The oil output at Organisation of the Petroleum Exporting Countries (Opec) has fallen in November, remaining below 30 million barrels per day for a second month, a Reuters survey found, due to strikes and protests in Libya and further trimming of Saudi Arabian output.

Supply from the Opec has averaged 29.64 million barrels per day (bpd), down from a revised 29.70 million bpd in October, according to the survey based on shipping data and information from sources at oil companies, Opec and consultants.

Outages in Libya and Nigeria have weighed on Opec output this year, offsetting extra US shale oil and other non-Opec supply and helping to keep oil prices well above Saudi Arabia's preferred level of $100 a barrel.

"The market is well supplied but not overly well supplied. Otherwise prices would be plunging," said Sam Ciszuk, an analyst at the Swedish Energy Agency.

"Libya is in a complete mess and there's been some positive signs about Iran, but I don't think the market sees any actual important volumes coming out of that in the coming few months."

In November, protests in Libya, maintenance in Nigeria and lower Saudi supply outweighed a partial recovery in Iraqi exports and a small rise in Iranian shipments.-Reuters