EssRisk is the first commercial tool which will provide validated probabilistic prediction uncertainty quantification for reservoirs. It calculates uncertainty for both appraisal and history match projects, and assists the history match process in the most efficient manner. It has all the diagnostic tools necessary, and links to many commercial simulations, such as Eclipse and CMG. It uses the latest statistical and Bayesian methods in an integrated framework, and bridges the gap between deterministic and probabilistic modelling.