Assuming EI 100, that is a four stop underexposure. Everything in your shots that would have been a midtone is now a very dark grey. Everything that would have been a high tone is now around a middle grey. Everything that would have been a low tone is now totally black. What pushing will do is allow you to increase the brightness of things that fell in the high mid range and the high range.
Might as well push it to see if you get some interesting graphic results, but don't expect anything resembling a "normal" picture. Why not try a really really long time and see what happens. Try super hot developer. Try making a martini. The pix are screwed anyhow, so might as well try to make something interesting out of it. Might be some fun pix!