There is a limited (and not fixed) amount of oil in the world, and the number of humans is rising.
It does not mean that the price of oil will increase to infinity.
Oil can be made synthtetically. Expansive but possible. Technology can adapt different fuels. So sooner or later noone would need to pay the price for oil anymore.
Easy said: Value = Demand / Supply
With BTC Supply can only decline while Demand can only rise. Given an infinite timespan, value goes infinite. In Real World that just means, that BTC will reach enormous value IF the above equation stays valid.
PS: Yes, Mr. Obvious, this is a simplification, not the "real world equation of death"