Pros
I worked in the north sea sector for 18 months as an MWD engineer. SLB is pretty meritocratic, so if you want to do well, you can. Payment is pretty good - at the time I left, the package was worth between 65-75k a year after only 18 months. Huge opportunities to travel, loads of genuine early responsibility and client interaction. Even if you don't stay long, it'll stand you in good stead for the rest of your career.
Cons
Limited and unpredictable time off - this is why I left in the end, as sustaining a relationship on the continent became quite difficult without knowing when I would next have time off. A lot depends on your line manager (Field Service Manager), as they mostly assign you jobs and are responsible for overseeing your career progression. The logistics are by the nature of the work, unpredictable and you're being payed a premium to be on call and available... Therefore it often feels like you're being taken advantage of and working every hour,- but that's what you're being paid for... I found it OK for a while, but didn't want to sacrifice my life for the corporation, so left. I always maintained great working relationships with my clients, who were always 100% satisfied with my work. Unfortunately this didn't get back to my FSM, so his impression of me was far less good. In retrospect, I should have spoken to him more and explained what I had been doing. When starting, I was given less than 48 hours notice that my start date had been delayed by a month.