Property, Plant and Equipment (Tables)

3 Months Ended

Mar. 31, 2014

Property Plant And Equipment [Abstract]

Net Changes in Capitalized Exploratory Well Costs

The following table reflects the net changes in capitalized exploratory well costs during the three-month periods ended March 31, 2014 and 2013.

(Thousands of dollars)	2014		2013
Beginning balance at January 1	$	393,030		445,697
Additions pending the determination of proved reserves		2,919		26,929
Reclassifications to proved properties based on the determination of proved reserves		0		(28,398	)
Balance at March 31	$	395,949		444,228

Aging of Capitalized Exploratory Well Costs

The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed for each individual well and the number of projects for which exploratory well costs have been capitalized. The projects are aged based on the last well drilled in the project.

	March 31
	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		56,324		6		3
One to two years		56,702		6		1		40,721		3		1
Two to three years		31,224		2		0		79,446		8		2
Three years or more		275,831		22		7		267,737		24		5
	$	395,949		32		9		444,228		41		11