ALE uses new offshore skidding technique

Heavy lift and transportation specialist ALE has said it used a unique offshore skidding technique for the first time to assist with the offshore installation of the satellite platform (SP) topside, weighing 2,565 tonnes, for the Korchagin oil field development project in Russia.

ALE was contracted to perform the engineering, weighing, jacking and load-out of the SP topside, as well as the mooring and ballast supervision for load-out.

The first stage of the project started in November 2018 and involved jacking and weighing the topside, before performing the mooring and pulling operations for the load-out onto the transport barge in December 2018. In April 2019, ALE executed the offshore skidding of the topside on the substructure during the float-over operations in the Caspian Sea. This was achieved using eight strand jacks and specialist 300 tonne breakout jacks.

According to ALE, the methodology involved skidding the topside transversally off the barge and onto a cantilever frame. It was then installed using a traditional floatover method. Tolerances were carefully monitored throughout, said ALE, with a retrieval system available for contingency purposes.

To control the skidding operation ALE said the barge was kept with a positive heel at all times, so the skidding was always with a positive gradient to ensure any effects of free sliding were removed. To further mitigate this risk, ALE’s retrieval system was setup to anchor the topside in position if required.

“This methodology was unique and posed many challenges, largely in terms of controlling the barge’s heel during the transverse skidding,” explained David Le Masurier, project engineer for ALE’s offshore services. “We skidded in stages incrementally to control the heel motion of the barge, stopping the skidding operation and holding the topside in position while the barge was ballasted to keep a positive heel at all times.

“This was not only a technically challenging project where we could find a smart and safer solution but the short weather window also meant that we had to remain flexible. By deploying our specialists in offshore engineering, we could devise this unique solution and complete the manoeuvre safely and successfully.”