“We’re delighted to bring Sondre in and see how his qualities help us improve,” ’Well manager Graham Alexander told the club website.
“We’ve watched a lot of him and been impressed with his defensive attributes, plus his technical ability is an added bonus.
“He’s shown a great willingness to come here and we know he will enjoy his time at the club.”
The 26-year-old started his career with Strømsgodset, his move to Mjøndalen in 2017 saw him gradually rise to prominence in Norway’s top flight.
Sondre passed a medical on Monday this week, with a governing body endorsement towards a work permit granted last Thursday.