The mass take-over caused staff to be held on a station and for oil output to be interrupted.
"Yesterday morning 200 youths from the Kula community invaded some of our facilities, Ekulama I and Ekulama II," a Shell spokesman said on Monday.
"They shut the flow stations causing a loss of production of 70,000 barrels per day."
There were no staff at Ekulama I, he said, but 75 employees of Shell and its subcontractors had been blockaded on board the second flow station by the demonstrators, some of whom were armed with machetes, he said.
"It is not a hostage situation. They don't have guns to their heads, they are simply being prevented from leaving," the spokesman said of the trapped workers. He could not say if any of the those being held were foreign staff.
"Efforts are being made through the state government to dialogue with the protesters to at least know their demands," he added.
"It is not a hostage situation. They don't have guns to their heads, they are simply being prevented from leaving"
"As of this morning most of the youths have left the area, but they've left 20 of them to stay behind and make sure the staff don't leave," he said.
Shell and the other international companies operating in the Niger Delta are regularly the target of community protests and hostage-takings.
A large majority of the Nigerian
population is mired in poverty
Villagers accuse the firms of taking huge profits from Nigeria's oil industry, which is the biggest in Africa with exports of around 2.5 million barrels per day, while putting next to nothing back into the community.
Press reports on Monday suggested that the youths who occupied Ekulama were demanding greater investment in their impoverished fishing community.
In November, an attempt by a different community to occupy a drilling rig being operated for Shell on the Bomadi Creek turned bloody when Nigerian soldiers opened fire on the protesters.
Villagers from the Ojobo community said that seven young men were killed and showed reporters seven fresh graves. The Nigerian army has insisted that no one died in the clash, but confirmed that 12 people were seriously injured.
Shell has launched an investigation into the incident.
Although Nigeria is the world's sixth largest exporter of oil, the vast majority of its 130-million-strong population remains poverty-stricken, increasing the resentment felt towards wealthy multinational corporations.