Is there any way to equate annual fossil fuel usage to a temporal measurement?

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In other words, since fossil fuels are essentially products of a natural process of the decay of living organisms, and since we likely have estimates of how much fossil fuel is consumed on a global scale an on annual basis, and since we also likely know how long it takes organic matter to decay into a usable energy form, then:

Has anyone tried to estimate how many years' worth of ancient organic matter (gas/coal/etc.) is consumed on an annual basis today? For example, the Earth's people consume each year today 100 years' worth of dinosaurs/megafauna/etc. from 50 million B.C.