Based on context may mean either Estimated Ultimate Oil Recovery (EUOR) or Estimated Ultimate Gas Recovery (EUGR).
In both cases it means refers to the maximum recoverable volume of Hydrocarbon Reserves (HCR).
The percentage of Estimated Ultimate Recovery taken from the total Surface Tank Hydrocarbon Initial In Place (STHCIIP) is called Estimated Ultimate Recovery Factor (EURF).
See Also
Petroleum Industry / Upstream / Production / Subsurface Production
[ Estimated Ultimate Oil Recovery (EUOR) ] [ Estimated Ultimate Gas Recovery (EUGR) ]