Oil prices around the world should start falling if Libyan rebels succeed in toppling Muammar Gaddafi's regime, though the full effect won't be felt for months.
Overnight, rebel forces pushed into Tripoli without meeting much resistance, hours after they overran a major military base that defended the capital.
The opposition's leaders said Gaddafi's son and one-time heir apparent, Seif al-Islam, has been arrested.
Independent analyst Andrew Lipow says oil markets will likely respond by sending prices lower in a sign of relief.
But it will take time for the market to erase the hefty price increase that resulted from the suspension of Libyan oil exports since the rebellion began in February.
Analysts estimate the situation in Libya has increased oil prices by $US10 ($A9.67) to $US20 ($A19.35) a barrel.