Communication for Sustainable Development

Arctic may reveal more hydrocarbons as shrinking ice provides access

Geographically, the Arctic polar regions correspond to the whole of the land and sea area north of the Arctic Circle (66° N. Lat.), roughly from north of Iceland on one side and south of the Bering Strait on the other. It represents around 20 million sq km.
Within the Arctic areas around 400 billion boe has been already discovered, 80% being gas!

The main proved basins and mostly untapped reserves are located in Russia, the Barents Sea, the Kara Sea, and the Yamal Peninsula for gas and in Alaska, the North Slope basin for oil. Others important basins are Timan-Pechora in Russia as well as the MacKenzie Delta and Sverdrup basin in Northern Canada.
Several basins mainly located in Eastern Russia are totally virgin, devoid of any exploratory wells, and are conceived only through neighboring outcroppings as well as sparse 2D seismic lines. They are mainly the offshore North Kara Sea, Laptev Sea, East Siberia platform, and North Chukchi that together represent more than five times the surface area of Texas.

For explorationists, two key questions are:
Why so much gas at a scale unknown in any other region of the world?
Can we find oil in the Arctic and where? The latter question is important, because Arctic gas except in the Yamal Peninsula and Barents Sea could be stranded for long periods.

Assessments of the Arctic endowment

The Arctic Polar Regions owe their principal bathymetric and orographic features to two oceans, the North Atlantic Ocean and the Arctic Ocean .
The geological organization results from geologically speaking recently created oceanic crusts in Cretaceous times for the Eastern Canadian basins and in early to late Tertiary times for the Atlantic and the Arctic Oceans that have triggered off the separation of the North American plate and the Eurasian plate.
These oceanic openings and continental drifts have been preceded by tectonic tension phases since Middle Triassic, having created rift and graben structures followed by platform sags. This history is similar in a lot of Arctic basins, the differences coming mainly from presence of Tertiary orogenic events north of Alaska and East Siberia.

Such a structural configuration induces four main post-Hercynian petroleum systems linked to four source-rock deposits:
• Late Triassic marine source rocks extended in practically all the known already drilled basins from the Chukchi Sea westward to the Yamal Peninsula eastward.
• Late Jurassic exceptionally rich marine source rocks spread over the Barents, West Siberian, Yamal, and probably Kara seas (the well-known Bazhenov source rock) as well as in the North Slope.
• Then in Upper Cretaceous marine source rocks are known in North Canadian and North Alaskan basins as well as possibly in western Greenland and Baffin Bay.
• And finally, since Oligocene deltaic source rocks, more gas prone, were deposited in big northward-prograding deltas like the Mackenzie and Lena rivers.

When source rocks are superimposed with already discovered fields, an amazing anticorrelation appears between largely predominant marine, oil prone source-rocks and gas fields, implying that mechanisms other than the nature of source rocks are needed to explain the gas discoveries.
The only exceptions are clearly Prudhoe Bay and adjacent fields and very rare oil tests such as Goliath in the Barents Sea. There the two excellent marine oil prone source-rocks have generated an exceptionally high quantity of oil in stacked fluvial channel deposits, sandstone reservoirs of Triassic age. Both Triassic and Jurassic source rocks are within the oil window as exhibited by the maturation indexes.
Other oil discoveries are possible in the offshore part of this basin even if these source rocks are without any doubt much more deeply buried (>5,000 m). But liquids could be present as condensate given the probable high pressure (600 to 800 bars) and nature of the source rock. More than 1 billion bbl of condensate has been calculated on the Dinkum South undrilled area where the excellent Sadlerochit reservoir seems present and thickens from south to north.
The Beaufort Sea basin in Canada is also marked by an important orogenic compressive event in Mid-Tertiary followed by an important prograding Tertiary delta linked to the paleo and present Mackenzie River. Mainly gas discoveries have been found in Tertiary platform or turbiditic sandy reservoirs associated with gas prone source rocks.
Northwards more distal conditions should prevail according to Total's paleogeographical reconstructions. Therefore oil prone marine source rocks could be encountered. Huge folded structures are present there and should intersect distal channel and levee turbiditic complexes mainly in the Oligo-Eocene series. Therefore both Dinkum and North Beaufort clearly exhibit promising plays for the present decade of exploration.
The Hammerfest basin in northern Norway is well known through the development and production of the most northwards LNG production to date, the Snohvit field complex. But it is above all the perfect example of a basin, rich in excellent marine oil-prone source rocks both in Triassic and above all in Jurassic layers and finally very poor in oil discoveries except for Goliath field on the southern edge of the basin. The Snovhvit complex, however, has been fed with oil as witnessed by the numerous oil shows located below the gas pool in the presently water-bearing zone. Several hypotheses have been contemplated for explaining this result, the first one being the past oil flushed by the subsequent gas generation with consequent oil migrating towards the southern updip basin edge.
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