Are you talking about plain nitrogen, or a nitrogen/carbon dioxide blend? You'll probably want a blend to keep the beer carbed while you're serving it. After that, to figure out whether that will be enough to move the beer, we'll need a little more info. There are several factors to take into account, including the size of beer lines, pressure used (which will depend on the gas used) and carbonation level of the beer desired. With that horizontal raise you'll probably want to go with nitrogen, but its possible you'd be able to use straight CO2 with a large enough hose.