Property, Plant and Equipment (Tables)

6 Months Ended

Jun. 30, 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		1,620	3,376
Reclassifications to proved properties based on the determination of proved reserves		–	–
Capitalized exploratory well costs charged to expense		–	–
Balance at June 30	$	122,075	396,406

Aging of Capitalized Exploratory Well Costs

		June 30,
	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	$	217	2	1	$	32,192	2	1
One to two years		32,192	2	1		50,333	3	1
Two to three years		27,842	2	–		37,969	5	–
Three years or more		61,824	4	2		275,912	22	7
	$	122,075	10	4	$	396,406	32	9