Ptil Seminar 06.12.12:

«Subsea Wellhead fatigue – Learning and experience sharing,

preventing major accidents»

“WH Fatigue reducing Well construction:

We CAN do much better with available means!”

www.neodrill.no

WH Fatigue problems sources are: 1. Equipment design 2. Equipment application

1. Inherent equipment design challenges:

• Ultimate well pressure barrier also the main load carrier for external mechanical loads:

• BOP loads

• Riser induced lateral loads (rig movements)

• VIV (Vortex induced vibrations)

• Accidental loads

• Increasing WH loads: • Much higher BOP loads (250 => 400 ton)

• New tensioning systems & higher riser tensions

Equipment standards render design improvements difficult to undertake

Enormous consequences of design changes

2. Equipment installation & utilisation risks: • Cementation dependent installation process; not a

predictable & reliable load transfer; depends on: • Slurry quality (consistency & contamination) ? • Slurry placement, loss to softer formations => TOC? • Cement curing temperature • Hole geometry / conditions / cleanliness • Conductor movement during cement setting

• Imperfect installation will significantly reduce: Bending & Fatigue life capacity of well Axial/lateral load capacity Contingency preparedness

• Accidental loads much higher than operational loads (drift off & drive-off)

However: By application of new installation methods, the inherent installation risks CAN now be mitigated.

Main functions of CAN : 1. Provide mechanical load support to WH / Conductor

(Capacity ‘’booster’’)

2. Remove cement dependency (Warrants meeting design requirements)

1. Install CAN (ConductorAnchor Node)

Method (by vessel): • Self weight penetration • Suction

2. Install Conductor by: • Driving (Vessel + hammer) • Jetting (Rig) • Drill & cement (Rig)

High and testable load capacity: Example: @ ∆P=2 bar; (CAN D= 6m) ~600 ton axial

Alternative top hole well construction:

FE Model: CAN system analyses results:

2012-01-30 Slide 5

Hotspot #2: Cond/1st

Conn. weld

Hotspot # 4: WH/20’’ weld

Hotspot #3: 30’’Conn. Hotspot #5:

20’’Conn.

Hotspot # 1: WHH/

Cond. weld

Cases studied:

1. Stand alone conductor: • Full soil support and

• 12m free standing

2. CAN supported conductor

Slide 6

Hotspot analyses; Main Conclusions:

Conductor Soil support to seabed

Reduced soil support

Hot spot # 1: Housing/Conductor weld

2012-01-30 PPT1169-05_revA.ppt Slide 7

Reduced soil support

Hot spot # 2: Cond./1st Connector weld

Hot spot # 3: 1st Connector

Reduced soil support 1E+11 * lifetime

1E+13 * lifetime

2012-01-30 PPT1169-05_revA.ppt Slide 8

Reduced soil support

Hot spot # 4 : WHH / 20’’ weld

Hot spot # 5 : 1st 20’’ connector

~1000 * lifetime

~50 * lifetime

~10 000 * lifetime

~500 * lifetime

FEM Fatigue life results:

Notes: • The CAN support case gives a predictable & safe operating condition for the WH equipment!

• The case ‘’Without CAN – soil to mudline’’ is an «ideal case», as it will not be possible to provide

‘’perfect’’ soil support to mudline for conventionally cemented conductors over time.

• Experience show:

• Initially most wells will be between having ‘’Soil to mudline’’ and ‘’12 m soil shortfall’’

during drilling operations

• The conductor free-point will be gradually worked downwards due to BOP movements.

Trends: Use high capacity Well Head with heavy duty, large dimension conductor:

«-- the larger diameter does

not necessarily translate into

better fatigue performance» (2H Offshore Engineering)

Lessons learnt (1):

36’’ Friction type Conductor Hanger (Design / analyses: Dr. Techn. Olav Olsen)

1. Conductor Hanger design importance:

Slots for ‘’peeling’’ at extreme bending loads

Lessons learnt (2): Effects of elevator rings! 30’’ Conductor Hanger mounted between elevator rings:

Conclusion: Never use elevator rings on upper conductor joint!

CAN-BOP supporter

14.06.10 Page 1

2. BOP Supporter Pistons

actuated:

- Transfers pre-set part of

BOP weight directly to CAN

- Adapts to BOP frame

- ROV operated

1. BOP set down on Well Head

and connected to same by

WH Connector: (250-350 ton

set down weight)

Axial BOP load transferred to

CAN through WH Connector

and Conductor hang-off

gimble.

Sea Bed

CAN

Reinforcement

for BOP

Stabiliser

Conductor

BOP

CAN Conductor & BOP Support System: Technology developments: Sea bed BOP Supporter will remove BOP / Riser induced WH-bending moments (JIP next year):

For safer support of: • BOP, plus • X-mas tree, and • Capping unit

Bending moment

=> Fatigue life

problem area

Peon: 370 m WD Dovregubben: 270 m WD CAN size: D= 6 m; H= 12 m Cooper: 250 m WD Cooper size: D= 6m; H= 8m

CAN installations:

Gemini CAN: 1 100 m WD Cygnus CAN: 860 m WD

Jette CAN: 125 m WD CAN size: D= 6 m; H= 12 m

Flat top design

Conductor installation options: 1. Gemini: Jetted 2. Cygnus: Jetted 3. Peon: Toe Drive 4. Dovregubben: Drill & cement 5. Jette: Drill & cement 6. Jette: Drill & cement 7. Cooper: Drill & cement

CAN technology experience:

Equipment availability (as for WH):

• Available off the shelf for: • Exploration wells: Reuse rental item • Production wells: Sales item

Clean and reuse at next

location

Well architecture; CAN facilitates optimised well design:

30’’

30’’

20’’

20’’x13 3/8’’ String

CAN

300m

13 3/8’’ 800m

Drilling time:

Drill 26’’ hole + 20’’ set: 2 days

Drill 9 5/8’’Pilot Hole: 0 days

Drill 17 ½ ‘’ hole + 13 3/8’’ set: 5 days Total: 7 days

Cuttings disposal volume:

26’’; 0.35m3/m => 35m3

17 ½ ‘’: return to rig => 0m3 = 35m3

Cement volumes (w/sea bed return):

Conductor: 0m3

Surface casing (20’’): 15m3 = 15m3

Drilling time: 1. Drill 36’’ hole + conductor set: 3 days 2. Drill 9 5/8’’Pilot Hole: 2 days 3. Drill 17 ½ ‘’ hole + 13 3/8’’ set: 5 days Total: 10 days

Cuttings disposal volumes:

36’’; 0.7m3/m => 70m3

17 ½ ‘’; 0,16m3/m => 80m3 = 150m3 Cement volumes (w/sea bed return):

Conductor (200% excess) = 70m3

Surface casing: (20’’x13 3/8’’) = 50m3 = 120m3

Conventional

Sea bed 200m

Example CAN enabled new well architecture:

• Pre-installed, tested conductor

• Rig time & cost savings

• Environmental footprint reduction

Closing remarks: Cement is an unreliable means of Conductor / WH installation!

Bigger is not always better! (Larger conductor OD ≠ higher fatigue life capacity!)

Better well foundation ≠ added well costs! (Saves rig time & troubles!)

Method of installation of WH-Systems is the key to satisfying ALARP requirements (also for production wells)!

The industry has the means to attain much higher fatigue life time and load capacity from all present Well Head systems! (Especially if removing bending moments from the WH!)

Yes, we CAN!