Casing/Tubing design manual october 2005 Chevron
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N
N
Nomenclature
English Symbols
()
ave
average value of
(
)
()
e
elastic part
()
te
due to temperature
()
p
plastic part
()
pr
due to pressure, ballooning
()
sh
due to shoulders
()
wt
due to self weight
A
cross-sectional area variable in API collapse formula
A
i
inside area of tube cross section
A
o
outside area of tube cross section
A
p
cross-sectional area of packer
b
~
unit binormal vector
B
variable in API collapse formula
BF
buoyancy factor
c
local curvature
C
variable in API collapse formula
D
tube outside diameter
′
D
tube mean diameter
E
Young’s modulus
E
s
secant modulus
Casing/Tubing Design Manual N-1
October 2005
English Symbols
E
t
tangent modulus
f
yield function
F
variable in API collapse formula
F
~
force vector
F
c
critical buckling force
F
e
effective tension
F
f
fictitious force
F
s
stability force
F
z
axial force
g
acceleration of gravity
G
variable in API collapse formula
I
moment of inertia of tube cross section
i
r
~
unit vector in radial direction
i
~
θ
unit vector in circumferential direction
i
z
~
unit vector in axial direction
L
length
M
bending moment
M
~
moment vector
n model
work hardening parameter, Needleman’s
n
~
unit normal vector
N
normal force per length
N-2 Casing/Tubing Design Manual
October 2005
English Symbols
p
pressure
p
~
position vector
P
Collap s e
API collapse value (prior to correction for internal pressure)
p
E
API elastic collapse pressure
p
i
internal pressure
p
o
external pressure
p
P
API plastic collapse pressure
p
T
pressure
API transition collapse
p
Y
API yield collapse pressure
Q
equivalent external pressure
r
radius, radial coordinate
r
c
radial clearance
r
i
internal radius
r
o
external radius
R
radius of curvature
s
distance along tubular string
s
~
position vector of undeformed configuration
s
~
'
position vector of deformed configuration
t
tube wall thickness
t
~
unit tangent vector
T
temperature
Casing/Tubing Design Manual N-3
October 2005
English Symbols
u
~
displacement vector
u
r
displacement in radial direction
u
z
displacement in axial direction
w
weight per length
w
~
distributed load vector
w
s
(air) weight per length of steel tube
w
e
effective weight
W
p
work due to pressure
z
axial coordinate
Greek Symbols
α
coefficient of linear thermal expansion inclination from vertical
γ
f
fluid weight density
γ
g
gas weight density
γ
i
weight density of internal fluid internal pressure gradient
γ
o
weight density of external fluid external pressure gradient
γ
s
weight density of steel
γ
T
temperature gradient
γ
z
axial stress gradient
δ
incremental distance
()
δ
change in
()
∆L
BKL
length change due to helical buckling
N-4 Casing/Tubing Design Manual
October 2005
Greek Symbols
ε
strain
ε
r
radial strain
ε
y
strain corresponding to yield
ε
z
axial strain
ε
θ
circumferential strain
µ
Poisson’s ratio coefficient of friction between tube and confining hole
σ
stress
σ
~
stress vector
σ
API
API or specified minimum yield stress
σ
b
bending stress
σ
e
effective stress (von Mises criterion)
σ
f
fictitious stress
σ
py
pseudo yield stress
σ
r
radial stress
σ
s
stability stress
σ
u
ultimate stress
σ
y
yield stress, initial yield stress
σ
z
axial stress
σ
za
contribution to
σ
z
from axisymmetric loading
σ
zb
contribution to
σ
z
from bending
σ
θ
circumferential or hoop stress
Casing/Tubing Design Manual N-5
October 2005
Greek Symbols
θ
circumferential coordinate
χ
~
body force vector
N-6 Casing/Tubing Design Manual
October 2005
G
G Glossary
closure stress
The closure stress of a formation is the least
principal total stress, and represents the
pressure that would be necessary to barely
maintain a previously opened fracture, assuming
no fluid loss to the formation. At most depths of
interest, the principal stresses align with vertical
and horizontal and the closure stress is equal to
the minimum horizontal principal stress.
drift diameter
Drift diameter is an assured inside diameter. It is
typically defined in terms of a standard mandrel
of given diameter and length which will pass
unobstructed through the tube.
intermediate casing
All tubular strings between the production casing
string and the surface casing string are
intermediate casing for the purpose of design
load definition.
isotropic
An isotropic material has the same properties in
all directions. With particular reference to
tubulars, isotropy means no difference between
axial, radial, and circumferential (hoop)
mechanical properties.
kick
A kick is defined as flow of formation fluid into
the wellbore. An uncontrolled kick is a blowout.
production casing
The tubular string that encloses the production
tubing is the production casing string. In case of
annular reservoir fluid production, the next outer
casing string not contributing to the annulus is
considered the production casing for the
purpose of design load definition.
production tubing
Production tubing is any tubular string through
which reservoir fluids are conveyed to the
surface. If reservoir fluid production occurs in the
annulus between two tubular strings, both
Casing/Tubing Design Manual G-1
October 2005
tubular strings are considered production tubing
for the purpose of design load definition.
SMYS
Specified minimum yield stress
surface casing
Surface casing is the outermost tubular string
that is required to contain a differential pressure.
G-2 Casing/Tubing Design Manual
October 2005