The initial scenarios IIRC for the known reserves of the USA, Saudi Arabia and Russia were to run out in about 50 years, at that point if we haven't found a bet

The initial scenarios IIRC for the known reserves of the USA, Saudi Arabia and Russia were to run out in about 50 years, at that point if we haven't found a better power source our grandkids could use coal to make petroleum like Germany in WW2. https://en.wikipedia.org/wiki/Coal_to_oil https://en.wikipedia.org/wiki/Coal_to_oil On the otherhand fracking probably changed that timeline for Canada and the USA with the tradeoff of freshwater for oil so we'll have to wait and see how that turns out and moves the end date for our estimated petroleum reserves.