Casing/Tubing design manual october 2005 Chevron
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The design collapse pressure is listed in the last column of the following example
spreadsheet, which is the internal pressure (load) minus the external pressure
(backup), when multiplying the burst design factor of 1.20.
DEPTH LOAD BACKUP RESULTANT DESIGN
(ft) (psi) (psi) (psi) (psi)
0 0 0 0 0
4,000 2,496 0 2,496 2,496
4,000 2,496 0 2,496 2,496
8,000 4,992 0 4,992 4,992
COLLAPSE CASING DESIG
N
0
24962496
4992
0
1000
2000
3000
4000
5000
6000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
DEPTH (FEET)
PRESSURE (PSI)
LOAD BACKUP RESULTANT DESIGN
Figure A-3. Collapse Load Spreadsheet
From the calculated burst and collapse loads, the following weight and grade of
9-5/8-in. casing can be selected to meet the burst and collapse design:
9-5/8 in., 47#, C90
• Burst rating: 7,720 psi > 7,253 psi (max. burst design load)
• Collapse rating: 5,000 psi > 4,992 psi (max. collapse design load)
Calculate casing tension load:
• Casing tension load at shoe: 100,000 lb
• Casing tension load at surface: 100,000 + 47*(1-12/65.5)*8,000 =
406,585 lb
• Tension rating: 1,221,000 lb > 650,355 lb
Casing/Tubing Design Manual A-3
October 2005
The design collapse pressure is listed in the last column of the following example
spreadsheet, which is the internal pressure (load) minus the external pressure
(backup), when multiplying the burst design factor of 1.20.
DEPTH LOAD DESIGN
(ft) (lb) (lb)
0 406,585 650,535
2,000 329,938 527,902
4,000 253,292 405,268
6,000 176,646 282,634
8,000 100,000 160,000
TENSION DESIG
N
0
100000
200000
300000
400000
500000
600000
700000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
DEPTH (FT)
TENSILE LOAD (LBSF)
AXIAL LOAD DESIGN
Figure A-4. Collapse Load Spreadsheet
The final designation of this 9-5/8-in. casing is then 9-5/8-in., 47#, C90, which
meets the burst, collapse, and tension design requirements.
A-4 Casing/Tubing Design Manual
October 2005
B
BCasing Design Software
B.1 Introduction ......................................................................................................................B-2
B.2 StressCheck
™
..................................................................................................................B-2
B.2.1 What StressCheck
™
Will Not Do..................................................................................B-2
B.2.1.1 Tubing Design....................................................................................................B-2
B.2.1.2 Connection Design.............................................................................................B-2
B.2.1.3 Sulfide Design....................................................................................................B-2
B.2.2 Design and Analysis....................................................................................................B-3
B.2.3 Input Guidelines...........................................................................................................B-3
B.2.3.1 File Menu...........................................................................................................B-3
B.2.3.2 Edit Menu...........................................................................................................B-4
B.2.3.3 Wellbore Menu...................................................................................................B-4
B.2.3.4 Tubular Menu.....................................................................................................B-5
B.2.3.5 View Menu.........................................................................................................B-6
B.2.3.6 Options Menu.....................................................................................................B-6
B.2.3.7 Window Menu....................................................................................................B-7
B.2.3.8 Help Menu..........................................................................................................B-7
B.2.4 Design Assumptions....................................................................................................B-7
B.2.5 Temperature Profile.....................................................................................................B-8
B.2.5.1 Production Load Cases......................................................................................B-8
B.3 Matching StressCheck™ Load Cases to Recommended Design Load Cases for
Standard Wells...............................................................................................................................B-9
B.3.1 Production Tubing .......................................................................................................B-9
B.3.2 Production Casing.......................................................................................................B-9
B.3.3 Intermediate Casing ....................................................................................................B-9
B.3.4 Surface Casing..........................................................................................................B-10
B.4 Matching StressCheck™ Load Cases to the Recommended Design Load Cases
for HPHT Wells.............................................................................................................................B-11
B.4.1 Production Tubing .....................................................................................................B-11
B.4.2 Production Casing.....................................................................................................B-12
B.4.3 Intermediate Casing ..................................................................................................B-12
B.4.4 Surface Casing..........................................................................................................B-13
B.4.5 Special Notes ............................................................................................................B-13
B.5 CWEAR..........................................................................................................................B-14
B.5.1 CWEAR Options........................................................................................................B-14
B.5.1.1 Tortuosity (Survey Data)..................................................................................B-15
B.5.1.2 Dogleg Insertion (Survey Data)........................................................................B-15
B.5.1.3 Drill Pipe Protector Calculation (Tubular Data) ................................................B-15
B.5.1.4 Calculation Parameters (Tubular Data)............................................................B-16
B.5.1.5 Revised Burst and Collapse Resistance (Parameter Data)..............................B-16
B.5.1.6 Collapse...........................................................................................................B-16
B.6 Wear and Casing Design Software................................................................................B-16
B.6.1 Wear in Directional Wellbores ...................................................................................B-17
B.6.2 Wear in Vertical Wellbores ........................................................................................B-17
B.6.2.1 Generating a Trajectory Based on Helical Buckling.........................................B-18
B.6.2.2 Inputting a Trajectory Based on Helical Buckling.............................................B-19
Casing/Tubing Design Manual B-1
October 2005
B.1 Introduction
Tubular design, particularly for directional wells, involves substantial calculations
offering ample opportunity for human error. A recommended alternative to hand
calculations is a qualified casing design computer program. The recommended
tool for all tubular design calculations within Chevron is StressCheck
™
, a product
marketed by Landmark
1
.
