Extreme oil: Scraping the bottom of Earth's barrel  

David Strahan has an article in New Scientist about peak oil and the Canadian tar sands - Extreme oil: Scraping the bottom of Earth's barrel.

EIGHTY-FIVE million barrels. That's how much oil we consume every day. It's a staggering amount - enough to fill over 5400 Olympic swimming pools - and demand is expected to keep on rising, despite the impending supply crunch.

The International Energy Agency forecasts that by 2030 it will rise to about 105 million barrels per day with a commensurate increase in production (see graph), although whistle-blowers recently told The Guardian newspaper in London that insiders at the IEA believe the agency vastly over-estimates our chances of plugging that gap. The agency officially denies this.

Wherever the truth lies, it is widely expected that by 2030 we will have passed the peak of conventional oil production - the moment that output from conventional oil reserves goes into terminal decline. A report from the UK Energy Research Centre (UKERC) published in August said there was a "significant risk" it would happen before 2020. And that means we will soon be staring down the barrel of the ultimate oil crisis.

Some governments and corporations are waking up to the idea and beginning to develop alternatives to keep the world's transport systems moving when cheap oil runs out. These include biofuels, more energy-efficient - or electric - carsMovie Camera, and hydrogen. But none of these is likely to make up the global shortfall in time. The pressure is on to keep the black stuff flowing and so the next two decades will see an unprecedented effort to exploit increasingly exotic and unconventional sources of oil. They include tar sands (a mixture of sand or clay and a viscous, black, sticky petroleum deposit called bitumen), oil shale (a sedimentary rock containing kerogen, a precursor to petroleum) and synthetic liquid fuels made from coal or gas.

Purely in terms of geological abundance, these sources look more than sufficient to meet global demand. According to the IEA, taken together, they raise the remaining global oil resource to about 9 trillion barrels (see map) - almost nine times the amount of oil humanity has consumed to date. The trouble is that the name "non-conventional oil" hides several dirty little secrets and a whole host of huge challenges.

Conventional oil refers to liquid hydrocarbons trapped in deep, highly pressurised reservoirs, which means that when the wells are drilled, the oil usually gushes to the surface of its own accord. Non-conventional oils are not so forthcoming, and need large amounts of energy, water and money to coax them from the ground and turn them into anything useful, like diesel or jet fuel.

As a result, non-conventional oil production to date has been slow to expand - with current output of just 1.5 million barrels per day. Not only that, because they take so much energy to produce, they are responsible for higher carbon emissions per barrel than conventional oil.