At any time, the degree of exploration may vary widely within a region or between regions. Regional assessments or inter-regional comparisons based on projections of field-size distributions in time-series discovery data are therefore dependent upon non-uniform evaluation of oil potentials. In this study, drilling history data from wells in Kansas are used to identify the various times at which all locations within regions of the state achieve selected exploration levels. Maps of the regional variation in time associated with a uniform level of exploration demonstrate the historical step-out pattern of the industry.

Known oil fields in Kansas are ranked in relation to prior exploration in the vicinity of discovery wells, with low-rank values corresponding to low density of prior exploration. All known fields within a region are classified into sets. Each set consists of fields discovered at various times, but at a uniform exploration level. Probabilities of discovering fields at different levels of exploration are developed in relation to field size. Projections of the ultimate number of fields in each size class expected within a region are then obtained through analysis of field-size distributions within each of the uniform exploration sets. By subtracting known fields from the ultimate number expected in each size class, a measure of future regional potential for continued exploration is obtai ed. Measurements of the success of exploration by the petroleum industry relative to the potential success from random drilling are also obtained.

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