Arctic Ocean. As depicted in the cross section (Figure 17-3), pres- sure ridges, both first year and multiyear, can occur in all the ice zones. The probability of seeing multiyear ice in the near-shore zones is quite low; in fact, it usually invades only during those summers when the permanent polar pack is driven south by onshore winds. This occurs on average about once every five years. Pressure ridges, especially multiyear ridges, are the ice features that create the greatest difficulty for offshore operations. The movement of multiyear floes and ridges against offshore platforms causes high lateral loads, and these also create the most difficult obstacles for ice- breaking vessels. Multiyear ridges up to about 25 m thick can occur. The pressure ridges that ground in the near-shore zones cause gouging of the seafloor. Numerous gouges several meters deep have been observed. Any seafloor facilities, such as pipelines and wellheads, have to be protected against this ice action. The present approach is to put such facilities into trenches, so that they are below the depth of the deepest gouge likely during their lifetimes. The open water in the coastal zones does allow floating operations to be conducted during the short summer season. In the southern Beaufort Sea, the period of open water averages about 100 days. This period gets shorter with increasing distance offshore. Off Canada's east coast, annual pack ice occurs south to about 45°N latitude. The open-water period off Newfoundland can range from about 200 to 365 days per year. Further north in the Davis Strait, it reduces to about 100 days.

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248 o f~ t~ I. _ ·o - Shoe 5, at, _ ._ C, ' (,0 HI J a] ,~@ a) .,, .,, Sit a' O O i.,, Nat fir . /~ ' ~ C am ° o 0 0 . o _' ~~ - ~ a) 1

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249 I 0, 1 l l l A. , _ C _ . , STATUTE MILES 100 50 0 100 200 :300 400 · ~ ~ __ ~ ARCTIC PACK ICE ; B~/ 1 \5~U A\ MAINLY OLD ICE 3-4 MEtERS THICK MOVING SLOWLY YEAR ROUND. SOLID AND UNMOVING OLD OR FIRST YEAR ICE OR A MIXTURE OF BOTH COMPLETELY COVER I NO TH E WATERWAY. MORE THAN 7/8ths MAINLY FIRST YEAR ICE 1-2 METERS THICK IN INTERMITTENT RESTRICTED MOTION. FIGURE 17-2 Typical winter ice conditions in the Beaufort Sea area (February) (Department of Energy, Mines, and Resources, 1970) (Reprinted with permission) \ \ .

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250 I LANDFAST ICE MOBILE POOR PACK ,. ~ . BorrOM FLOATING ICE GROUNDED ICE SEASONAL ICE ZONE FAST ZONE ZONE TRANSITION FIRST YEAR GROUNDED · ZONE PRESSURE FIRST _" ~ MULTI-YEAR FLOES Ah) ~ ~~ 'I FIGURE 17-3 Near-shore winter ice conditions in the Beaufort Sea. In addition to pack ice, there are many icebergs off Canada's east coast. The major source of icebergs in the eastern Arctic is the Greenland ice cap, which annually calves about 240 km3 of glacier ice into the surrounding seas. This results in about 20 to 34 thousand icebergs per year, although on average only about 500 per year will reach the Grand Banks area off Newfoundland. These icebergs are much smaller than those in the Antarctic. There are no icebergs in the Beaufort Sea, but large pieces of ice shelf ice can occur, which are called ice islands. Ice islands are calved from a relic Pleistocene ice shelf that still exists along the north coast of Ellesmere Island. When calved, the thickness of an ice island can be greater than 50 m, and ice islands can be as much as 10 km in extent. However, large ice islands are so rare (perhaps only one still exists in the Arctic Ocean) that offshore platforms justifiably need not be designed for them. The probability of a collision is extremely low, and ice islands could be detected well ahead of a collision so that people could be evacuated and oil wells sealed off below the ocean floor. (A similar approach is used for hurricanes in the Gulf of Mexico.) The water depths of the continental shelves surround- ing the Arctic Ocean are shallow relative to the Antarc- tic. In the Arctic the shelf break starts at about 100 m depth. Most offshore operations to date have been con- ducted within this water depth (although wells off the East Coast of Canada have been drilled in water out to about 1,000 m).

