Asset Retirement Obligations and Accrued Environmental Costs (Tables)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations and Accrued Environmental Costs

Asset retirement obligations and accrued environmental costs at December 31 were:

	Millions of Dollars
	2011			2010
Asset retirement obligations	$	8,920			8,776
Accrued environmental costs		922			994
Total asset retirement obligations and accrued environmental costs		9,842			9,770
Asset retirement obligations and accrued environmental costs due within one year*		(513	)		(571	)
Long-term asset retirement obligations and accrued environmental costs	$	9,329			9,199

* Classified as a current liability on the balance sheet, under the caption “Other accruals.”

Changes in Overall Asset Retirement Obligation Changed

During 2011 and 2010, our overall asset retirement obligation changed as follows:

	Millions of Dollars
	2011			2010
Balance at January 1	$	8,776			8,295
Accretion of discount		435			422
New obligations		153			64
Changes in estimates of existing obligations		29			744
Spending on existing obligations		(327	)		(314	)
Property dispositions		(60	)		(394	)
Foreign currency translation		(86	)		(41	)
Balance at December 31	$	8,920			8,776