Was first called up to attend a presentation in a career fair, where they explain the nature of the job, etc. Thereafter, called up again for a group interview held in a hotel. During the group interview phase, groups of 5 people were asked to build a tower using 50 sheets of paper with the aim of being the highest, and at the same time has the stability to withstand the weight of a dozen eggs. Your group will then be required to present why you come up with the design, and they want to see everyone in the group present.
After that, there's a lunch break, and by the time you get back, the interviewers will decide who gets to the next round, which is a 10-15 minute 1:1 interview with a field engineer from the field/personnel with field experience. Basically asked questions about independence, flexibility in terms of location, which division within SLB you're interested in, etc.
When interview's over, they took about 2 months to get back to me, when I got the offer. But was not called back again to attend OFS-1, their orientation program until another 6 months.