Spot oil prices, now just above $50 a barrel, usually attract all the attention. Recently, however, the price movements in some far forward contracts have been more dramatic, with prices hovering at a five-month high of about $80 a barrel. Take the West Texas Intermediate contract for delivery in December 2015, a relatively liquid future used as a proxy for long-term prices, which closed last week at $79.8 a barrel, the same level as 18 months ago. Spot prices, meanwhile, are at levels of four years ago.

The strength of forward oil prices reflects the concern that while the credit crisis has an impact on demand, supply-side impacts will lag behind and become evident only from next year. The International Energy Agency, the western countries' oil watchdog, estimates that spending on exploration and production of oil this year is likely to drop by 20 per cent, double the initial forecast. “Non-Opec project cancellations and slippage out of the 2009-2010 start-up horizon alone stand at 1m barrels a day or more,” it says, adding that supply losses could be even bigger as oil companies curtail maintenance in mature fields in the key regions of North America, the North Sea and Russia.

The investment thesis in forward oil prices says that when the economy starts to recover next year it will discover that supply is falling, pushing prices sharply higher. It also reflects higher costs in areas such as deep water or oil sands and Opec's desire to lift prices towards $75 a barrel in the medium term. It is a plausible investment scenario. But it could still suffer if the natural sellers of forward oil contracts – companies seeking to secure their cash flow to finance projects, which until now have been almost absent – return to the market, taking the opportunity of high forward prices to raise finance, bringing prices down. For investors, it is still a two-way street.