Successful underwater decommissioning with 1Diamond and Tyrolit

Published 27/12, 2018 at 10:04

As part of an offshore decommissioning project for Fieldwood Energy, one of the largest producers of oil and gas 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 the two offshore service providers Manson Gulf and Proserv 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. Fieldwood Energy therefore referred to the Norwegian decommissioning company 1Diamond AS, whom in conjunction with Tyrolit, provides respective technology for demanding underwater cutting. 

 

Cutting great diameters under challenging conditions

The task presented included cutting a 50mm thick caisson sleeve with a diameter of 4m as well as 76mm of concrete, and the respective 76mm thick caisson with a diameter of 3.9m at 4.5m below sea level. It was recommended that the contractors use the 1Diamond Green Sawfish System, and apply a step by step approach for this challenging project. This was in order to prematurely identify potential difficulties with deployment and cutting operations, 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 

Proserv 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 4.85m x 4.85m as deep as 120m below sea level. The remote control reduces any potential risks for the user, as it allows for a usage at a distance of 100m. The Tyrolit DHL***-SL diamond 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 by Proserv on time. 

 

Tyrolit and 1Diamond

Tyrolit and 1Diamond AS (Part of Quanta Services) are partners in offshore and subsea operations. 1Diamond offers machines that cut structures up to 7.5m, and in addition, have the capability to saw at any inclination at a diving depth up to 3,000m. Together with diamond tools from Tyrolit, it is now possible to set a new standard for submarine wire cutting, and thus better meet the high demands in this growing market segment. 

The demolition work on the project was performed with the Green Sawfish which is a ground breaking modular system for last phase removal of deck frames (MSF), and gravity based structures (GBS). The Green Sawfish is a surgical, heavy duty subsea sawing machine that employs state of the art diamond wire cutting technology to dismantle structures of virtually any weight, design and material. Safe, cost effective, and environmentally friendly, the Green Sawfish System is a complete success. The electroplated Tyrolit diamond wire DWH***-SL was developed for complex and challenging cutting work in steel. The wire offers very high cutting performance, a long lifetime and noticeable smooth running thanks to an optimised bead structure and a high bead count. Its robust structure also provides high workplace safety.

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