As part of an offshore decommissioning project for a major U.S. oil company in the Gulf of Mexico, a stub had to be removed within a short time frame in the last quarter of 2018.

The platform operator employed two leading decommissioning experts, specialised in offshore services, to carry out the cutting work. After some initial difficulties, it soon became clear that conventional cutting technology would not be sufficient to get the job done. The oil company therefore referred to the professional Norwegian decommissioning company 1Diamond AS, who – together with TYROLIT – offers the respective technology for demanding underwater cutting.

Cutting great diameters under challenging conditions

The task included cutting a 50 mm thick caisson sleeve with a diameter of 4 m as well as 76 mm of concrete and the respective 76 mm thick caisson with a diameter of 3.9 m at 4.5 m below sea level. The 1Diamond Green Sawfish System came highly recommended as well as the application of a step-by-step approach for this challenging project in order to identify potential difficulties with deployment and cutting operations on time, and to bypass them, if necessary. The cutting of the stub took the crew four days.

One of a kind: 1Diamond’s Green Sawfish System

EThe decommissioning experts cut the stub with the 1Diamond Green Sawfish System equipped with the TYROLIT DWH***-SL diamond wire. The Green Sawfish is a hydraulic wire saw capable of cutting max. 4.85 m x 4.85 m as deep as 120 m below sea level. The remote control reduces any potential risks for the user, as it allows for a usage at a distance of 100 m. The TYROLIT DHL***-SL wire, on the other hand, is a electroplated diamond wire specially developed for steel cutting, providing advanced performance regardless of the cutting environment, which makes it the perfect tool for the Green Sawfish.

The biggest challenges of the project were the timing and complexity as well as the size of the caisson. The double wall of the caisson was by far too challenging for conventional tools. The dual axis rotation of the Green Sawfish System combined with the bespoke TYROLIT DWH***-SL diamond wire, however, proved just right for the task, which was successfully completed on time.