This simply isn't how reservoir economics works. At the start of industrial revolution, we had access to shallow reserves of high-BTU thermal and metallurgical coal, and geopressured oil and gas in highly permeable salt domes. Those days are gone. The quality of our coal, oil, and gas reserves has been declining. For example, people say "peak coal" in the USA was in 2007, but the peak thermal content of the coal was in 1996. (Also, keep in mind that coal only peaked in the USA due to an explosion of fuel-switching to natural gas). As the quality declines, the price increases, and this drives investment into much larger, but lower quality reserves. So now we are using sub-bituminous coal and lignite for power generation, and hydraulic fracturing, horizontal drill string steering, reservoir simulation, and deep water drilling for oil and gas, fracking and horizontal drilling being especially important in impermeable shale formations. As the price rises further, it would make other technologies viable. In electricity, space heating, and possibly industrial process heat, I could see nuclear fission replacing fossil fuels. Conventional nuclear fuel reserves could last 10,000 years, and seawater uranium could make that hundreds of millions of years. Liquid oil has extreme portability which makes it uniquely useful for transportation and heavy industrial equipment, which also makes it extremely difficult to see what could replace it. High prices on oil will eventually drive the conversion of coal and natural gas to liquid fuels using the Fischer-Tropsch process. The reality is that the fossil fuels could probably last a few centuries. The declining quality of the fossil fuel reserves also means that they are becoming more and more energy-intensive to extract, which also leads to declining Energy-Return-On-Energy-Invested, which has its own set of implications for industrial civilization.