Has someone done the math on what Hydrocarbons (coil, oil) would have been available 60 million years ago? Would they have been using the same deposits we are

Has someone done the math on what Hydrocarbons (coil, oil) would have been available 60 million years ago? Would they have been using the same deposits we are suing, or would new deposits have formed over the last 60 million years? Or could they have depleted their own, but what was un-usable 60 million years ago, have become usable today. Like something that was marsh land 60 million years ago, be coal today?