19.
Casing Design PETE 411 - Well Drilling Slide 1 of 28
PETE 411
Drilling Engineering
Lesson 19
Casing Design
19. Casing Design PETE 411 - Well Drilling Slide 2 of 28
Lesson 19 - Casing Design - contd
Casing Threads
Using the Halliburton Cementing Tables
Yield Strength of Casing (in tension)
Burst Strength
Effect of Axial Tension on Collapse Strength
Effect of Pipe Bending
Effect of Hydrogen Sulfide
Selection of Casing Settling Depths
19. Casing Design PETE 411 - Well Drilling Slide 3 of 28
Read:
Applied Drilling Engineering, Ch.7
HW #9 - Velocity Profiles
Due 10-15-2001
Multimedia Programs can be found at:
Network Neighborhood juvkam-wold/Super Pentium
or juvkam-wold2
19. Casing Design PETE 411 - Well Drilling Slide 4 of 28
Rounded Threads
* 8 per inch
~ Square Threads
* Longer
* Stronger
Integral Joint
* Smaller ID, OD
* Costs more
* Strong
19. Casing Design PETE 411 - Well Drilling Slide 5 of 28
19. Casing Design PETE 411 - Well Drilling Slide 6 of 28
<--- BURST ---> <--- TENSION --->
19. Casing Design PETE 411 - Well Drilling Slide 7 of 28
Tensional force balance on pipe body
Example 7.1:
Compute the body-
yield strength for 20-
in., K-55 casing with a
nominal wall thickness
of 0.635 in. and a
nominal weight per
foot of 133 lbf/ft.
A * F
s yield ten
o =
19. Casing Design PETE 411 - Well Drilling Slide 8 of 28
Tensional force balance on pipe body
Solution:
This pipe has a minimum
yield strength of 55,000 psi
and an ID of:
. in 730 . 18 ) 635 . 0 ( 2 00 . 20 d = =
K55
A * F
s yield ten
o =
19. Casing Design PETE 411 - Well Drilling Slide 9 of 28
Tensional force balance on pipe body
Thus, the cross-sectional area of steel is
and a minimum pipe-body yield
is predicted by Eq. 7.1 at
an axial force of:
. in . sq 63 . 38 ) 73 . 18 20 (
4
A
2 2
s
= =
t
lbf 000 , 125 , 2 ) 63 . 38 ( 000 , 55 F
ten
= =
A * F
s yield ten
o =
19. Casing Design PETE 411 - Well Drilling Slide 10 of 28
Pipe Body Yield Strength
where
p
2 2
y
Y ) d D (
4
P =
t
in pipe, of diameter inside d
in pipe, of diameter outside D
psi strength, yield minimum specified Y
lbf strength, yield body pipe P
p
y
=
=
=
=
19. Casing Design PETE 411 - Well Drilling Slide 11 of 28
Pipe Body Yield Strength
Example
What is yield strength of body of 7, 26 #/ft,
P-110 casing?
p
2 2
y
Y ) d D (
4
P
t
=
402 , 830 000 , 110 ) 276 . 6 7 (
4
2 2
= =
t
lbs 000 , 830 P
y
~
(nearest 1000 lbs).
agrees with Halliburton
19. Casing Design PETE 411 - Well Drilling Slide 12 of 28
Internal Yield Pressure for Pipe (Burst)
where
(
=
D
t Y 2
875 . 0 P
p
in pipe, of O.D. D
in , thickness wall nominal t
psi strength, yield minimum Y
psi pressure, yield internal P
p
=
=
=
=
F
P
= DLP
F
T
= 2tLY
P
DLP = 2tLY
P
(
=
D
t 2Y
P
p
F
P
F
T
19. Casing Design PETE 411 - Well Drilling Slide 13 of 28
Example
For 7, 26 #/ft P-110 pipe
9,955
7 * 2
6.276) - (7
* 110,000 * 2 * 0.875
=
=
psi 960 , 9 P = (nearest 10 psi)
agrees with Halliburton Tables.
(
=
D
t Y 2
875 . 0 P
p
19. Casing Design PETE 411 - Well Drilling Slide 14 of 28
Ellipse of
Plasticity
19. Casing Design PETE 411 - Well Drilling Slide 15 of 28
TENSION
19. Casing Design PETE 411 - Well Drilling Slide 16 of 28
19. Casing Design PETE 411 - Well Drilling Slide 17 of 28
AL = (R + r)Au - RAu
u A = u A = A
2
d
r L
n
( ) 180 100 12 2
d
L 2
d
L
L
n n
t o
=
u A
=
A
= c A
n n
6
d 218 d
180 400 , 2
10 * 30
E o = o
t
= c A = o A
n
d 218o = o A
Au
R + r R
Length of arc, L = RAu
R
s n
A d 218 F o =
(7.14a)
L
19. Casing Design PETE 411 - Well Drilling Slide 18 of 28
Figure 7.14 - Incremental stress caused by
bending of casing in a directional well
The area of steel, A
s
, can be expressed
conveniently as the weight per foot of
pipe divided by the density of steel.
For common field units, Eq. 7.14a
becomes
) 14 . 7 .........( .......... .......... 64 b w d F
n ab
o =
ly. respective lbf/ft, and in., ft, 0 degrees/10 lbf,
of units have and , , , where w d F
n ab
o
19. Casing Design PETE 411 - Well Drilling Slide 19 of 28
Example
) 14 . 7 .........( .......... .......... 64 b w d F
n ab
o =
/ 5 3
in 7
100 deg/ 5
,
ft lbf w
d
ft
n
=
=
= o
F
ab
= 64 * 5 * 7 * 35 = 74,400 lbf
F
ab
= 74,400 lbf
19. Casing Design PETE 411 - Well Drilling Slide 20 of 28
R
c
= 22
19. Casing Design PETE 411 - Well Drilling Slide 21 of 28
19. Casing Design PETE 411 - Well Drilling Slide 22 of 28
19. Casing Design PETE 411 - Well Drilling Slide 23 of 28
19. Casing Design PETE 411 - Well Drilling Slide 24 of 28
19. Casing Design PETE 411 - Well Drilling Slide 25 of 28
Production casing design load for burst.
19. Casing Design PETE 411 - Well Drilling Slide 26 of 28
Production casing design load for collapse.
19. Casing Design PETE 411 - Well Drilling Slide 27 of 28
Tensile Strength of Casing
What is the maximum
length of N-80 casing that
can hang in an air-filled
wellbore
without exceeding the
minimum yield strength
of the pipe?
19. Casing Design PETE 411 - Well Drilling Slide 28 of 28
Tensile Strength of Casing
What is the maximum length of N-80
casing that can hang in an air-filled
wellbore without exceeding the
minimum yield strength of the pipe?
F
W
F
MAX
= 80,000 A
s
= A
s
L
MAX
490/144
L
MAX
= 80,000 * 144/490
L
MAX
= 23,510 ft
{ With a 1.8 design factor, L
MAX
= 13,060 ft }
