OPEC oil output has fallen for a second month in October as reduced supplies from Iraq, Nigeria, Saudi Arabia and Angola offset a further rise in Libyan supply, a Reuters survey found on Monday.

Supply from all 12 members of the Organisation of the Petroleum Exporting Countries is expected to average 29.59 million barrels per day (bpd) this month, down from a revised 29.90 million bpd in September, the survey of sources at oil companies, OPEC officials and analysts found.

A further recovery in Libyan output in 2012 could prompt larger reductions by other OPEC members next year, analysts said. Output would have been up this month without disruptions to supplies in Iraq and Nigeria.

It looks to us like you are going to have the potential for stockbuilds in the second quarter, so some sort of cutback in OPEC production looks like it might be on the table for that time period, said Paul Tossetti, senior energy adviser at PFC Energy.

OPEC supply has fallen for a second month from August's total of 30.15 million bpd, which was the group's highest since October 2008, according to Reuters surveys.

Saudi Arabia and its Gulf OPEC allies raised production unilaterally after failing at the group's last meeting in June to convince other members to agree a coordinated increase to meet a shortfall in supplies from Libya.

OPEC holds its next meeting on December 14. Its secretary general, Abdullah al-Badri, predicted in an interview earlier this month the group would come to an agreement when it meets in Vienna.

Officials in OPEC have said the prospect of the Gulf members cutting output substantially is unlikely at current prices, which are well above $100 a barrel for Brent crude.

IRAQ

The biggest drop in output this month has been in Iraq, which in September had achieved a sharp increase in exports.

Iraqi output declined by 190,000 bpd, the most in the group, because of reduced exports from the country's south due to a pipeline bombing and as bad weather disrupted shipments.

Oil production at Iraq's Rumaila oilfield was cut by 700,000 bpd for a few days in early October, after two bombs halted some of its production, Iraqi officials said.

Nigerian supply was reduced because of disruptions to exports from the Bonny and Forcados streams, operated by Royal Dutch Shell's Nigerian venture.

Angolan supply fell in October, despite the onset of supplies of a new crude, Pazflor, export schedules showed. Shipments are expected to rise above 1.8 million bpd in November, in part due to Pazflor's contribution.

Among the Gulf OPEC members, supply from Kuwait and the United Arab Emirates was little changed in October.

Saudi Arabian supply fell further, sources in the survey said, citing a fall in domestic use from peak summer demand and reduced purchases from Shell which cancelled some October-loading shipments after a fire at its Singapore refinery.

Libya was the only OPEC member to boost output substantially in October.

Exports and domestic use rose to 250,000 bpd, according to the survey, from 80,000 bpd in September. Supply is still a fraction of the 1.6 million bpd it produced before the uprising in February against the rule of former leader Muammar Gaddafi.

OPEC has not officially changed its output policy since cutting output by a record 4.2 million bpd in December 2008 to 24.84 million bpd for 11 members, all except Iraq, to combat falling prices and a collapse in demand due to recession.

The group does not provide timely official production figures, so the oil industry relies on outside supply estimates from news agencies, consulting firms and government organisations.

(Reporting by Alex Lawler; editing by James Jukwey)