The men, aged in their late teens to 40s, have been taken to Ballina Garda Station.
The Shell to Sea group - who is against the Corrib Offshore Pipe - said it plans to dismantle fencing around the compound this evening, which they claim has been erected illegally.
Shell EP Ireland said all necessary consents had been given for the laying of the Corrib Offshore pipeline in 2009, including the associated works around Glengad.
Demonstrators criticised the strong garda presence around Glengad tonight but Inspector John Ferris said the numbers had been allocated on the basis of the threat posed by the demonstrators.
Shell to Sea spokesperson Terence Conway, said the demonstration was about sending a message to the Government about the local community's opposition to the pipeline coming ashore.
