Advanced Drilling Practices - Casing Design.pdf

Master of Petroleum Well Engineering Ad A d v an anc c ed Dr Drii l l i n g Pr Prac actt i c es CASING DESIGN

April – 2005 Assoc. Prof. Sampaio

jsampaio@peten [email protected] g.curtin.edu.au jsampaio@peteng. curtin.edu.au

Casing Design Why Run Casing?  Types of Casing Strings  Classification of Casing  Wellheads  Burst, Collapse and Tension 

– Ex Exa ampl ple es 

Effect of Axial Tension on Collapse Strength – Ex Exa ampl ple es

Casing Design Why Run Casing?  Types of Casing Strings  Classification of Casing  Wellheads  Burst, Collapse and Tension 

– Ex Exa ampl ple es 

Effect of Axial Tension on Collapse Strength – Ex Exa ampl ple es

Casi Ca sing ng De Desi sign gn - In Intr trod oduc ucti tion on What is casing? Why run casing? 1. To prevent the hole from caving in, 2. Onsh shor ore e - to pr pre eve vent nt contamination of fresh water sands, 3. To prevent water migration to producing formation,…

Casing

Cement

Casing Design - Why run casing - cont’d 4. To confine production to the wellbore, 5. To control pressures during drilling, 6. To provide an acceptable environment for subsurface equipment in producing wells, 7. To enhance the probability of drilling to total depth (TD). e.g., you need 14 ppg to control a lower zone, but an upper zone will fracture at 12 lb/gal. What to do?

Functions of Casing Individu Drive pipe

Conductor pip

Provides a means of nippling up diverters  Provides a mud return path  Prevents erosion of ground below rig





Same as Driv  Supports the weight of nex casing strings  Isolates very formations

Functions of Casing Individu Surface casing 





Provides a means of nippling up BOP Provides a casing seat strong enough to safely close in a well after a kick Provides protection of fresh water sands

Intermediate ca 





Usually set in th abnormally pres zone Provides isolatio potentially troublesome zon Provides integrit withstand the h

Functions of Casing Individually – Production casing 





Provides zonal isolation (prevents migration of water to producing zones and isolates different production zones) Confines production to wellbore Provides the environment to install

Liners 

Drilling liners

– Same as Interm casing 

Production liner

– Same as produc casing 

Tieback liners

– Tie back drilling production liner surface. Conver

Types of Strings of Casin Diameter 1. Drive Pipe or Structural Pile (Gulf Coast and offshore only) 150’-300’ BML

16”-60”

2. Conductor String 100’ - 1,600’ BML

16”-48”

3. Surface Pipe 2 000’ 4 000’ BML

85 /8”-20”

Exa

1

Types of Strings of Casing – con Diameter 4. Intermediate String 5. Production String 6. Liner(s)

75 /8”-133 /8” 4½”-95 /8”

Exa

9

Example Hole and String Size Hole Size

Pipe Size

36”

Structural casing

30”

26”

Conductor string

20”

17½”

Surface pipe

12¼”

Intermediate String

133 /8” 95 /8”

Classification of CSG.

Outside diameter of pipe (e.g. 95 /8”)  Wall thickness (e.g. ½”)  Grade of material (e.g. N-80)  Type to threads and couplings (e.g. A LCSG)  Length of each joint (e.g. Range III)  Nominal weight (e.g. 47 lb/ft) 

Most Common Grades

Minimum Yield Strength (KPSI)

Ultimate Strength

H-40

40

60

J-55

55

75

K-55

55

95

C-75

75

95

L-80

80

95

N-80

80

100

C-90

90

100

C-95

95

105

P-110

110

125

V-150

150

160

Length of Casing Joints RANGE

LENGTH (ft)

I

16 - 25

II

25 - 34

Casing Threads and Coupli API round threads – short  API round thread - long  Buttress  Extreme line  Other … 

( CSG ( LCSG ( BCSG ( XCSG

Casing Threads and Couplings –

Wellhead & Christmas Tre •Wellhead •Hang Casing Strings •Provide Seals

•Christmas Tree •Control Production from Well

Wellhead & Christmas Tree – co

Casing Performance - Unia

Loadings  Axial Tension (couplings & bo  Burst Pressure  Collapse Pressure  Bending  Buckling

Casing Performance - Uniaxia 

Tension Strength/Failure

Tension Strength 

Tension Strength – Couplings: API Tables for various couplings – Body (perm. deform.)

