Chevron Australia’s Thevenard Island oil facility off the WA coast near Onslow produced approximately 150 million barrels of oil between 1989 and 2014 but now all the activity is focused on decommissioning and rehabilitation.

For Thevenard Island Retirement Project Manager Chris Jones, 2023 will be a milestone year for the project.

Rehabilitation of the 35-hectare site that once featured production, processing and accommodation infrastructure will deliver an end state compatible with the adjacent nature reserve including plants that have been reared in a nursery from seed and cuttings taken from the island and replanted.

It’s part of what Mr Jones says is an industry-leading rehabilitation program for the island.

Australia is facing an era of decommissioning activity, estimated to cost around $56 billion to 2050, as production ends at long-established oil and gas fields.

Chevron ceased production on Thevenard Island in 2014. The offshore and onshore decommissioning project that followed is one of the most comprehensive decommissioning projects to date in Western Australia featuring both onshore and offshore infrastructure in close proximity to several stakeholders while being located on and adjacent to a nature reserve.

Mr Jones, with Chevron since 2008 and with extensive onshore and offshore decommissioning experience in the United States including in the Gulf of Mexico, joined the Thevenard Island project in 2016.

“There were a lot of complicating factors,” Mr Jones said. “The site is located adjacent to a tourism facility who are actively operating a tourism venture while we are involved in demolition and earthworks. Careful management of these activities, minimising the active execution timeframe and compressing the rehabilitation phase has therefore been a priority and shaped how the works were undertaken”.

“We are in the backyard of Onslow, you could see the terminal tanks from the town, so the Onslow community and local government have been very engaged and interested in the decommissioning project.  There are also logistical challenges that come with operating on an island as well the environmental management complexities associated with the island’s nature reserve status and the surrounding marine environment”.

“Shallow water is a key challenge for offshore decommissioning, restricting the size and types of vessels available for use. The water depth and geographic location also mean that other environmental sensitivities such coral habitat, turtle nesting and migratory marine fauna need to be considered as well as the recreational users from the nearby town of Onslow.”

Mr Jones has co-authored a review of the Thevenard Island project (Jones CM et al. (2022) The APPEA Journal 62(1), 1–13. doi:10.1071/AJ21216) in which he concludes “decommissioning presents a myriad of challenges to operators, which often require a different mindset and approach to traditional project planning and execution to ensure timely, safe and efficient execution”.

“Taking a proactive approach to planning, investigations and approvals and commencing these activities well in advance of Cessation of Production is critical to ensure that stakeholder expectations on timely and quality decommissioning and rehabilitation are met while also enabling a cost-effective approach and minimising missed opportunities.”

Speaking to the Energy Club for its August newsletter, Mr Jones said the approach to decommissioning was very different to a construction project.

“When you’re building a facility, everything is well defined and known – that’s not the case for decommissioning. It is often assumed that you can manage decom using the same project management tools used to build a new facility; same contract strategies, same methodologies, but it can really get you unstuck because we are dealing with so many unknowns,” he said.

For Thevenard Island, the project team is working toward the goal of relinquishing the operating title and returning the land back to the owner, the Department of Biodiversity, Conversation and Attractions (DBCA). There are multiple regulators involved and this requires all parties to align on an end state for onshore and offshore facilities.

“It’s trying to get very clear upfront alignment on end state and what that looks like, and it is critical we capture the necessary information along the way,” he said.

“Onshore, we won’t relinquish title until we reach our rehabilitation completion criteria which could be 10 or more years away. At that point, there may be people working for the regulator who have no experience in the history of the project, and new people within Chevron, so we need to carefully document arrangements now to assist with this process in the future.

“That means working today to reach alignment and ensuring that the decisions we make together now will stand the test of time.”

Offshore, Mr Jones expects that work will start next year on removing the platforms associated with the facility.

He said a major lesson learned involved contingencies and planning.

“You don't want to lock yourself in on how you execute the work because things never go to plan in decommissioning,” he said.

“Make sure you’ve got your contingency plans in place, and you’ve considered that in your approvals and your risk assessments, and you're ready to go with a contingency plan.”

In his review, Mr Jones said: “The obvious solution is to commence planning early, including the collection of data to support a project’s end-state vision.”

“This requires recognition from the business of the impact of deferral on the total cost of operations and licence to operate.”

“Planning creates both flexibility and predictability; however, planning must be at an appropriate level given the inherent uncertainty associated with decommissioning. Given the non-routine nature of decommissioning it is critical that operators implement a learning culture to continually improve upon existing plans and share across projects.

“As an industry, these learnings are invaluable and there is significant opportunity to further improve performance through collaboration and sharing.”

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