The cement head provides the connection between the discharge line from the cement unit and the top of the casing (Figure 9). This piece of equipment is designed to hold the cement plugs used in the conventional primary cement job. The cement head makes it possible to release the bottom plug, mix and pump down the cement slurry, release the top plug and displace the cement without making or breaking the connection to the top of the casing. For ease of operation the cement head should be installed as close to rig floor level as possible. The cement jobs will be unsuccessful if the cement plugs are installed in the correct sequence or are not released from the cementing head.
Mud is normally used to displace the cement slurry. The cement pumps or the rig pumps may be used for the displacement. It is recommended that the cement slurry is displaced at as high a rate as possible. High rate displacement will aid efficient mud displacement. It is highly unlikely that it will be possible to achieve turbulence in the cement slurry since it is so viscous and has such a high density. However, it may be possible to generate turbulence in the spacer and this will result in a more efficient displacement of the mud.