Two men were arrested at the fracking site in Preston New Road following a lock-on protest, say police.
Police were called to the site just before 7am after two protesters locked-on at the site entrance.
Traffic was stopped for a short time to allow police to create a blockade around the protesters to keep them safe from passing vehicles.
A spokesman for the police said: "Campaigners locked-on in the site entrance and as such we have had to create a sterile area with police vehicles in order for us to deal with the lock on and to ensure the safety of the campaigners in the road.
"Kirkham bound traffic was stopped for a short time to enable police to create the sterile area.
Police say the road fully re-opened at around 12.30pm.
A 30-year-old man and a 56-year-old man, both of no fixed abode, were arrested under the Trade Union Act.
Both men remain in police custody.