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251 TECHNOLOGY FOR ARCTIC OFFSHORE PETROLEUM OPERATIONS General Potential hydrocarbons have to be drilled into in order to confirm their presence. So one of the first tasks for the oil industry in the Beau for t Sea was to consider various methods of offshore drilling in ice covered waters. Figure 17-4 was drawn about 10 years ago. It shows the various concepts being considered at that time. These ideas range from building artificial islands in the very shallow waters (which can be used year-round) to floating drilling in the deeper waters during the ice- free periods. Also shown are gravity-founded mobile drilling units, which could be ballasted down onto the seafloor, and drilling off the landfast ice during the winter. Active systems using ice cutters in order to remain on location in moving ice were also proposed. Some of the systems shown in Figure 17-4 have been put to use during the past decade, and these will now be described in the context of main geographic areas. The Beaufort Sea Of all the concepts shown, in the Beaufort Sea the artificial island has been one of the most successful, especially in water depths out to about 20 m. ESSO Canada built the first artificial island in 1972. A typical island in summer conditions is shown in Figure 17-5. To date, well over 20 islands have been built and PACK ICE FAST ICE (YEAR ROUND) ///" //: GRAVITY CONE ~ OR MONOPOD GRAVEL ISLANDS I'd Hi. .;..; ~ ; . .. , ..; .__ 1 , , 0 2 6 20 WATER DEPTH (m) ~C,, ~ 0 — ICE CUTTER — SEMI SILT ISLANDS RCRAFT BARGE FAST ICE (WINTER ONLY) 74-='>~ LOCAL ICE THICKENING ~- ~ ' 1 ' -' ' ' ~ OPEN WATER DRILLSHIP DRILL BARGES - 1 00 700 FIGURE 17-4 Exploratory drilling concepts for ice infested waters (Croasdale, 1983) (Reprinted with permission).

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253 drilled from in the Beaufort (Figure 17-6). This map also shows locations drilled using ships, which I will discuss later. Islands constructed in the summer by dredging have been a favored technique for Canadian Beaufort exploration in the shallow water. In contrast, most islands constructed off Alaska have used land sources of gravel. Islands have proved very adequate in resisting the ice, but their cost effectiveness decreases with water depth. In water depths beyond about 20 m the fill requirements tend to be prohibitive, especially for in the summer islands with very shallow slopes. Also, islands are susceptible to wave erosion during the summer months particularly during construction. For these reasons retained islands were conceived both to reduce fill volumes and to provide immediate wave protection at the waterline. One of the first designs for a caisson-retained island was Esso Canada 's. This consists of a ring of steel caissons retaining an interior sand fill. The caissons are placed on a berm, which can be adjusted in size according to water depth. The Esso retained island has drilled two exploration walls to ~At" in wager A=~Eh~ ^ to 26 m. A different design of caisson-retained island was used —- -,=~ &- A_—_— —~ ~~—~ ~ 11 ~~ ~~ ~C~11= Vim ~ at Tarsiut in about 22 m of water. Here, four concrete caissons were placed on a berm and filled with sand to provide the retaining structure for an interior sand fill. The Tarsiut island also utilized steep dredged slopes; one in 5 compared with one in 15 on most Esso islands. The Tarsiut island set a record for drilling at the very edge of the landfast ice in the winter of 1981/1982 and is shown in Figure 17-7. The island proved well able to resist the ice forces but had a rather limited surface area. Another disadvantage of the retained islands shown so far is the need to Diane two ~ a land rig on them after construction. In a short Arctic summer this can be a problem, and icebreaker support is often required. The Gulf Canada Molliqpak was conceived to overcome this problem by designing it with a rig permanently mounted on the caisson structure. The caisson has a hollow core, which is sand filled to provide sliding resistance. The Molliqpak was constructed in Japan and is now on location in the Canadian Beaufort, drilling its first well in 26 m of water. A similar philosophy of a ready-mounted rig was adopted with the design of the dome single steel drilling caisson

