7. PROPERTY, PLANT AND EQUIPMENT AND INTANGIBLE ASSETS

Property, plant and equipment, net

Property, plant and equipment, net is comprised of the following as of each period presented:


	Estimated
	Useful	December 31,		December 31,
In thousands	Lives (Years)	2015		2014
Gathering pipelines and related equipment	45	$	319,058	$	28,358
Gas processing and compression facilities	20		173,679		278,547
Buildings	30		2,175		2,058
Other depreciable assets	5 - 15		5,589		2,405
Land and rights of way			9,027		827
Construction in progress			277		895
Total property, plant and equipment			509,805		313,090
Accumulated depreciation			(24,650)		(8,915)
Total property, plant and equipment, net		$	485,155	$	304,175

Depreciation expense was $15.5 million for the year ended December 31, 2015 and $8.0 million for year ended December 31, 2014. Depreciation expense was $1.0 million for the period November 15 to December 31, 2013 and $10.0 million for the period January 1, 2013 to November 14, 2013.

Intangible assets, net

Intangible assets consist of the Partnership's existing customer contracts and relationships, and were identified as part of the purchase price allocation to the Partnership's assets acquired by the Azure System. The customer contracts and relationship intangible assets are amortized on a straight-line basis over the expected period of benefit of the customer contracts and relationship, which we have concluded is a ten year period. The amortization expense associated with the customer contracts and relationship intangible asset, which is included within depreciation and amortization expense within the statement of operations was $5.4 million for the year ended December 31, 2015. Amortization expense is expected to be $6.5 million annually over the ten year period. The Azure System had no intangible assets for the year ended December 31, 2014.