I don't know for sure where Jorge Oliveira got his black belt, but I'm reasonably confident it wasn't from Carlos Gracie, Sr. or Carlos Gracie Jr.
I did see on the interwebs that he competed as part of the Ralph Gracie team for a while, but I don't know whether he came to them as a black belt. He's also done seminars and such for RCJ Machado, so it could be Carlos Machado.
Why are you asking, if you don't mind sharing?