Supplementary information

3 Months Ended

Mar. 31, 2015

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Supplementary information

Supplementary information

Costs incurred in oil and natural gas property acquisition, exploration and development activities

Costs incurred in the acquisition, exploration and development of oil and natural gas assets are presented below for the periods presented:

	Three months ended March 31,
(in thousands)	2015		2014
Property acquisition costs:
Evaluated	$	—	$	25
Unevaluated	—		7,280
Exploration	4,513		8,499
Development costs(1)	206,672		188,313
Total costs incurred	$	211,185	$	204,117

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(1) The costs incurred for oil and natural gas development activities include $0.5 million and $0.6 million in asset retirement obligations for the three months ended March 31, 2015 and 2014, respectively.