The US Geological Survey (USGS) on Oct. 21 estimated that Alaska's North Slope holds a mean 96 tcf of technically recoverable, undiscovered conventional natural gas resources, nearly three times the roughly 35 tcf of proven gas reserves already identified in the region.

The assessment covers the Northern Alaska Province and includes both gas associated with undiscovered oil accumulations and nonassociated gas. USGS evaluated 21 geological assessment units spanning the Ellesmerian, Beaufortian, and Brookian sequences.

The 96-tcf figure represents the mean estimate. USGS calculated a range from 17.3 tcf at the F95 probability level to 276.7 tcf at the F5 level. These estimates reflect the uncertainty in the volume of undiscovered gas: F95 represents a 95% chance of at least that amount, while F5 represents a 5% chance. The assessment addresses technically recoverable resources, not the volume that could be produced economically.

Despite the region's known and potential gas resources, Alaska has no infrastructure capable of moving North Slope natural gas to markets at large commercial scale, USGS said. Most natural gas produced alongside oil is reinjected into reservoirs for pressure management.

The assessment identifies an estimated ultimate recovery of about 25 tcf of gas in Prudhoe Bay field's gas cap and 8 tcf at Point Thomson field. Other known gas accumulations in the Brooks Range foothills have estimated ultimate recoveries of 4 bcf to 600 bcf.

The resource estimate comes as Glenfarne Group advances the proposed Alaska LNG project, which would provide a pipeline route for North Slope gas to reach south-central Alaska and an LNG export plant at Nikiski, which is designed to export up to 20-million tonne/year (tpy) of LNG to international markets.