No companies in the Bakken have publicly stated what the breaking point is. I've heard anywhere from $40 to $75. Hess put out a statement before the OPEC meeting that said if oil prices stay around the $60/bbl range they will cut back 25% in the Bakken in 2015. That tells you it becomes expensive at $60, but is still profitable or they would cut back more than 25%. I'd imagine the big guys (Hess, Continental, Conoco, Whiting) will cut back slightly in the Bakken if the prices stay down. The small guys up there (QEP, Newfield, Halcon) will pack up and leave.

In any case if prices stay low you will see the domestic U.S. shale producers cut back. How much is the big question nobody really knows.