Section 3 : Casing DesignSection 3 : Casing Design
WELL CONSTRUCTION COURSEWELL CONSTRUCTION COURSE
1
FUNCTIONS FUNCTIONS OF CASINGOF CASING
WELL CONSTRUCTION
CASING DESIGN
2
1. To KEEPKEEP the hole open and prevent collapse
2. To ISOLATEISOLATE porous different pressure regimes so that production or injection may be controlled from a specific section
3. To PROTECTPROTECT formations from contamination and fracture
4. To CONTROLCONTROL any pressures encountered in the well
5. To provide structural SUPPORTSUPPORT for the BOPsBOPs on the wellhead
6. To ALLOWALLOW the passage of testing and completion equipment
WELL CONSTRUCTION
CASING DESIGN
3
Q. Why not just drill to TD ?
A. Due to the nature of sedimentary basins : • Unstable formations and differing pressures necessitate
casing off the open hole at certain depths to enable the final well objective to be met
• Too long an open hole will collapse and pack off - possible SIDETRACK SIDETRACK or REDRILLREDRILL
• Exposed High and Low Pressure Zones - BLOWOUT- BLOWOUT
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CASING DESIGN
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1.1. Largest tangible costLargest tangible cost on any well
2. Performs critical functions - support, stability
3.3. Errors in calculationsErrors in calculations can impact cost, safety
4. Every design has two areas in common
• Subjective assumptions have to be made concerning maximum loads
• After the loads are calculated a design factor will apply
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CASING DESIGN
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1. Data is taken from offset wellsoffset wells or local geological knowledge - but actual lithologies may differ
2.2. LOTLOT datadata may be different from the predicted values - need to be able to adjust the wellplan while drilling
3. The controllable kick size must be known at all times while drilling the well - KICK TOLERANCEKICK TOLERANCE
4.4. Inter-relationships MUST be known between LOT, PP, Inter-relationships MUST be known between LOT, PP, potential drilling problems and KTpotential drilling problems and KT
WELL CONSTRUCTION
CASING DESIGN
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UK North Sea Examples
30”
20”
13-3/8”
9-5/8”
30”
20”
30”
20”
30”
20”
30”
20”
9-5/8”
9-5/8” 9-5/8” 9-5/8”
13-3/8” 13-3/8”
7” Liner 7” Liner 7” Liner 7” Liner
A BC ERD
E
WELL CONSTRUCTION
CASING DESIGN
7
CASING TYPE
COMMON SIZES
FUNCTIONS NORMAL RANGE
Conductor 30”, 26” Conduit for the drilling fluid. Cases off shallow, unconsolidated formations. Allows diverter installation
50 – 1500’
Surface 20”, 13-3/8” A/A plus protect against shallow gas. Case off lost circulation zones. First casing on which a BOP can be run
100 – 5000’
Intermediate 13-3/8”, 9-5/8” A/A plus allows heavier weight muds to be used. Set in transition zone of abnormally pressured formations
1000 – 15000’
Production 9-5/8”, 7” Casing inside which the production casing will be run. Seperates production zones from other reservoir forms
Above of across Reservoir
Liners 7”, 5” A/A plus facillitate testing and act as part of the completion in conjunction with the production tubing.
Across Reservoir
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CASING DESIGN
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1. Shoe depth chosen so that next hole section will not be fractured with higher mud weights
