The oil supply of Organization of the Petroleum Exporting Countries (Opec) in October has fallen by 120,000 barrels per day (bpd) due to lower production in Angola and Nigeria, a Reuters survey found, although recovery in Libya and growth in Iraq kept output close to September's two-year high.

The survey also indicates Saudi Arabia and heavyweight Gulf producers are showing no sign of deliberately cutting exports to address oversupply and support prices that slipped to a four-year low below $83 a barrel this month.

Opec supply has averaged 30.72 million bpd in October, down from a revised 30.84 million bpd in September, according to the survey based on shipping data and information from sources at oil companies,Opec and consultants.

The organisation pumps a third of the world's oil and meets in November to set output policy for early 2015. Despite oil's drop below $100, the price manyOpec members had endorsed, the group appears unwilling to forego market share by cutting supplies.

"The big question for me is willOpec be willing to reduce its supply sufficiently to rebalance the market next year," Carsten Fritsch, analyst at Commerzbank in Frankfurt, said in the Reuters Global Oil Forum. "I have doubts."

September's output wasOpec's highest since November 2012, when it pumped 31.06 million bpd, according to Reuters surveys. Involuntary outages, such as in Libya, kept output belowOpec's nominal 30 million bpd target in earlier months of the year.

Lower exports scheduling from Angola and Nigeria reduced supplies by a combined 100,000 bpd, while Saudi output was assessed a marginal 50,000 bpd lower due to a reduced need for crude to fuel domestic power plants.

"Exports are flat, refinery runs are not much changed and direct burn lower, so overall supply is down," said one of the sources who monitors Saudi output.

The shutdown of the Khafji oilfield, jointly run by Saudi Arabia and Kuwait, slightly curbed Kuwaiti output but has not affected Saudi production as Riyadh holds a vast amount of capacity in reserve, sources in the survey said.

Of the countries boosting output, the largest gain has come from Libya. Supply has edged up another 40,000 bpd in October, although it fluctuated during the month due to bouts of unrest and the rate of increase has slowed from earlier months.

In Iraq, oil output rose due to higher exports from the country's southern terminals, despite some weather-related delays, and increased output from fields in Kurdistan.

While someOpec members have voiced concern over the drop in prices, indications are thatOpec is unlikely to cut its output target when it meets in Vienna on Nov. 27.

OPEC's most recent published forecast suggests demand for its crude will fall to 29.20 million bpd in 2015 due to rising supply of U.S. shale oil and supplies from other producers outside the group.

However,Opec Secretary-General Abdullah al-Badri this week said demand forOpec crude could be as high as 30 million bpd in 2015, taking into account "abnormal circumstances" such as unplanned outages.

"I don't think 2015 will be far away from 2014 in terms of production," he said during a visit to London. "I am sure the market will balance itself."-Reuters