Page 53 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 29

1.3.4
Precompletion and Completion Design [ ]

Just above the dual packer, the long string side will have a tele-
scopic joint (TJ). This is to allow the strings to be equalized before set-
ting the slips, and because joint lengths vary slightly, if there was no TJ
then much effort would have to be made to pick up joints in matching
pair lengths. Sometimes the TJ may become fully opened or fully
closed and a pup joint has to be placed in one of the strings to put the
TJ around 50% open.
Another problem is with the placement of accessories. Side pock-
et mandrels can be a particular headache. Since they are not round
but rather elliptical in cross section, you have to be careful not to
place nipples where they could move opposite the side pocket man-
drel during running (i.e., due to movement of the telescopic joint). It
is possible that the side pocket mandrel, if the opposite string is
aligned with its widest section, will crush nipples, collars, or some-
times even the tubing itself, depending on the clearance inside the
production casing.
If you are planning a well that would benefit from a dual comple-
tion, it would be worthwhile to find somebody who has operational
experience of running dual completions to aid in well design.

1.3.4. Completion Fluids

Often wells are perforated and completions are run in a packer
fluid that is designed to protect the well during production. This
requires careful consideration and expert input at the design stage
of the well. This section covers the important points behind comple-
tion fluid decisions, but it is important to realize that this specialist
area should have input from someone with expertise in completion
fluids design.
Completion fluids must be as nondamaging to the formation as
possible so they do not compromise productivity. Apart from being
chemically and physically compatible with the reservoir and its con-
tents, the solids content of the mud must be kept as low as possible.
Any solids must also be removable by acid or other treatments.
Damaging solid precipitates or emulsions can be formed downhole by
chemical reaction between formation fluids and mud or brine filtrates,
which also need to be prevented.

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