The theory of peak oil was first presented in 1956 by the American geophysicist M. King Hubbert
. While working at Shell's research lab in Houston, he theorized that petroleum resources were finite, and that the rate of production on any oil field would resemble a bell curve, peaking around the point when half the oil in the field had been drilled and then slowly declining as it took an ever-increasing amount of effort to get the same amount of oil.
Hubbert predicted that American production would peak between 1965 and 1970, a prediction that was dismissed at the time on account of how many similar peak oil predictions had come and gone in the last half-century. Those predictions, however, were based on simplistic interpretations of the reserves-to-production ratio that did not take into account new reserves being discovered and tapped, which Hubbert's did. Sure enough, US conventional oil production peaked in 1970, and while it has gone back up at various points since, these came from either previously known but untapped resources being brought online (most notably with the opening of the Alaskan Pipeline in 1977) or new technologies allowing for the exploitation of reserves previously thought inaccessible (most notably with the hydraulic fracturing boom of the 2010s).
Considerable debate exists as to when a global oil peak will come, largely because considerable debate exists as to just how much petroleum is still in the ground. In oil-rich Iraq, chronic instability has limited oil exploration, while Russia's economic crisis in the '90s did the same there for a good long while. As mentioned above, new technologies for oil exploration and drilling have also greatly expanded the definition of "recoverable" petroleum reserves since Hubbert was writing in the '50s and '60s, and the melting of the ice caps from Global Warming means that oil sources that couldn't be reached because they were under, well, ice caps can now be tapped (ironically feeding into the same problem that made those oil sources accessible in the first place).
That said, the fact that unconventional reserves like tight oil, oil sands, and heavy crude have become viable at all demonstrates a side-effect of this trope: namely, that it has pushed money into investment in petroleum technologies in order to maximize the amount of oil recovered. Until the spike in oil prices in the mid-late 2000s, few considered the Bakken formation of western North Dakota and eastern Montana as a viable source of oil, but today, it has joined Texas as one of the bedrocks of the American oil industry.
Peak Oil as understood may never happen, or at least might be much less severe than feared, as Technology Marches On and alternative sources of energy (such as nuclear, better batteries, hydrogen fuel cells, bioplastics or biofuels) are developed or improved which can replace oil in cars, power plants or manufacturing. The finite nature of oil, and our understanding of the associated dangers, mean that investment in alternatives is more and more attractive to many. As Ahmed Zaki Yamani (the Minister of Oil for Saudi Arabia for more than twenty years) said, "The Stone Age didn’t end for lack of stone, and the oil age will end long before the world runs out of oil".
