If you want to think about which refineries might be interested in Bakken crude, a way to approach it is to look at 1) how reconfigurable they are, and 2) what kind of crude they use now. Bakken is light, sweet crude. Many others are not. In the old days, refineries were designed to use one type or only a few related types of crude from a local area. So switching from, say, California San Joaquin Valley crude (much of which is a very heavy, dirty oil that requires a lot of processing) to Bakken is like jumping to the other end of the scale: you would nearly have to build a new refinery. Newer refineries are more flexible - they're designed to operate on whatever's least expensive at any given time for a desired product mix. Refineries that have traditionally used imported oil are also usually more flexible. So look at where those are and you can make a good guess as to where the Bakken is going first. Main question regarding routing is whether the trains go all the way to the refinery (probably requiring expanded loading racks) or whether they stop short at a truck or pipeline transload.

Again, Bakken isn't the only crude on rails. Some Canadian crude that is nearly solid tar at normal temperatures is riding trains too, as well as the more traditional types, as has been the case for a long time. What the Bakken situation (lots of oil, no pipes to move it) did, though, was wake up the oil industry to the ability of railroads to deliver small tanker loads (unit trains or large blocks) nearly anyplace, while pipelines are pretty well fixed in place and very expensive to move or extend. So trains are now used in many oil markets, and are in effect rolling tank farms that can be redirected in transit if needed (or more profitable to be delivered) someplace other than where they were originally directed.