Those quantities of petroleum which are estimated, on a given date, to be potentially recoverable from known accumulations but which are not considered to be commercially recoverable due to one or more contingencies which may include factors such as economic, legal, environmental, political, commercial, regulatory matters or a lack of markets. It is also appropriate to classify as contingent resources the estimated discovered recoverable quantities associated with a project in the early evaluation stage. Contingent resources are further classified in accordance with the level of certainty associated with the estimates and may be subclassified based on project maturity and/or characterized by their economic status