Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2012

Asset Retirement Obligation Disclosure [Abstract]

Schedule Of Asset Retirement Obligations

The following table shows certain information about our AROs for the periods indicated:

	Nine Months Ended September 30,
	2012				2011
	(In thousands)
ARO liability, January 1:	$	96,446			$	69,265
Accretion of discount	3,215				2,598
Liability incurred	52,306			(1)	12,674
Liability settled	(1,606		)		(831		)
Liability sold	(1,258		)		—
Revision of estimates	(4,254		)	(2)	9,096
ARO liability, September 30:	144,849				92,802
Less current portion	2,857				2,074
Total long-term ARO	$	141,992			$	90,728

(1) The liability incurred increased $46.7 million related to the Noble properties acquired in September 2012.

(2) Plugging liability estimates were revised in March 2012 for updates in the cost of services used to plug wells over the preceding year. Although cost per well increased, a slight decrease in the inflation factor resulted in a decrease in estimated cost.