PNG media said a group of about 40 to 50 landowners entered Oil Search's Moran oilfield in the Southern Highlands early on Tuesday morning, turning off two oilfield valves.
"We, the real landowners of Northwest Moran (Blcok 1933), are frustrated with the action taken by both the National Government and resource developer Oil Search," said Pai Hoya Resource Owners Association chairman Elvis Alungi, reported in The National newspaper.
Alungi said the group was unhappy over the inclusion of certain clans - namely the Ali Wepo, Toma and Wepo Kambolo - in the ministerial determination and that the correct selection procedures were not followed.
The protestors are from other clans of the Huli tribe.
Australian-listed Oil Search said it was aware of the site walk-in and its company community affairs officers had met with the protestors.
Oil Search said the protestors have taken their complaints to court while the oil company had referred the matter to the police, The National reported.
Shares in Oil Search gained 16c to $5.86 before slipping to $5.85.