Suspended Wells and Exploration Expenses	12 Months Ended
Suspended Wells and Exploration Expenses	Dec. 31, 2021
Suspended Wells and Exploration Expenses [Abstract]
Suspended Wells and Exploration Expenses	Note 6—Suspended Wells and Exploration Expenses The following table reflects the net changes in suspended exploratory well costs during 2021, 2020 and 2019: Millions of Dollars 2021 2020 2019 Beginning balance at January 1 $ 682 1,020 856 Additions pending the determination of proved reserves 10 164 239 Reclassifications to proved properties - (42) (11) Sales of suspended wells - (313) (54) Charged to dry hole expense (32) (147) (10) Ending balance at December 31 $ 660 682 1,020 * Includes $ 313 million of assets held for sale in Australia-West at December 31, 2019. For additional details on suspended wells charged to dry hole expense, see the Exploration Expenses section of this Note. The following table provides an aging of suspended well balances at December 31: Millions of Dollars 2021 2020 2019 Exploratory well costs capitalized for a period of one year or less $ 4 156 206 Exploratory well costs capitalized for a period greater than one year 656 526 814 Ending balance $ 660 682 1,020 *Includes $ 313 million of assets held for sale in Australia-West at December 31, 2019. Number of projects with exploratory well costs capitalized for a period greater than one year 22 22 23 The following table provides a further aging of those exploratory well costs that have been capitalized for more than one year since the completion of drilling as of December 31, 2021: Millions of Dollars Suspended Since Total 2018-2020 2015-2017 2004-2014 Willow—Alaska (1) 313 262 51 - Surmont—Canada (1) 121 2 19 100 PL 1009—Norway (1) 43 43 - - PL 891—Norway (1) 34 34 - - Narwhal Trend—Alaska (1) 25 25 - - WL4-00—Malaysia (1) 24 24 - - PL782S—Norway (1) 22 22 - - NC 98—Libya (2) 13 - - 13 Other of $10 million or less each (1)(2) 61 21 11 29 Total $ 656 433 81 142 (1)Additional appraisal wells planned. (2)Appraisal drilling complete; costs being incurred to assess development. Exploration Expenses The charges discussed below are included in the “Exploration expenses” line on our consolidated income statement. 2020 In our Alaska segment, we recorded a before-tax impairment of $ 828 million for the entire associated carrying value of capitalized undeveloped leasehold costs related to our Alaska North Slope Gas asset. We no longer believe the project will advance, and there is no current market for the asset. In our Other International segment, our interests in the Middle Magdalena Basin of Colombia are in force majeure. As we had no immediate plans to perform under existing contracts; therefore, in 2020, we recorded a before-tax expense totaling $ 84 million for dry hole costs of a previously suspended well and an impairment of the associated capitalized undeveloped leasehold carrying value. In our Asia Pacific segment, we recorded before-tax expense of $ 50 million related to dry hole costs of a previously suspended well and an impairment of the associated capitalized undeveloped leasehold carrying value associated with the Kamunsu East Field in Malaysia that is no longer in our development plans. 2019 In our Lower 48 segment, we recorded a before-tax impairment of $ 141 million for the associated carrying value of capitalized undeveloped leasehold costs and dry hole expenses of $ 111 million before-tax due to our decision to discontinue exploration activities related to our Central Louisiana Austin Chalk acreage.