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The maximum volume of Oil Reserves for a newly explored field is called Estimated Ultimate Oil Recovery (EUOR).
The current Oil Reserves (OR is ) is often split into Drainable Oil and Non-drainable Oil:
OR = Drainable Oil + Non-drainable Oil
The Non-drainable Oil is a result of deviation from the current Field Development Plan (FDP) or mistakes in FDP itself.
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology / Oil In Place (OIP)
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