The normalized measures of exploration performance defined in this paper are the exploratory drilling density (in feet per cubic mile of sediments) and the hydrocarbon discovery density (in BOE per cubic mile). These density measures provide a convenient means for summarizing the status of exploration in the sedimentary provinces of the lower 48 states of the United States, revealing that the smaller hydrocarbon-rich provinces have been explored much more intensely than the larger ones.

The most important application of the drilling and hydrocarbon discovery densities is in defining normalized discovery functions, that is, the relationships between the normalized measures of cumulative exploratory drilling and discoveries. Normalized rather than absolute discovery functions are necessary for proper comparison of the results of exploration in regions or depth zones of differing sizes. The normalized drilling and discovery measures are also useful for developing meaningful statistics of exploration performance.