文档介绍：LIFTING CAPACITY
The primary function of the
drilli ng fl uid i s t o cl ean th e h ol e
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Lifting Capacity
Poor hole cleaninggy may be
responsible for up to 70% of all
drilling problems
Drag forces on a particle will
det ermi ne h ow f ast a par ticl e will
fall through a fluid
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Lifting Capacity
Gravity will cause the
particle to fall through
the fluid
When the drag forces are
equal to the acceleration
due to gravity, the
particle will reach its
terminal velocity
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Lifting Capacity
For a spherical particle, the settling
velitilocity is represent tdbthed by the
following equation
⎡⎤1/2
⎢ d pp(ρρ− f)⎥
Vs = 113. 4 ⎢⎥
C ρ
⎣⎢ d f ⎦⎥
Settling velocity is a function of the
diameter of the particle, drag
coefficient, viscosity of the fluid and
ditdiffdensity difference
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Lifting Capacity
The drag coefficient can be
determined from Figure 55--11 if the
particle Reynolds number is
known
p ρ f Vs
Rp =
μe
Unfortunately, the settling
velocity is required to determine
the Reynolds number
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Lifting Capacity
Based on Figure 55--1,1, an equation
can be written for portions of the
graph
For a Reynolds number of 1 or
lthtiiless, the equation is
Cd =24 / Rp
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Lifting Capacity
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Lifting Capacity
Substituting into equation 55--11
yields
2
d pp(ρ−ρ f)
Vs = 8289,
μe
Equation 3 would be used very
seldom unl ess th e d rilli ng fl uid i s
extremely thick
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Lifting Capacity
Between a Reynolds number of
500 and 200,000, the drag
coefficient can be assumed to be
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