Interwell is using thermite to melt rocks and seal wells, potentially transforming how the industry approaches P&A
The need for new plug and abandonment (P&A) solutions has pushed operators to look increasingly outside the proverbial “box.” In the case of Norwegian well management firm Interwell, this has meant disintegrating the box itself.
In 2012 one of the company’s technical advisors for P&A, Michael Skjold, floated a radical new idea: using thermite to melt materials in the wellbore, forming an impermeable barrier and sealing the well. Given the company’s history in shallow and deep-set well barriers, well integrity and niche completion products, this offered a wealth of new potential opportunities in the decommissioning space.
Primarily, Skjold says, the idea came in response to the need for cost reductions within P&A. As many operators are exploring options which dispense with the need for rigs, this method could be deployed from a single vessel with little external equipment (the process would also remove the need for cement or even coiled tubing). If successful, this could streamline the P&A process and potentially save significant time and money.
The idea itself is remarkably simple. When ignited, thermite – a compound of metal powder fuel and metal oxide (most commonly iron oxide) – burns at around 2,500°C, enough to melt through tubing, casing and cement. It is also hot enough to melt the surrounding rock, bonding the materials together and – in theory – forming an ideal barrier with which to plug the well. In addition, because the reaction produces its own source of oxygen, no external supply is needed and almost no other gases are produced, making it a sound choice for use downhole.
So far, so good – but a lot of this was unproven. Given the novelty of the technique, there was a severe lack of scientific study which could qualify any of the process. Interwell therefore brought in certification agency DNV GL in 2013, to help investigate and ultimately qualify the “Exothermic P&A Solution,” (as it was initially referred to) for commercial use.
Back to basics
A lot of fundamental work was needed to underpin what the team was attempting to achieve. This meant studying rock analogues, the processes behind their formation and the resulting mineralogy and how well molten materials might bond within these formations.
In addition to funds from the Research Council of Norway, in 2014 Statoil and BP were also brought in as partners in a joint industry project (JIP), allowing the company access to a wealth of information on wells and formations in the companies’ databases, in addition to their perspective as potential clients. The same year also saw patents granted on the technology.
Alongside this, Interwell ran exhaustive tests to develop a system which could be deployed in the wellbore. In a video interview from 2014, Skjord explains: “The whole idea is to keep it as simple as possible. We want to make a man-made rock and to do this we want to enter the wellbore with a carrier device run on wireline. The carrier device will be placed on a wellbore annular heat shield, and activated to provide enough energy to convert all materials into an everlasting deep barrier that hopefully will bond to the surrounding materials.”
Following the group’s 2014 feasibility certificate from DNV GL, they began scaled up testing of the tool. In 2015, they undertook onshore tests and small-scale subsea testing – crucial to determine whether the equipment would stand up to offshore conditions – before eventually building and testing a prototype in a specially designed test tank in Norway. This allowed Interwell to examine the system’s performance under simulated high-pressure, high-temperature (HPHT) conditions. The learning process also took the team to the Iceland Deep Drilling Project to study the behaviour of supercritical liquids – fluids above 347°C and at pressures greater than 220 bar – to support further tests of the P&A process in HPHT environments.
With over 4 years of experience and 200 tests under its belt, the company is now heading towards field trials in onshore wells in Canada and aims to have 4 pilot wells completed by the end of the year. According to a recent presentation, this would allow Interwell to commercialise the P&A tool fully for onshore and offshore during 2017, and for subsea operations in 2018.
Although it has been a long road since the idea was first mooted, progress on the tool has moved at a pretty rapid pace – in an update in late 2015 Skjold noted that the team was “thorough but in a hurry.”
InnovOil hopes to revisit the tool later in 2016, following the results of Interwell’s field trials. We will keep you posted on their progress.