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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


Facts and Principles of World Petroleum Occurrence — Memoir 6, 1980
Pages 987-988
Symposium Abstracts

Probability Methods and Assessment of Drilling Outcomes in Frontier Areas: Abstract

John C. Davis1, John W. Harbaugh2

Accurate estimates of the probability of success in drilling ventures in frontier areas, such as the National Petroleum Reserve in Alaska (NPRA), are essential if these areas are to be developed rationally. Unfortunately, by definition, frontier areas have no extensive history of drilling and production on which to base estimates of their potential. Evaluations must be highly subjective, based upon intuitive appraisals, estimates of the volume of sedimentary rocks within the basin that might be productive, and qualitative comparisons with more thoroughly explored regions that appear geologically similar. These regional evaluations are highly uncertain and may be unduly influenced by the biases of those making the appraisals.

More accurate and reliable estimates of the probability of discovery within frontier plays may be obtained by systematic, quantitative comparisons with analogous regions. If no subsurface information is available in the frontier area, estimates of the probability of a discovery in a drilling venture must be based on geometric probabilities derived from statistics on field sizes in the analogue areas. However, if seismic information is available, the probability of success may be dramatically altered. The marginal increase in probability of success due to seismic coverage can also, with proper data, be estimated from analogue areas.

Constructing probability distributions in analogue areas may be arduous and frustrating, especially if proprietary seismic data must be considered. However, unpublished studies of the offshore U.S. Gulf Coast serve as an example of how such probabilities can be obtained, and indicate the improvement in probability estimates that result from detailed seismic information. Although the Gulf Coast is not an appropriate analogue for plays within the 95 800 km2 (37 000 square miles) of the Petroleum Reserve in Alaska, the Gulf Coast study is relevant because it indicates the approximate effort that must be expended in an analogue study which involves seismic factors. NPR-A, as of August 1977, contains over 12 400 km (7 700 miles) of seismic lines and only 42 wells, so success probabilities for the area must be strongly conditional upon seismic results.

Acknowledgments and Associated Footnotes

1 Kansas Geological Survey, The University of Kansas, Lawrence, Kansas 66044

2 Department of Applied Earth Sciences, Stanford University, Stanford, California, U.S.A. 94305

Copyright © 2009 by the Canadian Society of Petroleum Geologists