A probabilistic discovery model modified after Kaufman's earlier model is simplified to reduce computational demands and to reduce the sensitivity of the resulting estimates. The model is applied to the North Sea to estimate remaining oil reserves and forecast future discoveries. The simplification jeopardizes some informational detail, but the errors and approximations inherent in historical data sometimes overvalue the available information. A broader categorization scheme helps to control errors in this case. The model uses a stochastic production function based on a timing relationship between exploratory efforts and reservoir discovery and on a dynamic relationship of productivity and resource depletion. 21 references, 4 tables. (DCK)

A current trend among oil-producing nations with private oil sectors is to move toward tax systems that are based upon pr ofits rather than production. The authors present a case study of wha t can go wrong with profit-based tax schemes. They study the implemen tation of the net profit share leasing system in the United States in the early 1980s. They conclude that the information requirements of the scheme are heavy, perhaps prohibitive, and that the net profit sh are system can easily backfire if the informational requirements can not be met. The authors also show that the U.S. government misused th e limited amount of information that was available to it.