Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2014

Property, Plant And Equipment [Abstract]

Net Changes in Capitalized Exploratory Well Costs

(Thousands of dollars)	2014		2013
Beginning balance at January 1	$	393,030	445,697
Additions pending the determination of proved reserves		13,595	28,168
Reclassifications to proved properties based on the determination of proved   reserves		–	(52,865)
Balance at September 30	$	406,625	421,000

Aging of Capitalized Exploratory Well Costs

		September 30,
	2014				2013
(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	$	36,424	2	2
One to two years		36,676	2	1		51,444	6	–
Two to three years		51,898	6	–		35,504	3	3
Three years or more		285,859	22	7		297,628	27	5
	$	406,625	32	9	$	421,000	38	10