Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs (Tables)

3 Months Ended

Mar. 31, 2019

Extractive Industries [Abstract]

Aging of Capitalized Well Costs

The following table provides an aging of capitalized exploratory well costs based on the date that drilling commenced:

(millions, except number of projects)	March 31, 2019		December 31, 2018
Exploratory Well Costs Capitalized for a Period of One Year or Less	$	9	$	6
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	350		348
Capitalized Exploratory Well Costs, End of Period	$	359	$	354
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling	7		7

Rollforward of Undeveloped Lease Costs

Changes in undeveloped leasehold costs were as follows:

(millions)	Three Months Ended March 31, 2019
Undeveloped Leasehold Costs, Beginning of Period	$	2,306
Additions to Undeveloped Leasehold Costs	47
Transfers to Proved Properties	—
Assets Sold	(2		)
Undeveloped Leasehold Costs, End of Period	$	2,351