The development of a new field requires a special effort to recognize and evaluate static and dynamic reservoir uncertainties. Since there is limited information of the fields during exploration and appraisal phases, reservoir modeling is such a challenging task towards managing uncertainties and assessing the risk associated to it. The first step towards managing reservoir uncertainties is to identify and rank key reservoir parameters affecting hydrocarbon in place and recovery factor; then, key variables impact should be quantified by tornado or Pareto plots. The current study gives an approach about Petrel™ tools in order to perform sensitivities and uncertainties analysis to some parameters; therefore, obtaining a reliable variation range of main outputs in this evaluation; in addition, achieving an indicator of main variables that affects the original volumes in place and recovery factors. Copyright 2014, Society of Petroleum Engineers.