Page 48 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 24

[ ] Well Design
1.3.1

will move relative to each other during running as the telescopic
joints take up the differences in joints run. Thus, tubing acces-
sories may move opposite collars on the other string.
In high-angle wells, the maximum practical deviation for cable or
wireline tools is about 60˚. This may necessitate alternative strate-
gies such as using coiled tubing or, if possible, pump down tools
or setting nipples higher up in the well.
The type of completion will also dictate what kind of wellhead
system to use and how it is to be configured.

Pressure testing the completion.

Fluid gradients, temperatures, and potential surface pressures will
dictate the minimum strength of the casing required during pres-
sure testing. Tubing and packer leaks must also be considered in
terms of where the pressures may be exerted and whether in col-
lapse or burst. Temperature correction factors (TCF) are needed
in hotter wells. (Note: TCF at 200˚C = 0.81 for Nippon steels!)
In deviated wells, consider the potential for casing wear and the
effect on the pressure rating of the casing. Burst strength will be
determined by the thinnest part of the casing wall.

Production.

Fluid gradients, temperatures, and potential surface pressures will
dictate the strength of the casing required during production.
Tubing and packer leaks must also be considered in terms of
where the pressures may be exerted and whether in collapse or
burst. Temperature correction factors are needed in hotter wells.
In deviated wells, consider the potential for casing wear and the
effect on the pressure rating of the casing.
Produced fluids and temperatures could affect the grade of cas-
ings used.
Produced fluids could affect the completion fluid chemistry.

Stimulation including gas lift.

Fluid gradients, temperatures, and potential surface pressures will
dictate the strength of the casing required for any treatments car-

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