Intangible assets (Tables)

12 Months Ended

Dec. 31, 2017

Intangible Assets [Abstract]

Disclosure of detailed information about intangible assets

The carrying amount, by location, of exploration and appraisal expenditure capitalized as intangible assets at 31 December 2017 is shown in the table below.

Carrying amount	Location
$1 - 2 billion	Angola; India; Egypt; Middle East
$2 - 3 billion	US - Gulf of Mexico; Canada; Brazil

											$ million
					2017						2016
	Exploration and appraisal expenditurea		Other intangibles		Total		Exploration and appraisal expenditurea		Other intangibles		Total
Cost
At 1 January	18,524		4,035		22,559		19,856		4,055		23,911
Exchange adjustments	—		197		197		—		(149	)	(149	)
Acquisitions	—		41		41		—		15		15
Additions	2,128		310		2,438		2,896		251		3,147
Transfers	(451	)	—		(451	)	(1,629	)	—		(1,629	)
Deletions	(2,315	)	(95	)	(2,410	)	(2,599	)	(137	)	(2,736	)
At 31 December	17,886		4,488		22,374		18,524		4,035		22,559
Amortization
At 1 January	1,564		2,812		4,376		2,570		2,681		5,251
Exchange adjustments	—		107		107		—		(96	)	(96	)
Charge for the year	1,603		335		1,938		1,274		351		1,625
Impairment losses	—		—		—		62		—		62
Transfers	—		—		—		(5	)	—		(5	)
Deletions	(2,307	)	(95	)	(2,402	)	(2,337	)	(124	)	(2,461	)
At 31 December	860		3,159		4,019		1,564		2,812		4,376
Net book amount at 31 December	17,026		1,329		18,355		16,960		1,223		18,183
Net book amount at 1 January	16,960		1,223		18,183		17,286		1,374		18,660

^a For further information see Intangible assets within Note 1 and Note 6.