Wellsafe has carved an expert niche in undertaking difficult and technical well decommissioning projects, including using its consultative strengths to negotiate fair and equitable service provider contracts that reflect the company’s principles.
The company’s pedigree in the breadth of decommissioning and abandonment activities covers initial file reviews through to providing the client all necessary advice and paperwork to apply for surrendering the licence.
This includes design of the abandonment, the regulatory interface, the procurement of services, execution of the work program, and remediation of the surface environment.
Wellsafe Managing Director Jamie Wilson told Petroleum Australia there was not a lot of this EPC-styled management in the space in which Wellsafe works.
Wilson said: “We’ve previously had some craftily-constructed contracts of many hundreds of pages given to us by large Australian petroleum companies, where they seek to distribute related content throughout the entirety of the contract and transfer all risk to the service provider.
“It’s important in difficult or unconventional decommissioning projects for there to be an equitable sharing of the risk, which focuses each of the parties to be collaborative for the entire project outcome and do the best possible job within their area of responsibility.”
“We strike a good balance of sharing those risks with the client and service providers in our commercial relationships, with each of us bearing the risk to the extent it is reasonable for us to do so.”
This reputation led to Wellsafe being engaged to design and execute a plug, abandon and remediation program for the decommissioned Caroline 1-well in South Australia, which included complete engineering design and project execution of a compliant plug and abandon program.
Constructed in 1967 in a pine forest plantation near Mount Gambier, the Caroline-1 well produced carbon dioxide for industrial use for half a century, most recently for Air Liquide Australia.
Wilson noted the plug and abandonment program was quite outside of Air Liquide’s expertise, and so took some convincing and guidance for them to have the confidence to allow Wellsafe to do the work.
He said: “It was a process of educating the client and carrying them along with us while we do the design and contracts.
“That provides the client with only one interface which is a much more efficient approach – they come only to us and we manage everything for them.
“We’re able to take all of our expertise, cleverness and easiness to work with, and deliver an efficient project for the client, even where there are lots of challenges to overcome.”
Due to the age of the well, multiple methods were required to free the production tubing and casing, which have since been stored by the South Australian Department of Energy and Mining due to their specialised nature having being exposed to carbon dioxide.
Wilson explained: “Anybody that is looking at carbon dioxide storage will be wanting to get access to that material so they can see what the effect on that steel is over any prolonged period.”
The Caroline borehole is unique in that it provides a glimpse into how carbon dioxide can accumulate (or be stored) in subsurface reservoirs, allowing a better understanding of the capacity of the earth’s crust in holding fluids over long geological timescales.
Wellsafe Director and Principal Advisor Phil Smith said the project was quite a challenge, as Wellsafe was told the annulus was full of diesel but it was actually full of 50-year-old drilling mud with a bit of diesel on top.
Smith said: “The borehole used several casing strings, so we had to be conscious of what was on the outside of those as that’s what needs to be isolated.
“Because of the tubing’s unknown status after producing carbon dioxide for 50 years, it was assessed that the best process was to leave the packer and bottom hole assembly downhole – so we set a plug inside that tubing and cut it above the packer to leave that as a base for the cement plugs.
“As there was a lot of 50-year-old mud that had settled out and secured the tubing, we recovered different casing strings while moving up the hole.
“As with all of our projects we were fortunate enough to have really good and capable people on it; a good regulator to work with through the process; and Air Liquide, while it was outside of their space, were supportive that it was done appropriately.”
The inherent challenges posed by the age and service of the well were overcome by the Wellsafe team’s extensive experience and pragmatic approach to problem solving.
Several subcontractors were sourced and engaged by Wellsafe to deliver the program, while Wellsafe provided continual infield supervision supported by remote engineering advice and instruction.
The high-level work program included setting a bridge plug in the packer at 2,470 metres, cutting and removing production tubing from 2,383 metres to surface and setting a cement plug in the casing, removing the casing from 976 metres to surface, and cementing the casing shoe in two places.
This work was carried out by TDC Drilling, Kinetic Well Intervention Services, and Superior Cementing, under Wellsafe’s supervision, resulting in a seamless outcome with all cement plugs installed as required.
