Page 117 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 93

Casing Design [ ]
1.4.21

ommends no centralization, this will normally be to reduce wear on
the wellhead inner profile and sealing surfaces. However, centralization
is so important to getting a satisfactory cement job that it may be
thought necessary to run some centralizers, even if it is the minimum
number at critical depths and around the shoe only.

5
Casings 18 /8 in or larger:
Two springs on the bottom two joints
One spring per joint in the cemented section
One rigid inside the conductor shoe and one at 10-20 m below the
top of the previous casing or conductor
For subsea wellheads run one rigid in the joint below seabed

Casings smaller than 18 /8 in and larger than 9 /8 in:
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5
Two springs on each of the shoetrack joints
One spring per two joints over the cemented section, straight hole.
Use one per joint if the calculated centralization is close to or
below the API recommended minimum of 67%.
One per joint in the buildup section only if cemented
One rigid inside the previous casing shoe
One rigid at 10-20 m below the hanger

The number of spring centralizers in the open hole may be reduced
if wear is likely in a subsea wellhead inner profile.

Casings 9 /8 in or smaller (springs between stop collars if small annu-
5
lar clearance):

Two springs on each of the first two joints
One spring per two joints over the cemented section, straight hole.
Use one per joint if the calculated centralization is close to or
below the API recommended minimum of 67%.
One rigid inside the previous casing shoe
One rigid at 10-20m below the hanger

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