Page 104 - Well Control for Completions and Interventions

96 Well Control for Completions and Interventions

requirements differ significantly. In addition, the sequence of events during
a completion or workover is very different when using a horizontal tree.
As described, a conventional (vertical) Christmas tree has the valves
controlling flow arranged vertically through the bore of the tree. A con-
cept that will be very familiar with anyone working on wells (Fig. 3.8).
During the construction of a well with a vertical tree a typical sequence of
events might be:
• Drill to TD.
• Run and cement liner.
• Clean out wellbore.
• Run and land completion. When the completion is landed the tubing
hanger rests inside the uppermost spool in the wellhead—the tubing
hanger spool.
• Install mechanical barriers in the well.
• Nipple down (remove) drilling BOP.
• Install and test Christmas tree.
• Remove mechanical barriers.

Figure 3.8 Simplified schematic of a conventional Christmas tree with the valves
arranged vertically.