I know a bit about Schlumberger interview process since I did my my internship with the company. Are you applying for a field or office position?
Usually for field engineer position, they would ask you what your preference would be, i.e. which segment e.g. drilling and measurement or wireline etc, where you want to be based, what you know about SLB business...Sometimes they also ask things like what were your favorite subjects back in college, your work experience etc.
Btw, you do know there are 3 levels of interviews right? In the second or third level, they'll put you in a group and ask you construct a structure using cups, sticks and stuff. Don't know if it's the usual procedure but my friend was given a case study and has to answer some questions based on it.
Not sure about office position though...