2. North Sea the average 30” 30” settingsetting depth 340’ below sea 340’ below sea bedbed.
3. Returns to seabed.4. Cemented back to sea bed5. Conductor analysis determines
minimum height of cement to avoid a top up job
6. Can be pile driven on land - often called STOVE PIPESTOVE PIPE
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CASING DESIGN
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1. Combats weak formations found at shallow depths
2. Usually set in competent rock - hard limestone etc
3. Usually the first casing that the BOP stackBOP stack is set on
4. Normally 20” in the North in the North SeaSea or 18-5/8” in the in the Middle EastMiddle East
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CASING DESIGN
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1. Usually set to case off a potentially unstable formation - Eocene Shales
2. Good cementation must be ensured - multi-stage cement jobs or multi-stage collars
3. Traditionally 13-3/8”13-3/8” or 9-5/8”9-5/8” casing
4. Connectors are usually Buttress - not premium sealing
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CASING DESIGN
11
1. Production Casing represents the last casinglast casing string
2. Run to isolate producing zones, to provide reservoir fluid control and to permit selective production of specific reservoir zones
3. This is the size through which the well will be completed
4. Usual size is 9-5/8”9-5/8” or 7”
WELL CONSTRUCTION
CASING DESIGN
12
• Does not reach the surface
• Hung off using a liner hanger
• As set on bottom, main criteria is max collapse pressure
• Advantages - lower costs, less pipe, faster running times
• Disadvantages - any leaks, tie-back packer, small bore - difficult to always get a good cement job
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CASING DESIGN
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Casing is usually described in terms of :
1. Outside Diameter
2. Nominal unit weight and wall thickness
3. The grade of the steel
4. The type of Connection
5. The Range and length of joint
6. The Manufacturing Process
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CASING DESIGN
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1. The diameter referred to is the pipe body
2. The diameter of the coupling is larger
3. OD tolerance permitted for casing is +1, -0.5%
4. Wall thickness tolerance is +0, -12.5%
5. More specific requirements are set for upset
ends of pipe and tubing
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CASING DESIGN
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• Mechanical and physical properties dependent on chemical composition and heat treatment
• API has defined 8 gradesAPI has defined 8 grades [see API specs 5A, 5AC, [see API specs 5A, 5AC, 5AX]5AX]
• HH4040 JJ5555 KK5555 L L8080 NN8080 CC9595 andand PP110110
• The numbers indicate The numbers indicate MINIMUM YIELD STRENGTHMINIMUM YIELD STRENGTH in in thousands of psi.thousands of psi.
• The letters serve to prevent oral confusion, although The letters serve to prevent oral confusion, although some have additional meaningsome have additional meaning• KK : > minimum ultimate tensile strength than : > minimum ultimate tensile strength than JJ• CC andand L L : ‘Restricted Yield Strength’ : ‘Restricted Yield Strength’• P P :: “High Strength” material “High Strength” material
WELL CONSTRUCTION
CASING DESIGN
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• PHYSICAL PROPERTIESPHYSICAL PROPERTIES: defined in terms of : defined in terms of MinMin and and MaxMax Yield Strength and Yield Strength and MinMin Tensile Strength Tensile Strength
• MINIMUM Yield StrengthMINIMUM Yield Strength: most important in casing : most important in casing design - used to calculate minimum performance design - used to calculate minimum performance propertiesproperties
• P110P110: : can now be used in most normal operations.can now be used in most normal operations.
• API TESTINGAPI TESTING; ; Limited, thus clientsLimited, thus clients may require extra may require extra inspection of critical strings whose failure could have inspection of critical strings whose failure could have serious consequences [i.e., HPHT, sour gas wells]serious consequences [i.e., HPHT, sour gas wells]
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CASING DESIGN
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• Standardised at API Convention in 1924 - they are:1. API Short Round Thread STC2. API Long Round Thread LTIC3. Buttress Thread BTC4. Extreme Line XL
• BUTTRESS THREADS: surface and intermediate casing
• PREMIUM THREADS: for production casing strings.
• PREMIUM SEALS metal to metal sealing, > cost.• Estimated 86% of LEAKS occur on CONNECTIONS
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CASING DESIGN
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Not equal lengths, API specify the range
Range Length (ft) Average (ft) 1 16 - 25 22 2 25 - 34 31 3 > 34 42
RANGE 3 PIPE; is longer and minimises the number of connections (hence the possible leak areas).
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CASING DESIGN
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Normally specified as
1. YIELD STRENGTH
1. Pipe Body and Coupling
2. COLLAPSE STRENGTH
3. BURST STRENGTH
• Pipe Body and Coupling
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CASING DESIGN
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PRELIMINARY PRELIMINARY CASING DESIGNCASING DESIGN
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CASING DESIGN
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1. Casing is designed to support three different loads
1. Collapse
2. Burst
3. Tension
2. A standard design process is as follows
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CASING DESIGN
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Define Load Cases Determine
COLLAPSE and BURST loads
Define Initial Casing String
Determine TENSILE Loads
Adjust Initial Casing String
Determine TRIAXIAL loads if
required
Finalise Casing String
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CASING DESIGN
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1. COLLAPSE is calculated first
• calculations based on pore pressure or mud weight that the casing is set in, with the pipe evacuated.
