STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

834 Drilling and Well Completions
Reynolds number (use Equation 4-90)
Inside drill pipe
Inside drill collars
In drill collar annulus
(8.5-6.75)(4.282)(10) = 496
Re = 928
(140.1)
In drill pipe annulus
(8.835- 4.5)( 1.977)(10)
Re = 928
= 340
(233.6)
Prlnciple of Additive Pressures
Applying the conservation of momentum to the control volume for a onedimensional
flow conduit, it is found that [62]
where p = fluid density
A = flow area
dv/dt = acceleration (total derivative)
v = flow velocity
zW = average wall shear stress
Pw = wetted perimeter
g = gravity acceleration
a = inclination of a flow conduit to the vertical
dP/dl = pressure gradient
1 = length of flow conduit
(4-102)
For a steady-state flow, Equation 4102 is often written as an explicit equation
for the pressure gradient. This is
-
dP --- Tw -pv--pgcosa dv
(4-103)
dl A dl
The three terms on the right side are known as frictional, accelerational (local
accelaration) and gravitational components of the pressure gradient. Or, in other