STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

940 Drilling and Well Completions
The benefits of such a tool are apparent in the following instances:
kickoffs and sidetracks
correction runs
high stuck-pipe risk
high temperature
slim hole
low-budget drilling
Velocity and Attenuation of the Pressure Waves. The velocity and attenuation
of the mud pulses or waves have been studied theoretically and experimentally.
The velocity depends on the mud weight, mud compressibility, and on the
drillpipe characteristics, and varies from 4920 ft/s for a light water-base mud
to 3,940 ft/s for a heavy water-base mud. An oil-base mud velocity will vary
from 3,940 ft/s for a light mud to 3,280 ft/s for a heavy mud.
The propagation velocity can be calculated using the equation
(4-182)
and
M=E
(a' - b2)
4 b2( f - 1)+2(1+ 1)(a2 + b2)
(4-1 83)
where V = pressure wave velocity in ft/s
g, = acceleration due to gravity: 32.17 ft/s2
B = mud bulk modulus in psi (inverse of compressibility)
E = steel Young modulus of elasticity in psi
a = OD of the pipe in in.
b = ID of the pipe in in.
h = steel Poisson ratio
y = mud specific weight in lb/ft3
For example, in a 9 lb/gal water-base mud, and a 44-in. steel drillpipe, the
pressure wave velocity is 4,793 ft/s.
The attenuation of the pressure waves increases with depth and with the mud
pressure wave velocity. More attenuation is observed with oil-base muds, which
are mostly used in deep or very deep holes, and can be calculated with the mud
and pipe characteristics [ 1081 according to the equations
--
x
P(x) = P(O)(e ") (4- 184)
L = di 0 V . E
(4-185)