Reserves estimation is one of the most essentialtasks in the petroleum industry. It is the process by which theeconomically recoverable hydrocarbons in a field, area, orregion are evaluated quantitatively. A major goal in thisinitiative is preparation of training modules that representindustry’s “recommended practices.” Long before the issuecaught the public’s attention, how- ever, reserves estimationwas a challenge for the industry. The challenge stems frommany factors, tangible and intangible, that enter theestimation process, and judgment is an integral part of theprocess. Uncertainty, along with risk, is an endemic problemthat must be addressed. Consequently,the industry’s record ofproperly predicting reserves has been mixed. Despite appealsfrom some quarters, there currently is no standardizedreserves-estimation procedure.