Oil and Gas Properties (Tables)

6 Months Ended

Jun. 30, 2011

Oil and Gas Properties

Components of Exploration Expense

		Three Months Ended					Six Months Ended
		June 30,					June 30,
		2011		2010			2011			2010
Delay rental and geological and geophysical costs...	$	1,299	$	1,182		$	1,654		$	1,528
Impairment of unproved properties (a)		6,640		0			6,640			0
Dry hole expense		0		(10	)		(9	)		(190	)
Total exploration expense	$	7,939	$	1,172		$	8,285		$	1,338

a. Reflects costs associated with a deepwater lease in which the term expired during the second quarter of 2011.

Changes in Asset Retirement Obligations

Asset retirement obligation at December 31, 2010	$	234,936
Liability incurred during the period		672
Liability settled during the period		(25,273	)
Revision in estimated cash flows		12,842
Accretion expense (included in depreciation and amortization)		7,630
Asset retirement obligations at June 30, 2011	$	230,807