Most of them are due to bad management. They've killed moral & removed any reason to stay. Most of the people still employed are already looking for work outside the company.
Its why the retention is so low and short term. When people get in the doors, are there a while and see what is going on, they start to look for life again on the outside. The price of oil is a big hit to the problems, but only because the reduced revenue stream exposes a lot of the shortcomings of management.
When oil was high and the company was making more money, it was easier for management to get away with mistakes and low moral. It pretended to care while handing out the occasional small bonus check. (not that bonuses came very often even in 'good times.')
Now with oil lower in cost, reduced benefits, low or no raises, more bureaucracy and no bonuses, they have nothing left that would give anyone a reason to put up with bad management and stay.