The 21-year-olds have signed new two-year contracts with the Power, ending speculation they could return to their home states.
Victorian Chaplin and West Australian Surjan have emerged as key components of Port's defence this season.
"We have got a good mix of youth and experience and I want to be involved with a club that is going to be successful in the next few years," said Chaplin, recruited by Port as a first-round selection in the 2003 draft.
"To sign is great personally because I have always said that I want to be a one club player."
Surjan, signed by Port in the 2004 draft, predicted Port would soon enjoy success after missing the finals last season.
"We have got a great up and coming list and I'm really looking forward to some success in the near future," Surjan said.