Safe removal of subsea flexibles for decommisssioning

With our global network of bases and several experienced technicians stationed worldwide, Altrad Sparrows can provide offshore and onshore support for the energy sector from multiple regions.

This was recently showcased by our Cable and Pipe Lay Solutions(CPLS) team, who worked with a commercial diving and ROV contractor to retrieve various subsea flexibles from the Tui Oil Field, offshore New Zealand.

Safe removal of subsea infrastructure

This offshore campaign was our first decommissioning project in New Zealand and is the most extensive decommissioning package the team has provided.

Supplying a complete flexible recovery equipment package, we provided a 36-tonne tensioner to retrieve various Subsea Umbilicals, Risers, and Flowlines (SURF) as well as three sets of shear cutters (two for use and one as a spare) to cut them into manageable sections on the vessel.

Though the client initially approached us for just one piece of equipment, we bid to provide both the tensioner and the shear cutters. This approach provided a much more convenient and cost-effective equipment package for the client, where the entire process, including shipping to Singapore, was handled by Altrad Sparrows.

We also provided a team of six skilled technicians to manage the equipment mobilisation onto the vessel in Singapore and the offshore operations in New Zealand, supported by onshore personnel in Aberdeen, Singapore, and Australia.

Flexible recovery equipment package

Our work began three months before the start of the campaign with preparing the tensioner to be mobilised from Singapore. This 36-tonne tensioner was designed and built in-house and is a part of our global rental fleet. It was taken through a rigorous, planned maintenance scheme to ensure it was in full and safe working order before sailing out to New Zealand.

Following the tensioner’s successful load tests, our team of six technicians travelled to Darwin, Australia to meet the client’s Dive Support Vessel (DSV) before heading to the Tui Oil Field. The campaign got underway, with the team pulling in different products such as Subsea Umbilicals, Risers, and Flowlines (SURF) and small coiled tubing. The tensioner was used in two and four-track modes with various track pads depending on the diameter of the flexible being retrieved.

As the operation progressed, the client also spooled umbilical sections onto a reel offshore before transferring the reel to quayside to unspool and cut them down into more manageable sections with the spare set of shear cutters. This time-saving technique meant we could continue with our offshore recovery in tandem while supporting their team quayside with any assistance they needed. During the project, we have also been using our experience to provide consultancy to the client as they develop their recovery procedures

Communication and safety offshore

One of the most challenging aspects of this work arose from its location and the different regions involved – i.e., Aberdeen, Singapore, Australia and New Zealand. However, having offices and a network of technicians within these regions meant we could meet the client’s expectations across different time zones.

Weekly meetings were held to ensure the client was updated on progress and made aware of anything that needed to be addressed before the next stage. During the operation, Altrad Sparrows set up 24-hour communication with the offshore team to manage updates and provide support from onshore as necessary.

The safety of all personnel is crucial. Before the project began, the client invited input from all main stakeholders to take part in the project Hazard Identification (HAZID). Our team also undertook full operational risk assessments on all equipment, and pre-mobilisation briefs ensured safety expectations and ‘stop-job’ procedures were consistent and clear. To supplement this, toolbox talks, which supervisors attended, were undertaken twice a day so everyone would be on the same page and could raise any concerns.

Success across all time zones

Throughout the operation, our equipment remained operational with zero downtime, and the entire team, from multiple time zones, supported each other throughout.

By supporting the client from the start to the end of this project with a complete equipment package and a global team, we provided a convenient solution and round-the-clock support.