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INVENTORY (Tables)
 12 Months Ended
Dec. 31, 2017
Inventories [Abstract]  
Disclosure of current inventories
US$ MILLIONS
 
2017
 
2016
Current:
 
 
 
 
Natural gas inventory
 
$
84

 
$
82

Raw materials and consumables
 
24

 
19

Carrying amount of inventories
 
$
108

 
$
101