Don Boudreaux makes sense about global oil supplies

here:

Imagine, Russ says, a room full of pistachio nuts. You love pistachios and can eat all that you wish as long as you throw each empty shell back into the room whenever you eat a nut. You might suppose that you'll eventually devour all of the nuts in the room. Their number, after all, is finite.

But some thought reveals this conclusion to be, well, nutty. At the start it's easy to find pistachio shells containing nuts. The more you eat, though, the more difficult it becomes to find uneaten nuts among the increasing number of empty shells. Eventually, it will not be worth the time and effort required to search amidst the empty shells for the relatively few remaining nuts. You'll voluntarily leave uneaten pistachios in the room.

And so it is with oil. As we continue using oil, getting more of it becomes increasingly difficult. This increasing difficulty of finding and extracting oil is reflected in its higher price -- a phenomenon that prompts consumers to consume oil more carefully and prompts producers to explore for alternatives.

Also, just as it would be absurd to estimate your household's lifetime supply of food based only upon the stock in your pantry, it's absurd to estimate the world's long-term supply of oil based only upon today's proven reserves of that resource. There simply is no good way to know how much oil exists in the Earth beyond the always-limited amounts that oil producers have proven to exist through their economically constrained explorations.