Formal instruction in the use of StressCheck
™
, including user manuals, is
available through the normal company educational channels and this training is a
prerequisite to gaining full benefit from the material to follow. This discussion is
intended as a supplement to the StressCheck
™
user manuals and its purpose is
to:
• Link the use and understanding of StressCheck
™
to the design principles
and equations presented in this text.
• Document the internal assumptions in StressCheck
™
for company and
regulatory audits.
B.2 StressCheck
™
The following material supplements, but is not a replacement for, the extensive
help accompanying the StressCheck
™
software.
B.2.1 What StressCheck
™
Will Not Do
StressCheck
™
performs most of the calculations necessary to ensure a safe well
design. There exist areas, however, where additional external calculations will be
necessary.
B.2.1.1 Tubing Design
StressCheck
™
does not design tubing. A separate Enertech model, WELLCAT
™
,
is capable of analyzing (but not designing) tubing movement and stresses.
B.2.1.2 Connection Design
StressCheck
™
performs a design on the tube body only. Connections may then
be analyzed by attaching them to the design body but this is a manual process
totally controlled by the user.
B.2.1.3 Sulfide Design
The ability of convention grades to be used in a sulfide environment, provided the
temperature remains above a certain (grade dependent) value, is not addressed
in StressCheck
™
. This determination must be performed separately by the user.
1
Enertech, 5847 San Felipe, Suite 1000, Houston, TX 77057. Telephone (713) 789-
0055. Fax (713) 789-7633. Internet enertech@halnet.com. Enertech is a subsidiary of
Halliburton.
B-2 Casing/Tubing Design Manual
October 205
B.2.2 Design and Analysis
StressCheck
™
is capable of both design and analysis. The analysis function
compares an existing user-supplied tubular string to environmental load
conditions assumed to occur at various times in the life of the well. The design
function precedes the analysis function and attempts to assemble a tubular string
that will just meet the demands of the environmental load conditions. A design, if
requested, is always followed by analysis.
B.2.3 Input Guidelines
The following sections give additional guidance on input for StressCheck
™.
B.2.3.1 File Menu
Figure B-1. Input Tips and Guidelines for the StressCheck™ File Menu
Table B-1. StressCheck™ File Menu Options
Menu Option Input Tip/Guideline
New When starting a new design, selecting the Normal and
Document.
Properties This command allows additional cross-referencing information to
accompany a design, and is recommended for anyone
continually using the software. Input, such as keywords can
prove invaluable in organizing a large number of StressCheck
™
executions.
All other commands under the File menu are common to the Windows
®
environment.
Casing/Tubing Design Manual B-3
October 2005
B.2.3.2 Edit Menu
Figure B-2, Input Tips and Guidelines for the StressCheck
™
Edit Menu
Table B-2. StressCheck™ Edit Menu Options
Menu Option Input Tip/Guideline
Import From/Export To Library StressCheck
™
allows commonly used and customizable
features, such as inventories and connection properties
to be stored in a library. The contents of a library may
be accessed or altered during program execution.
Properties The properties of the active window can be altered.
B.2.3.3 Wellbore Menu
Figure B-3. Input Tips and Guidelines for the StressCheck
™
Wellbore Menu
Table B-3. StressCheck™ Wellbore Menu Option
Menu Option Input Tip/Guideline
Casing Scheme Casing strings should be entered in the order in which
they are run and not, for example, in descending order
according to outside diameter. A liner will, therefore,
appear in the casing scheme list before its
corresponding tieback.
When defining the casing scheme for a TLP with a riser,
use the Subsea Well option under Wellbore/Offshore.
This will default all strings to the mudline, but you may
then force the riser and tubing back to the datum.
Each spreadsheet row needs every cell completed in
B-4 Casing/Tubing Design Manual
October 205
Menu Option Input Tip/Guideline
order to be recognized by StressCheck
™
.
Pore Pressure You must enter a pore pressure profile to execute a
design or analysis.
Frac Gradient You must enter a frac gradient profile to execute a
design or analysis.
Squeezing Salt/Shale This optional spreadsheet should not be used under
any circumstances, as its application may result in a
non-conservative design. If interaction between the
casing and a mobile formation is anticipated, special
design considerations are in order and should be
addressed outside the context of StressCheck
™
.
