ever heard of "fracking"?
There's lots of oil, gas (and of course, coal) in the ground, almost none of it accessible at the surface or by using hand tools. It's the current state of extractive technology, not the total fuels in the ground, that determines how much of those fuels we have access to. That technology is constantly improving, making more fossil fuels accessible -- as with fracking.
Those who claim we need to worry about "peak oil" or "peak gas" are ignoring the consistent history of technological development enabling access to ever larger amounts of fossil fuels.