The amount of energy needed to extract and refine crude oil depends on the source. For conventional oil in a relatively shallow well the energy return on investment (EROI, calculated as energy gained/energy used) can be as high as 40/1; crude oil extracted from oil shales is very inefficient, having a EROI barely above 1, meaning the energy gains are very low when compared to expenditures.
20 is the typical value one sees for EROI for conventional oil, as borne out by the nice chart jw provided. To add a couple other values, the EROI for ethanol is usually determined to be about 1 (meaning it costs as much in energy in as you get out) to 1.5; tar sands are usually given as 1 to 4 depending on the nature of the mining and processing and the original material.
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