2. BURST Loads are then calculated
• At shoe – the lessor of PP at next setting depth minus the gas column to the shoe or the FP at the shoe
• At surface – a/a + gas column to surface, minus the decreasing PP (or salt water column) to surface
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CASING DESIGN
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4. Design Factors are then applied
• See WC manual
5. Initial Casing Selected
• Advise maximum three sections per string
6. TENSILE Loads are then calculated
• Based on selected casing weights
• Buoyed tension compared to pipe body strength and connector strength to ensure design factors OK
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CASING DESIGN
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Load cases are calculated in the order
that they appear
3. Production
1. Completion / Kill Fluids
2. Tubing Leaks
3. Functioning DST Tools etc
1. Installation
• Casing Running
• Casing cementing
• Plug bump etc
2. Drilling
1. Pressure Testing after WOC
2. Maximum Mud Weight
3. Lost Circulation, Well Control
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CASING DESIGN
26
Load Component Installation Drilling Production
Weight in Air X X X
Buoyancy X X X
Bending (Fb) X X X
Shock Load (Fs) X
Weight of Cement X
Pressure Testing X X
Total
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CASING DESIGN
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MANUAL
DESIGN FACTORS
Collapse 1.00
Burst 1.10
Tension 1.30
Triaxial 1.25
1. Casing properties are downrated by a design factor to ensure a margin of safety.
2. Note : Local legislation and individual Operators may have different design factors
WELL CONSTRUCTION
CASING DESIGN
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CASING SETTING CASING SETTING DEPTH SELECTIONDEPTH SELECTION
WELL CONSTRUCTION
CASING DESIGN
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WELL ABCMud Weight Vs Fracture / Pore Presure Curves
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
100006 7 8 9 10 11 12 13 14 15 16
Equivalent Mud Weight (ppg)
Dep
th
Pore Pressures
Fracture Pressures
WELL CONSTRUCTION
CASING DESIGN
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WELL ABCMud Weight Vs Fracture / Pore Presure Curves
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
100006 7 8 9 10 11 12 13 14 15 16
Equivalent Mud Weight (ppg)
Dep
th
Pore Pressures
Fracture Pressures
DepthLithology
0
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
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CASING DESIGN
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WELL ABCMud Weight Vs Fracture / Pore Presure Curves
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
100006 7 8 9 10 11 12 13 14 15 16
Equivalent Mud Weight (ppg)
Dep
th
Pore Pressures
Fracture Pressures
DepthLithology
0
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
WELL CONSTRUCTION
CASING DESIGN
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WELL ABCMud Weight Vs Fracture / Pore Presure Curves
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
100006 7 8 9 10 11 12 13 14 15 16
Equivalent Mud Weight (ppg)
Dep
th
Pore Pressures
Fracture Pressures
DepthLithology
0
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
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CASING DESIGN
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Construct
1. Mean Pore Pressure gradient curve
2. Mud Weight curve (+ 200 - 400 psi or 0.5ppg)
3. Fracture Gradient curve
4. Add Safety Margin Line (0.3 – 0.5ppEMW less)
5. Check Offset Mud weights and LOT data results
WELL CONSTRUCTION
CASING DESIGN
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1. Check the mud weight curve at point A
2. Move up vertically to point B
B is the setting depth for
PRODUCTION casing
A
B
WELL CONSTRUCTION
CASING DESIGN
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3. Move to point C - the mud weight at this depth
4. Move up vertically to point D.
D is the estimated setting depth
for INTERMEDIATE
casing
C
D
WELL CONSTRUCTION
CASING DESIGN
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5. Move to point E to check the mud weight required. As the pore pressure is normal at this depth casing is not required for mud weight.
E
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CASING DESIGN
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CASING DESIGN
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1. Shallow gas zones2. Lost circulation zones3. Lithologies4. Unstable formations5. Well profile6. Hole cleaning7. Salt sections or high pressure zones8. Kick Tolerance
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CASING DESIGN
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KICK TOLERANCE KICK TOLERANCE CONSIDERATIONSCONSIDERATIONS
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CASING DESIGN
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TWO TYPES
1. Kick Intensity
2. Kick Volume
WE WILL DO THIS ONE
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CASING DESIGN
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1. Look at the problem in Section 3
2. Draw a brief Well Schematic
We will then work through the problem together
WELL CONSTRUCTION
CASING DESIGN
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SCHEMATIC
TD = 13,123 ft
8,842 ft
4281ft
WELL CONSTRUCTION
CASING DESIGN
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KICK
INTENSITY
TD = 13,123 ft
Dwp = 8,842 ft
TD - Dwp = 4281ft
MW = 13.2 ppg
MAASP = 8,842 x (14.3 - 13.2) x .052
506 psi
MAASP
KI = MAASP - ( MW x .052 x Hi )
.052 x TVD
MAMW = 14.3 ppg
* Assumes gas has no weight so it is not included in the formulae.
