FACTBOX-Why is Nigerian oil militant attack significant?

(Reuters) - Militants in speedboats attacked Royal Dutch Shell's main offshore facility in Nigeria on Thursday.

Below are answers to some questions about the attack and what it could mean:

WHY IS THIS ATTACK DIFFERENT?

Militant attacks on oil installations in Nigeria have mostly targeted facilities in the shallow creeks of the Niger Delta, where pipeline bombings and kidnappings of expatriate oil workers have been frequent.

Thursday's attack targeted Shell's Bonga oilfield, which lies some 120 km (75 miles) off the Nigerian coast.

Such offshore facilities have been considered safer and easier to protect and attacks of this kind have been relatively rare. International oil companies have been focusing investment offshore partly because of the perceived lower risk.

HOW ARE WORLD OIL PRICES AFFECTED?

Global oil prices are already near record highs above $130 a barrel. With the bullish sentiment already in the market, news of any supply disruption in a major oil-producing country will spark further buying.

Militant attacks and a workers' strike in late April slashed more than half of Nigeria's production, helping oil prices surge to a then-record $120 a barrel.