A procedure and apparatus for cementing and cleaning a reservoir liner 3 comprises installing a reservoir liner using a drill string 4 which extends only as far as the distal end of a cased part 2 of the well, then, using the drill string, displacing cement into the reservoir liner using completion fluid whereby, when the cement is in place in the annulus around the reservoir liner, the reservoir liner is already clean and filled with completion fluid. A ball valve 6 at the top of the reservoir liner 3 is then closed before the cased part 2 of the wellbore is cleaned, to avoid debris entering the reservoir liner.