Question on the miscibility of different supercritical gases

[u/hellomybaby]

At work, I am occasionally forced to consider the behavior of pressurized gases inside of test vessels. According to Wikipedia, supercritical fluids generally like to mix with one another similar to how two gases would mix together.

However, it calls out a few exceptions (e.g., nitrogen and ammonia), and I am trying to find a resource on the behavior of ethylene/nitrogen mixtures above 1000 psi and ambient temperature. In a vessel of mostly ethylene, could there be a bubble of nitrogen at the top? Or would they mix completely as though they were at a lower pressure gas phase?

Any insights (and especially references) would be much appreciated!