Interwell’s thermite P&A tool has undergone trials in Canada, where results so far have been highly promising
Even in difficult times, good ideas shine through. Back in June 2016, InnovOil explored a radical new method proposed by Interwell for the plugging and abandonment (P&A) of decommissioned wells. The company was experimenting with thermite as a means of melting the well tubing, casing and the surrounding rock formation, bonding the media together in a new rock plug and sealing the well. If it was successful, it would represent a truly new method of approaching one of the industry’s thorniest – and costliest – problems.
In the nine months or so since, the company has been conducted a number of trials, including an initial two-well pilot in Canada, with a view to fully qualifying the technology.
To reiterate the theory behind the technique: 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.
This is deployed via a specially-engineered tool. An anchor is set, heat protective material is placed above and the tool is lowered and activated. P&A Engineer Henriette Horjen explained that: “This will melt all the well elements and establish a cross-sectional, formation-to-formation barrier. The barrier can be divided into three components – in the middle a melt zone which will solidify into a synthetic igneous rock. Moving out there will be a thermal contact – a bonding between the synthetic igneous rock and the host rock caused by crystallisation. Outside of this we will have a thermal alteration or metamorphic zone in the host rock.” 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. No workover rig is required, meaning P&A operations could be performed quicker and at a lower cost than conventional techniques. Moreover, the hope is that the new bonded rock barrier could better prevent potential oil and gas leaks more securely than the current methods of sealing and/or cementing abandoned wells.
A very good year Having been investigated since 2012, last year proved to be a breakthrough for the technology as a viable and commercial option. May 2016 saw the Interwell team undertake a full-scale test in a dummy well, with a full-size tool deployed above ground for trial and inspection.
P&A Engineer Kai Rune Finnes commented: “This test has been very good experience... We have verified that the tool can be assembled, handled and installed quite easily. We also had an ignition where we had an immediate activation and exothermic reaction after we pushed the button so we can really build confidence to go on further.” The next stage was to deploy the technology in a real-world setting. Gas-focused operator Centrica stepped forward and, finding the technology “very intriguing,” sought approval for a two-well pilot with Albertan regulators. Begun in August 2016, this would form perhaps the most important verification of the barrier. According to Interwell P&A Operations Manager Lars Albertsen, the two wells offered 7-inch casing at the correct depth and pressure – optimum specifications in terms of the team’s base-case scenarios – and would allow them to place the well in underbalance for the 6-month test period.
Testing included the running of cement evaluation tools and logs and casing inspection logs, both before and after deployment, as well as positive and negative pressure tests.
Deployment and initial tests proved successful, but further results from the six-month trial have not yet been made public. Further tests are ongoing, with sources indicating to InnovOil that results are expected in early summer. However, based on the initial months of trials, the company is confident that the technology works in wellbore conditions, and that the properties of the barrier have been proved. Previous reports indicated that the company would look to commercialise the P&A tool fully for onshore and offshore during 2017, and for subsea operations in 2018, although we are unsure if this is still the company’s intention.
To do so, however, will require more operators with more well candidates in order to bolster the verification programme. Operators looking to tackle the problem of P&A would do well to consider a technology which could yet become a new standard.