Asset Retirement Obligations

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligation [Abstract]

Asset Retirement Obligations

Note 3. Asset Retirement Obligations

The following table summarizes the changes in our asset retirement obligations for the years ended December 31, 2012 and 2011:

	Year Ended December 31,
In thousands	2012			2011
Beginning asset retirement obligation	$	93,468		$	85,744
Liabilities incurred and assumed during period	50,956			12,477
Revisions in estimated retirement obligations	5,334			12,217
Liabilities settled and sold during period	(50,556		)	(23,257		)
Accretion expense	7,228			6,287
Ending asset retirement obligation	106,430			93,468
Less: current asset retirement obligation (1)	(3,700		)	(4,742		)
Long-term asset retirement obligation	$	102,730		$	88,726

(1) Included in "Accounts payable and accrued liabilities" in our Consolidated Balance Sheets.

Liabilities incurred and assumed generally relate to the drilling of incremental wells and liabilities assumed upon the acquisition of Thompson, Webster and Hartzog Draw fields during 2012. Liabilities settled include the plugging of old wells in the Tinsley Field during 2012 and 2011. Sales of properties in 2012 primarily represent the sale of non-core assets located in the Paradox Basin of Utah, Gulf Coast region and Bakken area assets in North Dakota and Montana.

We have escrow accounts that are legally restricted for certain of our asset retirement obligations.  The balances of these escrow accounts were $35.2 million and $34.1 million at December 31, 2012 and 2011, respectively.  These balances are recorded at amortized cost and are included in “Other assets” in our Consolidated Balance Sheets.  The estimated fair market value of these investments approximate cost at December 31, 2012 and 2011.