A new methodology is presented for aggregating individual and fragmentary pieces of geologic information to assess the outcomes of prospect evaluation. The new method is based on possibility, rather than probability theory, and is coupled with multiple-criteria decision-making theory. In essence, the method employs fuzzy implications to gauge satisfaction levels associated with each measure of the characteristics associated with the source, reservoir, seal, and trap. The method is suitable where some data are missing, vague, or subjective. Thus, it is an alternative approach, not a substitute for conventional methods based on probability theory.