WELL CONSTRUCTION
CASING DESIGN
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KICK INTENSITY
TD = 13,123 ft
Dwp = 8,842 ft
TD - Dwp = 4281ft
MW = 13.2 ppg
300 ft
Height of influx based on a 25 bbl kick
KI = MAASP - ( MW x .052 x Hi )
.052 x TVD506 psi
MAASP
= 0.44 ppg
KI = 506 - ( MW x .052 x 300 )
.052 x TVD
WELL CONSTRUCTION
CASING DESIGN
45
KICK INTENSITY
13,123 ft
8,842 ft
4281ft
MW = 13.2 ppg
300 ft
Height of influx based on a 25 bbl gas kick
506 psi
MAASP
KI = 506 - ( 13.2 x .052 x 300 ) =
.052 x 13,123
.44 ppg
SO WHAT DOES IT MEAN ?
This is the maximum mud weight increase to circulate out a 25bbl kick without fracturing the weak point.
Mud weight to balance the formation pressure is 13.2 ppg + 0.44 ppg
= 13.64ppg
WELL CONSTRUCTION
CASING DESIGN
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WELL ABCMud Weight Vs Fracture / Pore Presure Curves
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
100006 7 8 9 10 11 12 13 14 15 16
Equivalent Mud Weight (ppg)
Dep
th
Pore Pressures
Fracture Pressures
DepthLithology
0
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
Use the Offset Well Data + your Pore Pressure and Fracture Gradient Plot information to select the 13-3/8” and 9-5/8” setting depths
WELL CONSTRUCTION
CASING DESIGN
47
KI = MAASP - ( MW x .052 x Hi )
.052 x TVD
Calculate the Kick Intensity for your selected casing depths for the 12-1/4” and 8-1/2” Sections
Example: for the 12-1/4” hole you need:
1. Your selected setting depth for the 13-3/8” shoe
2. LOT at the 13-3/8” shoe (from your plot)
3. Mud Weight for the 12-1/4” (from your plot)
4. Your selected 12-1/4” TD
5. 8” Collars (Assume 600ft length)
6. Assume 25bbl kick and 0.5ppg minimum KI
WELL CONSTRUCTION
CASING DESIGN
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HOWEVER !!
As we have offset data we need to use it to plan our well. Recalculate the KI using offset well data
1. Your selected 13-3/8” setting depth
2. The LOT at the 13-3/8” shoe (from your plot)
3. 12-1/4” Mud Weight (estimate from your offset data)
4. Your selected 12-1/4” TD
5. 8” Collars (estimate from the offset data BHAs)
6. Use 25bbl kick and 0.5ppg minimum KI
WELL CONSTRUCTION
CASING DESIGN
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WORKED EXAMPLEWORKED EXAMPLE
WELL CONSTRUCTION
CASING DESIGN
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1. Calculate for COLLAPSE 1. Collapse drilling Load
2. Selecting casing based on collapse
2. Calculate for BURST 1. Burst drilling Load
2. Selecting casing based on burst
3. Check Tensile Loads
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CASING DESIGN
51
The summary well data for the worked casing design is:
13⅜” casing set at 9,750 ft
External Mud weight (outside) 11 ppg
Internal Mud Weight (inside) 11.2 ppg
Next Section TD (12¼”) 13,360 ft
Draw a Schematic
WELL CONSTRUCTION
CASING DESIGN
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BASIC WELL DATA
Mud Weight Inside
11.2 ppg
13,360 ft MD
9,750 ft MD
Mud Weight Outside
11.0 ppg
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CASING DESIGN
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The worst case collapse load during drilling occurs if lost circulation is encountered and the internal hydrostatic pressure decreases. Let us assume Lost Circulation while drilling 12¼” Hole below 13⅜” Casing. The well information is:
13⅜” casing 9,750 ft
External Mud weight 11 ppg
Internal Mud Weight 11.2 ppg
Drilling ahead,12¼” hole 13,360 ft
Losses and fluid drop to 2,528 ft
Schematic
WELL CONSTRUCTION
CASING DESIGN
54
MUD LEVEL INSIDE DROPS
TO 2528 ft
Mud Weight Inside
11.2 ppg
13,360 ft MD
9,750 ft MD
Mud Weight outside
11.0 ppg
2,528 ft MD
MUD LEVELDROPS
WELL CONSTRUCTION
CASING DESIGN
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Calculate the INTERNAL Pressure Profile
at surface =at 2528 ft =at casing shoe =
= psi
Calculate the EXTERNAL Pressure Profile
