Trouble is even if you could, all that would show is what would happen under the developer’s implementation of the concept in their simulation, not what would happen if portals were real and you tried this which is really the spirit of the question.
EDIT: Actually mate, if you want to know what the game does with it, looks like a few people actually managed to experiment with this https://www.youtube.com/watch?v=S85nudR6D-Y ages back. Disappointing result, again it just shows what the game would do though.
Trouble is even if you could, all that would show is what would happen under the developer’s implementation of the concept in their simulation, not what would happen if portals were real and you tried this which is really the spirit of the question.
EDIT: Actually mate, if you want to know what the game does with it, looks like a few people actually managed to experiment with this https://www.youtube.com/watch?v=S85nudR6D-Y ages back. Disappointing result, again it just shows what the game would do though.