F ten =

π

4

(d

2 n

− d

2

)

σ

yield

F ten = pipe body yield strength d n = nominal diameter

Tension Strength – Example 1

Compute the body-yield strength fo 7”, N-80, 23 lb/ft casing. Solution: From API Table (1 & 2) d n = 7 in d = 6.366 in σ

yield

= 80,000 psi

Tension Strength Formula

Uses Nominal Diameter  API minimum Thickness 87.5% o original (nominal) thickness  Yield Strength  Rupture much larger  May deform plastically 

Casing Performance - Uniaxia Burst (Internal Pressure)  Yield the body  Yield the coupling  Leak the coupling

P

Burst (Internal Pressure) 

Barlow (API allows 87.5% of thickness)



Thin Wall Assumption

Pbr =

2(0.875 t ) d n

σ

yield

P br = pipe body burst pressure d n = nominal diameter

Burst

(Internal Pressure) – Example Exampl

Compute the body burstpressure fo 7”, N-80, 23 lb/ft casing. Solution:  From API Table d n = 7 in d = 6.366 in σ

→ t =

80 000 psi

7 − 6.366 2

= 0.317 in

Collapse (External Pressure

Collapse (External Pressure) – con

The following factors are importan  The collapse pressure resistance of a depends on the axial stress (biaxial s  There are different regimes of collaps failure (depends on ratio dn /t) Yield Strength Collapse (thick wall)  Plastic Collapse  Transition Collapse  Elastic Collapse 

Collapse (External Pressure) – con 

Yield Strength Collapse Pressure

⎡ (d n t ) − 1⎤ ( pcr ) yield = 2(σ yield )e ⎢ 2 ⎣ (d n t ) ⎦ P cr = pipe body collapse pressure d n = nominal diameter


Plastic Collapse Pressure

( pcr ) plastic

⎡ F 1 ⎤ = (σ yield )e ⎢ − F 2 ⎥ ⎣ (d n t ) ⎦

P cr = pipe body collapse pressure d n = nominal diameter


Transition Collapse Pressure

( pcr )trans

⎡ F 4 ⎤ = (σ yield )e ⎢ − F 5 ⎣ (d n t ) ⎦



Elastic Collapse Pressure

( pcr )elast =

46.95 × 10

6

(d n t )(d n t − 1)


2

Collapse (External Pressure) – con  





F 1, F 2, F 3, F 4, F 5 … These values are for the uniaxial stress Different values for effective yield stress For Biaxial calculate the effective Yield Stress and interpolate the F’ s


Upper Limit for Yield Strength Collaps

⎛ F 3 ⎞ ⎟ + (F (F 1 − 2) + 8⎜⎜ F 2 + ⎟ σ ( ) yield e ⎠ d n ⎝ ≤ t ⎛ F 3 ⎞ ⎟ 2⎜ F 2 + ⎜ ⎟ σ ( ) ⎝ ⎠ 2


Upper Limit for Plastic Collapse

d n t

≤

(σ yield ) e (F 1 − F 4 ) F 3 + (σ yield ) e (F 2 − F 5 )


Upper Limit for Transition Collapse

d n t

≤

2 + F 2 F 1 3 F 2 F 1


Boundaries for Axial Stress = 0

Collapse (External Pressure) – Exam

Calculate the Collapse pressure rating for a 7 N-80, 23 lb/ft casing. Solution: 7 in, N-80, 23 lb/ft → t = 0.317 in Grade

F1

F2

F3

F4

N-80

3.071

0.0667

1,955

1.988

d

7

Collapse (External Pressure) – Exam

( pcr ) plastic

( pcr ) plastic

⎡ F 1 ⎤ = (σ yield ) e ⎢ − F2 ⎥ − F 3 ⎣ ( d n t ) ⎦

⎡ 3.071 ⎤ = 80,000 × ⎢ − 0.0667⎥ − 1,955 = 3,83 ⎣ 22.08 ⎦

Triaxial Collapse 



Effect of Axial Stress in the Colla Resistance – Effective Yield Stres Von Mises Criteria (Distortion En 

(σ

Material fails (ductile – yield failure) w total distortion energy equals uniaxial energy

σ

) + (σ 2

σ

) + (σ 2

σ

) ≤ 2

Triaxial Collapse – cont’d 

Triaxial

(

σ



)

yield e

2

=

2 σ yield

⎛ σ z + pi ⎞ ⎛ − 3⎜ ⎟ + 3σ z pi − ⎜ ⎝ 2 ⎠ ⎝

Biaxial

(

σ

(σ

)

yield e

=

2 σ yield

) = effective yield stress

− 0.75σ z

2

⎛ σ z ⎞ −⎜ ⎟ ⎝ 2 ⎠

Triaxial Collapse – cont’d

Linear Interpolation for F’ s  F’ s depend on Yield Stress  For σA < σe < σB interpolate using (lin

