Esso Australia completes Mackerel plug and abandonment campaign

Esso Australia has completed its campaign to plug and abandon 22 wells on the platform, meaning that all 25 Mackerel wells are now abandoned.

“This was the first time that we used a hydraulic workover rig to abandon an entire platform of wells, but it certainly won’t be the last,” said Wells Engineering Supervisor, Sarah Robertson.

The experience provided the wells engineering team with plenty of learnings that will improve the efficiency of future plug and abandonment works. For example, after completing wells on the western side of the platform, the team took a more innovative approach for the eastern side wells.

“We took a batch-style approach for wells on the east side, meaning that, rather than completing the abandonment one well at a time, we completed abandonment activities on the lower sections of all wells, followed by works on the upper sections,” said Sarah.

“We found this batch-style of abandonment activity to be very efficient and we will use this process for our works to plug and abandon wells at Kingfish B and Fortescue later this year."

The team also worked with offshore regulator, NOPSEMA, on an innovative approach to managing tubing.

“On Mackerel we completed our first through-tubing abandonment of the reservoir by pumping cement into the Xmas tree, down the tubing and around the outside into the production casing to form a rock-to-rock barrier across the cap rock, which is the sealing rock that keeps the hydrocarbons in place. This is much faster than having to pull all of the tubing out of the well to set a cement plug and just as effective,” said Sarah.

“We worked closely with NOPSEMA to ensure they were comfortable with this technique and after we were able to demonstrate its success on Mackerel, they approved use of the same approach for Whiting.”

Decommissioning Asset Manager Simon Kemp said that everyone involved in safely completing the Mackerel plug and abandonment campaign should be congratulated for their part in the complex, but very successful campaign.

“Successful abandonment of Mackerel involved a great deal of collaboration across many people in our Gippsland business exemplifying a continuous improvement approach from Wells, Geoscience, Care and Preservation, Logistics, Decommissioning, SSHE, Procurement and multiple other support  teams,” said Simon.

“Not only was this a multifaceted and extended campaign, with many factors to consider and manage carefully, a lot of this work took place during varying levels of Victorian bushfire and COVID19 restrictions which added complexity to the already challenging task.”