Petroleum and Natural Gas Sales (Tables)

12 Months Ended

Dec. 31, 2017

Revenue [abstract]

Schedule of petroleum and natural gas sales

(000s)	2017		2016
Petroleum and natural gas sales	$	252,591	$	122,360
Less: Royalties	104,127		59,226
Petroleum and natural gas sales, net of royalties	$	148,464	$	63,134