Page 100 - Well Control for Completions and Interventions

92 Well Control for Completions and Interventions

Figure 3.4 A Cameron type tubing hanger two-way check.

Nearly all tubing hangers have a profile machined into the bore
designed to accept a plug, back pressure valve or check valve. The most
common use for the tubing hanger plug is to provide a well control bar-
rier when removing the drilling BOP and installing and testing the
Christmas tree (or vice versa). A tubing hanger can also be used to pro-
vide a well control barrier when repairing Christmas tree valves
(Fig. 3.4).
Many tubing hangers have one or more specially prepared penetra-
tions that enable hydraulic control lines, instrument cables or electric sub-
mersible pump (ESP) power cables to be fed past the hanger and out
through an exit block in the wellhead.

3.1.3 Wellhead and Christmas tree service tools
Because the wellhead is required to last for the life of the well there will,
from time to time, be a requirement to repair or replace the side outlet
valves, or remove and replace the Christmas tree. A range of tools has
been developed to allow this to take place in a safe and controlled man-
ner. These are summarized in Table 3.1 (Figs. 3.5 and 3.6).