Offshore Well Construction Casing Design

 

WELL CONSTRUCTION COURSE

Section 3 : Casing Design 1

 

WELL CONSTRUCTION

CASING DESIGN

FUNCTIONS OF CASING

2

 

WELL CONSTRUCTION

CASING DESIGN

1. To KEEP the KEEP the hole open and prevent collapse 2. To ISOLATE ISOLATE  porous different different pressure regimes so that production or injection may be controlled from a specific section contamination and 3. To PROTECT formations PROTECT formations from contamination fracture 4. To CONTROL CONTROL any  any pressures encountered in the well SUPPORT for  for the BOPs BOPs on  on the 5. To prov provid ide e stru struct ctur ural al SUPPORT wellhead 6. To ALLOW  the passage of testing and completion euipment 3

 

WELL CONSTRUCTION

CASING DESIGN

Q

W!" not #$st %&i'' to TD (

A

D$e to t!e nat$&e o) se se%i*enta&" +asins :   !

"nstable formations and differing pressures necessitate casing off the open hole at certain depths to enable the final well objective to be met

!

Too long SIDETRACK an open hole or willREDRILL collapse and pac# off $ SIDETRACK or SIDETRACK possible

!

%&posed 'igh and (ow )ressure *ones , BLOWOUT

4

 

WELL CONSTRUCTION

CASING DESIGN

cost on any well 1. (argest tangible cost on 2. )er )erfor forms ms crit critica icall func functio tions ns $ suppor support+ t+ sta stabil bility ity 3. %rrors in calculations can calculations can impact cost+ safety 4. %ve %very ry des design ign has two two area areas s iin n co common mmon !

Subjective assumptions have to be made concerning maximum loads

!  After the loads loads are calculated calculated a design design factor will will apply  5

 

WELL CONSTRUCTION

CASING DESIGN

1. ,ata iis s ta ta#en fr from offset wells or wells or local geological #nowledge $ but actual lithologies may differ  - LOT data may be %i))e&ent %i))e&ent from  from the predicted values $ need to be able to adjust the wellplan while drilling

3. while The cont control rolla lable ble well #ic# #ic# $s si-e i-e must mus t be #now #nown n at all all time times s drilling the KICK TOLERANCE elationships /"0T be #nown between be tween (T ( T++ ))+ ))+ 4. nter$relationships nter$r nter$ relationships potential drilling problems and T 6

 

WELL CONSTRUCTION

CASING DESIGN

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WELL CONSTRUCTION

CASING DESIGN



 

WELL CONSTRUCTION

CASING DESIGN

1. 0hoe depth chosen so that ne&t hole section will not be fractured with higher mud weights 2. orth 0ea the average 37 setting setting depth  depth 348 below sea bed. bed 3. 9eturns to seabed. 4. :emented bac# to sea bed 5. :onductor analysis determines minimum height of cement to avoid a top up job 6. :an pile driven land $ oftenbe called STO.EonPIPE

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WELL CONSTRUCTION

CASING DESIGN

1. :omba mbats wea# formations found at shallow depths 2. "sua "suall lly ys set et in comp compet eten entt roc# $ hard limestone etc 3. "sua "suall lly y tthe he fi firs rstt cas casin ing g that the ood >ood ce ceme ment ntat atio ion n mus mustt be be ensured $ multi$stage cement  jobs or multi$stage multi$stage collars 3. Traditionally 13$3=7 or 13$3=7 or ;$5=7 ;$5=7   casing 4. :onn :onnec ecto tors rs are are usu usual ally ly ? asing. he e in#or/ation is= 13>? casing

@A750 #t

'Bterna Mud eight

11 ppg

:nterna Mud Weight

11.2 ppg