We understand that decommissioning can be a complex business. Our approach is to simplify the process as far as possible by focusing on the key drivers whilst adhering to the standards necessary for executing such a large, multi-phase project. This principle has been embedded in the planning and execution of the five main work streams within the Greater Dunlin Area Decommissioning Project.
Platform Wells Plug & Abandonment
The plug and abandonment (P&A) of the 45 platform wells on the Dunlin Alpha is a time-critical and significant work scope, involving numerous technical challenges. The Dunlin Alpha wells will be plugged and abandoned in accordance with Oil and Gas UK recommended standards and the well activity governed by our Well Integrity Management System (WIMS) and Well Operating Procedures (WOPS) standards and procedures to ensure safe and technically appropriate methodologies are applied. We have undertaken interventions on 30 out of the 45 wells on Dunlin since its acquisition from Shell in 2008. A robust planning process accompanied with an inventory of wells with pre-approved P&A programmes is designed to mitigate the schedule risk from specific wells challenges and to maximise productivity.
Subsea Wells Plug & Abandonment
The plug and abandonment (P&A) of the 16 Osprey and Merlin subsea wells will be executed in a single campaign with a Mobile Offshore Drilling Unit (MODU). These wells will be plugged and abandoned in accordance with Oil and Gas UK recommended standards, with well activity governed by our Well Integrity Management System (WIMS) and Well Operating Procedures (WOPS) standards and procedures to ensure safe and technically appropriate methodologies. The commencement of this campaign will be circa Q2 2017 to allow sufficient time for the learnings from the Dunlin Alpha P&A campaign to be fully incorporated into the design of the well programmes. This will also greatly increase the availability of original equipment manufacturer (OEM) running tools required for well access.
Subsea Infrastructure Decommissioning
We will be responsible for the management of extensive subsea infrastructure associated with the Osprey and Merlin subsea fields tied back to the Dunlin Alpha, as well as the subsea infrastructure associated with the platform and Concrete Gravity Base Structure. In order to ensure regulatory-compliant solutions, we will apply industry guidance in the form of the BEIS ‘Guidance Notes – Decommissioning of Offshore Oil and Gas Installations and Pipelines under the Petroleum Act 1998’, Version 6, March 2011 and OGUK ‘Guidelines for Comparative Assessment in Decommissioning Programmes’, Issue 1, October 2015. All viable options will be identified and screened before the remaining options are assessed in accordance with the comparative assessment guidelines. Key stakeholders will be engaged to ensure that the final comparative assessment reports have been verified as fit for purpose solutions for Osprey, Merlin & Dunlin related subsea infrastructure. This will inform the subsea infrastructure removal scope of work which will be competitively tendered for execution following approval of the appropriate decommissioning programmes.
Make Safe, Prep for Handover
The Make Safe and Prep for Handover team will be responsible for transitioning the Dunlin Alpha platform from its live production state to a permanent shutdown state with process equipment cleaned, isolated and ultimately left in a safe state for the topsides preparation phase. Key Dunlin offshore and onshore engineering and operations personnel will provide in-depth asset knowledge and awareness that will be critical in avoiding abortive work and optimising the efficiency of work execution on platform systems. The short term focus of the team is to ensure wellheads related to the Plug & Abandonment (P&A) programme are isolated and disconnected from process equipment, allowing free access to the well bays with the aim of ensuring an uninterrupted P&A programme that is critical to the overall progress of the project.
We will undertake initial feasibility studies to understand the key technical challenges and execution risks associated with each of the available topsides removal methodologies. On completion of methodology evaluation, the work scope for the project Define phase will be informed by the overall execution strategy as well as the outcome of stakeholder consultation and comparative assessment that will determine the key interfaces between infrastructure to be removed and infrastructure planned to be left in-situ. During the Execution phase of the topsides removal work stream, focus will be directed towards ensuring safe and efficient removal of the platform modules in accordance with the agreed removal methodology, sequence and disposal strategy.