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Working together for a safer world
Technical safety of subsea workover systems
Timothy Greer
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Lloyds Register Consulting
Agenda
Overview of workover systems. Workover stack technical safety. Example systems and studies.
EDP/LRP Landing string
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Workover systems in general
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WO System
Technical safety: Hazards and barriers
Hazard definition : Potential source of Harm
Disconnect i.e. spurious operation
Well kick
Compensator lock up
Hydrocarbon release
Explosion
Loss of buoyancy
Fire
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Workover technical safety
There can be multitude of reasons and each has own demands and risks to consider
Temporary barrier. ISO 13628-7: Completion/workover riser
systems .
HAZID:
Safety Critical Element Identification:
BowTie Diagrams: HAZOP:
Performance Standards
ALARP Demonstration
QRA: Subsea Release and Consequence
Modelling:
System Level
HAZOP:
Sub-System Level
FMECA:
Functional Requirements
Component Level
FMECA:
SIL
Human Factors: Working Environment
SIL:
SIL:
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EDP/LRP XT mode
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EDP/LRP XT mode
Considerations Interfaces to other systems Independence between control and safety Flowing conditions (sequencing) Energy required to close and cut coil tubing
requires subsea accumulators. Cutting of moving coil tubing Interlock between retainer valve and
disconnect Safe State for emergency shutdown and
emergency quick disconnect Disconnection is energize to function Sub-System FMEA to identify single points of
failure.
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Marine Riser Subsea Test Tree (SSTT) Landing string
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Marine Riser Subsea Test Tree (SSTT) Landing String
Considerations SSTT is a safety system and should be
independent of operational items. Energy required to close and cut coil tubing
requires topside hydraulic supply or subsea accumulators.
Sequencing of valves Safe State for emergency shutdown and
emergency quick disconnect Interlocks between SSTT and latch disconnect Interlock between Retainer valve and latch
disconnect
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Possible Studies
HAZID HAZOP Bow tie Input to performance standards FMEA/FMECA RAM SIL Studies
o Safety and V&V Plan o Safety Requirement Specification o SIL Verification/Compliance Reports o Safety Manual o Input to testing procedures
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Lloyds Register and variants of it are trading names of Lloyds Register Group Limited, its subsidiaries and affiliates. Copyright Lloyds Register Consulting. 2013. A member of the Lloyds Register group.
Working together for a safer world
Questions Timothy Greer Senior Consultant T +08 94661403 E [email protected] Lloyds Register Consulting www.lr.org/consulting