B.2.3.4 Tubular Menu
Figure B-4. Input Tips and Guidelines for the StressCheck™ Tubular Menu
Table B-4. StressCheck™ Tubular Menu Options
Menu Option Input Tip/Guideline
Design Parameters Always enable the Buckling option.
Cementing and Landing The density of the mix-water is used in some
calculations for backup pressure in cemented intervals.
The density of the slurry is used to determine the
hydrostatic pressure acting at the lower end of the
casing during WOC. There is no option for allowing the
hydrostatic pressure of the cement column to approach
pore pressure during WOC.
Minimum Cost Be very careful with the Design tab. See "Special
Notes" on page B-13 of the manual for a complete
discussion of this feature.
Burst Loads When choosing one of the default load cases, Drilling
Loads can be selected when the current casing shoe is
shallower than the well depth. Production Loads can be
selected if the casing name (see Wellbore/Casing
Scheme) is Production.
Collapse Loads When choosing one of the default load cases, Drilling
Loads can be selected when the current casing shoe is
shallower than the well depth. Production Loads can be
Casing/Tubing Design Manual B-5
October 2005
Menu Option Input Tip/Guideline
selected if the casing name (see Wellbore/Casing
Scheme) is Production.
Axial Loads Always enable the Service Loads option.
Custom Loads Input of custom loads for a deviated (particularly
horizontal) wellbore is very inconvenient. Because the
pressures and temperature profiles are referenced to
measured depth, with linear interpolation between
points, a large number of points should be supplied to
insure accuracy of the profile.
Pipe Grade Properties StressCheck
™
only adjusts the yield strength for
temperature. Other factors, such as Young's modulus,
Poisson's ratio and the coefficient of thermal expansion
are not adjusted. Whether this simplified treatment
results in over- or under-conservatism is problem
dependent.
B.2.3.5 View Menu
Figure B-5. Input Tips and Guidelines for the StressCheck™ View Menu
Table B-5. StressCheck™ View Menu Option
Menu Option Input Tip/Guideline
Tabular Results It is not currently possible to easily move all
StressCheck™ information to other software. For
example, copying and pasting the MMS report to a word
processor will not preserve the look of the form.
B.2.3.6 Options Menu
Figure B-6. Input Tips and Guidelines for the StressCheck™ Options Menu
B-6 Casing/Tubing Design Manual
October 205
Table B-6. StressCheck™ View Options Option
Menu Option Input Tip/Guideline
Preferences Plot fonts, curves, legends, markers, and grids can be
customized under this command.
Reports You can build a custom report displaying only the
information you wish summarized.
In the current version of StressCheck™, a report cannot
be written to file and then mailed electronically to a co-
worker. Reports can only be printed.
B.2.3.7 Window Menu
Figure B-7. Input Tips and Guidelines for the StressCheck™ Window Menu
All of the commands under Window are standard Microsoft
®
Windows
®
features.
B.2.3.8 Help Menu
Figure B-8. Input Tips and Guidelines for the StressCheck™ Help Menu
Table B-7. StressCheck™ Help Menu Options
Menu Option Input Tip/Guideline
Contents The help system for StressCheck™ is detailed and
should provide answers to most questions.
About StressCheck This dialog window will contain the version of
StressCheck™ you are using.
B.2.4 Design Assumptions
Chapter 6 – Tube Loads sets forth design assumptions for a standard and a
high-pressure, high-temperature (HPHT) well. These assumptions can, with
minor modifications, be accommodated by StressCheck™.
If more than one load case is selected, StressCheck™ will base its design on a
composite load that represents the maximum differential pressure at each depth.
Casing/Tubing Design Manual B-7
October 2005
B.2.5 Temperature Profile
StressCheck™'s load cases have built-in assumptions regarding the variation of
temperature for post-initial load cases. Should a reliable estimate of the actual
temperature profile for a design load case exist or should a temperature
simulation be performed, that information will supersede the more extreme
values assumed by the software.
B.2.5.1 Production Load Cases
For production load cases, the temperature profile is constant and equal to either
the undisturbed temperature at perforation depth (production) or the undisturbed
surface ambient temperature (injection).
Table B-8. Production Load Cases in StressCheck™
Loading Load Cases
Collapse
•Full Evacuation
•Above/Below Packer
•Gas Migration
Burst
•Tubing Leak
•Stimulation Surface Leak
•Injection Down Casing
•Gas Migration
B.2.5.1.1 Drilling Load Cases
For drilling load cases, the temperature profile is a straight line defined by two
points:
• The calculated API circulating temperature.
• The mid-point of the undisturbed temperature profile.
Table B-9. Drilling Load Cases in StressCheck™
Loading Load Cases
Collapse
•Full/Partial Evacuation
•Lost Returns with Mud Drop
•Cementing
Burst
•Displacement to Gas
•Gas Kick Profile
•Frac @Shoe w/Gas Gradient Above
•Frac @Shoe w/1/3 BHP at Wellhead
•Lost Return with Water
•Surface Protection (BOP)
•Pressure Test
•Green Cement Pressure Test
B-8 Casing/Tubing Design Manual
October 205