This week the USGS released a new assessment of gas resources in the Marcellus Shale, Appalachian Basin. The rerport is a reasonable effort by the USGS to sort out some of the wheat from the chaff. The 84 Tcf technically recoverable undiscovered resource for the Marcellus is a considerable downgrade from the 262 Tcf technically recoverable resource reported by NETL of the DOE in 2009. Others have been using numbers for the Marcellus in the mid-400’s of Tcf – see for example Engelder (2009) who claims the Marcellus has 489 Tcf of P50 technically recoverable resources.

This number fits with that of Powers, who was citing about 60 Tcf. 84 Tcf, which of course, is less than four years of US consumption. And the question is – how long would it take to produce it??? – and at what environmental costs??? As with all USGS estimates this is a probabilistic estimate, with 84 Tcf being a P50 estimate (ie. a 50% chance of having at least 84 Tcf). The P95 number is 43 Tcf (ie. a 95% chance of having at least 43 Tcf). So, as always with undiscovered resource estimates, roll the dice and take your chances – ARE YOU FEELING LUCKY?

I welcome this from the USGS as it puts a bit more rigor into the hype on the Marcellus and radically reduces some of the numbers floating around – a good effort with a generous amount of CYA factored in by the USGS given its probabilistic, undiscovered, nature.

See Geologists Sharply Cut Estimate of Shale Gas

Also David Hughe's report Will Natural Gas Fuel America in the 21st Century?