Some Practical Approaches to World Petroleum Resource Assessment
Uncertainty in petroleum resource estimation can be mitigated by using different approaches in making resource estimates for a given area. We divide methods and data into two broad categories. The first is based on geologic data, which aim at estimating the resources of a basin by gaining an understanding of the processes of petroleum formation, migration, and trapping. The second is based on statistical methods, which estimate the resources of a basin by extrapolating the industry’s past experience in drilling and discovery to forecast future discoveries. Results of these approaches are compared for Nigeria, North Africa, and many of the world’s offshore areas. Undiscovered offshore petroleum resources outside the United States, Canada, and communist countries were estimated by both methods to be ~ 130 billion bbl. For Nigeria the two methods agree at about 4-6 billion bbl of undiscovered oil. In contrast, for North Africa, where the geologic estimate of undiscovered petroleum is 16 billion bbl and the statistical estimate is 5 billion bbl, the two methods are not in close agreement.
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There is a continual need to update estimates of oil and gas resources remaining to be discovered, and also to refine the methodologies for making these assessments. In 1974, AAPG sponsored a research conference dealing with the above topics, and many of the papers presented there were published in AAPG Studies in Geology 1. As a follow-up to that volume, a U.S. Geological Survey workshop was held in 1983, and many papers from talks presented there, in addition to several other papers, are contained within this volume. The 22 papers have been grouped into two types: those describing methodologies for evaluating resources and those presenting assessments of both conventional and unconventional resources.