Cutting the cost of well P&A with alternative well barriers
Well abandonment accounts for 45% of the total 2020 UK decommissioning estimate, equating to £23bn. Implementing innovative technologies and techniques for well P&A activities is a key opportunity for cost reductions providing benefits for operators whilst also aiding in achieving the MER UK decommissioning cost reduction target of 35%. Historically, “Portland” cement has been the accepted medium for plugging and abandoning wells on the UKCS however it has been recognised that the development of alternative P&A barriers with the ability to be deployed utilising rig-less techniques could be a game changer.
Interwell’s alternative barrier technology is based on using thermite, a pyrotechnic composition of metal powder – which serves as fuel to set the product – and metal oxide.
Thermite products typically use aluminium oxide, elemental iron and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation. When ignited, it undergoes an exothermic reduction-oxidation (redox) reaction, which, when deployed in a well, creates a molten metal plug that melts the adjacent casing strings and, on solidification, fuses to the rock. This creates a metallic barrier in the wellbore and is an alternative to conventional cement.
Interwell’s thermite barrier technology had been trialled in land wells in western Canada across clay and siltstone formations. NZTC collaborated with Spirit Energy and Interwell on a series of trials to test thermite technology in the UK, which included the first trial in a salt formation and the first offshore deployment.
This has the potential to substantially reduce the cost of P&A operations, potentially saving approximately 10-14 days per well.
By applying this approach to just 10% of the projected 1,400 wells to be abandoned over the next 10 years, could save the UKCS around £0.5 billion.
Key results / Lessons learned:
The first phase of the trial successfully deployed a thermite plug in a salt formation in the Caythorpe gas storage land well. The second phase of the trial also deployed a thermite plug in a well on the Audrey platform, set across a salt interval. This was the first ever offshore deployment of the material. While the thermite was successfully deployed, on testing the material had only created a partial fluid tight seal within the wellbore.
The success in deploying thermite in the wellbore but subsequent failure to achieve a fluid tight seal demonstrated the requirement for further technical evaluation of the thermite material by Interwell at their Norwegian facilities before further trials.
Thermite is one of the technologies focused upon by the Thermite Collaboration Forum, a cross-industry partnership established by NZTC and Spirit Energy, and this made it possible to accelerate development and technology qualification during this project. This collaboration was recognised with the “Excellence in Collaboration” award at the 2019 Decom North Sea 2019 Awards. It has since developed as a wider-reaching collaborative partnership of the Technology Leadership Board (TLB) industry sponsor programme’s ‘Alternative Well’s P&A Barriers Initiative’. It is aimed at expediting the development, trials, verification, and qualification of new barrier materials, whilst driving acceptance and routine use for P&A activities on the UKCS. NZTC also chairs the Alternative Barrier Collaboration (ABC) forum, in order to promote and share alternative barrier material development, field trial test results, regulatory guidance development and encourage multi operator support regards field trial opportunity. The Alternative Barrier Collaboration forum also has two separate focus groups with a goal of identifying technology gaps in barrier verification technology and P&A Assisting technologies.
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