Pros
Schlumberger offers an extremely competitive salary compared to its competitors (e.g. FracTec, BJ, Halliburton). There are also tons of perks to working as an engineer in this company- housing assistance/stipend/payment, excellent benefits, etc. There is also plenty of opportunity to move around after a few years.
Cons
The work life "balance" is almost non-existent, or rather- completely one-sided. It's the oil and gas industry, a very fast-paced environment that requires a certain level of immediacy from an oilfield services company such as Schlumberger. Working 100 hrs a week wouldn't be so bad if there was more respect and recognition of the adaptability required in doing so form management. Also, there is no stability in terms of location- many field engineers move around once every couple of years as needed. It is for these reasons that retention is so poor.