(12) Oil and Gas Reserves Information (Unaudited)

Set forth below is a summary of the changes in Comstock's net quantities of oil and natural gas reserves for each of the three years in the period ended December 31, 2017:

	2015						2016						2017
	Oil (MBbls)			Natural Gas (MMcf)			Oil (MBbls)			Natural Gas (MMcf)			Oil (MBbls)			Natural Gas (MMcf)
Proved Reserves:
Beginning of year		20,854			495,266			9,229			569,596			7,277			872,468
Revisions of previous estimates		(5,096	)		(41,437	)		(406	)		130,416			1,232			33,721
Extensions and discoveries		231			168,539			64			285,076			1			291,881
Sales of minerals in place		(3,671	)		(5,096	)		(222	)		(58,942	)		(7	)		(7,593	)
Production		(3,089	)		(47,676	)		(1,388	)		(53,678	)		(951	)		(73,521	)
End of year		9,229			569,596			7,277			872,468			7,552			1,116,956
Proved Developed Reserves:
Beginning of year		16,247			324,598			9,229			311,130			7,277			321,527
End of year		9,229			311,130			7,277			321,527			7,552			436,114
Proved Undeveloped Reserves:
Beginning of year		4,607			170,668			—			258,466			—			550,941
End of year		—			258,466			—			550,941			—			680,842

Reserves associated with Assets Held for Sale:
Proved Reserves
Beginning of year		16,282			14,716			8,701			9,119			6,950			9,915
End of year		8,701			9,119			6,950			9,915			7,116			10,484
Proved Developed Reserves
Beginning of year		14,028			14,071			8,701			9,119			6,950			9,915
End of year		8,701			9,119			6,950			9,915			7,116			10,484
Proved Undeveloped Reserves
Beginning of year		2,253			645			—			—			—			—
End of year		—			—			—			—			—			—

The upward revisions to previous estimates in 2016 were primarily performance-related and were attributable to the Company's well performance in the Haynesville shale as well as the expansion of the Company's future drilling plans. The revisions in 2015 and 2017 were primarily related to changes in oil and natural gas prices.

The proved oil and gas reserves utilized in the preparation of the financial statements were estimated by Lee Keeling and Associates, independent petroleum consultants, in accordance with guidelines established by the Securities and Exchange Commission and the Financial Accounting Standards Board, which require that reserve reports be prepared under existing economic and operating conditions with no provision for price and cost escalation except by contractual agreement. All of the Company's reserves are located onshore in the continental United States of America.

The following table sets forth the standardized measure of discounted future net cash flows relating to proved reserves at December 31, 2016 and 2017:

	2016			2017
	(In thousands)
Cash Flows Relating to Proved Reserves:
Future Cash Flows	$	2,267,877		$	3,588,764
Future Costs:
Production		(798,454	)		(986,398	)
Development and Abandonment		(502,848	)		(672,559	)
Future Income Taxes		(6,488	)		5,239
Future Net Cash Flows		960,087			1,935,046
10% Discount Factor		(530,812	)		(1,053,502	)
Standardized Measure of Discounted Future Net Cash Flows	$	429,275		$	881,544
Standardized Measure of Discounted Future Net Cash Flows Related to Assets Held for Sale	$	77,146		$	109,134

The standardized measure of discounted future net cash flows at the end of 2016 and 2017 was determined based on the simple average of the first of month market prices for oil and natural gas for each year. Prices were $37.62 per barrel of oil and $ 2.29 per Mcf of natural gas for 2016 and $48.71 per barrel of oil and $ 2.88 per Mcf of natural gas for 2017. Prices used in determining quantities of oil and natural gas reserves and future cash inflows from oil and natural gas reserves represent prices received at the Company's sales point. These prices have been adjusted from posted or index prices for both location and quality differences. Future development and production costs are computed by estimating the expenditures to be incurred in developing and producing proved oil and gas reserves at the end of the year, based on year end costs and assuming continuation of existing economic conditions. Future income tax expenses are computed by applying the appropriate statutory tax rates to the future pre-tax net cash flows relating to proved reserves, net of the tax basis of the properties involved. The future income tax expenses give effect to permanent differences and tax credits, but do not reflect the impact of future operations.

The following table sets forth the changes in the standardized measure of discounted future net cash flows relating to proved reserves for the years ended December 31, 2015, 2016 and 2017:

	2015			2016			2017
	(In thousands)
Standardized Measure, Beginning of Year	$	1,090,660		$	372,139		$	429,275
Net change in sales price, net of production costs		(751,774	)		(45,379	)		326,662
Development costs incurred during the year which were previously estimated		157,390			45,648			119,864
Revisions of quantity estimates		(111,454	)		113,583			57,042
Accretion of discount		114,427			37,251			43,130
Changes in future development and abandonment costs		14,901			5,315			(62,509	)
Changes in timing and other		(44,439	)		(38,071	)		(15,565	)
Extensions and discoveries		56,216			70,149			167,135
Sales of minerals in place		(43,694	)		(22,449	)		(6,027	)
Sales, net of production costs		(163,336	)		(107,253	)		(194,562	)
Net changes in income taxes		53,242			(1,658	)		17,099
Standardized Measure, End of Year	$	372,139		$	429,275		$	881,544