Supplementary information (Tables)

3 Months Ended

Mar. 31, 2017

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Capitalized costs

Capitalized costs

			March 31,		December 31,
(in millions)			2017		2016
Oil and natural gas properties:
	Proved		$	17,081	$	16,620
	Unproved			2,206		1,856
	Less: accumulated depletion			(7,667)		(7,390)
		Net capitalized costs for oil and natural gas properties	$	11,620	$	11,086

costs incurred for oil and natural gas producing activities

Costs incurred for oil and natural gas producing activities

		Three Months Ended
		March 31,
(in millions)		2017		2016
Property acquisition costs:
	Proved	$	127	$	252
	Unproved		306		139
Exploration			235		170
Development			158		83
	Total costs incurred for oil and natural gas properties	$	826	$	644