Page 105 - Well Control for Completions and Interventions

Completion Equipment 97

A horizontal tree is configured very differently from a vertical tree.
Valves are positioned on the outside of the tree block, not through the
vertical bore of the tree. The other fundamental difference from the verti-
cal tree is that the tubing hanger rests inside the tree spool, not the well-
head (Fig. 3.9).
Because the hanger sits inside the tree, it follows that the completion
cannot be run until after the tree block has been installed. A drilling
BOP still needs to be in place during the running of the completion, but
now has to be connected to a hub on the top of the tree. A typical
sequence of events for installing a completion on a well equipped with a
horizontal tree is:
• Drill to top reservoir.
• Run bridge plug or mechanical set, retrievable packer.
• Nipple down BOP.
• Install horizontal tree.
• Nipple up BOP (on top of horizontal tree) and install wear bushing in
tubing hanger profile inside tree body.
• Drill to TD.
• Run and cement liner (or run lower completion).
• Recover wear bushing.

Figure 3.9 A simplified representation of a horizontal tree. The tubing hanger the
yellow block in the center of the diagram.