Property, Plant and Equipment (Tables)

3 Months Ended

Mar. 31, 2015

Property, Plant And Equipment [Abstract]

Net Changes in Capitalized Exploratory Well Costs

(Thousands of dollars)	2015		2014
Beginning balance at January 1	$	120,455	393,030
Additions pending the determination of proved reserves		141	2,919
Reclassifications to proved properties based on the determination of proved reserves		–	–
Balance at March 31	$	120,596	395,949

Aging of Capitalized Exploratory Well Costs

		March 31,
	2015				2014
(Thousands of dollars)	Amount		No. of Wells	No. of Projects	Amount		No. of Wells	No. of Projects
Aging of capitalized well costs:
Zero to one year	$	–	–	–	$	32,192	2	1
One to two years		32,192	2	1		56,702	6	1
Two to three years		33,744	4	2		31,224	2	–
Three years or more		54,660	2	–		275,831	22	7
	$	120,596	8	3	$	395,949	32	9