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Homework #3:
Axial Tension in Casing String
Due Wednesday, September 22, 2004
A.
A 13 3/8in OD, 85 lb/ft casing string, 5,000 ft long, is hanging in an open
hole filled with air.
Please
calculate
and
plot
axial tension vs. depth (see first part of Lesson 4).
(i)
Axial tension at surface (Hook Load)
=
………………….
.
lbf
5000 x 85 = 425,000
lbf
(ii)
Axial tension at the bottom (Buoyancy Force) =
……………0…….
.
lbf
Since this is in an air filled hole, the buoyancy is essentially nil and axial
tension at the bottom is zero
B.
A 13 3/8in OD, 85 lb/ft casing string, 5,000 ft long, is hanging in an open
hole filled with 13 lb/gal drilling mud.
Please
calculate
and
plot
axial tension vs. depth (see first part of Lesson 4).
(i)
Axial tension at surface (Hook Load)
=
………………….
.
lbf
Here we assume that there is 13.0 ppg fluid inside and outside of the casing
Weight of the mud inside the casing is:
6.0319 Gal/ft
x 5000 ft x 13.0 ppg = 392,074 lbf
Buoyancy force = 7.2987 gal/ft x 5000 ft x 13 = 474,416 lbf
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 Fall '11
 Dr.JeromeJ.Schubert

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