Proved reserves don't equal total reserves. As an economic incentive to explore for new reserves arises, new reserves are found. See this graph of proved reser

Proved reserves don't equal total reserves. As an economic incentive to explore for new reserves arises, new reserves are found. See this graph of proved reserves by year since 1900: https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=RCRR01NUS_1&f=A https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=R... Of course at some point there must be a limit, but thus far when there's been sufficient incentive to look, more reserves have been found (including via new technology such as fracking).