Supplementary information (Tables)

9 Months Ended

Sep. 30, 2017

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Capitalized costs

Capitalized costs

			September 30,		December 31,
(in millions)			2017		2016
Oil and natural gas properties:
	Proved		$	17,950	$	16,620
	Unproved			2,804		1,856
	Less: accumulated depletion			(8,167)		(7,390)
		Net capitalized costs for oil and natural gas properties	$	12,587	$	11,086

costs incurred for oil and natural gas producing activities

Costs incurred for oil and natural gas producing activities

		Three Months Ended				Nine Months Ended
		September 30,				September 30,
(in millions)		2017		2016		2017		2016
Property acquisition costs:
	Proved	$	162	$	1	$	301	$	257
	Unproved		472		14		865		172
Exploration			252		177		725		513
Development			175		97		478		287
	Total costs incurred for oil and natural gas properties	$	1,061	$	289	$	2,369	$	1,229