High Latitude Exploration And Production

There has been much speculation on the hydrocarbon potential of Antarctica (e.g., Wright and Williams, 1974; Ivanhoe, 1980; Mitchell and Tinker, 1980; Cameron, 1981; Apostolescu and Wanneson, 1982; Auburn, 1982; Behrendt, 1983b, in press; Bergsager, 1983; Guillaume, 1983; Garrett, 1984; Quilty, 1984, 1987; Tessensohn, 1984, 1986; Aleyeva and Kucheruk, 1985; Cortes, 1985; Shapley, 1985; Davey, 1985; Ivanov, 1985; Roland, 1986; St. John, 1986; Anderson, 1987; Crockett and Clarkson, 1987; Larminie, 1987; Parsons, 1987; Elliot, 1988). For instance, St. John (1986) identified 21 sedimentary basins for the Antarctic and immediately adjacent areas. Of these, 10 basins were estimated to contain approximately 16.9 million km3 of sediment with a potential hydrocarbon yield of 203 billion barrels of oil equivalent. However, Parsons (1987) would speak for most in stating that estimates of the hydrocarbon resources of Antarctica are without scientific foundation and at best can only be categorized as guesses. In his opinion, it is hard to see how Antarctica could come anywhere but last on a global rating of known sedimentary basins in terms of the hydrocarbon potential. Further, unconventional sources of hydrocarbons may well be cost competitive with Antarctic oil (Garrett, 1984).

While hydrocarbons may or may not be present in the basins offshore Antarctica, it is important to recognize that, unlike other regions of the world, the harsh climate and remoteness bring into question the viability of exploring areas with even good geological potential. It is an important part of assessing the overall potential of these Antarctic basins to review the physical and logistical difficulties that would have to be overcome (Holdgate and Tinker, 1979; Mitchell and Tinker, 1980; Sanderson, 1983; Anonymous, 1986c; Parsons, 1987).

Exploration in the Northern Hemisphere high latitudes has shown that explorers can now cope with the cold, ice and snow (cf. Anonymous, 1986b; Curlin et al., 1986). Even the problem of icebergs off the east coast of Canada has been overcome for exploration purposes so that the north can be explored without too many problems apart from seriously raising costs.

While the problems of cold, snow and ice are similar in the Southern Ocean, these factors are compounded in the south by major additional factors. Winter temperatures are more extreme with low temperatures from -80°C on the high ice plateau to -60°C near sea level. The continental size more than doubles during the winter with the ocean freezing out beyond the 200 m isobath (Ivanhoe, 1980). The land and sea distribution of the Antarctic and Arctic are in fact reversed. The Arctic is an ocean surrounded by land whereas the Antarctic consists of a continent surrounded by ocean. Throughout the year, the ice-choked and stormy seas around the Antarctic continent hinder access. Great cyclonic storms circle the Antarctic with no land to break their progress and relentless force. Moist maritime air interacts with the cold polar air which makes the Antarctic Ocean in the vicinity of the Polar Front one of the world's stormiest.

Access

The extreme remoteness of Antarctica contrasts with the Arctic. In the Arctic, materials can be moved north to the Arctic sea coast from ice-free harbours or across land whereas Antarctica is surrounded by vast Southern Ocean where 2-3,000 km of some of the world's roughest waters must be negotiated. In addition, there is a very short period of only 2-4 months a year when the continent can be reached by ship and then only with icebreaker assistance. This means that supply lines would be tenuous.

Drilling

Then come the problems with drilling. Since all of the Cretaceous and Tertiary basins of the Pacific margin of Antarctica are located under major shelf ice or in the offshore areas, conditions relevant to these areas must be considered. The Ross Ice Shelf is not a stable platform but has a horizontal movement of up to 6 m per day. This would cause serious drilling problems necessitating continuous hole widening and moving of the rig. Offshore, in the Ross Sea (the most likely area for initial exploration), the first problem is the depth of water. Water depths are typically 400-600 m and almost never less than 200 m. The sea is subject to violent wind and wave conditions and during much of the year is covered with 1-2.5 m of ice. Extremely large icebergs are common in these Antarctic waters. They are typically 200-400 m thick and 700-1,000 m across but have been known to exceed 150 x 70 km.

To overcome these drilling problems, Sanderson (1983) has suggested that, while there is often only about 10 m of water beneath the Ross Ice Shelf, there are points where the ice grounds on a shoal. The ice then becomes stationary and this would allow year round drilling. However, there are only a few shoals. Only a very limited area for exploration would therefore be available from these locations.

Another solution suggested by Sanderson (1983) would be to form an ice island by grounding a large iceberg at the location of interest by adding ice to its upper surface. This is a much cheaper and environmentally more acceptable than building an artificial island of gravel (which would require up to 5 km3 of gravel at these water depths) since on completion of the work the grounded berg can be left to melt and drift away.

Production

While exploration is used to assess the potential of a region, there is little point in finding oil unless it can be produced economically. To be economic, almost year-round production would be required. Whereas exploration requires suitable conditions over a few months, production requires these conditions over many years. With the water depths involved, the only realistic techniques would again be to ground an iceberg and to keep adding new ice to it to keep it grounded over many years or to produce from a totally subsea system where the units would be buried 25-30 m below the seafloor in water depths of up to 500 m to protect them from ice scour (cf. Keys, 1984; Barnes and Lien, 1988). These units would only be able to be maintained during the summer ice-free period and by submarine.

At present, this is still not technically feasible (Mitchell and Tinker, 1980; Sanderson, 1983; Crockett and Clarkson, 1987; Parsons, 1987). Even when the problems in developing the production facility have been overcome, the oil has still to be transported to markets. Unlike in the Arctic, the oil cannot be piped ashore and then overland to markets.

In the Antarctic, there are still the problems of nine months of sea ice and the vast Southern Ocean over which to transport the oil. Only questions can be raised at this point. Is it viable to store the whole year's product adjacent to the facility and ship it out during the summer? This idea ignores the fact that, as in 1985-86, severe ice can restrict or curtail all shipping even during the normal time period. It also ignores the environmental questions of storing and moving huge quantities of oil through very dangerous and difficult regions. Would a pipeline north to Australia or New Zealand be possible considering it would be 2-3,000 km long with ocean depths in excess of 5 km? Whatever, the cost of production of Antarctic oil it is likely to be extremely high and this is likely to be the main constraint to exploitation (Garrett, 1984).

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