− σ A (F B − F A ) F e = F A + σ − σ B A σ

e

F’s Formulas (API Bull. 5C3 F 1 = 2.8762 + 0.10679 × 10

−5

σ

F 2 = 0.026233 + 0.50609 × 10

Y

−6

+ 0.21301× 10

−10

2 σ Y

σ

Y

F 3 = −465.93 + 0.030867σ Y − 0.10483 × 10 − 3

7

2 Y

σ

+ 0.36989

⎡ 3( F 2 / F 1 ) ⎤ 46.95 × 10 ⎢ ⎥ F F 2 ( / ) + 2 1 ⎦ ⎣ F 4 = 2 ⎡ 3( F 2 / F 1 ) ⎤⎡ 3( F 2 / F 1 ) ⎤ σ − ( F 2 / F 1 )⎥ ⎢1 − Y ⎢ ⎥ F F F F + + 2 ( / ) 2 ( / ) 2 1 2 1 ⎦ ⎣ ⎦⎣ 6

− 0.5313

Triaxial Collapse – Example 4 

For the casing of Example 3, calculat corrected critical collapse pressure if section of 2000 ft , 7 in, N-80, 23 lbm casing is suspended below it (assume linear weight of 23 lbf/ft and empty borehole - no buoyancy effect). What the corrected collapse pressure if the internal pressure is 1000 psi?

Triaxial Collapse – Example 4 Solution: Weight of Casing Below Point in Question F = 2000 ft × 23 lbf/ft = 46,000 lbf

Cross Section Area Ac =

Axial Stress

(7

π

2

− 6.366 2 ) 4

= 6.6555 in

2

Triaxial Collapse – Example 4 Effective Yield Stress (biaxial)

(

σ

(

σ

)

yield e

)

yield e

=

2 σ yield

− 0.75σ z

2

⎛ σ z ⎞ −⎜ ⎟ ⎝ 2 ⎠

⎛ 6,912 ⎞ = 80,000 − 0.75 × 6,912 − ⎜ ⎟ = 76,32 ⎝ 2 ⎠ 2

2

Triaxial Collapse – Example 4 Interpolated F’ s Grade

F1

F2

F3

F4

C-75

3.054

0.0642

1,806

1.990

“N-76.32”

3.058

0.0649

1,845

1.992

N-80

3.071

0.0667

1,955

1.998

API F’ s Formulas (MsExcel Spreadsheet) σyield

F

76320 F

F

F

F

Triaxial Collapse – Exampl d n

Collapse Regime 

t

=

7 0.317

= 22.08

Yield Regime U-Limit: ⎛ F 3 ⎞ ⎟ + (F 1 − 2 ) (F 1 − 2) + 8⎜⎜ F 2 + ⎟ ( ) σ yield e ⎠ d n ⎝ ≤ t ⎛ F 3 ⎞ ⎟ 2⎜ F 2 + ⎜ ⎟ ( ) σ yield e ⎠ ⎝ 2

(

)

2

⎛ ⎜

1 845 ⎞

⎟ (

)

Triaxial Collapse – Example 4 Plastic Regime U-Limit: d n t

22.08 ≤

≤

(σ yield ) e (F 1 − F 4 ) F 3 + (σ yield ) e (F 2 − F 5 )

76,320 × (3.058 − 1.992 ) 1,845 + 76,320 × (0.0649 − 0.0422 )

= 22.79

Collapse occurs in the Plastic Regime

Triaxial Collapse – Example 4

Plastic Collapse Strength ( pcr ) plastic

( pcr ) plastic

⎡ F 1 ⎤ = (σ yield )e ⎢ − F 2 ⎥ − F 3 ⎣ (d n t ) ⎦

⎡ 3.058 ⎤ = 76,320 × ⎢ − 0.0649⎥ − 1,845 = 3,772 ⎣ 22.08 ⎦

Triaxial Collapse – Example 4 Effect of Internal Pressure

Critical pressure expressions are for pressure differential. However, the effective yield s should account or the internal pressure, s the yield will start at the internal wall. The triaxial expression must be used:

(

)

2

⎛ σ + pi ⎞ ⎜ ⎟

2

⎛ σ + p ⎜

Triaxial Collapse – Example 4 2

(

σ

)

yield e

⎛ 6.912 + 1 ⎞ ⎛ 6.9 = 80 − 3 ⎜ ⎟ + 3 × 6.912 × 1 − ⎜ 2 ⎝ ⎠ ⎝ 2

(

)

