The Swede will again line up alongside Dani Sordo in the Prodrive-run team for the event.
"I've done this rally twice before, so I know the roads and have an idea on what awaits me," said Sandell. "But it still feels a bit special to know that I will be sitting in a WRC car this time."
Sandell made his debut in the team in Sweden earlier this month, and finished eighth.
That encouraged his Sweden World Rally Team backers to ensure he was swiftly back in the car, as team manager Jan Pettersson explained.
"We have reasoned together with Prodrive, and concluded that Portugal is a perfect next step for us in the WRC investment we are making," said Pettersson. "It is also important for Patrik to get back into the car as soon as possible, while he has the momentum going from the Swedish Rally."
Dave Wilcock, head of Prodrive's MINI squad, had said after Sweden that Sandell had the potential to be a podium finisher in the WRC.
"Patrik has a very mature rallying head on his shoulders," said Wilcock. "He has maintained a consistent pace throughout the rally, managed his Michelin tyres very well and hasn’t put a mark on the car.
"He has achieved all his goals and to be honest, eighth place is a good as he and we could have hoped for on his debut with so many experienced WRC drivers ahead of him.
"I think he has a great future and I fully expect him to be challenging for podiums."