Creep behaviour of novel alloys for well plugging and abandonment
Rawwater Engineering Company Ltd (RECL) is an oilfield services company specialising in reservoir souring management and metal alloy development for permanent barriers in well sealing applications.
As depleted reservoirs become economically unviable, well plugging and abandonment (P&A) programmes will accelerate. Currently, well P&A is completed almost exclusively by the use of cement. This is intended to create a permanent barrier, sealing off the well and enclosing downhole fluids and gases. However, the application of some cement plugs have been found to fail over time as a consequence of the presence of microcracks and the subsequent extent of permeability resulting in leakages and loss of integrity of the barrier. These leaks are both an environmental risk, and a financial consequence for the operating companies who will be exposed to additional re-abandonment costs should the plug fail.
Recognising the opportunity for an alternative solution to cement plugs, Rawwater have developed a range of metal alloy plugs which are sufficiently strong, relatively ductile, impermeable and non-toxic. Metal alloy plugs are capable of operating effectively in shallow to deep wells. Furthermore, the installation of metal alloy plugs significantly reduces deployment costs by well over £1.4m compared to cement plugs as a consequence of reducing deployment time to 1.5 days and the inevitable saving on vessel costs for offshore wells.
Having undertaken onshore deployment trials of a Rawwater developed novel alloy specifically formulated for P&A applications, Rawwater needed to establish the mechanical properties and creep behaviour of the alloy as a simulation of service pressure and temperature conditions. Rawwater partnered with the University of Aberdeen who determined the alloy’s creep parameters at stress and temperature conditions similar to that experienced downhole.
“The understanding of the creep behaviour of novel alloys for downhole well plugging applications has strengthened the interest of the Principal Investigator in the design and development of oil and gas well technology, tools and components. The project complements other sub-surface well plugging and abandonment as well as decommissioning research activities at the School of Engineering, University of Aberdeen. The good working relationship between Rawwater and the Principal Investigator and the successful completion of the first phase of the project, has led to a second follow-on project with OGIC“.
Prof Alfred Akisanya, University of Aberdeen
“Through partnering with the University of Aberdeen, Rawwater has been able to establish essential creep parameters of the metal plug alloy, such as activation energy, creep rate, strain rate sensitivity and material creep constant. The extensive test facilities at the School of Engineering made this possible within the project’s limited time frame. These results now serve as input data for Rawwater’s reliability and long-term performance modelling of the various plug designs.
“Following the successful completion of the first phase of the project, further studies have now been proposed to fully characterise the creep behaviour of another Rawwater developed metal plug alloy which is designed for wellbore environments experiencing higher temperature (140°C – 160°C) and differential pressure (> 5,000 psi) wellbore environments.
“We are delighted with the progress achieved on the project and OGIC’s effort and support has been very much appreciated. The pairing of Rawwater with the University of Aberdeen has been of great benefit to both parties.”
Dr Joseph Oluleke, Rawwater