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255 .. __ ~ ~ _ ~ a: :: :: _ :: _ - .- . :Si ~- _ ,. . FIGURE 17-7 The Tarsiut Drilling Island in the Beaufort Sea (Courtesy of Dome Petroleum Ltd.). (SSDC). This concept was designed for rapid deployment by water ballasting down onto a prebuilt underwater berm (at -9 m below seabed). The main structure of the SSDC is actually the con- verted for ebody of a very large crude [oil] carrier specially strengthened to resist the ice loads. It was designed and brought into the Beaufort ice in less than nine months. The SSDC also holds the record for the greatest water-depth drilled by fixed platforms in the Arctic. This was at Uviluk in 31 m of water, well outside the landfast ice. Meanwhile, the U.S. operators have been busy in the Alaskan Beaufort. Several artificial islands have also been built there in recent years for exploratory drilling. This year the Global Marine concrete island drilling system (CIDS) is drilling its first well for Exxon in 15 m of water. The CIDS is a self-contained caisson system that relies on water ballast and can, therefore, be rapidly deployed. Also of significance is that at its present location no foundation preparation was done; it was put down directly onto the seafloor. It is also worth noting that at this location Exxon will be building a spray-ice barrier to provide additional sliding resistance against late winter ice. Spray-ice barriers

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256 and rubble-protected systems may enable exploration concepts to be used in the future. In the even deeper Beaufort waters, Dome Petroleum has pioneered the use of drill ships, which were brought into the Beaufort in 1976. The drill ships are, of course, ice strengthened, and when the ice is managed with icebreakers, drilling can continue into freeze-up. However, it is not usually possible to drill much beyond late November or when the ice is about 0.3 m thick. A late-season drilling situation is depicted in Figure 17-8. The summer drill ship season is short, hardly long enough to drill and test one well. For most of the year the drill ships remain unused in a winter harbor. To extend the floating drilling season, the Gulf subsidiary Beaudrill designed and built a round drill ship, the Kulluk (Figure 17-9). Kulluk is designed to stay on location with 1.3 m of ice moving against it. It is held on location with twelve 9 cm mooring lines. Ice management is provided by two Class 4 icebreakers and two ice-class supply ships. So far Kulluk has drilled two discovery wells and apparently has a performance record that exceeds expectations. Incidentally, Kulluk was FIGURE 17-8 Late summer drilling in the Beaufort Sea (Courtesy of Dome Petroleum Ltd.).

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/ / / moo q - ~ _ 1 1 ~ ~- HULL TANKS 257 Li me 1 AT 1 ~ Ill \ - \N \ a_ DRILL FLOORS I I T 11 i''j'''''i'''1 ~ _ ll - 44 - . MAIN DECI ELEVATION (FEET) ~ - ~ 1 HULL TANKS 1 ~ FIGURE 17-9 Typical cross section of Kulluk, showing mooring wire routing (Frankovich, 1984) (Reprinted with permission). recently approved by the regulatory agency--the Canada Oil and Gas Lands Administration--as a relief well- drilling system for the fixed-caisson systems described earlier. For floating drilling, regulations require that no drilling into hydrocarbon (or potential hydrocarbon) zones take place during the last month of the season, in

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258 order that time be available to drill a relief well in the event of a blowout. During the decade of Beaufort Sea drilling there have been no blowouts and (as far as I can judge) no damage to the environment. However, because of the high logistics . . . costs, the special equipment, and the short season of use, it is not untypical for an exploration well to cost 3100 million. No commercial fields have yet been found, but many encouraging finds suggest that oil and gas production will occur sometime in the next 10 years. The kinds of Production concepts that have been considered for ice-covered waters are shown in Figure 17-10. In the near-shore Beaufort Sea it is expected that artificial islands and/or bottom-founded steel or concrete structures will be used. Fixed platforms in ice-covered regions are probably feasible out to 100 m water depth. Beyond that, some kind of subsea production technology, which is currently being developed for other deep-water offshore areas, will likely be needed. If oil production does occur from the Beaufort Sea, the oil will be transported to market by either pipeline or tanker; both alternatives are being studied. On the U.S. side, the existing Alaskan pipeline will likely be used for future offshore production. On the Canadian side, a new pipeline down the Mackenzie Valley would be required. However, as the reader may be aware, a large- diameter gas pipeline down the Mackenzie Valley was ruled out in 1977. At that time, an independent review com- mission advised the Canadian government that construction of a large-diameter line would have an adverse effect on local communities. Since then, however, a small 30 cm oil line has been built to Normal Wells (halfway down the valley), and by analogy it could be extended to the Beaufort by the early 1990s. . The alternative, icebreaking tankers, has of course been under consideration since the late 1960s when the Manhattan performed trials in the Arctic in 1969. Since that time, there have been significant advances in ice- breaker design, motivated by Beaufort Sea exploration. Some of the small icebreakers designed by Beaufort operators do incorporate features that could be used on large icebreaking tankers. It is claimed by their proponents that icebreaking tankers would be much safer than conventional tankers. This is because, to combat the ice, they have to be much stronger and incorporate significant redundancy. Thus, an icebreaking tanker

