Role of Reservoir Engineering in the Assessment of Undiscovered Oil and Gas Resources in the National Petroleum Reserve, Alaska (NPRA)

By

M.K. Verma and K.J. Bird (U.S. Geological Survey)

The role of reservoir engineering has taken on greater importance in USGS evaluations of undiscovered oil and gas resources, particularly as economic analysis becomes an integral part of the assessment process. This paper describes the role of reservoir engineering in the recent USGS assessment of undiscovered oil and gas resources of the NPRA, a challenging role because of limited data.

The NPRA, located on the North Slope of Alaska, is one of the few remaining areas in the U.S. yet to be fully explored, despite nearly six decades of intermittent exploration. The need to assess its potential now takes on greater urgency in light of declining U.S. petroleum reserves and production. The USGS deposit simulation method of assessment requires an integration of geology and reservoir engineering. While geology provides the basic information on sizes and numbers of petroleum accumulations, reservoir engineering helps convert hydrocarbon volumes from sub-surface to surface conditions and provides guidelines for development of pools/reservoirs, information required for economic evaluation.

The NPRA assessment consisted of the identification and evaluation of 15 petroleum plays. For most plays, analog pools/reservoirs were identified either within the NPRA or elsewhere on the North Slope. The reservoir engineering effort consisted of compilation and review of all available data on analog pools/reservoirs (43 reservoirs in 38 fields) from public and proprietary databases. These data were used to develop correlations to estimate reservoir parameters, e.g. correlations between temperature and pressure versus depth; formation volume factor (FVF) versus solution gas-oil ratios; solution gas gravity versus oil gravity, pressure and temperature. How to check the accuracy of some important parameters is also described. Based on this study, a set of guidelines has been proposed for carrying out similar studies in other prospective areas.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.