I've had more than a few friends do very well in O&G, riding through a downturn, getting a fat severance, taking a prolonged vacation / working in a smaller company for a few years, then getting hired back when the original company rebuilds.

Schlumberger, in particular, has been through this cycle twice. Exxon has done it on and off for a century. My own firm is the reconstituted remains of Enron, now highly profitable thanks to its stake in the Permian Basin.

Lots of these companies have people who know each other and have worked together for decades.