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directly or indirectly involved is essential to successful drilling/completion practices.
α
m
= activity in drilling mud, dimensionless
α
s
= activity in shale pore fluid, dimensionless
A
c
= area
of contact, L
2
, in.
2
D
h
= diameter of the hole, L, in.
D
op
= outside diameter of the pipe, L, in.
E
m
= efficiency, dimensionless
f
= coefficient
of friction, dimensionless
F
l
= lateral force, F, lbf
F
p
= pull force, F, lbf
h
mc
= mudcake thickness, L, in.
L
ep
= length of the permeable zone, L, in.
p
cap
= capillary
pressure, F/L
2
, psi
p
ff
= formation-fluid pressure, F/L
2
, psi
p
m
= mud pressure, F/L
2
, psi
p
os
= osmotic pressure, F/L
2
, psi
r
= pore-throat radius, L, in.
T
= tension in the drillstring
just above the key-seat area, F, lbf
Δ
p
= differential pressure, F/L
2
, psi
Δλ
αf
=
additional mud weight caused by friction pressure loss in
annulus, F/L
3
, lbm/gal
Δλ
s
= additional mud weight caused by surge pressure, F/L
3
, lbm/gal
ϴ
= contact angle between the two fluids,
degrees
ϴ
dl
= abrupt change in hole angle, degrees
λ
eq
= equivalent mud circulating density, F/L
3
, lbm/gal
λ
frac
=
formation-pressure fracture gradient
in equivalent mud weight,
F/L
3
, lbm/gal
λ
mh
= static mud weight, F/L
3
, lbm/gal
μ
c
= chemical potential, dimensionless
σ
= interfacial tension, F/L, lbf/in.
Nomenclature
References