at surface =at casing shoe =
= psi
Calculate the NETT Collapse Load at the Casing Shoe
Nett collapse at shoe = ________psi
This is the pressure Acting inside the casing
This is the pressure Acting outside the casing
WELL CONSTRUCTION
CASING DESIGN
56
Internal pressure profile at surface = 0at 2528 ft = 0at casing shoe = (9750’ - 2528’) x 11.2 ppg x 0.052 =
4,206 psi
External pressure profileat surface = 0at casing shoe = 9750’ x 11.0 ppg x 0.052 = 5,577 psi
Nett collapse at shoe = 5,577 psi - 4,206 psi = 1,371 psi
13-3/8 casing 9,750 ftMud weight 11 ppgInternal Mud Wt 11.2 ppgDrilling ahead12-1/4” 13,360 ftFluid drop to 2,528 ft
WELL CONSTRUCTION
CASING DESIGN
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Pressure
Depth
Nett Collapse Line
1371 psi 4206 psi 5577 psi
1446 psi 2528 ft
0 ft
9750 ft
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CASING DESIGN
58
1. The following casings are available – 13-3/8”, 68lb/ft K55 and 13-3/8”, 72lb/ft, N80.
2. The Transocean design factors for collapse is 1.0
Size
ins
Grade Wt per foot
lbs
Inside Diameter
ins
Collapse Resistance
psi
Body Yield Strength
x1000 lbs
Burst Pressure
psi
Downrated Burst Pressure
(Transocean DF = 1.1)
Coupling
Buttress Thread
psi
13-3/8” K55 68 12.415 1,950 1,069,000 3,450 3,450
13-3/8” N80 72 12.347 2,670 1,661,000 5,380 5,380
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CASING DESIGN
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Casing Wear• reduces wall thickness
Fill-up of casing strings while running• inadequate fill-up can result in casing
collapse
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CASING DESIGN
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The worst case Burst Load occurs either during pressure testing or during a well control event. Let us assume the 13-3/8” casing is being pressure tested to 3,000psi
13-3/8 casing 9,750 ftMud weight 11.5 ppg
Top of Cement (TOC) at 3000’ Previous Casing shoe at 1500’ Pressure test to 3000 psi Note: assume that, in the
annulus, the cement has deteriorated to normal Pore Pressure at 8.6ppg EMW and the mud has deteriorated to ‘brackish’ water at 8.33ppg EMW.
Schematic
WELL CONSTRUCTION
CASING DESIGN
61
PRESSURE
TESTING TO
3,000 psi
9750’
11.5ppgMud
Surface
TOC at 3000’
TOC
‘Water’(8.33ppg)
‘Cement’(8.6ppg)
3,000 psi PRESSURE TEST
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CASING DESIGN
62
Calculate the INTERNAL Pressure Profile [psi]at Surface = psiat Casing Shoe = psi
Total = psi
Calculate the External Pressure Profile [psi]
at Surface = __________psi
at TOC = ______________________________psi
at Casing Shoe = ______________________________psi
Total = ________psi
Calculate the NETT Burst Load at surface and the casing shoe [psi]at Surface = psiat Casing Shoe = psi
WELL CONSTRUCTION
CASING DESIGN
63
at surface = 3000 (ie, the casing test pressure)
at casing shoe = 3000 psi + (9750 x 11.5 x .052)
= 8,831 psi
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CASING DESIGN
64
at surface = 0
at TOC= 3000ft x 8.33 ppg x 0.052 = 1299 psi
Between TOC at 3000 ft & the shoe at 9750 ft
= 6750 ft x 8.6 ppg x .052 = 3019 psi
Total = 4,318 psi
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CASING DESIGN
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at surface = 3000 psi
at shoe = 8831 psi – 4318 psi
= 4,513 psi
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CASING DESIGN
66
Production Casing Surface Tubing LeakProduction Casing Surface Tubing Leak
Load at shoe = gas at surface + HH of fluid
Development DrillingDevelopment Drilling
Can use oil gradient for invading fluid if no gas present
Pressure TestingPressure Testing
Lowest of Max WH pressure, 80% of burst, WH or
BOP rating
Surface Equipment LimitationsSurface Equipment Limitations
WELL CONSTRUCTION
CASING DESIGN
67
Surface
9750 ft
TOC – 3000 ft
3000 6000 9000
3000 psi
PRESSURE (psi)
DEPTH (ft)
