I think there is/was validity to the concept of EROEI: energy return on energy invested. The EROEI of oil has decreased over time. What they got wrong was the

I think there is/was validity to the concept of EROEI: energy return on energy invested. The EROEI of oil has decreased over time. What they got wrong was the overall estimate of how much of this stuff there is to be extracted. The easy oil is indeed being used up, but as you invest more and more energy (EROEI decreases) the amount of oil available actually increases. Look at how much tar sands, oil shale, offshore, and heavy crude there is, but all that requires more energy to get. We would eventually run out of oil to be had at a reasonable energy (and thus economic) cost, but after that if we still needed it we could get it by converting coal. That assumes we decide we don't need the ice caps, or the coastal cities. We probably have enough carbon to destroy the world.