Ecosse Subsea Systems has announced that they have completed a major seabed clearance project on the Laggan-Tormore project west of Shetland. The project was completed on behalf of TOTAL E&P Ltd and its partner DONG E&P (UK) Ltd.
The company deployed its SCAR1 trenching tool to remove up to 1000 boulders which were delaying progress on cable laying and umbilical installation work.
The SCAR1 cut a 10 meter wide swathe over a 67km route, displacing boulders up to two meters in diameter and removing soil to leave a flat seabed to begin pipe laying.
Seabed clearance is usually done using a ‘boulder grab’ device, which is a slow process as it displaces rocks one by one, with operators reluctant to tackle boulders larger than half a meter in size.
Originally developed as a subsea plough, the SCAR system was redesigned and fabricated to suit TOTAL’s requirements and mobilized within a ten day window. The clearing plough worked at depths of 640 meters, believed to be a record for this type of equipment, and at optimum performance cleared up to 1000 meters of seabed per hour.
“Boulder clearance during seabed preparation is a real problem for some operators and is so arduous and expensive that often they opt to move the route of the pipeline. Our method, including preparation, vessel charter and deployment is considerably less expensive than the traditional alternative methods,” said Ecosse Subsea Systems managing director, Mike Wilson in a press release. “Our SCAR system is extremely robust, easily mobilized, can work in the harshest environments and in up to depths of 3000 meters. The success of this project has demonstrated there is a much more efficient and less costly way of tackling seabed clearance and we anticipate this will lead to work on similar projects in the North Sea and other major oil and gas producing regions.”