The smaller operators are.
Pioneer, Apache, EOG, Continental, Concho, etc - along with a few majors that are involved - will withstand the oil decline. More specifically, they'll gobble up the smaller debt-ridden players as they collapse, accumulating vast resources for pennies on the dollar.
If someone like EOG tips over, a major like Exxon will scoop them up in the same way. Exxon would love to continue boosting its domestic holdings (after making a few big bakken acquisitions previously). Exxon for example has managed to drop its bakken production costs by 25% in less than five years.
Indeed, this process will lower the cost level US oil can be produced at even further. When the debt heavy players collapse, their existing property and assets will be liquidated for cheap, bringing down the cost for the acquirer - they won't have to pay a premium for the assets. Debt makes the net operational costs higher; if you wipe it out in bankruptcies, the total industry production costs will fall proportionally.
Simultaneously, the producers are getting a lot more production per rig. In the bakken, the average new well production has increased from 200 barrels per day to 600, in five years.