Inventories	12 Months Ended
Inventories	Dec. 31, 2021
Inventories [Abstract]
Inventories	Note 2—Inventories Inventories at December 31 were: Millions of Dollars 2021 2020 Crude oil and natural gas $ 647 461 Materials and supplies 561 541 Total inventories $ 1,208 1,002 Inventories valued on the LIFO basis $ 395 282 The estimated excess of current replacement cost over LIFO cost of inventories was approximately $ 251 million and $ 87 million at December 31, 2021 and 2020, respectively.