Pros
Because many people have left to go to other companies there is huge advancement opportunities. Schlumberger still has the best training in the industry. So if you can put up with everything for 4-5 years you can get a job anywhere.
Cons
Compensation is poor compared to other companies. They move management around often so the disconnect between field and office is large. People are only in their position in the office for 2 years so they base all their decisions to make them look good for that period of time then they move on. We used to have the best medical insurance, but they cut it down to bare bones and unless you have a catastrophic accident its not worth using. Because people are leaving they need to work you longer to make up for the attrition. The vacation you earn will be taken from you when you have earned days off so their books look better and there is nothing you can do about it.