A UK continental shelf operator required an emergency preparedness response scheme (EPRS) for an ultra-high pressure high temperature (UHP/HT) gas condensate export pipeline system linking a production and processing platform complex to a subsea tee in third-party gas transmission network.
The operator needed a practical and justifiable basis to reduce exposure to the commercial consequences of integrity loss and resultant loss of operation or loss of containment. Like any subsea pipeline system, there are many credible failure scenarios within the pipeline system, including third-party damage, corrosion or material defects, blockages and component failures. The key technical challenge was to determine a level of preparedness for emergency response that mitigated risks to acceptable levels whilst also providing a justifiable cost benefit to the operator.
Jee developed an emergency preparedness response scheme using risk assessment to identify significant and credible failure scenarios and cost benefit analysis to quantify the mitigation gained by pre-procuring repair equipment and material spares.
The pipeline system was divided into segments depending on relevant failure scenarios, associated risks and appropriate repair options. For each segment and each likely failure scenario, probabilities of occurrence were determined based on industry statistics modified as appropriate to represent the specific operational, configural and protection characteristics of the pipeline system within that segment.
Repair procedures were established, schedules for inspection, procurement and construction developed and resultant costs of implementing repairs calculated. Based on the repair schedules, shut-down durations and resultant costs of deferred production were determined.
Jee also developed criteria for third-party impact damage to define what level of damage require the pipeline to be shut down with immediate repair, what level of damage can continue to operate for a limited period prior to repair, and what level of damage can be left without repair.
Having established failure modes, associated consequences in terms of repair costs and deferred/lost production, and probabilities of occurrence, the Risk Assessment was used to determine which failure modes present significant risk. The Cost Benefit Assessment was carried out for all significant risks to determine whether the procurement and storage of spare materials and equipment is commercially justified. It was found that holding certain spares can reduce the overall incurred cost by reducing downtime and subsequent lost production costs. However, the holding of spares involves procurement and storage costs for equipment that may never be used.
The Cost Benefit Assessment therefore makes the cost comparison by considering the pro and cons of holding spares and helps us determine which option will be the most cost effective.
Benefits and outcomes
The EPRS provided clear, quantified recommendations on preparedness measures that reduce downtime exposure, defining what materials and equipment should be held in storage.
By linking credible failure modes to repair options and commercial consequences, the operator gained a defensible basis for spares strategy and a defined response and clear criteria for impact damage scenarios.
For more information, visit www.jee.co.uk/integrity-management
To contact Jee’s Technical Authority, Graham Wilson, email Graham.Wilson@jee.co.uk.