Exploration And Evaluation Assets (Tables)

12 Months Ended

Dec. 31, 2017

EXPLORATION AND EVALUATION ASSETS

Exploration and Evaluation Assets rollforward

($ millions)	2017		2016
Beginning of year	2 038		1 681
Acquisitions and additions (notes 7, 8 and 34)	53		787
Transfers to oil and gas assets	—		(65	)
Dry hole expenses	(41	)	(204	)
Impairment (note 11)	—		(152	)
Amortization	(1	)	(1	)
Foreign exchange adjustments	3		(8	)
End of year	2 052		2 038