MELBOURNE, Jan 15 (Reuters) - Top global miner BHP Billiton BHP.AX BLT.L said on Friday it would book a $4.9 billion post-tax writedown on the value of its U.S. shale assets reflecting the sharp slump in oil and gas prices, volatility and a bleak near-term outlook.
The hefty impairment is the latest spawned by BHP's badly timed push into U.S. shale in 2011, when it spent $17 billion on two acquisitions at a time when oil and gas prices were much higher than they are now.
"Although we expect prices to improve from their current lows, we have reduced our oil price assumptions for the short to medium term," BHP said in a statement to the Australian stock exchange.
The writedowns will take the carrying value of its U.S. onshore assets down to about $16 billion, BHP said.