Oilfield service giants Schlumberger, Halliburton and Baker Hughes saw their combined revenues tumble by $21bn last year from 2015 but they expect revenues to begin rebounding this year.

Of the three, only number one Schlumberger made a 2016 profit ($1.57bn), partly due to the costs accrued by Halliburton and Baker Hughes following their failed $30bn merger last year.

Baker Hughes sought out cooperation with US engineering conglomerate General Electric (GE) following that collapse. GE...