Supplemental Oil and Natural Gas Disclosures (Tables)

12 Months Ended

Dec. 31, 2019

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Cost Incurred in Oil and Gas Property Acquisition, Exploration, and Development Activities

Costs incurred in oil and natural gas property acquisition, exploration and development, whether capitalized or expensed, are presented below:

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Acquisition Costs of Properties1:
Proved	$	2,288	$	13,438	$	96,596
Unproved	41,643		136,079		383,535
Exploration Costs	3		13,544		618
Development Costs1	34,617		165,198		81,056
Total	$	78,551	$	328,259	$	561,805

¹ See Note 4 – Oil and Natural Gas Properties for further discussion. Unproved properties include purchases of leasehold prospects. Development costs include costs incurred on farmout wells subject to reimbursement under the Partnership's farmout agreements.

Capitalized Costs Relating to Oil and Gas Producing Activities

Aggregate capitalized costs related to oil and natural gas production activities with applicable accumulated depreciation, depletion, and amortization, including impairments, are presented below:

	As of December 31,
	2019		2018
	(in thousands)
Proved properties1	$	2,228,893	$	2,377,305
Unproved properties	1,073,447		1,063,883
Total	3,302,340		3,441,188
Accumulated depreciation, depletion, amortization, and impairment	(1,870,412)		(1,865,692)
Oil and natural gas properties, net	$	1,431,928	$	1,575,496

¹ Proved properties include capitalized costs related to farmout wells not yet assigned.

Schedule of Oil and Gas In Process Activities

The following table sets forth estimated net quantities of the Partnership’s proved, proved developed, and proved undeveloped oil and natural gas reserves. These reserve estimates exclude insignificant natural gas liquid quantities owned by the Partnership. Estimated reserves for the periods presented are based on the unweighted average of first-day-of-the-month commodity prices over the period January through December for the year in accordance with definitions and guidelines set forth by the SEC and the FASB.

	Crude Oil (MBbl)	Natural Gas (MMcf)	Total (MBoe)
Net proved reserves at December 31, 2016	18,368	270,339	63,425
Revisions of previous estimates 1	(2,298)	14,505	120
Purchases of minerals in place2	2,335	31,323	7,555
Extensions, discoveries and other additions3	3,046	43,886	10,360
Production	(3,552)	(59,779)	(13,515)
Net proved reserves at December 31, 2017	17,899	300,274	67,945
Revisions of previous estimates1	(35)	(11,027)	(1,873)
Purchases of minerals in place4	227	419	297
Extensions, discoveries and other additions3	4,438	95,976	20,434
Production	(4,962)	(71,622)	(16,899)
Net proved reserves at December 31, 2018	17,567	314,020	69,904
Revisions of previous estimates1	951	19,136	4,140
Purchases of minerals in place4	46	279	92
Extensions, discoveries and other additions3	3,263	53,158	12,123
Production	(4,777)	(77,635)	(17,716)
Net proved reserves at December 31, 2019	17,050	308,958	68,543
Net Proved Developed Reserves5
December 31, 2017	17,891	233,017	56,727
December 31, 2018	17,567	278,233	63,939
December 31, 2019	17,050	263,371	60,945
Net Proved Undeveloped Reserves6
December 31, 2017	8	67,257	11,218
December 31, 2018	—	35,787	5,965
December 31, 2019	—	45,587	7,598

¹ Revisions of previous estimates include technical revisions due to changes in commodity prices, historical and projected performance and other factors. The most notable technical revisions are related to well performance in certain Haynesville/ Bossier wells.

² Includes the acquisition of mineral and royalty reserves primarily in East Texas, the Permian Basin, and the Williston Basin.

³ Includes extensions and additions related to drilling activities within multiple basins.

⁴ Includes the acquisition of mineral and royalty reserves primarily in East Texas and the Permian Basin.

⁵ As of December 31, 2018 and 2019, no proved developed reserves were attributable to noncontrolling interests in the Partnership's consolidated subsidiaries. As of December 31, 2017, proved developed reserves of 61 MBoe were attributable to noncontrolling interests.

⁶ As of December 31, 2018, 2017, and 2016, no proved undeveloped reserves were attributable to noncontrolling interests.

Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Future cash inflows	$	1,619,147	$	2,038,508	$	1,643,582
Future production costs	(177,550)		(222,342)		(211,064)
Future development costs	(54,132)		(58,403)		(70,111)
Future income tax expense	(5,244)		(6,333)		(2,655)
Future net cash flows (undiscounted)	1,382,221		1,751,430		1,359,752
Annual discount 10% for estimated timing	(534,327)		(663,814)		(497,103)
Total1	$	847,894	$	1,087,616	$	862,649

¹ Includes standardized measure of discounted future net cash flows of approximately $0.5 million for December 31, 2017 attributable to noncontrolling interests in the Partnership’s consolidated subsidiaries.

Schedule of Changes in Standardized Measure of Discounted Future Net Cash Flows

The following summarizes the principal sources of change in the standardized measure of discounted future net cash flows:

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Standardized measure, beginning of year	$	1,087,616	$	862,649	$	603,015
Sales, net of production costs	(384,745)		(475,742)		(295,941)
Net changes in prices and production costs related to future production	(229,651)		275,091		161,221
Extensions, discoveries and improved recovery, net of future production and development costs	186,424		370,695		166,616
Previously estimated development costs incurred during the period	—		14,509		11,118
Revisions of estimated future development costs	1,198		(558)		2,653
Revisions of previous quantity estimates, net of related costs	51,405		(5,401)		60,476
Accretion of discount	109,158		86,441		60,512
Purchases of reserves in place, less related costs	1,730		8,975		113,342
Changes in timing and other	24,759		(49,043)		(20,363)
Net increase (decrease) in standardized measures	(239,722)		224,967		259,634
Standardized measure, end of year	$	847,894	$	1,087,616	$	862,649