Kinsaele Brava topside is removed; Kinsaele Brava topside is removed;

Kinsale Head decommissioning, Celtic Sea

Advising on the decommissioning of Ireland’s first gas field

Located in the Celtic Sea, the Kinsale Area Gas Fields were Ireland’s first and only indigenous gas fields until 2015 and supplied all the country’s natural gas for almost two decades.

Developed in 1977, the gas fields consisted of two piled steel platforms located about 60km offshore in 100m of water, each weighing around 12,000 tonnes. As well as the two platforms, Kinsale Alpha and Bravo, a network of 153km of subsea pipelines connected the offshore facilities back to a small onshore terminal.

In 2020, the Kinsale Head gas fields came to the end of their productive life.

Over the last decade, Arup’s energy and environmental specialists worked with PSE Kinsale Energy to investigate how best to decommission the offshore facilities; the first project of its kind in Ireland.

From 2017 to 2022, our focus shifted to preparing the required planning and regulatory consent submissions, providing various engineering support to the project and health and safety advisory services to Kinsale Energy and contractors.

Decommissioning gas infrastructure is a delicate task requiring detailed studies such as structural assessments, rigorous environmental impact assessments to obtain the necessary consents, in addition to various other engineering consulting services.

During the decommissioning, which was mainly completed in the summer of 2022, approximately 90% of materials recovered from the gas fields were recycled or reused, aligned with best practice. As part of the process, the gas field facilities were made hydrocarbon-free, with wells plugged and capped, platforms and subsea facilities removed, subsea pipelines made safe and onshore facilities safely disposed of.

In 2023, Kinsale Energy appointed Arup as the consultant to manage and administer a post-decommissioning pipeline inspection and monitoring programme. At regular intervals over a period of ten years, Arup will obtain consent, procure, manage and supervise offshore surveys of the pipelines to ensure all pipelines and umbilicals remain stable on the seabed. Following each survey, our civil and mechanical engineers and environmental consultants will prepare reports to share with Kinsale Energy and the Irish Regulator.

Project Summary

2 offshore steel platforms

160kmsubsea pipelines and associated facilities

~90%of recovered materials recycled or reused

This was a project of firsts: the first offshore decommissioning project and first associated consenting process in Ireland and built on over 30 years of collaborative engineering support with our client on these two offshore platforms. ” Paul Brady headshot Paul Brady Associate Director

A long history

Since the early 1990s, Arup was involved in several structural modifications to the original platforms, including subsea field developments that required the addition of major cantilever structures: a new 800 tonne compression cantilever and 400 tonne process cantilever; the addition of risers, j-tubes and ship fenders on the platform jacket legs; blast wall modifications; crane replacements; and wellhead protection structures. Analysis of the complete platform deck was carried out for a large number of static load permutations, dynamic response characteristics and fatigue loading conditions using SACS.

Our teams provided topsides structural engineering services on all of these projects and provided structural advice on the platform jackets, in addition to decommissioning studies. Arup also fulfilled project management and co-ordination roles.