I've been doing a pre-session using Verys Arkon's rules.
You don't need miniatures.
But they make measuring distances easier.
What you do need though is players that are willing to ask questions. Say you as the DM describe, "You come into a room, and see a hobgoblin archer off to the left, and two warrior-types off to the right"
Basically, you just have to be fair and accurate, not down to the nth degree, but seriously, things like "You're engaged with this guy, moving away is going to draw an Opportunity Attack".
Another example that comes up is that players want to catch as many enemies as possible in an area of effect. Obviously, they can't measure that out, so they want to ask how many they can affect with their fireball (or whatever). You have to explain "You can get 3 guys easily, but you could nail 6 if you included this party member", giving them decisions like that.
Obviously, everyone's mileage may vary, but you need miniatures just as much as you needed them before, which is not at all. Just enhance communication all around, and you'll be fine.