Page 95 - Well Control for Completions and Interventions

CHAPTER THREE

Completion Equipment

Completions vary hugely in their complexity, and the range of equipment
components is correspondingly large. Some items of completion equip-
ment are safety critical and in many instances the failure of a critical com-
ponent equates to a barrier failure, perhaps even a loss of integrity.
Completion engineers, well site supervisors, and those responsible for
producing the well need to have a broad understanding of what each
component is used for, where it is located in the well, and how it is
installed and maintained.

3.1 THE WELLHEAD, TUBING HANGER, AND
CHRISTMAS TREE

Although the wellhead, tubing hanger, and Christmas tree are sepa-
rate components they form part of an integrated assembly. As such they
must be compatible, and are usually supplied by the same manufacturer.
In a well equipped with a conventional (vertical) tree, the tubing hanger
is designed to sit within the wellhead. In some cases a separate tubing
hanger spool is attached to the top of the wellhead to accommodate the
tubing hanger. The Christmas tree is attached to the top of the wellhead
(or tubing hanger spool), and seals around the neck of the tubing hanger.
Fig. 3.1 shows a wellhead with the tubing hanger in place. The tree is
above.

3.1.1 The wellhead

The wellhead is an integral and important part of the well integrity enve-
lope and is designed to:
• Support each casing string.
• Support the production tubing (the completion).
• Provide a base (support) for the drilling blowout preventer (BOP)
while the well is being drilled.

Well Control for Completions and Interventions. © 2018 Elsevier Ltd.
DOI: https://doi.org/10.1016/B978-0-08-100196-7.00003-8 All rights reserved. 87