STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

MWD and LWD 951
x = distance in ft
L = distance at which the amplitude falls to l/e of its original value
Thus, the length can be expressed as
where Di = internal pipe diameter in ft
Vw = wave velocity in ft/s
o = angular frequency in rad/s (o = 2nf)
F = wave or pulse frequency
q = kinematic viscosity in ft2/s
Also,
P(x) = P(0)
2-"D
where D = distance at which the amplitude falls to + of original value (half depth)
and
P(x) = P(0)
lO-"B
where B = distance at which amplitude falls to +, of its original value (attenuation
of 2 bel or 20 dB)
Attenuation at distance x in dB is
P(x) (20.x)
x(dB) = 20.log- = --
P(0) B
Kinematic viscosity (in consistent
units) is
11 = P/P
(4-189)
where 9 = kinematic viscosity
= absolute viscosity
p = fluid density
Conversion equations are
.( f$) = Mcp) 2.09 x 10" g,
Y
where g, = 32.18 ft/s2
y = mud specific weight in lb/fts
and