DESIGN AND PLANNING
Stockton held full responsibility for the HDD design, and supported E.ON in obtaining all necessary permits, including approvals from Network Rail due to the proximity of railway infrastructure.
The installation of the second export cable was critical to the wider wind farm programme. From preliminary design through to mobilisation of the jack-up platform and drilling spread, the full scheme was delivered within a six-month window, demonstrating strong programme control and coordination.
OFFSHORE DRILLING OPERATIONS
The pilot bore was drilled initially through a gravel section before progressing into sand and clay strata. An 18” casing was installed at the entry point to stabilise the bore through the gravel layer during drilling and reaming.
During offshore operations, the drill string was guided through the riser pipe to the jack-up platform deck. The 500mm reaming phase was then completed offshore, with additional drill pipe attached behind the advancing reamer.
The 355mm HDPE duct was towed offshore by two tugs, ballasted with water, and connected to the 500mm pullback reamer via a swivel. The pullback operation was completed successfully within eight hours.
The project also involved the supply, welding, and installation of a 2300m 6” HDPE drilling fluid return line to support the drilling process and maintain environmental control.
ENVIRONMENTAL MANAGEMENT
Works were undertaken in environmentally sensitive areas, including locations close to a designated migratory bird breeding zone and a sabellaria reef habitat.
Through careful planning, controlled operations and precise drilling methodology, Stockton completed the HDD installation while maintaining strict environmental safeguards and minimising disruption to protected habitats.
