ANWR Potential - What do the estimates mean?
The scientific community, oil industry and government geologists all generally believe that the oil and gas resource potential for ANWR to be very high. They all agree that ANWR ranks as a major petroleum province that could contribute significantly to the nation's energy supplies in the early 21st century when production from other areas, including Prudhoe Bay, has significantly declined.The geologic indicators are very favorable for the presence of significant oil and gas resources in ANWR, but the limited data means that there is a high level of uncertainty about how much oil and gas may be present. However, most geologists agree that the potential is on the order of billions of barrels of recoverable oil and trillions of cubic feet of recoverable gas and that these resources may rival the initial reserves at Prudhoe Bay. The Department of Interior (DOI) and USGS estimates of recoverable oil ranges from 590 million barrels at the low end to 9.2 billion barrels at the high end. The validity of these estimates can only be proved by drilling exploratory wells.
1987 DOI Resource Assessment
From 1980 to 1987 a comprehensive geologic and environmental analyses study was conducted by the DOI on the Coastal Plain of ANWR. A series of biologic and surface geologic studies were conducted, along with 1,300 line miles of (2-D) seismic to image the subsurface geology. Estimated recoverable oil resources were made based on 26 structural prospects were identified, each large enough to contain commercial quantities of oil. The Department's analysis predicted a 95 percent chance of the Coastal Plain containing more than 4.8 billion barrels of oil inplace. Inplace oil is the total volume of oil present. It is always larger that the amount which can be economically produced. And a 5 percent chance that the area contains more than 29.4 billion barrels of oil. The average range of in-place estimates yields a mean estimate of 13.8 billion barrels of oil.
1991 BLM Update
In 1991 the Bureau of Land Management (BLM) conducted an update of the 1987 resource estimates that began in 1989. Based on analysis from 4 exploration wells, economic and tax data and 800 miles of reprocessed seismic data, the in-place and recoverable resources estimates for ANWR were updated. The up-dated study reaffirmed most of the conclusions and estimates made in the 1987 DOI original report, and increased the level of confidence that ANWR is part of the North Slope oil province. This was demonstrated by the increase in the marginal probability of economic success from 19 percent in the original assessment to 46 percent in the 1991 BLM assessment. The increase in marginal probability means that ANWR has a higher potential for oil discovery. The mean resource estimate increased from 3.23 to 3.57 billion barrels of oil.
Draft USGS Reassessment - 1995
The 1995 Reassessment of ANWR reserves was requested on May 10, 1995. A draft report was released on June 5, 1995. This new information, only in draft form, was released just days before Senate action on the ANWR legislation and was characterized by Survey authors as a "three day back-of-the envelope style assessment." This reassessment was politically motivated, relying on no new information and was not exposed to peer review or public comment, as all other assessments have.
USGS Resource Update - expected in 1998
U.S. Geological Survey (USGS) is currently involved in a two year reassessment of the Refuge's oil and gas potential for the past two years, (since release of the 'draft June 5, 1995 reassessment). Their preliminary analysis indicates a significant upgrade in the refuge's oil and gas potential for the area. This upgrade on the 1995 figures is based on reprocessing of the refuge's existing seismic lines and the extension of geologic information from recent oil discoveries just west of the Coastal Plain border. The new USGS assessment is expected to be released later this year.