Page 258 - Hydrocarbon Exploration and Production Second Edition
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Well Dynamic Behaviour 245
barefoot pre-drilled or cemented open hole cased hole
slotted liner & sand control gravel pack
perforated screens/ or
liner or casing gravel pack frac-pack
Figure 10.16 Reservoir completion summary.
block production or produce solids to surface. However, on the upside, there is
a large flow area and some future interventions such as sidetracking to a new
reservoir location are relatively simple as there is no equipment in the way. Barefoot
completions are common in land locations – especially those producing from
competent limestones and dolomites.
The pre-drilled or pre-slotted liner is slightly more complex. The liner has holes
or slots milled in it before it is installed. It is still an openhole completion in
that whatever is drilled is open to production. The liner however will stop the hole
from totally collapsing and aid in getting intervention or logging tools down. It
is however usually impossible to make the slots small enough to stop individual
grains of sand from being produced. These types of completions can use openhole
packers in order to isolate water or gas intervals. An application of these in a
horizontal well is shown in Figure 10.17.
These openhole packers are either inflated or can be designed to swell once in
contact with reservoir fluids. They then provide a location for setting plugs or
straddles when needed.
The cemented and perforated liner is more complex still, but has distinct advantages.
The casing or liner is run across the reservoir section and cemented in place. Once the
cement has set the well can then be perforated – typically running the perforation guns
on drill pipe. Alternatively the upper completion can first be run and then the
perforations run through the completion – typically with electric line. The perforation
guns contain many shaped charges. In each shaped charge (Figure 10.18), there is a cone
of explosive. When detonated, this sends out a high-pressure unidirectional jet which
punches through the casing, the cement, and several feet into the formation.
Once at the correct depth the gun (as shown in Figure 10.19) is fired from surface
usually either by electric cable or by hydraulic pressure. The big advantage of a