Small multidisciplinary geoscience-engineering teams of 5 to 10 professionals searched for large volumes of low risk reserves in poorly performing oil fields. Between 1981-1996 over 350 mature fields in the Permian and Gulf of Mexico basins were scanned looking for fields to purchase. Forty-six fields were purchased. The purchased fields include those producing by (1) primary recovery without secondary recovery potential, (2) primary recovery with supplemental recovery potential and (3) those undergoing waterflooding. Finding large volumes of low risk, presently non-producing reserves within fields involves several steps. First, the team searches in reservoir systems that appear more massive and homogeneous than they are. Second, the team scans the geoscience and engineering data to quickly estimate original oil-in-place, percent recovery, remaining reserves and potential bypassed reserves. Third, the team makes an economic analysis including recovery cost estimates for the volume of missed low and high-risk reserves. Candidate fields for purchase all have new low to moderate risk reserves amounting to at least 5% of the cumulative reserves already produced. Forty-one fields are economically successful with an after-tax rate of return (ATROR) of 12 to 41% (average 21%) and three fields made 5-7% ATROR. Two fields are economic failures. Payout for the 44 economically successful fields ranged from 11 months to 5.8 years.