Maybe I'm just not seeing it, but what is the range of an invocation?
Yes, they emulate the spells using Warlock level as caster level.no, not the blasts, the 'regular' invocations.
Like Baleful Utterance.
Or do they duplicate the range of the spells they reference?
The eldritch blast is short-range, meaning 25 feet, plus 5 ft/2 levels. Eldritch Spear can increase that dramatically, though. I think it's 250 feet.
Eldritch Blast is 60 ft range, fixed from level 1. But you're correct on Eldritch Spear.
As for the invocations, their ranges should be included in the text, and if not, are the same as the mimicked spell.