wellhead growth spreadsheet

7/21/2019 Wellhead Growth Spreadsheet

1/46

Read me

Page 1

This workbook calculates the wellhead growth expected from thermal loading for platform-completed wells.The spreadsheet is applicable in any load combination where the average temperature of the casing strings isincreased when compared to geothermal (hot injection, production, etc).

Before using the spreadsheet, the following steps should be completed:

1. ata on the wellbore schematic, casing strings, well survey, mudline depth and platform elevation abovewaterline, injection!production parameters and rates, geothermal temperature gradient, top-of-cement, fluidproperties above T"# should be gathered.

2. This data should be input into a suitable thermal program such as $T%&", and the injection!productiontemperatures should be calculated for all of the casing strings.

3.The average difference between the injection!production temperature and geothermal temperature over theunsupported lengthof each casing string should be determined. ' length-weighted average should be taken,since the temperature results are given by depth. 'n example of length averaging is given in the 'veragingspreadsheet.

4.sing the *rowth spreadsheet, the wellhead growth can now be calculated. 'll input data for thespreadsheet are described in the spreadsheet itself. The spreadsheet also calculates the forces on each string,which can be used for design purposes as appropriate.

Basic theory:

+or a system with n casing strings, using strain compatibility and balance of incremental forces due to growth,the growth in inches is given by

/i

i!/

i,

where summation is over all the casing strings that are tied to the wellhead, /iis the axial stiffness of the ith

casing string over the unsupported section, and iis the unrestricted growth of the ithstring due to the average

temperature increase (in deg +) over the unsupported section length i(in inches),

i Tavg,i i(for casing materials is usually taken as 0.12-0 ! deg +)

The initial force distribution is calculated based on the fact that for each string landed, the force is taken up byall the current strings according to their relative stiffness. 'fter thermal growth, since incremental forces alsomust balance, simple superposition gives the final force distribution.

Assumptions:

The following assumptions have been made in calculating the final growth.

3. 'll the casing!tubing strings are tied back to wellhead - i.e., no special suspensions.4. $ellhead is such that it does not allow free upward displacement of any single casing string (i.e., all stringsare fixed to the wellhead).5. 6o additional structural members (such as risers, support braces, etc.) between strings or between theoutermost string and platform are considered. This is a conservative assumption since any support tends toreduce wellhead growth.7. 8nitial thermal profile in all strings is assumed to be geothermal.9. The contribution of buckled inner strings with long unsupported lengths (in particular, tubing) to wellheadgrowth is ignored. This is a valid assumption within the design envelope, since the extent of buckling has to bevery severe and beyond the design envelope (neutral point above surface) before buckled strings can contributeto wellhead growth.0. 'lthough the force system as a result of growth can cause one or more of the unsupported strings to buckle, itis ignored insofar as wellhead growth is concerned. This results in a conservative estimate for wellhead growth.The force re-distribution on each casing string is calculated separately, and may be used for casing design

purposes.


2/46

Read me

Page 2

. ,run. 'll growth calculations are from this datum. 6ote that as strings are run and set, the wellhead moves, butthis movement does not impact facilities design for wellhead growth, since facilities are hooked only after thetree is run.;. 'xial drag between casing strings is ignored. This is a conservative assumption, since drag will tend toreduce string growth, and hence, wellhead growth.


3/46

Read me

Page 3


4/46

Read me

Page 4


5/46

Growth

Page 5

Wellhead growth spreadsheet

In the green highlighted area, enter each string from the outermost to innermost,

starting from the outermost casing that supports the wellhead.

To eclude a casing or tu!ing from consideration, simpl" ma#e its wall thic#ness $ %.

INPUTS:

Constants

Safety Factor 1.330 Calculato!s

Wellhead " Tree Wt #l$s% &'000 C(S

I) *rea

String Data #!%

U!supp. *+erage ,a!d!g 1&.124 2'.&1('5'

Str!g -) t eld ,e!gth Te!so! 12.34( 2%.('('')

/ Type #I!% #!% #s% #ft% #deg F% l$s ).535 15.54'4)5

1 *urface 2%.%%% %.43) 55 5)4.% 44.%% 53535 '.13 ).&(1')1)

Intermediate 13.3(5 %.514 )% 5)4.% 1%4.%% '5'(5 % %

3 Production &.'25 %.545 )% 25%%.% 13%.%% 32%%%% % %

2 Tu!ing (.%%% %.435 )% )5%%.% 1%%.%% 14%%%%

'

&

Material Properties (Change if appropriate)

3.%%+%( psi -odulus of +lasticit"/

'.&%+0%' deg -oefficient of Thermal +pansion/

T-T*, 45-WT6 7.7& !ches

18&.89

*ee Notes!elow for help on inputs

!

T

alpha #%

#;,

( ;

%


6/46

Growth

Page '

Notes:

Inputs Description:

1

2

3

4

calculated oer unsupported length. thermal program li#e +nertech6s 7TPR89 should !e used.

5This ma" !e calculated using a suita!le casingtu!ing design program,

or estimated from casing weight.

Be sure to zero out the input columns of any string not being entered.

Note that the spreadsheet does not display the zeroes.

Results Description:

Colu!


7/46

Growth

Page (

*>al U!restr. 6ooe?s Cuul. orces

Stff!ess growth law 4rowth

#l$(!% force@ l$s #!% Initial -s landed/

11522&.( 2.13 2451'' 2451'' 11523% 2.13

))&%2.'& 5.%3 44(%)' '&2252 2%4132 3.3&

1554'.4& 2'.&1 41)35' 111%'%) 21&'(& 5.%'

2'3).(3 (%.3) 1)5(14 12&'322 22231) 5.)3

% %.%% % 12&'322 22231) 5.)3

% %.%% % 12&'322 22231) 5.)3

,@ ! ,


8/46

Growth

Page )


9/46

Growth

Page &


10/46

Growth

Page 1%


11/46

Growth

Page 11


12/46

Growth

Page 12


13/46

Growth

Page 13


14/46

Growth

Page 14


15/46

Growth

Page 15


16/46

Growth

Page 1'


17/46

Growth

Page 1(


18/46

Growth

Page 1)


19/46

Growth

Page 1&


20/46

Growth

Page 2%


21/46

Growth

Page 21


22/46

Growth

Page 22


23/46

Growth

Page 23


24/46

Growth

Page 24


25/46

Growth

Page 25


26/46

Growth

Page 2'


27/46

Growth

Page 2(


28/46

Growth

Page 2)


29/46

Growth

Page 2&


30/46

Growth

Page 3%


31/46

Growth

Page 31


32/46

Growth

Page 32


33/46

Growth

Page 33


34/46

Growth

Page 34


35/46

Growth

Page 35


36/46

Growth

Page 3'


37/46

Growth

Page 3(


38/46

Growth

Page 3)


39/46

Growth

Page 3&


40/46

Growth

Page 4%


41/46

Growth

Page 41


42/46

Growth

Page 42


43/46

Growth

Page 43


44/46

Growth

Page 44


45/46

*heet3

Page 45

@ength eraging +ample

9epth InA Temp Geothermal


46/46

*heet4

*tring =-l!in/ T-l!/ orce

1 112532 53''5 112532 02122'(

2 )')21 '5353 1&&353 0&)415.4(

3 5&(& 32%%%% 2%5332 31%')2

5.)+0%11

=

wellhead growth spreadsheet

Documents