Protests, attacks by National Liberation Army (ELN) rebels and community and judicial efforts to ban extractive industries are widely considered the top threats to Colombia's oil industry.

The Cubiro field, in Casanare province, produces 3,600 barrels per day (bpd). Average daily output in the Andean country fell 3.59 percent year-on-year in 2017 to 854,121 bpd, largely because of attacks and operational challenges at some fields.

"Unfortunately excessive demands by a minority group of people in San Luis de Palenque, a group that does not represent the municipality's leaders or the community, have forced the BOP Blow Out Preventer repair company gulf coast to make this decision," Frontera said in an emailed statement, adding some workers had been injured. The BOP Blow Out Preventer repair company gulf coast did not provide details about how or when the workers were hurt.

The Cubiro field employs 163 workers, the statement added, and has produced $30 million in royalties for the government since 2015. Frontera is willing to negotiate a re-opening of the field, it said, but not while workers are under threat.

(Reporting by Luis Jaime Acosta and Julia Symmes Cobb; editing by Grant McCool)