Brent crude climbs towards $111 on North Sea, Libya worries

* Libya production could be hit by delay in return of expat oil workers

* Sept/Oct export delays of N.Sea Forties most significant since May

By Luke Pachymuthu

SINGAPORE, Sept 21 (Reuters) - Brent crude rose towards $111 on Friday as concerns about Libya's precarious security situation and lower production in the North Sea triggered worries about supply.

OPEC member and Africa's third biggest producer Libya swiftly ramped up oil output after last year's revolution, but an assault last week on the U.S. consulate heightened fears about the new government's ability to impose its authority, and this is likely to delay the already-slow return of expatriate oil workers to the country.

"We saw oil prices spike up around 30-32 percent last year when Libya was out of the market," said Natalie Rampono, a commodity strategist at ANZ.

"This is something to focus on, especially if the security situation deteriorates," she added.

Brent rose 32 cents to $110.35 a barrel at 0323 GMT, recovering from a six-week low after dipping below $110 in the previous session.

U.S crude was up 58 cents at $93 a barrel. The October contract expired on Thursday at $91.87 a barrel.

Brent futures are down 5.3 percent so far this week, heading for their steepest fall in percentage terms since late June, after key exporter Saudi Arabia pledged to keep prices low, the U.S. mulled release of strategic reserves and the still weak global economy kept demand subdued.

U.S. crude is also down 6 percent for the week, poised for its biggest drop in percentage terms in about four months.

Adding to the worries about supply disruptions, two more cargoes of North Sea Forties crude loading in October were delayed because of lower production.

Export delays in September and October have been the most significant since May's loading programme, when 11 Forties cargoes out of 19 originally planned were deferred, according to Reuters records based on information from trade sources.

The North Sea Forties crude is the most important of the four grades that form the Brent crude basket, and disruptions in its supply exert more influence on the benchmark's prices.

The 200,000-bpd Buzzard field, the largest connected to the Forties pipeline, began a shutdown around Sept. 5 that is expected to take 28 days. Traders said it was now expected to restart three to five days later than originally planned.

SUPPLIES COULD IMPROVE

Unless there is an uptick in demand, analysts say the medium term-outlook for crude remains weak, as supplies are plentiful while the global economy struggles.

On Thursday, manufacturing reports from the euro zone, China and the United States showed factory activity remained lacklustre, further evidence of sluggish growth globally.

"As the much anticipated monetary stimulus programs are now more or less in place, the focus is shifting back towards economic data and key political milestones for the Eurozone," J.P. Morgan analysts said in a report.

"US data has been mixed... the most recent Chinese trade and survey data also offers few signs of a turnaround. Next week the Eurozone will likely return to focus, with Greece, Spain and France unveiling fiscal plans and budgets," they added. (Editing by Miral Fahmy)