Exploration And Exploitation

Subantarctic New Zealand

There is considerable offshore petroleum potential for areas to the south and southeast of New Zealand (Katz, 1974; Cook and Davey, this volume). Explora tory drilling in the Great South Basin east and southeast of Stewart Island and Solander Basin immediately to the west has proved promising but exploitable hydrocabon accumulations await discovery (Sanford, 1980). Management plans prepared for The Snares, Campbell and Auckland Islands (Department of Lands and Survey, 1983, 1984, 1987) acknowledge the environmental problems that an offshore oil spill could create for these protected Nature Reserves.

Gregory (1985) has noted that Campbell, Auckland and The Snares Islands lie to the west and south of Great South Basin hydrocarbon prospects. Spills at these sources would degrade and disperse rapidly bcause of stormy seas. The persistent, strong westerly wind and wave climate should also ensure that oil slicks are carried rapidly away from these islands. Solander Trough prospects lie to windward of The Snares, but they would be a small target, and again distance and stormy seas should ensure that spills there have minimal shoreline impact. Similarly, the Bounty and Antipodes Islands, although lying downwind from possible spill sites, are small and so distant that little impact can be envisaged.

The towering cliffed and rocky coasts of these islands are high energy exposed shores which, in the event of an oil spill, can be considerd "low risk" for they would self cleanse rapidly of any impacting oil (Gregory, 1985). Wave reflection would probably keep most oil offshore. Oil fouling of the few sandy beaches is unlikely to persist for more than a few months. With the prevailing strong westerly winds, it is most improbable that oil slicks would ever reach the areally-restricted, tidal flats and salt marshes at the heads of east-facing fjards of Campbell and Auckland Islands. These are sensitive "at risk" environments, which, if experience following the Metula spill in the Straits of Magellan is any guide (cf. Gundlach et al., 1982), could take decades to re-establish.

Long term, chronic low-level releases of hydrocarbons from offshore production platforms, would probably have little environmental significance because of dilution, dispersal and rapid degradation. Of more immediate concern would be massive, acute, spills following catastrophic platform failure, rupture of seabed pipelines, tanker groundings or accidents involving onshore (storage) facilities. These could have immediate detrimental effects upon fisheries, sea birds and sea mammals.

One can conclude that for the present the probability of an oil spill in the vicinity of New Zealand's Subantarctic islands is extremely remote, and that clean-up intervention would only be warranted in most exceptional circumstances. There were no reported oil or other pollution incidents during exploratory drilling around this region.

Large icebergs occasionally stray from their usual southern tracks, reaching waters as far north as Chatham Rise (Brodie and Dawson, 1971; Burrows, 1976). It is not idle comment to suggest that they could be an unexpected and unpredictable threat to large, fixed, offshore production platforms, in these middle latitudes.

Ross Sea Prospects

Authorities and observers from many countries have speculated for a number of years on the hydrocarbon prospects for parts of the over-deepened continental margin encircling Antarctica (cf. Cook and Davey, this volume). Of the ten offshore basins that St. John (1986) considered to be viable hydrocarbon targets, those of the Ross Sea region rank highly (e.g., Holdgate and Tinker, 1979; Lock, 1983). Modelling studies suggest that, of the three Ross Sea basins (Fig. 11.11), the Eastern and Victoria Land basins have good exploration potential, while the Central Trough is barely marginal (Cook and Davey, 1984). Discovery of ashphal-tic residues at a depth of c. 633 m near the base of CIROS-1 (Barrett, 1987) will further tantalize hydrocarbon prospectors.

Any commercial hydrocarbon development in the Ross Sea, as elsewhere around Antarctica, would of necessity be at a large scale. It is difficult to establish minimum or optimum sizes for such operations, but a productive field will need to be of giant (500 x 10s barrels) to supergiant (500 x 109 barrels) proportions, and with a daily yield capability of at least 3^100,000 barrels (see Holdgate and Tinker, 1979; Ivanhoe, 1980; Gregory, 1982; Garrett, 1985; St. John, 1986).

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