OIL AND GAS RESERVE INFORMATION - UNAUDITED (Tables)

12 Months Ended

Dec. 31, 2012

Estimated Proved Oil and Natural Gas Reserve

Reserve volumes for the years ended December 31, 2010 and 2009 have not been reclassified to conform to the current presentation given the immateriality of NGL volumes in such periods.

	Oil (MBbls)			NGLs (MBbls)			Natural Gas (MMcf)			Oil, Natural Gas and NGLs (MMcfe)
Estimated proved reserves as of December 31, 2009		32,336			—			216,694			410,711
Revisions of previous estimates		3,299			574			12,670			35,906
Extensions, discoveries and other additions		2,668			—			82,846			98,854
Purchase of producing properties		637			—			3,816			7,637
Sale of reserves		(23	)		—			(153	)		(289	)
Production		(5,714	)		(574	)		(41,168	)		(78,896	)
Estimated proved reserves as of December 31, 2010		33,203			—			274,705			473,923
Revisions of previous estimates		2,889			4,911			(26,725	)		20,075
Extensions, discoveries and other additions		3,544			—			93,520			114,784
Purchase of producing properties		14,396			—			24,595			110,971
Sale of reserves		(1,950	)		—			(2,150	)		(13,850	)
Production		(6,427	)		(506	)		(38,466	)		(80,064	)
Estimated proved reserves as of December 31, 2011		45,655			4,405			325,479			625,839
Revisions of previous estimates		(1,559	)		9,349			(26,694	)		20,050
Extensions, discoveries and other additions		3,681			4,856			131,408			182,633
Purchase of producing properties		4,336			619			8,168			37,895
Sale of reserves		(60	)		—			(418	)		(775	)
Production		(7,135	)		(1,163	)		(42,569	)		(92,357	)
Estimated proved reserves as of December 31, 2012		44,918			18,066			395,374			773,285
Estimated proved developed reserves:
as of December 31, 2010		25,000			—			174,876			324,876
as of December 31, 2011		30,914			3,195			171,871			376,528
as of December 31, 2012		29,005			8,593			210,956			436,540

Standardized Measure of Discounted Future Net Cash Flows

	Standardized Measure Year Ended December 31,
		2012			2011			2010
Future cash inflows		$	6,295,455		$	6,171,279		$	3,803,004
Future production costs			(1,946,426	)		(1,747,806	)		(1,191,718	)
Future development costs			(1,241,531	)		(1,219,214	)		(907,956	)
Future income taxes			(799,007	)		(852,364	)		(330,651	)
Future net cash flows			2,308,491			2,351,895			1,372,679
10% annual discount			(794,632	)		(808,933	)		(415,050	)
Standardized measure of discounted future net cash flows		$	1,513,859		$	1,542,962		$	957,629

	Changes in Standardized Measure Year Ended December 31,
	2012			2011			2010
Standardized measure at beginning of year	$	1,542,962		$	957,629		$	614,987
Sales and transfers of oil, gas and NGLs produced, net of production costs		(697,741	)		(670,347	)		(487,418	)
Changes in price, net of future production costs		(380,841	)		502,324			485,272
Extensions and discoveries, net of future production and development costs		178,272			293,168			270,629
Changes in estimated future development costs, net of development costs incurred during the period		212,329			97,852			119,986
Revisions of quantity estimates		76,450			(27,854	)		147,509
Accretion of discount		207,292			118,722			64,836
Net change in income taxes		22,947			(300,363	)		(196,219	)
Purchases of reserves in-place		276,389			567,286			21,264
Sales of reserves in-place		2,480			(36,278	)		1,424
Changes in production rates due to timing and other		73,320			40,823			(84,641	)
Net increase (decrease) in standardized measure		(29,103	)		585,333			342,642
Standardized measure at end of year	$	1,513,859		$	1,542,962		$	957,629