NOTE H—GOODWILL AND INTANGIBLE ASSETS

The changes in the carrying amount of goodwill (in thousands) consisted of the following:



	Goodwill
Balance at December 31, 2017	$	272,079
EPMH acquisition	139,378
MS Sand acquisition measurement period adjustment	2,800
Balance at June 30, 2018	$	414,257

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:



		June 30, 2018							December 31, 2017
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	76,588	$	(8,413	)	$	68,175	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	80,279		(11,777		)	68,502		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	156,867	$	(20,190	)	$	136,677	$	131,932	$	(14,993	)	$	116,939
Trade name		58,118		—			58,118		33,068		—			33,068
Total intangible assets:		$	214,985	$	(20,190	)	$	194,795	$	165,000	$	(14,993	)	$	150,007

Amortization expense was $2.9 million and $5.2 million for the three and six months ended June 30, 2018, respectively. Amortization expense was $2.2 million and $4.2 million for the three and six months ended June 30, 2017, respectively.

The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows:



2018	$	5,586
2019	10,894
2020	10,894
2021	10,894
2022	10,894