Julimar Walking Mitigation

Australasia

01 June 2021

Summary

Year
2021
Client
Subsea7
Location
Western Australia

Project Overview

In 2019, Subsea7 was awarded Julimar Development Phase 2 by Woodside Energy Ltd. The Julimar field is located approximately 200 km offshore North-Western Australia. The full scope of work included the design, procurement, installation and commissioning of a 22 km 18” Corrosion Resistant Alloy (CRA) gas production flowline and an umbilical system. A key feature of Subsea7’s installation was the use of reel-laid pipeline and buckle initiation using the Residual Curvature Method (RCM). Subsea7 selected MMA's Pipe Clamping Mattresses (PCMs) as the preferred walking mitigation system during the detailed design phase instead of piled restraints.

MMA Solution

MMA designed a PCM solution specifically for the Julimar project, optimised for the pipeline coating, maximum submerged weight, installation and distribution along the pipeline. 36 PCM sets were deployed at 3 locations, ensuring that the pipeline walking rate would remain within allowable limits. The solution also included restraining the end terminations and an in-line tee.

Outcome

Subsea7 engaged MMA to conduct an extensive design phase in collaboration with S7 engineers in France, England and Australia. The design phase was followed by the execution phases which included tool production, a factory acceptance test to demonstrate correct fit up and validate the deployment philosophy. The PCMs were fabricated in Karratha before being placed into temporary storage ready for rapid deployment. Subsea7 successfully deployed in April 2021 with the PCMs continuing to provide walking restraint for the pipeline.

Technical Details

PCM Dry Weight	32.1 Te
PCM Submerged Weight	18.6 Te
Total Axial restraint Load	~340 Te
Pipeline to soil interface friction coefficient	~0.61
Qty of PCMs	36
Pipeline Nominal Diameter	18”
Pipeline Type	CRA-clad gas production flowline
Coating Type and Thickness	MLPP Parent Coating ~68mm Wall Thickness
Water Depth	147 – 174m
Soil Type	Calcareous silty sand

MMA Innovation / Value Added

The application of PCMs provided Subsea7 with unique flexibility in their design of the walking mitigation scheme compared to traditional piled solutions. The design team were able to adjust the location and quantities of the PCM’s at a very late stage in the design process enabling them to respond with agility and confidence to evolving design parameters.

About PCMs

PCMs were originally developed for the Malampaya field for Shell. PCM patents are held by Shell, which has made the technology available to the market through an exclusive global distribution license granted to MMA.