Arctic may reveal more hydrocarbons as shrinking ice provides access

May 2, 2011
Condensed from a presentation at the first Offshore Technology Conference Arctic Conference Feb. 6-9, 2011, in Houston.

Marc Blaizot
Total SA
Paris

Condensed from a presentation at the first Offshore Technology Conference Arctic Conference Feb. 6-9, 2011, in Houston.

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 (Fig. 1).

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 (Fig. 2):

• 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.

Influence of Barents Sea uplift

The picture could be more complex if we remember the last several million years' history of this basin, which underwent a large erosion of more than 1,000 m in Tertiary (Fig. 3).

This induced a beginning of hydrocarbon migration southwards and gas expansion due to shallow burial and a decrease of reservoir pressure. But more striking have been the onsets of a thick ice cap associated with permafrost in Quaternary that has increased the pressure at depth particularly of the cap rock inducing important leakage and within the reservoir generating fluid shrinkage. Melting of the ice cap in recent times induced again a pressure decrease and gas expansion and therefore generalized gas caps.

The amplitude of these phenomena of icing and melting has been so huge in Quaternary with so many periods of green and icehouse effect that it has been detrimental to the presence of oil. As a consequence oil could be found only on the edges of the basins or at very important depth where hydrocarbons always remain in monophasic (critical fluids) phase.

Accordingly where thick ice caps have expanded associated with uplifts and erosion at the edges of the newly created oceans, gas probability will be high. Total has developed a model based on ice pack history allowing to define these gas prone areas (dark blue in Fig. 3). These regions encompass a large part of the Russian arctic basins, whereas the light blue areas would be more oil prone and mainly located in the US, Canada, and Greenland.

The Arctic predominance of gas

Geological and ice extension histories, therefore, should permit the forecasting of what could be found even in poorly explored frontier basins.

As an example here is the Kara Sea (Fig. 4) where two huge gas fields were discovered in the 1980s and presenting however excellent oil prone source rocks in Jurassic seems to be quite similar to the Hammerfest basin. In such a configuration gas should be expected, oil being still possible at the edges of the basins in prospects mapped both northwards and southwards.

The Laptev Sea basin in Eastern Siberia is a frontier basin. It should have both gas and oil-prone source rocks according to Total's geological interpretations, but there too gas is the most probable fluid as it could be witnessed by the direct hydrocarbon indicators exhibited on the rare seismic lines shot there.

In terms of resources, the amount of hydrocarbons to be discovered is huge and could be between 65 billion boe and 215 billion boe of risked resources, the most important part being located in Kara and Barents Sea basins, 80% of it gas by Total's analysis. Naturally, this potential becomes the focus of much interest, sparking often less than friendly competition from both states (disputed frontiers, a Russian flag "flying" at the North Pole in summer 2007…) and businesses ("battles" between oil companies). And all this notwithstanding that due to the extreme climatic conditions, the economics of producing any oil or gas from possible discoveries is uncertain, at least at current oil and gas prices.

Prevailing fluids and yet-to-find volumes

Large exploration potential still exists both in prolific and frontier basins, mainly in Russia, where the predominant fluid will be gas by far (Figs. 5 and 6).

Oil should be and would be explored for thanks to two main criteria: source rock nature and maturation as well as quaternary icing history.

Exploration will be difficult owing to the exceptional climate conditions, equally hostile to man and equipment.

The inventory of these regions' oil and gas potential is far from complete. This is due chiefly to lack of seismic acquisition and exploratory drilling, the only techniques capable of verifying at depth the existence of hydrocarbon accumulations, as both are hampered by the frequent presence of pack ice in winter and marshy areas onshore in summer.

Moreover, due to the rich array of flora and fauna—above ground, fresh water or marine conditions with planktonic and-or benthic fauna—highly specific precautions have to be taken in deploying equipment that may prove harmful in the medium term.

Pack ice shrinks to permit exploration

Taking into account 30 years' global warming, it is reasonable to assume that in most of the shallow-water offshore locations in the Arctic surface pack ice coverage will drastically shrink over the next 20 years, even in winter.

This warming is thought to be essentially due to human activity (anthropogenic): the emission of greenhouse gases, the products of pollution generated under latitudes far removed from the Arctic, in industrialized countries.

Even though exploring for and producing hydrocarbons in Arctic regions will cause only an infinitesimal increase in GHGs compared with the emissions from agriculture, industry, or global transport, every possible effort must be made to keep the impact of these activities on the extremely fragile, pristine Arctic environment (in terms of its biodiversity and communities) to an absolute minimum.

In managing these activities, the oil companies and the states bordering the Arctic must therefore treat this environment with the greatest care and attention to detail. Effectively, they are very capable—working in cooperation—of undertaking these highly costly explorations and developments, in coordination with national governmental organizations and local communities.

On this condition, global warming may prove to be a genuine opportunity for growth and sustainable development, for the planet as a whole and for the circumpolar regions in particular.

The author

Marc Blaizot is exploration director of Total Exploration & Production. He began as a geologist with Elf Aquitaine in 1979, holding a variety of positions focusing on basin evaluation, prospect generation, and appraisal of discoveries in Italy, Norway, and the UK. Appointed senior vice-president, exploration, in Angola in 1992, he headed the team of geologists and geophysicists that discovered giant Girassol field. From 1996 to 2001, he conducted geoscience analyses for Syria, Iraq, Qatar, and Asia at the Scientific and Technical Center in Pau, France. He was appointed senior vice-president, geosciences, in December 2008. He is a graduate of Ecole Nationale de Geologie.

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