Pros
Made close and lifelong friends with some fellow Field Engineers. Learned to read and interpret Open Hole Logs proficiently. If you manage to stay in the Upstream Oil & Gas industry after doing your time at Schlumberger, they do look good on your resume and experience list.
Cons
Very Long HOURS. Usually staying up over 24 hours or more on jobs. Usually 100 hours a week. A junior field engineer didn't really have days off, and is on call 24/7 to go catch hot shots and "kill rats" at the whim of FSM and senior engineers. Recruiter completely lied about bonuses and making 100k a year. I made an average of 60k a year, which was not worth the work at all. Very unsafe, you were expected to lie on your driving hours and hours you have slept in order to make jobs or you would have been laid off immediately. Expected to be at shop at 8am everyday regardless of job volume or tool calibrations that needed doing. Very limited upward mobility unless you make it all the way to General Field Engineer Status, and the chance of being laid off is extremely high before you get to that point. Out of my initial onboarding PEPTEC class, only one person has made it to General Field Engineer, the rest 60 or so have all been laid off.