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259 TUNNELS ALL ICE ZONES W I TIN —PROTECTION A I— Q —(~ ~) ~ ~ Am, ~ / / / / '7 GRAVITY CONE OR MONOPOD ISLANDS l / '/'// / / / / j A-/ _ SUBSEA PRODUCTION o l 6 20 100 WATER DEPTH ( m) 7a 0 FIGURE 17-10 Production concepts for ice infested waters (Croasdale, 1983) (Reprinted with permission). would have double hulls, twin screws, and twin rudders; it would also have a much greater power-to-displacement ratio than conventional tankers. The other commodity of interest is, of course, natural gas. From the Beaufort we would see pipelines as the favored system, either linking with a gas pipeline from Alaska or being part of a polar gas pipeline bringing gas from the High Arctic. For the gas from the High Arctic. liquefied natural gas (LNG) tankers have been considered. These would ply the Northwest Passage and take gas to eastern markets or even to Europe. LNG tankers have also been designed and would contain many of the features discussed for oil tankers. Currently, the Arctic Pilot Project, proposing to ship LNG from the High Arctic, has been shelved, primarily because of lack of markets for gas rather than concern about technical feasibility. It should be noted that the distances that the Arctic tankers would have to travel to reach either Europe or the eastern United States are about the same as the distances from the Antarctic to such areas as South

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260 America, Australia, or New Zealand. Furthermore, they are less than the distance from the Middle East to the United States. The Canadian Arctic Islands (High Arctic) The ice between the islands of the Canadian archipelago is quite different from that in the Arctic Ocean, primarily because it moves less. Over much of the area it becomes landfast every winter. This, combined with the deeper water (typically 200 to 300 m), has enabled exploration drilling to be conducted using ice as the platform for the drilling rig (Figure 17-11). This method requires ice thickening by flooding, to support the rig and avoid creep failure of the ice under sustained loading. Such techniques are now routine, and several oil and gas discoveries have been made using this very cost effective method. Small ice movements can be tolerated by the marine riser system (as used in floating drilling). Larger movements can be accommodated by moving the rig, but these movements have to be less than about 10 m during the period of drilling the well (say, 30 to 50 days). Production methods from this area will need to be based on subsea production technology. A trial subsea completion for a gas well with pipeline to shore has already been implemented. SURFACE B.O.P. STACK TRIG 770 TONNE _~ I ~ ~ NATURAL ICE _ ~~M BUILT UP ICE i 'I 1 WATER DEPTH 130 M HYDRAULIC CONNECTOR 130 M j _ MARIN E R ISE R ORILL STRING ~ _ 2~ SUBSEA B.0.P. STACK OCEAN FLOOR t~ ,. T: .,,, ~~ FIGURE 17-11 Drilling off the landfast ice in the Canadian Arctic (Croasdale, 1977) (Reprinted win permission).