σ

yield e

σy ield

= 75.800 ksi = 75,800 psi

75800

F1

F2

F3

F4

F5

3.056

0.0646

1830

1.991

0.0421

⎡ 3.056

⎤

Pressure Collapse Table

Casing Design Criteria

Biaxial Method or Uniaxial Method  Burst – Conductor – Surface and Intermediate Casing – Production Casing

Collapse  Tension 

Casing Design Criteria – cont Burst Conductor:

– External pressure is zero – The maximum internal pressure is the formation fracture pressure at the depth conductor set depth. If the fracture pres unknown, assume ∇ pff =1 psi/ft – F.S.=1.1 – Neglect the gas density inside the condu

Burst of Conductor

Casing Design Criteria – cont Burst of Surface & Intermediate Csg.: 



External pressure: hydrostatic pressure of the heav used to drill the hole and set the casing Internal pressure: based on pore pressure at the fin of the next casing. If the pore pressure at the botto next casing is not known, assume the following:

⎧∇ p p = 0.564 psi/ft Depth next casing < 8000 ft ⎨ ⎩∇ p p = 0.650 psi/ft Depth next casing ≥ 8000 ft 

Assume that a fraction f (usually not less than 40% length is evacuated by gas and (1-f ) fraction of the remains filled with drilling fluid.

Burst of Surf. & Interm. Csg

Casing Design Criteria – cont Burst of Production Casing: 



External pressure: hydrostatic pressure due to formation saltwat = 1.1542) Internal pressure: based on pore pressure at the final depth Dc (production depth). If the pore pressure at the bottom of the cas known assume the following:

⎧∇ p p = 0.564 psi/ft Depth casing < 8000 ft ⎨ ⎩∇ p p = 0.650 psi/ft Depth casing ≥ 8000 ft  

Assumed the whole internal casing filled with gas (gas lift prod Pressure inside the casing determined as follows: Mg

−

p

p e

RT

( DC − D )

≅ p e

DC − D

−

40000

Burst of Production Casing

Casing Design Criteria – cont Collapse: 



  

Collapse due to fluid in the annulus betwee casing and the borehole Considered the heaviest drilling fluid used t the hole and set the casing Assume casing empty No buoyancy F.S.=1.0 (neglect the strengthening effect cement; most of the casing will not be emp

Collapse of Casing

Casing Design Criteria – cont

Tension:  Corresponds to the weight of the casing weight measured in the a (no buoyancy effect)  F.S.: – 1.6 for couplings – 1.8 for casing body

Casing Design Example

Evaluate the burst and collapse pressu loadings and design an appropriate sur casing using the biaxial method. Check axial load. – – – – –

Setting depth of the casing string: 4000 Mud density as setting the string: 10.0 l Setting depth of the next csg. string: 11 Mud density of the next phase: 10.5 lb/ Casing size and coupling: 103 /4” Buttres threads, minimum grade K-55

Casing Design Example con

Burst Loading (this is a surface cs 

External Pressure:

po(psi) = 0.052 x 10 lb/gal x D(ft po = 0.52 x D

Casing Design Example con 

Internal Pressure: ∇pp=0.650 psi /ft /ft (Dnc>8,000 ft) pp = 11,000 x 0.650 = 7,150 psi (1-0,4)xDnc = 6,600 ft p6600= 7,150-0.052x10.5x6,600=3,546 pi= 3,546 psi

Casing Design Example con Burst Pressure – cont’ d: d: F.S. = 1.1 pab = (pi-po) pab= 3,546 – 0.52D

Casing Design Example con Collapse Loading External Pressure: po = 0.52 x D  Internal pressure = 0 psi  F.S. = 1.0 

Casing Design Example con Design for Burst 

Start at bottom (minimum burst pres

pab,4000 = 3,546 – 0.52 x 4000 = 1,466 p

Cheapest casing: (p.320-321) K-55, 40.50 lb/ft, Burst Strength 3,130 p Minimum depth that can go: p 3 546 0 52 x D 3130 psi / 1.1


Continue with next cheapest Cas

K-55, 45.50 lb/ft, Burst Strength 3,580 p

Minimum depth that can go: pab,D = 3, 3,546 – 0.52 x D = 3,580 psi / 1.1 Dmin = 561 ft



K-55, 51.00 lb/ft, Burst Strength 4,030 p

Minimum depth that can go: pab,D = 3, 3,546 – 0.52 x D = 4,030 psi / 1.1 Dmin = -226 ft (above surface)

Casing Design Example con Burst Diagram 0 ft 103 /4 K-55 51.00 lb/ft 561 ft 103 /4 K-55 45.50 lb/ft 1347 ft

