Disclosures About Oil and Gas Producing Activities (unaudited) (Tables)

The following table summarizes the prices used in the reserve estimates for 2012, 2011 and 2010. Commodity prices used for the reserve estimates, adjusted for basis differentials, grade and quality, are as follows:


	2012		2011		2010
Oil (per Bbl)	$	90.21	$	89.65	$	74.90
Natural gas liquids (per Bbl)	$	37.88	$	49.63	$	39.25
Gas (per Mcf)	$	2.62	$	3.97	$	4.13

The following table provides a summary of the changes of the total proved reserves for the years ended December 31, 2012, 2011 and 2010, as well as proved developed and proved undeveloped reserves at the beginning and end of each respective year.


Total Proved Reserves	Oil (MBbls)			NGLs (MBbls)			Natural Gas (MMcf)			Total (MBoe)
Balance — December 31, 2009		4,338			4,094			168,334			36,488
Extensions and discoveries		984			1,395			8,365			3,773
Purchases of minerals in place		383			786			4,736			1,958
Production		(247	)		(261	)		(6,290	)		(1,556	)
Revisions to previous estimates		(507	)		14,685			(24,756	)		10,052


Balance — December 31, 2010		4,951			20,699			150,389			50,715
Extensions and discoveries		11,847			7,010			40,146			25,548
Purchases of minerals in place		2,200			4,284			24,083			10,498
Production		(482	)		(798	)		(6,345	)		(2,338	)
Revisions to previous estimates		(465	)		(2,072	)		(29,466	)		(7,448	)


Balance — December 31, 2011		18,051			29,123			178,807			76,975
Extensions and discoveries		21,993			8,639			49,372			38,861
Production		(969	)		(904	)		(6,089	)		(2,888	)
Revisions to previous estimates		(1,823	)		(7,758	)		(47,330	)		(17,469	)


Balance — December 31, 2012		37,252			29,100			174,760			95,479


Proved Developed Reserves:
January 1, 2010		1,239			1,879			74,804			15,585
December 31, 2010		2,146			11,193			74,739			25,795
January 1, 2011		2,146			11,193			74,739			25,795
December 31, 2011		5,542			13,945			84,743			33,611
January 1, 2012		5,542			13,945			84,743			33,611
December 31, 2012		8,816			11,761			73,178			32,774

Proved Undeveloped Reserves:
January 1, 2010		3,099			2,215			93,530			20,903
December 31, 2010		2,805			9,506			75,650			24,920
January 1, 2011		2,805			9,506			75,650			24,920
December 31, 2011		12,509			15,178			94,064			43,365
January 1, 2012		12,509			15,178			94,064			43,365
December 31, 2012		28,436			17,339			101,582			62,705

The following table provides the standardized measure of discounted future net cash flows at December 31, 2012, 2011 and 2010:


	Years Ended December 31,
	2012			2011			2010
Future cash flows	$	4,920,231		$	3,772,633		$	1,804,477
Future production costs		(1,220,403	)		(1,012,044	)		(499,321	)
Future development costs		(1,025,193	)		(625,994	)		(259,005	)
Future income tax expense		(692,528	)		(583,961	)		(282,628	)

Future net cash flows		1,982,107			1,550,634			763,523
10% annual discount for estimated timing of cash flows		(1,487,887	)		(1,136,253	)		(559,291	)

Standardized measure of discounted future net cash flows	$	494,220		$	414,381		$	204,232

The changes in the standardized measure of discounted future net cash flows relating to proved oil and natural gas reserves are as follows (in thousands):


	Years Ended December 31,
	2012			2011			2010
Balance, beginning of period	$	414,381		$	204,232		$	79,991
Net change in sales and transfer prices and in production (lifting) costs related to future production		147,421			334,104			120,520
Changes in estimated future development costs		(486,435	)		(395,037	)		(65,718	)
Sales and transfers of oil and gas produced during the period		(100,634	)		(89,253	)		(46,031	)
Net change due to extensions, discoveries and improved recovery		467,822			291,501			30,240
Net change due to purchase of minerals in place		—			119,780			15,696
Net change due to revisions in quantity estimates		(210,296	)		(84,988	)		80,564
Previously estimated development costs incurred during the period		285,039			182,522			40,265
Accretion of discount		60,162			32,793			17,166
Other		(11,281	)		(38,107	)		4,171
Net change in income taxes		(71,959	)		(143,166	)		(72,632	)

Standardized measure of discounted future net cash flows	$	494,220		$	414,381		$	204,232

- Definition

Tabular disclosure of the future net cash flows relating to proved oil and gas reserves and oil and gas subject to purchase under long-term agreements in which the enterprise participates in the operation of the properties on which the oil and gas is located or otherwise serves as the producer. This information is presented in aggregate and for each geographic area for which reserve quantities are disclosed.

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