While no one knows for certain how much oil remains, there is no dispute that there is a finite amount of oil on the planet. "Earth is swimming in the stuff. [...] When the worlds first oil well was sunk in Pennsylvania in 1859, the Earth contained at least 6 trillion barrels of crude oil, geologists estimate. So far we have used only about 1 trillion barrels." (1). However, " the industry is capable of extracting only about half of that amount, and those first 1 trillion barrels were among the easiest to reach. (1). Further "[I]t took 146 years for the world to use the first 1 trillion barrels. The next 1 trillion barrels will be gone around 2030." (1). Paul Roberts, in his critically acclaimed book, The End of Oil, puts it this way: "Thus, the real question is not whether oil is going to run out (it will) but whether we have the capacity, the political will, to see that outcome soon enough to prepare ourselves for it." (2). See "Bottomless Well" on unlimited energy supply.

Peak Oil
Of more immediate importance than completely running out of oil is when oil production will peak.

• Peaking "a term used in oil geology to define the critical point at which reservoirs can no longer produce increasing amounts of oil. (This tends to happen when reservoirs are about half-empty.)"
• Peak Oil "point at which maximum production is reached." (3).

There are varying estimates as to when peak oil will occur. "I think global oil production will peak between 2015 and 2025 and be a greater challenge than the 'looming crisis' in Social Security." (4). Optimistic projections put the peak around 2030. More pessimistic projections expect the peak in 2010. (5).

After the Peak
"[T]he peak isn't just an economic problem, it is one of the biggest social and political challenges for this century." (4). At the point of peak oil, no matter what happens with the world demand, the amount of oil able to be extracted cannot go up. It can only stay the same or decrease. The United States Department of Energy has reported that "Without massive mitigation more than a decade before the fact [of peak oil], the problem will be pervasive and will not be temporary. Previous energy transitions (wood to coal and coal to oil) were gradual and evolutionary; oil peaking will be abrupt and revolutionary." (3).

The best case scenario, in terms of oil production, would be that production would continue at that peak level, even though it could not increase. The other option is that it begins to decline. "The point to remember about production isn't that it peaks, but that it declines rapidly afterward, at a time when the world demand would be moving rapidly in the opposite direction." (6)

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Demand