Perenco UK faced the challenge of decommissioning a 24” × 1 km pipeline connected to the Trent 43/24 Platform in the UK Southern North Sea.
The pipeline, tied into the producing Cygnus–Bacton system via a subsea wye manifold located 1km from Trent platform, contained approximately 150m³ of condensate and required flushing to <30 ppm prior to cutting and platform removal.
Due to the existing pipeline being liquid filled including some seawater, deploying of pigs from the Trent Platform against a closed valve wye manifold was not feasible without the mobilisation of a diving support vessel and subsea intervention spread.
Technologies previously used by Perenco involving in-line isolation tools along with subsea clamp/hot-tap and flushing operations were assessed but discounted due to increased project risk associated with subsea intervention, vessel dependency, and weather-related schedule uncertainty.
To reduce risk and eliminate subsea activities, Perenco contracted Paradigm Flow Services in Q2 2024 to assess the application of its patented Flexi-Coil® technology for platform-based flushing.
The assessment addressed any concerns with the larger diameter of the Trent pipeline relative to previous Flexi-Coil® deployments (<12”). Flexi-Coil® is a composite, neutrally buoyant coiled tubing system designed for pipeline remediation, capable of navigating complex configurations and extended distances of over 6km removing a wide range of materials including waxes, sands, asphaltenes and hydrates.
The chosen Flexi-Coil® solution enabled full system flushing from the platform, providing improved operational control while also removing the impact of vessel availability or weather uncertainty.
Mobilised in November 2025 alongside plug and abandonment activities, the pipeline flushing was completed in under four days, exceeding the specified cleanliness requirements.
This case study details the engineering, planning, execution, and operational benefits achieved through collaboration between Perenco UK and Paradigm Flow Services along with how it can be applied to future decommissioning challenges.