Exploratory Costs (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of Capitalized Exploratory Wells

The following table sets forth capitalized exploratory well costs and includes additions pending determination of proved reserves, reclassifications to proved reserves and costs charged to expense:



	Three months ended March 31,
(in thousands)	2018			2017
Capitalized exploratory well costs at beginning of period	$	132,200		$	164,996
Additions pending determination of proved reserves	168,753			164,966
Reclassifications due to determination of proved reserves	(158,946		)	(161,697		)
Capitalized exploratory well costs at end of period	$	142,007		$	168,265

The following table sets forth capitalized exploratory well costs:



(in thousands)	March 31, 2018		December 31, 2017
Exploratory wells in progress (drilling rig not released)	$	13,644	$	10,879
Capitalized exploratory well costs capitalized for a period of one year or less	128,363		121,321
Total capitalized exploratory well costs	$	142,007	$	132,200