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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, for example, the overestimation of OR.
The Drainable Oil is often split into profitable oil recovery and non-profitable oil recovery.
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[ Estimated Ultimate Oil Recovery (EUOR) ]
[ Profitable Oil Recovery ][ Non-profitable Oil Recovery]