2011 - single vs dual barrier drilling risers - tim eyles 2h

8/13/2019 2011 - Single vs Dual Barrier Drilling Risers - Tim Eyles 2H

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Single / Dual BarrierHP Drilling Risers

Acteon HPHT Subsea Community Breakfast Meeting

23rd March 2011

Tim EylesDirector2H Offshore [email protected] / +44 1483 774908

mailto:[email protected]

mailto:[email protected]



Agenda

IntroductionDrilling Riser ConfigurationsDeepwater TLP Drilling RisersJack-up Drilling RisersConclusionsReferences and Further Reading

3



Introduction

4

Why are some deepwater HP drillingrisers dual barrier?

What is currentindustry bestpractise?

Why are most jack-up drilled tie-backwells drilled with asingle barrier HPriser?

Is a dual barriersystem lower riskthan a singlebarrier?



Drilling Riser Configurations

Shallow water – Jack-upSurface wellhead (Platform)

Surface BOPConductor/casing strings continuedNo dedicated drilling riser

Subsea wellhead (Tieback)

Surface BOP + High pressure drilling riser Avoid use of floating drilling unit

Deep waterSurface wellhead (Spar/TLP)

Surface BOP + High pressure drilling riserSubsea wellhead (Tieback - Floating Drilling Unit)

Subsea BOP + Low pressure drilling riserSurface BOP + High pressure drilling riser

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Drilling Riser Configurations

6



High Pressure Drilling RisersExisting Barrier Philosophies

7

Jack-up UnitTieback wells

Spars/TLPs

e.g.Shell MarsBP Horn MountainChevron Bigfoot

Floating Drilling Unite.g.

Total Donggalla (13-3/8”)Ophia/Shell (13-3/8")

Single Dual

Spars/TLPse.g.

Dominion Devils TowerStatoil Snorre



Deepwater TLP Drilling RisersPrimary drivers for dual barrier

Riser mud pressure significant contributionRiser mud loss could compromise well control

Excessive weight with a single barrier riserTensioner limitations

Excessive wall thickness with a single barrier

Pipe availabilityWeld quality

Local legislationSeen as “best practise”

8Shell Mars TLP



Deepwater TLP Drilling RisersDesign Selection Process

CAPEX – CAPital EXpenditure

OPEX – Operational EXpenditure

RISKEX – RISK EXpenditure

RAMEX – Reliability-Availability-Maintainability EXpenditure

Profit = Max(Revenue-CAPEX-OPEX-RISKEX-RAMEX)

Ref: Deepwater Development Lifecycle Costs for SubseaSystems JIP (1999)

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Deepwater TLP Drilling RisersDual Barrier Pros & Cons

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Pros

Inner string failure may not result in loss of well control Lower RISKEXCan monitor annulus pressure for leaks (small volume) Lower RISKEX

Reduced wall thickness (esp. if diff. pressure ratings) Lower CAPEX

Less demanding weld/material criteria Lower CAPEXReduced system weight (esp. if diff. pressure ratings) Lower CAPEX

Can continue drilling operations if small annulus pressure Lower RAMEX

Use inner string as casing on next well to improve wearmanagement Lower RISKEX

Easier mud control (smaller volume) Lower OPEX

Better cuttings management Lower OPEX



Deepwater TLP Drilling RisersDual Barrier Pros & Cons

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Cons

Increased riser hardware Increased CAPEXIncreased riser running time Increased OPEX

Increased riser weight (esp. if matched pressure ratings) Increased CAPEX

Reduced flexibility for optimised casing hanger andprogramme Increased OPEX

Limit on maximum number of casings Increased OPEX

Increased number of components (may have common

failure mode)

Increased RISKEX

Requires a good metal-to-metal seal at seabed Increased RISKEX



Deepwater TLP Drilling RisersSelection Process

Final selection should depend on full development lifecycleCAPEXOPEXRISKEXRAMEX

Different operators will have different EXpenditure profilesOutcome location, operator and market dependent

12



Jack-up HP Drilling RisersDesign Challenges

Increasing pressure, temperature, waterdepth, harsher environmentDemanding fluid compositionsReduced desirable risk profileIncreasing CAPEX

13

Increased wall thickness & riser weightHigh tensioner utilisationsRig modificationsSusceptibility to fatigue

Wave driven Vortex-induced-vibration

Increased riser wellhead loading/utilisationIncreased vessel motion



Jack-up HP Drilling RisersSelection Process

Consider project

CAPEXOPEXRISKEXRAMEX

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Jack-up HP Drilling RisersSingle Barrier System Considerations

Reducing OPEX Perform regular maintenance and inspection

Reducing CAPEX Consider high strength materials

Reduce wall thicknessReduce riser weightReduce rig modificationsDecrease tensioner utilisation

Consider alternative connection systems

Reduce need for integral forgingsPermit high strength materials

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Conclusions

Selection of single or dual barrier systems should betaken on a case-by-case basisShould consider

CAPEXOPEX

RISKEXRAMEX

Higher pressure, temperature and water depth, harsherenvironments and internal fluids increase the need for an

assessment to be performedHowever a dual barrier system may not always givereduced risk

17



Questions?

2011 - single vs dual barrier drilling risers - tim eyles 2h

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