Among the greatest uncertainties in future energy supply and a subject of considerable environmental concern is the amount of oil and gas yet to be found in the Arctic. By using a probabilistic geology-based methodology, the United States Geological Survey has assessed the area north of the Arctic Circle and concluded that about 30% of the world's undiscovered gas and 13% of the world's undiscovered oil may be found there, mostly offshore under less than 500 meters of water. Undiscovered natural gas is three times more abundant than oil in the Arctic and is largely concentrated in Russia. Oil resources, although important to the interests of Arctic countries, are probably not sufficient to substantially shift the current geographic pattern of world oil production.
Oil and gas resources in each of the 24 plays within the National Petroleum Reserve in Alaska (NPRA) were estimated using a play analysis. Assessors specified geologic attributes, risks, and number of prospects for each play. Some specifications established distributions, while others were given as single values. From this information, sizes of oil and gas accumulations were simulated using a Monte Carlo algorithm. The number of such accumulations considered in a given simulation run was obtained from the distribution of the number of prospects. Each prospect in each successful simulation run was risked. This process yielded size-frequency distributions and summary statistics for the various petroleum categories. Estimates of remaining resources from individual plays were then aggregated, and measures of uncertainty computed. Technically recoverable, undiscovered oil beneath the Federal part of NPRA likely ranges between 5.9 and 13.2 billion barrels, with a mean (expected) value of 9.3 billion barrels. Technically recoverable, undiscovered nonassociated natural gas for the same area likely ranges between 39.1 and 83.2 trillion cubic feet, with a mean (expected) value of 59.7 trillion cubic feet. Mean values of the corresponding associated dissolved gas and natural gas liquid are 10.3 trillion cubic feet and 1.4 billion barrels respectively. modified version of the methodology used in the U.S. Geological Survey's 1998 assessment of the 1002 Area of the Artic National Wildlife Refuge (ANWR) (Schuenemeyer, 1999). Improvements included modifications to the input form, fitting beta distributions to specified fractiles, and new petroleum engineering models. Minimum reservoir sizes for oil and for gas were established to facilitate estimation of the number of prospects. Approximate deposit size distributions were generated at the mean, median, and 5 th and 95 th levels of uncertainty. Play resources were allocated to Federal land based on estimated proportions of oil and gas resources. Estimates of remaining resources from individual plays were aggregated into distributions of remaining resources for the total NPRA land area and for a subset, the Federal land area. The aggregation procedures also were modified from those used in the 1002-ANWR assessment. This chapter begins with a discussion of the geologic and engineering input, which was specified by the assessors for each play and entered on the assessment form. Following this, the Monte Carlo simulation is presented. We conclude with a discussion of the aggregation procedure. After presentation of the methodology, results will be summarized for each play and for the aggregate total of oil and nonassociated gas and various derivatives. Detailed discussion of the results is presented elsewhere on this Web site. Definition of terms is given in the Glossary. SPECIFICATION OF THE INPUT Information used by the assessment algorithm consisted of statistical models with parameters and assessor-specified distributions and constants. An assessment form, which was a modified ve...
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