Research on metallurgical and chemical inhibition techniques to reduce corrosion in high-acid geothermal wells

Geothermal energy is a widely recognised renewable energy resource that provides reliable base load generation worldwide. The extraction of geothermal water for use as an energy source is of paramount importance and its usage is increasing. A problem in exploiting renewable geothermal energy sources is the production of acidic brine, that leads to excessive corrosion and often scaling issues of well casing, casing head perforation and well surface piping failures, that are often unmanageable. This study will improve our fundamental understanding regarding the corrosion behaviour and the corrosion mechanism of carbon steel and stainless steels exposed to an artificial geothermal brine influenced by carbon dioxide under strongly acidic (pH ~2.5-3) conditions. This knowledge will be used to assess relevant corrosion and scaling threats and their mitigation in geothermal assets. From this initial data set, a series of strategically selected surfactants will be evaluated in their ability to control corrosion in strongly acidic solutions. These observations will firstly enhance the understanding of corrosion inhibition in such systems and secondly, help guide the industry through the development of new methods, chemistries and guidelines/recommendations for corrosion control in geothermal environments.

The objectives of the work are to:
- Design and commission of a bespoke experimental autoclave system for mass loss and electrochemical analysis of corroding substrates in high temperature and high-pressure environments.
- Perform corrosion experiments for various high temperature conditions and fluid compositions to improve the understanding of corrosion mechanisms in high acidity geothermal systems.
- Use associated testing, analytical and surface characterization techniques and methods (mass loss, electrochemical methods, SEM-EDX, optical profilometry, FTIR spectroscopy) to determine the corrosion mechanisms
- Analyse the performance of candidate chemicals in high acidity systems, developing novel testing strategies for scaling of laboratory to geothermal fields.
- Focus on the development and improved testing methods for more environmentally friendly corrosion inhibitors, analysing their chemical and physical properties and linking this to inhibition performance to support the development of new chemistries with improved functionality.
- Highlight how the developed environmentally friendly surfactants perform in the presence of significant levels of mineral scaling (typical of geothermal systems)

The proposal aligns within the Energy and Engineering research themes (particularly within the sub themes of ''Electrochemical Sciences'' and "Materials for Energy Applications"). This proposal also aligns with EPSRCs prosperity outcomes framework, specifically: (i) Resilient nation, (ii) Productive nation (next generation solutions) and (iii) Productive nation (affordable solutions and sustainable society).