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261 The Canadian East Coast (Labrador and Newfoundland) Off Canada's east coast, exploratory drilling has been under way for about 15 years. All the drilling has been performed using either drill ships or semisubmersibles during the pack ice free periods. However, during the ice-free periods, icebergs can still occur, and techniques for dealing with them have been developed. Canadian operators off Labrador and Newfoundland have pioneered drilling among icebergs. The approach is essentially one of avoidance. Alert zones are estab- lished around the vessel; as icebergs enter these alert zones, various operational responses are implemented. In the zone farthest from the vessel, typically several miles, the iceberg is tracked using radar. If the iceberg continues to move in the direction of the vessel, then certain actions may be taken in the drilling opera- tion that would enable the well to be shut in. Also, towing vessels will be dispatched to tow the iceberg away from the drill ship. If for some reason this is unsuccessful, in the next alert zone the well is shut in. If the iceberg continues to move toward the ship, then the drill ship disconnects from the seafloor well- head (and blowout preventer) and moves out of the way of the iceberg. All vessels used in iceberg areas do not use mooring lines but are dynamically positioned (using thrusters). Therefore, the final move off can be accomplished in minutes. After the iceberg threat is passed, the drill ship moves back to the wellhead and continues drilling. To give some idea of the need for disconnects, it is useful to quote some statistics for the Labrador Sea, where drilling started in 1971. In the first season, one drill ship was used, and the season length was 67 days. During this period, 167 icebergs were tracked, 10 were towed, and there was one disconnect. From 1971 to 1982 there were 21 drill-rig seasons. About 2,600 icebergs were tracked, more than 600 were towed, and there was a total of 13 disconnects. It is envisaged that in certain areas of the antarctic offshore, methods similar to those developed for drilling off Canada's east coast could be used. Production from this area will utilize either fixed or floating platforms. It is considered technically feasible to build fixed platforms out to about 200 m; at this dis- tance the platforms can still withstand iceberg impacts. Floating systems, combined with subsea wellheads, are a

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2¢2 more likely alternative in deeper waters. Any subsea wellheads and pipelines would of course be placed in pits and trenches for protection from grounding icebergs. CONCLUSIONS It should be stressed that, even from the point of view of technology, the Arctic cannot be considered a direct analog for the Antarctic. There are some obvious differ- ences. For instance, water depths are generally greater in the Antarctic, icebergs are larger, and the distances to support infrastructure and markets are greater. On the other hand, pack ice conditions are probably less severe in the Antarctic than in the Arctic. Nevertheless, despite these differences, some of the methods developed for the Arctic could be used for exploration. These include (1) Drilling off the landfast ice and ice shelves; and (2) Floating drilling in the summer months combined with iceberg management, including quick disconnects from a protected subsea wellhead. The costs of exploration in the Antarctic are expected to be as great as or greater than the Arctic, where an exploration well costing $100 million is not uncommon. As far as production from the Antarctic is concerned, only in the narrow zone of shallow water (say, less than 50 m deep) could fixed platforms be used. In deeper water, subsea production systems combined with seasonal floating service platforms might be envisaged. These technologies are under development but have not yet been widely used. So far I have said little about research and lead times. It is important to recognize that in frontier areas, many years of research and data gathering are often needed before commencement of operations. For example, in the Canadian Beaufort, offshore leases were taken by the oil companies in the mid-1960s. Environmental data gathering and research commenced in the late 1960s. Exploratory drilling started offshore in 1973. Production has not yet taken place and is unlikely to occur before 1990. By analogy, even if a decision were made now to start looking for antarctic hydrocarbons, and even if feasible technology became available, and even if the economics

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263 were favorable, production and cash flow would probably be 20 to 30 years away. Furthermore, before then, vast investments would be required, and extensive research and data-gathering programs would have to be implemented. REFERENCES Croasdale, K. R. 1977. Ice Engineering for offshore petroleum exploration in Canada. In Proceedings of Fourth International Conference on Port and Ocean Engineering under Arctic Conditions, Memorial University of Newfoundland, Vol. 1:30. Croasdale, K. R. 1983. The present state and future development of arctic offshore structures. Proceedings of seventh POAC Conference, Technical Research Centre of Finland, Helsinki, Vol. 4:514. Department of Energy, Mines, and Resources. 1970. The Pilot of Arctic Canada (Ottawa, Canada), Vol. 1, 2nd ea., p. 89. Dome Petroleum Limited, ESSO Resources Canada Limited, and Gulf Canada Resources Limited. 1982. Beaufort Sea Production Environmental Impact Statement, Vol. 2:3.10. Frankovich, E. W. 1984. Kulluk extends the arctic offshore drilling season. In Proceedings of the Arctic Offshore Technology Conference. (Calgary), p. 17.

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