Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2021

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 nine-month periods ended September 30, 2021 and 2020.

(Thousands of dollars)	2021		2020
Beginning balance at January 1	$	181,616	217,326
Additions pending the determination of proved reserves	5,007		9,941
Capitalized exploratory well costs charged to expense	—		(39,408)
Balance at September 30	$	186,623	187,859

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.

	September 30,
	2021				2020
(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	$	3,297	2	2	8,000	1	—
One to two years	—		—	—	54,334	5	5
Two to three years	53,078		5	5	—	—	—
Three years or more	130,248		6	—	125,525	6	—
	$	186,623	13	7	187,859	12	5

Schedule of Recognized Impairments

The following table reflects the recognized impairments for the nine months ended September 30, 2021 and 2020.

	Nine Months Ended September 30,
(Thousands of dollars)	2021		2020
U.S.	$	—	1,152,515
Canada	171,296		—
Other Foreign	—		39,709
Corporate	—		14,060
	$	171,296	1,206,284