It does not take a refinery. North Dakota has already put the rule in place to make this happen. I believe it will take effect by the end of the month or so.
Pending North Dakota oil rules may have limited W. Virginia disaster
http://bakken.com/news/id/233179/pending-north-dakota-oil-rules-may-have-limited-w-virginia-disaster/
The article above calls it a filter but I believe it is more in the line of a separator/stablizer.
North Dakota to Reduce Volatility of Bakken Crude-By-Rail
http://www.planetizen.com/node/72791
thanks. I suspect the economics is thin and is justifiable only with government intrusion.