4513 psi
Nett Burst
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CASING DESIGN
68
1. The following casings are available – 13-3/8”, 68lb/ft K55 and 13-3/8”, 72lb/ft, N80.
2. Note: The Transocean design factors for burst is 1.1, so downrate the burst pressure accordingly.
Size
ins
Grade Wt per foot
lbs
Inside Diameter
ins
Collapse Resistance
psi
Body Yield Strength
x1000 lbs
Burst Pressure
psi
Downrated Burst Pressure
(Transocean DF = 1.1)
Coupling
Buttress Thread
psi
13-3/8” K55 68 12.415 1,950 1,069,000 3,450 3,136 3,450
13-3/8” N80 72 12.347 2,670 1,661,000 5,380 4,891 5,380
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CASING DESIGN
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0 ft
9750 ft
Nett Collapse Nett Burst
CONCLUSION
Both are suitable for CollapseOnly N80 suitable for Burst
RECOMMENDATION
Select 72ppf, N80
13-3/8” N80 - 72 ppf 2. Collapse 2670 psi4. Burst 5380 (4891 downrated for DF)
13-3/8” K55 – 68 ppf1. Collapse 1950 psi3. Burst 3450 (3136 downrated for DF)
1446 psi
1371 psi 4,271 psi
3,000 psi
WELL CONSTRUCTION
CASING DESIGN
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Load Component Installation Drilling Production
Weight in Air X X X
Buoyancy X X X
Bending (Fb) X X X
Shock Load (Fs) X
Pressure Testing X X
Total Load (lbs)
Once the casing meets collapse and design criteria, it is necessary to ensure that it will meet the Tensile design. It needs to withstand installation, drilling and production loads. It is assume that the casing is fixed at the surface but free to move at the shoe.. The following loads need to be considered.
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CASING DESIGN
71
Load cases are calculated in the order that they appear
1. Installation
2. Drilling
3. Production
Production
1. Completion / Kill Fluids
2. Tubing Leaks
3. Functioning DST Tools etc
Installation
• Casing Running
• Casing cementing
• Plug bump etc
Drilling
1. Pressure Testing after WOC
2. Maximum Mud Weight
3. Lost Circulation, Well Control
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CASING DESIGN
72
Let us assume two load scenarios:
1. The maximum installation (or running) load when running the 13-3/8” casing to 9,750ft. • Inside diameter 12.347”• Mud weight 11.0 ppg• Instantaneous Velocity 5 ft/sec
2. The maximum drilling load when cementing the 13-3/8” casing at 9,750ft.• Top of Lead Slurry 3,000 ft• Weight of Lead Slurry 11.6 ppg• Top of Tail Slurry 9,000 ft• Weight of Tail Slurry 15.8 ppg• Plug Bump Pressure 3,000 psi
Calculation: Use the data above + the attached handout (from the Well Construction Manual,
Section 3, to calculate the tensile loads and fill out the table on the next page.
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CASING DESIGN
73
Load Component Installation Drilling Production
Weight in AirFair = W x TVD
Buoyancy (note: needs to be subtracted)
Fbuoy = (Pe x Ao) – (Pi x Ai)
Bending (Fb)Fbend = 64 x DLS x OD x W
Shock Load (Fs)Fshock = 1,780 x V x As
Pressure TestingFptest = Pptest x Ai
Total Tensile Load (lbs)
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CASING DESIGN
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Load Component Installation Drilling Production
Weight in Air 702,000 702,000 702,000
Buoyancy (subtract) 115,821 168,425 115,821
Bending (Fb) 61,632 61,632 61,632
Shock Load (Fs) 184,832
Pressure Testing 359,198 359,198
Total Tensile (lbs) 832,643 lbs 954,405 lbs 954,405
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Load Component Installation Drilling Production
Weight in Air 702,000 702,000 702,000
Buoyancy 115,821 168,425 168,425
Bending (Fb) 61,632 61,632 61,632
Shock Load (Fs) 184,832
Pressure Testing 359,198 359,198
Total [lbs] 832,643 954,405 954,405
13-3/8” N80 Tensile
From tables = 1,661,000 lbs
Design Factor = 1.3 1.3 x 954,405 lbs= 1,277,923 lbs
Thus Tensile Design is OK
WELL CONSTRUCTION
CASING DESIGN
76
WELL CONSTRUCTION
CASING DESIGN
77