Page 77 - Well Control for Completions and Interventions

68 Well Control for Completions and Interventions

Completion engineers often differentiate between reservoir comple-
tions (alternatively called the lower or sand-face completion) and the
upper completion. The reservoir completion forms the connection
between the reservoir and the wellbore. The upper completion is the
conduit between the reservoir completion and the surface facilities.

2.2.1 The reservoir completion (sand-face or lower
completion)

A good completion engineer will focus much of their attention on the
lower completion design, since it is the efficiency of the lower completion
that has the biggest influence on well productivity. Lower completion
design will fall into one of only five categories. Within those five options
there are a huge number of variables. Getting it wrong will be costly.
The main design decisions affecting the choice of reservoir comple-
tion are:
• Well trajectory and inclination
• Open hole vs cased hole
• Sand control requirements
• Stimulation requirements (propped frac or acid stimulation)
• Reservoir conformance single or multi-layered reservoir and isola-
tion between zones.
The five categories of reservoir completion are:
1. Open hole barefoot. This type of completion is simply a hole drilled
through the hydrocarbon producing zone.
2. Open hole with slotted or predrilled liner.
3. Cased and perforated. A cemented liner or casing string is run across
the reservoir and cemented in place. The casing is then perforated to
provide a communication path between the reservoir and the
wellbore.
4. Sand control completions in open hole. Sand control completions are
required where sand production is anticipated. Sand production has
detrimental effects on completions if not controlled. Open hole sand
control completions include stand-alone screens and gravel packed
screens.
5. Sand control screens in cased hole. Sand control screens can be run in
to existing cased and perforated wells, or newly completed cased
wells, and include screen-only completions, gravel pack, or frac pack.
Expandable sand screens can and have been run in both open hole
and cased hole (Fig. 2.2).