January 2022, Vol. 249, No. 1

Tech Notes

Inspecting Deepwater Risers, Flowlines on a West Africa Flowline Loop

Effective integrity management of subsea pipelines has been especially challenging due to the difficulty of pipeline access, safety and other considerations.   

Quest Integrity recently successfully completed the inline inspection (ILI) of a 12-inch production flowline loop for a major deepwater pipeline operator in West Africa. The subsea system was configured as a 9.9-mile (16-km) piggable loop comprising two risers, four flowlines and two manifolds, supporting a total of seven producing wells.  

Inspection was required for regulatory compliance and to assess the integrity of the production flow loop, ensuring it was fit-for-service.  

The operator had experienced previous challenges with their conventional ILI vendor in similar assets and searched for a solution to inspect the production loop asset and to detect corrosion damage accurately.   

Inspection Challenges  

The flow loop posed several ILI challenges including the unknown extent of an inner diameter (ID) restriction from a defective valve on the pipeline end manifold (PLEM), previous ILI failures in similar assets and pipeline downtime and deferment limitations.   

Integrity personnel, along with two InVista Subsea inspection tools, were mobilized to the floating production system (FPSO). The inspection campaign commenced with a cleaning program, and four cleaning pig runs were conducted in dead oil using a progressive nonaggressive pigging approach.   

Upon completion of the cleaning runs, the ultrasonic (UT) ILI tool was launched and propelled in dead oil at 115 degrees F (46 degrees C), at a rate of 60 cubic feet per minute (102 cubic meters per hour) to achieve an approximate scan rate of 1 mile per hour (0.50 meter per second). All the data were collected in a single run.   

Upon retrieval of the tool, the UT measurement data were downloaded on the FPSO, and an initial field analysis was performed. The InVista Subsea ILI tool provided 100% circumferential and axial inspection coverage of each riser and flowline in the production loop.  

A preliminary report was delivered within 14 days and a Level 2 fitness-for-service final report, in accordance with API 579-1/ASME FFS-1, arrived within 45 days.   

The completion of the ILI provided the operator with a comprehensive understanding of asset and cost savings in overall project execution.   

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