Vantaggi
The world have no barriers, your manager will not be the same for more than 2 years (what can be a pro and a con, but I think generally speaking is a pro), you'll have international experience (you can start in your home country and a few years later be transfered overseas or the other way round), the payslip is greater comparing with other companies.
Svantaggi
It's very time consuming job (specially in the field and/or offshore), so it's really hard to keep a good work/personal life balance; and mainly, even the system inside the enterprise being very good (regarding promotions due by performance, avaliations in a 3 month basis, a lot of training including specialized training centers etc), in the end of the day your destiny is in the hands of your manager (I guess it happens in most enterprises, but specially in SLB, depending the segment, geomarket and area you are working in, that's absolutely 100% power on your manager. This can be really bad when you do not have a good manager, or when your manager tend to protect personal friends). That'sa big thing I see in many segments inside SLB.