Care to point to what you consider a giant oil field?
They are not claim no new fields, but the total amount of reserves added versus the amount consumed.
We Will Never Run Out of Oil
The Oil Supply - The Doomsday Scenarios are Flawed
http://economics.about.com/cs/macroeconomics/a/run_out_of_oil.htm
But maybe we don’t need to worry about oil if we just use hemp:
Is industrial hemp the ultimate energy crop?
http://theconversation.com/is-industrial-hemp-the-ultimate-energy-crop-20707
Devon Energy expects production to rise this year even as it cuts capital spending