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ASSET RETIREMENT OBLIGATION (Tables)
 12 Months Ended
Dec. 31, 2015
ASSET RETIREMENT OBLIGATION  
Schedule of changes in asset retirement obligation

                                                                                                                                                                                   

($ thousands)

 

 

December 31, 2015

 

 

 

 

December 31, 2014

 

 

 

Balance, beginning of year

 

$
288,692

 

 

 

$
291,761

 

 

Change in estimates

 

 
(35,386

)

 

 

 
4,378

 

 

Property acquisition and development activity

 

 
761

 

 

 

 
1,778

 

 

Divestments

 

 
(48,748

)

 

 

 
(4,313

)

 

Settlements

 

 
(14,935

)

 

 

 
(19,409

)

 

Accretion expense

 

 
15,975

 

 

 

 
14,497

 

 

 

Balance, end of year

 

$
206,359

 

 

 

$
288,692