Resource assessment is a people-oriented endeavor. At every stage of the exercise, good judgment is essential to satisfactory results. There is no single procedure that can guarantee an approximation of truth, but clearly there are procedures and techniques to be selected from within the context of the problem to be solved that serve to lessen subjectivity in the final outcome.
The U.S. Geological Survey has had the responsibility of determining petroleum potential, especially for basin size areas. This determination assists in the decision process relative to lease sales, wilderness areas, and international relations. Our requirement is basin understanding, not exploration well siting. Considering the dimension of the objectives, the time frame of need, and the resources available (both people and data), volumetric analysis at the level of the play (group of prospects) is rarely practical. Rather, as described in U.S. Geological Survey assessment documents, we have utilized a variety of volumetric/analogy techniques, sometimes comparing with Klemme classifications, with specific United States or foreign basins, or internally within the basin being assessed, which in effect is a degree of maturity analysis. The petroleum geology of the basin and the results of the various number-generating processes are then subjected to the Delphi process, as reported elsewhere, for the group assessment.
The assessment so determined is the hypothesis of the petroleum potential of the area. Because the hypothesis derives from an analysis of petroleum parameters such as source rock, reservoir rock, traps, and seals (which data are published), it is subject to testing as exploration proceeds or as new data are made available. The advantage of the assessment is only partly in the number. In addition, the organization of data permits the recognition of anomalies in the exploration process or in resource reports, thus permitting ongoing adjustments in the assessment or its analysis.