<Tr> <Td> Gas </Td> <Td> 36.4 </Td> </Tr> <Tr> <Td> Oil </Td> <Td> 8.1 </Td> </Tr> <P> These are the proven energy reserves; real reserves may be up to a factor 4 larger . Significant uncertainty exists for these numbers . Estimating the remaining fossil fuels on the planet depends on a detailed understanding of the Earth's crust . While modern drilling technology makes it possible to drill wells in up to 3 km of water to verify the exact composition of the geology, one half of the ocean is deeper than 3 km, leaving about a third of the planet beyond the reach of detailed analysis . </P> <P> In addition to uncertainty in real reserves, there is significant uncertainty in technological and economical factors that impact what percentage of reserves can be recovered gainfully . In general the easiest to reach deposits are the first extracted . Factors affecting the cost of exploiting the remaining reserves include the accessibility of fossil deposits, the level of sulfur and other pollutants in the oil and the coal, transportation costs, and societal instability in producing regions . </P>

Where can the resource for this energy type be found