it seems that what you are proposing to do is fly inside a ventilation shaft ,can you get to where the shaft comes out of the ground above the tunnel ,and more to the point does it have any form of grid covering it
dont laugh at my suggestion for doing the resulting ,video without actually having the drone flying during the ascent /descent
what you could do if you are able to get to the top of the shaft ,is just use the drone as a camera turned on without props get a fishing rod with a strong enough line to hold the weight of the drone and carefully lower the drone down the shaft and then if that is a success bring it back up then fly around the shaft and then with some clever editing it would appear that you had flown the drone ,a good fishing reel would be more than capable of lowering and retrieving the drone ,if you only wanted to do the descent just reverse the playback for the return journey
you would need some help from others, to be in the tunnel and watch the drone on the way down from the top as well ,but if you could pull it off it would be one cool video