Page 89 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 65

1.4.10
Casing Design [ ]

manufacturers should be requested from the manufacturer of the pipe
under consideration.

Temperature ˚C Temperature ˚F Yield Strength
Correction Factor
20 68 1.0
50 122 0.95
100 212 0.88
150 302 0.84
200 392 0.81

1.4.10. Methods of Applying Buoyancy Effects

Buoyancy creates an upward force on objects immersed in a fluid.
There are various ways to calculate buoyancy, depending on how you
want to use the information.
The upward force that we call buoyancy is caused by the hydrosta-
tic pressure imposed by the mud on an object increasing with depth.
For an immersed object, the pressure below the object is greater than
the pressure above. This pressure differential is what gives the net
upward force.

1. Apply a buoyancy factor
If a hollow object is immersed in fluid and if the hollow part can
be filled with the surrounding fluid (or if the object is solid),
then the weight in air of that object can be multiplied by a buoy-
ancy factor. The buoyancy factor depends on the specific gravity
(SG) of the object and the SG of the fluid. The formula for buoy-
ancy factor for a solid immersed in a liquid based on the relative
SGs is:

BF =− SGliquid
1
SGsolid

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