The Angola Deepwater Consortium (ADC) established a a custom emergency pipeline flowline repair system (PRS) for an offshore deepwater projects. The PRS study covered uninsulated (water and gas injection), wet insulated, and pipe-in-pipe (PiP) flowlines and pipelines. This article focuses on pipe-in-pipe repair feasibility via the diverless on-bottom spool repair method, cutting the pipeline and installing a spool using dedicated repair connectors. The operators focused on rigid and pipe-in-pipe technologies. These are the most common flowline types in Angolan deep waters. Replacing the damaged section of the line on-bottom with a spool allows repair of major damage (e.g., rupture with leak). Repairing PiP lines requires restoring mechanical integrity while also guaranteeing insulation properties similar to the original. PiP damage includes flooding its annulus with seawater, which destroys the dry insulation material and exposes the annulus to corrosion. The consortium focused on swaged J-lay (Category A) while long, continuous annulus (Category B) poses greater integrity issues stemming from the combined loss of thermal and mechanical integrity and the susceptibility to corrosion of the bare steel annulus. When a Category A PiP is damaged, it results in at most 48 m of flooded section. Given this relatively short length, the optimum solution would be to replace the entire damaged section with an insulated spool, restoring original PiP insulation performance. This approach also solves corrosion issues, as long as cathodic protection and electrical continuity are installed for the tie-in section. The partners focused on a concept for the repair connector, which allows the use of the same connector technology already available in PRS equipment for the repair of wet insulated flowlines. Once the damaged section of the pipe-in-pipe is cut, the now exposed inner pipe section can accommodate the connector. The operator must first cut the damaged section at the outer pipe swaged connection to avoid additional damage, relying on a compact cut-to-fit connector to join the spool and the inner pipe.
Custom offshore pipeline repair systems save money
Oil and Gas Journal ; 112 , 6 ; 100-105
2014
6 Seiten, Bilder, Tabellen
Article (Journal)
English
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