May 16, 2005
The central North Slope contains most of the commercial oil fields and virtually all of the petroleum-producing infrastructure and pipelines in northern Alaska, including the Trans-Alaska Pipeline System. To date, 15 billion barrels of oil have been produced from this area, and remaining reserves include 7 BBO of oil and 35 TCF of gas. USGS estimates that there are 4.0 BBO of oil resources that remain to be discovered, most in the northern part of the assessment area. For comparison, recent USGS estimates of undiscovered oil in adjacent areas include 10.6 BBO in the National Petroleum Reserve in Alaska (NPRA) and 10.4 BBO in the Arctic National Wildlife Refuge (ANWR) 1002 area. Most undiscovered oil accumulations in the central North Slope assessment area are expected to be relatively small in comparison to those already discovered.
There is estimated to be 37 TCF of undiscovered natural gas in the central North Slope, with the majority located in the southern half of the assessment area in the foothills of the Brooks Range. This is about half of what has been estimated to occur in NPRA (73 TCF of natural gas) and significantly more than has been estimated to occur in ANWR 1002 area (9 TCF of natural gas). The natural gas resources in the central North Slope are accessible to existing infrastructure and to the route of the proposed gas pipeline. Although large quantities of gas are estimated to be present, there is still a lot to learn about the geology of the foothills.
The central North Slope lies between the NPRA and ANWR, and extends from the Brooks Range northward to the State-Federal offshore boundary. The assessment area consists mostly of State and Native lands, covering about 23,000 square miles (about one-half the size of New York). The population in the area is limited to Prudhoe Bay and other oil-production facilities.
This USGS assessment was based on a comprehensive review of all available geological, geophysical, and geochemical evidence; including hydrocarbon source rocks, reservoir rocks, and traps. The minimum accumulation sizes considered in this assessment are 5 million barrels of technically recoverable oil and 100 billion cubic feet of technically recoverable gas.
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