Both oil benchmarks have lost Movement.down.loss more than 15 percent since hitting four-year highs Position.high in early October , as hedge funds have cut Cause.movement.down.loss bullish bets on crude to a one-year low Position.low .

OPEC has weathered conflicts Civil.unrest before , even between its members , but has so far been fortunate that the headwind of exports lost Movement.down.loss to Libya 's civil strife Civil.unrest has been eased by rising Movement.up.gain output elsewhere , most notably by the boom Grow.strong in U.S. production .

Brent has lost Movement.down.loss from a high Position.high of $ 68.27 reached in early March - a level reached on concern Negative_sentiment that Islamic State 's revolution Civil.unrest in Libya would reduce Cause.movement.down.loss its supplies .

Elsewhere , on the ICE Futures Exchange in London , Brent oil for December delivery lost Movement.down.loss $ 0.92 , or 1.07 % , to hit $ 85.34 a barrel , while the spread between the Brent and the WTI crude contracts stood at $ 4.91 .

Brent has lost Movement.down.loss from a high Position.high of $ 62.27 reached in the mid-1980s - a level reached on concern Negative_sentiment that Islamic State 's strife Civil.unrest in Libya would squeeze Cause.movement.down.loss its supplies .