Mathematically, this concept is possible. You'd need some extremely high-volume fans (4000 cubic feet per minute for 50N), and as your trailer filled up you'd lose a lot of your propulsion. The size of the fan required rules out quick reverses, not to mention that the structure of your robot ahead of the fan would reduce its efficiency.
I'm not sure why you'd want your wheels undriven though. You might as well make use of the 26 newtons of frictional force that the wheels provide. There's no good reason to simply have them be casters when they can provide as much propulsion as a big fan.
To see someone who ran the numbers, read drkiraco's post
here