In my mind, there could be a couple of motivations for the Oilers management in moving up from #31 at this year's draft.
First of all, the most obvious motivation would be selecting a player they are concerned might get snapped up in the late first round picks, before they start day 2 of the draft on Saturday. They do have a bunch of picks beyond the 2nd round if they want to move up to secure such a player. This is just a guess, but it wouldn't surprise me if the teams that trade up in any given draft are the teams that have extra picks, which the Oilers do.
Secondly, I think trading up from 31 to 29 or 30 is a wise move, depending on cost, since the 29th and 30th overall picks have insurance the 31st pick does not. Drafting, but not signing, a player selected 30th results in compensation to the tune of #60 overall in a later draft, while drafting, but not signing, a player selected 31st results only in heartache and woe.
I don't know if the following is truly a "reason" to move up, but another (very minor?) benefit the Oilers might receive from trading up would be to give the rabid fanbase something else to watch during the broadcast. This would seem to be pretty flimsy rationale for trading up, on its own, but there is likely to be more Oilers fans watching this draft that any other, and if they can generate some goodwill by moving up into the first and picking again, at a reasonable cost, I don't think that's necessarily a bad idea provided they're considering it anyways. Maybe it's better to think of it as a nice bonus in the event they do decide to move up, for one of the other reasons?
At the 2009 draft last June, TB traded up from 32 OV into the late first, 29 OV, at the cost of a 3rd round pick (75 OV). Would it be worth it for the Oilers to move 31 OV along with their 4th round pick (91 OV) to move up to 29th or 30th? Depending who they want, I think a decent case could be made.