103 /4 K-55 40.50 lb/ft

Casing Design Example con Design for Collapse (uniaxial) 

Start at top (minimum collapse press pac = 0.52 x D

Cheapest casing: K-55, 40.50 lb/ft, Collapse Strength 1,580 Maximum depth that can go: p = 0.52 x D = 1,580 psi / 1.0



K-55, 45.50 lb/ft, Collapse Strength 2,090 Maximum depth that can go: pac,D = 0.52 x D = 2,090 psi / 1.0 Dmax = 4.019 ft

Casing Design Example con Collapse Diagram 0 ft

103 /4 K-55 40.50 lb/ft

Casing Design Example con Combine Two Diagrams 0 ft

103 /4 K-55

561 ft

103 /4 K-55 1347 ft

+

=

burst

103 /4 K-55

collapse

Casing Design Example con Collapse Adjustment (Biaxial) Start at bottom (Iterative Process) 

No need to check at bottom of 45.50 lb/f



Bottom of 103 /4 K-55 40.50 lb/ft - 3,038 d n t

=

A =

10.75 0.350

π

4

= 30.71

2 2 2 − = 10.75 10.050 11.44 in ( )


Effective Yield Stress (biaxial)

(

σ

)

yield e

⎛ 3,828 ⎞

= 55, 000 − 0.75 × 3,828 − ⎜ ⎝ 2

σy ield

2

2

⎟ = 52, 986 ⎠

52986

F1

F2

F3

F4

F5

2 985

0 0530

1146

1 994

0 0354

Casing Design Example co 

Yield Regime U-Limit 1,146 ⎞ ⎛ + ( 2.985 − 2 ) ( 2.985 − 2 ) + 8 ⎜ 0.0530 + ⎟ 52,987 ⎠ ⎝ = 14. 1,146 ⎞ ⎛ 2 ⎜ 0.0530 + ⎟ 52,987 ⎝ ⎠ 2

Not Yield Regime


Plastic Regime U-Limit

52,987 × (2.985 − 1.994) 1,146 + 52,987 × (0.0530 − 0.0354)

Not Plastic Regime

= 25.26 < 30

Casing Design Example co 

Transition Regime U-Limit

2 + 0.0530 2.985 3 × 0.0530 2.985

= 37.84 < 30.71

Collapse occurs in the Transition Regim



( pcr ) trans

⎡1.994 ⎤ = 52, 986 × ⎢ − 0.0354 ⎥ = 1, 562 p ⎣ 30.71 ⎦

Maximum depth that can go: pac,D = 0.52 x D = 1,562 psi / 1.0

Casing Design Example con  

2nd Iteration Bottom of 103/4 K-55 40.50 lb/ft - 3,001

W = 45.50 lb/ft × (4000 ft − 3009 ft) = 45,318 lbf σ

z

=

45,318 lbf 11.44 in

2

= 3,963 psi


Effective Yield Stress (biaxial)

(

σ

)

yield e

⎛ 3,963 ⎞

= 55, 000 − 0.75 × 3, 963 − ⎜ ⎝ 2

σy ield

2

2

⎟ = 52, 91 ⎠

52911

F1

F2

F3

F4

F5

2 984

0 0530

1143

1 994

0 0354


Plastic Regime U-Limit 52, 911× ( 2.985 − 1.994 ) 1,144 + 52, 911× ( 0.0530 − 0.0354 )

= 25.26 < 3

Not Plastic Regime


Transition Regime U-Limit

2 + 0.0530 2.985 3 × 0.0530 2.985

= 37.86 > 30.71

Collapse occurs in the Transition Regim



( pcr ) trans

⎡1.994 ⎤ = 52, 911× ⎢ − 0.0354⎥ = 1,561 psi ⎣ 30.71 ⎦

Maximum depth that can go: pac,D = 0.52 x D = 1,561 psi / 1.0 D = 3,002 ft

Casing Design Example cont ’d Final Diagram 0 ft

1

561 ft

2

1347 ft

→ 3006 ft

103 /4 K-55

103 /4 K-55

3

103 /4 K-55

Casing Design Example cont ’d 

Check for Tension



Critical section: Top of section 3 – Axial Load W=45.50x(4000-3006)+40.50x(3006-1347)=112,417 lbf

103 /4 K-55 40.50 lb/ft – Body Strength: 629 kips/1.8 = 349 kips – Coupling Strength: 819 kips/1.6 = 512 kips

Csg. Design & Pore Pressure pressure

Abnormal ∇P: >0.4365 psi/ft

h t p e d

Normal ∇P: 0.433-0.4365 psi/ft

Advanced Drilling Practices - Casing Design.pdf

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