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Technical safety of subsea workover systems

Timothy Greer

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

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 timothyw.greer@lr.org Lloyds Register Consulting www.lr.org/consulting