The cuts are in addition to the 9,000 reduction it announced in January. The stock rose about 3 percent in after-hours trading.
The company blamed a decline in drilling activity.
"In spite of the detailed preparations we made in the fourth quarter, the abruptness of the fall in activity, particularly in North America, required us to take additional actions during the quarter," Schlumberger, world's No. 1 oilfield services provider, said in a statement.
"These included the difficult decision to make a further reduction in our workforce of 11,000 employees, leading to a total reduction of about 15 percent compared to the peak of the third quarter of 2014."
Separately, the company reported first-quarter revenue of $10.25 billion, down 9 percent year-over-year, and below expectations of $10.46 billion. Adjusted profit declined 12 percent from a year ago to $1.09 a share, but it topped estimates of 89 cents a share.