In April 1878 he founded the newspaper Dagen ('The Day') and subsequently earned his living as a journalist.
He has a background in the media, as journalist in Dagen from 1980 to 1987 and Stavanger Aftenblad from 1987 to 1989, and editor of Syn og Segn from 1993 to 1997.
In 1945 he started as a journalist in Bergen's Christian newspaper, Dagen.
Philippe Dagen, writing in Le Monde about Oehlen's 2011 exhibition in Nîmes, concluded that he was "of only limited importance. With about 30 canvases he reveals his system with absolute, but unfortunately appalling, clarity."
He was awarded the Prix Italia in 1973 for his audio play Den dagen du aldri skal glemme.