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

The following table summarizes the prices used in the reserve estimates for 2015, 2014 and 2013. Commodity prices used for the reserve estimates, adjusted for basis differentials, grade and quality, are as follows:


	2015		2014		2013
Oil (per Bbl)	$	50.16	$	94.56	$	97.28
Natural gas liquids (per Bbl)	$	15.13	$	31.50	$	30.16
Gas (per Mcf)	$	2.64	$	4.55	$	3.66

The following table provides a summary of the changes of the total proved reserves for the years ended December 31, 2015, 2014 and 2013, 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, 2012		37,252			29,100			174,760			95,479
Extensions and discoveries		14,252			6,531			38,993			27,282
Purchases of minerals in place		62			14			197			109
Production(1)		(1,444	)		(951	)		(6,737	)		(3,517	)
Revisions to previous estimates		(4,055	)		(2,102	)		8,789			(4,692	)


Balance — December 31, 2013		46,067			32,593			216,002			114,661
Extensions and discoveries		19,347			10,658			79,454			43,247
Production(1)		(2,024	)		(1,461	)		(10,773	)		(5,281	)
Revisions to previous estimates		(8,052	)		(883	)		15,337			(6,379	)


Balance — December 31, 2014		55,338			40,907			300,020			146,248
Extensions and discoveries		11,054			10,630			79,268			34,895
Production(1)		(1,882	)		(1,694	)		(13,262	)		(5,787	)
Revisions to previous estimates		(10,014	)		(357	)		9,962			(8,710	)


Balance — December 31, 2015		54,496			49,486			375,988			166,646

(1)	Production includes 560 MMcf, 1,390 MMcf and 1,530 MMcf related to field fuel in 2013, 2014 and 2015, respectively.


Total Proved Reserves	Oil (MBbls)		NGLs (MBbls)		Natural Gas (MMcf)		Total (MBoe)
Proved Developed Reserves:
January 1, 2013		8,816		11,761		73,178		32,774
December 31, 2013		13,646		14,919		99,742		45,189
January 1, 2014		13,646		14,919		99,742		45,189
December 31, 2014		17,978		19,082		138,961		60,220
January 1, 2015		17,978		19,082		138,961		60,220
December 31, 2015		15,667		20,414		154,652		61,856

Proved Undeveloped Reserves:
January 1, 2013		28,436		17,339		101,582		62,705
December 31, 2013		32,421		17,674		116,260		69,472
January 1, 2014		32,421		17,674		116,260		69,472
December 31, 2014		37,360		21,825		161,059		86,028
January 1, 2015		37,360		21,825		161,059		86,028
December 31, 2015		38,829		29,072		221,335		104,790

The following table provides the standardized measure of discounted future net cash flows at December 31, 2015, 2014 and 2013 (in thousands):


	Years Ended December 31,
	2015			2014			2013
Future cash flows	$	4,097,568		$	7,430,368		$	5,953,060
Future production costs		(1,237,888	)		(1,704,333	)		(1,372,005	)
Future development costs		(934,814	)		(1,247,446	)		(1,154,685	)
Future income tax expense		(307,374	)		(1,267,025	)		(919,454	)

Future net cash flows		1,617,492			3,211,564			2,506,916
10% annual discount for estimated timing of cash flows		(1,157,097	)		(2,155,749	)		(1,830,639	)

Standardized measure of discounted future net cash flows	$	460,395		$	1,055,815		$	676,277

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,
	2015			2014			2013
Balance, beginning of period	$	1,055,815		$	676,277		$	494,220
Net change in sales and transfer prices and in production (lifting) costs related to future production		(1,405,864	)		(59,920	)		74,088
Changes in estimated future development costs		231,900			(388,772	)		(301,132	)
Sales and transfers of oil and gas produced during the period		(91,278	)		(209,893	)		(149,310	)
Net change due to extensions, discoveries and improved recovery		156,783			534,231			360,080
Net change due to purchase of minerals in place		—			—			1,435
Net change due to revisions in quantity estimates		(59,305	)		(78,801	)		(61,931	)
Previously estimated development costs incurred during the period		146,237			382,995			287,898
Accretion of discount		105,582			113,188			87,937
Other		6,915			(11,897	)		1,896
Net change in income taxes		313,610			98,407			(118,904	)

Standardized Measure of discounted future net cash flows	$	460,395		$	1,055,815		$	676,277

- 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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