Despite the widespread realization that oil exploration is a high-risk, probabilistic business, little effort has been expended in developing objective means of estimating the outcomes of exploration plays and prospects. This book describes statistical methods for quantitatively estimating outcome probabilities that involve the systematic and objective use of geological information. These methods range from simple tabulation of outcome frequencies, to the use of advanced mathematical and statistical techniques such as machine contouring, trend-surface analysis, and discriminant-function analysis. These methods can be effectively used with computers to treat large volumes of information, including data derived from hundreds or thousands of wells.