Significant accounting policies, judgements, estimates and assumptions (Tables)

12 Months Ended

Dec. 31, 2017

Corporate Information And Statement Of IFRS Compliance [Abstract]

Summary of typical useful lives of other property, plant and equipment

The typical useful lives of the group’s other property, plant and equipment are as follows:

Land improvements	15 to 25 years
Buildings	20 to 50 years
Refineries	20 to 30 years
Petrochemicals plants	20 to 30 years
Pipelines	10 to 50 years
Service stations	15 years
Office equipment	3 to 7 years
Fixtures and fittings	5 to 15 years

															$ million
	Land and land improvements		Buildings		Oil and gas propertiesa		Plant, machinery and equipment		Fittings, fixtures and office equipment		Transportation		Oil depots, storage tanks and service stations		Total
Cost
At 1 January 2017	3,066		2,235		215,564		43,725		2,670		14,000		7,623		288,883
Exchange adjustments	264		42		—		1,251		91		28		772		2,448
Additions	264		94		12,366		1,890		240		347		575		15,776
Acquisitions	—		—		—		41		—		228		1		270
Transfers	—		—		451		—		—		—		—		451
Deletions	(120	)	(798	)	(2,327	)	(245	)	(148	)	(3,829	)	(223	)	(7,690	)
At 31 December 2017	3,474		1,573		226,054		46,662		2,853		10,774		8,748		300,138
Depreciation
At 1 January 2017	584		1,062		122,428		18,686		2,022		9,823		4,521		159,126
Exchange adjustments	33		27		—		647		67		19		466		1,259
Charge for the year	90		94		12,385		1,764		185		381		350		15,249
Impairment losses	3		35		624		35		—		479		17		1,193
Impairment reversals	—		—		(135	)	—		—		(72	)	—		(207	)
Deletions	(27	)	(400	)	(1,976	)	(136	)	(138	)	(3,107	)	(169	)	(5,953	)
At 31 December 2017	683		818		133,326		20,996		2,136		7,523		5,185		170,667
Net book amount at 31  December 2017	2,791		755		92,728		25,666		717		3,251		3,563		129,471
Cost
At 1 January 2016	3,194		2,877		215,566		45,744		2,866		14,038		8,418		292,703
Exchange adjustments	(119	)	(37	)	—		(342	)	(127	)	(9	)	(375	)	(1,009	)
Additions	106		24		12,036		1,699		192		156		568		14,781
Acquisitions	46		—		—		793		—		—		—		839
Remeasurementsb	—		—		—		(1,505	)	—		—		—		(1,505	)
Transfers	—		—		1,629		—		—		—		—		1,629
Deletions	(161	)	(629	)	(13,667	)	(2,664	)	(261	)	(185	)	(988	)	(18,555	)
At 31 December 2016	3,066		2,235		215,564		43,725		2,670		14,000		7,623		288,883
Depreciation
At 1 January 2016	642		1,157		123,831		20,652		2,084		9,439		5,140		162,945
Exchange adjustments	(9	)	(44	)	—		(264	)	(96	)	(6	)	(218	)	(637	)
Charge for the year	40		166		11,213		1,740		214		397		384		14,154
Remeasurementsb	—		—		—		(1,319	)	—		—		—		(1,319	)
Impairment losses	9		123		518		11		79		256		4		1,000
Impairment reversals	(2	)	—		(2,923	)	(12	)	—		(101	)	(4	)	(3,042	)
Transfers	—		—		5		—		—		—		—		5
Deletions	(96	)	(340	)	(10,216	)	(2,122	)	(259	)	(162	)	(785	)	(13,980	)
At 31 December 2016	584		1,062		122,428		18,686		2,022		9,823		4,521		159,126
Net book amount at 31  December 2016	2,482		1,173		93,136		25,039		648		4,177		3,102		129,757
Assets held under finance leases at net book amount included above
At 31 December 2017	—		2		16		238		—		233		7		496
At 31 December 2016	—		2		21		266		—		241		—		530
Assets under construction included above
At 31 December 2017															23,789
At 31 December 2016															29,177

^a For information on significant estimates and judgements made in relation to the estimation of oil and natural reserves see Property, plant and equipment within Note 1.

^b Relates to the remeasurement to fair value of previously held interests in certain assets as a result of the dissolution on 31 December 2016 of the group’s German refining joint operation with Rosneft.

Summary of new accounting standard impact

The group’s sales and other operating revenues as reported for 2016 and 2017 by product grouping are presented below:

		$ million
	2017	2016
Crude oil	49,670	32,284
Oil products	159,821	126,465
Natural gas and NGLs	16,196	11,337
Non-oil products and other operating revenues from contracts with customers	12,538	11,487
Revenue from contracts with customersa	238,225	181,573
Other revenues	1,983	1,435
Sales and other operating revenuesa	240,208	183,008

^a  Amounts presented for 2016 and 2017 include revenues from the production of oil and natural gas properties in which the group has an interest with joint operation partners determined using the entitlements method in accordance with the group's accounting policy for those periods (see Revenue above). The amounts presented do not, therefore, represent the Revenue from contracts with customers or Sales and other operating revenues that would have been reported for those periods had IFRS 15 been applied using a fully retrospective transition approach. The differences are not significant. No restatement of prior periods will be made in relation to this change.

The expected overall impact of transition on 2018 opening net assets is summarized below.

	$ million
	Net assets
At 31 December 2017	100,404
Adjustment on adoption of IFRS 9 net of tax and including the group's share of equity-accounted entitiesa	(180	)
At 1 January 2018	100,224

^a  The adjustment on adoption of IFRS 9 mainly relates to an increase in the credit reserve of financial assets in the scope of IFRS 9’s impairment requirements. IFRS 9 requires credit losses to be recognized on an expected rather than incurred loss basis as was the case under IAS 39. The profit and loss account reserve is expected to reduce by an equivalent amount.