Olivia Milton-Thompson

PhD Thesis: Developing a risk assessment model using fuzzy logic to assess groundwater contamination from unconventional gas development in the UK

Supervisors: Professors Akbar Javadi and Zoran Kapelan


Hydraulic fracturing is a viable method for extracting a wealth of natural gas from shale rock and has recently begun production in the UK. The process took off in the US but brought with it controversial debates over environmental protection. To feel confident in applying this technique to an apprehensive population in the UK, it is important to consider the science and engineering involved in the process. This project focuses on assessing the risks to groundwater contamination to help determine if the process is sufficient for use in the UK, and if so in which areas will this be most successful and least damaging to our environment.

The project highlights the potential contaminant pathways for gas reaching aquifers during the stages of an active well’s life. These pathways are developed from conceptual models and will be quantified using event tree analysis. Quantifying the branches of the event trees includes failure probability values from the literature, fuzzy logic inputs for geological and well construction properties and fuzzy fault tree analysis which utilises expert opinions. Currently fuzzy fault trees are being developed to understand cement failure in a gas well over time. The event tree branches leading to contamination will be quantified to obtain a probability of contamination. The fuzzy logic inputs can be changed by the end-user to see how the probability could change depending on geological conditions, well construction and abandonment procedures. The risk model is built and validated using well data from British Columbia, Canada but discussions on how this can be applied to a UK context will be important.


Olivia obtained her BSc from Durham University in Chemistry and her MSc from Cranfield University in Environmental Water Management. A dissertation was undertaken at Durham University in aromatic trifluoromethylation and the MSc thesis at Cranfield focused on the application of barely straw to reduce algal growth in reservoirs.

Before undertaking the MSc, Olivia worked as a laboratory analytical chemist at Huntingdon Life Sciences focusing on analytical methods such as LCMS, GC and HPLC. A summer placement as a research assistant at the University of Nevada, Reno in the Environmental Chemistry department ensured her interest in hydraulic fracturing where Olivia undertook work on inorganic contamination from fracking from the Pennsylvania Wells in the USA.

Contact: om271@exeter.ac.uk

Keywords: Hydraulic fracturing, groundwater contamination, fuzzy logic, fault tree analysis, event tree analysis, risk assessment.


WISE 2017 Summer School Presentation: Olivia_Milton-Thompson_Jun17[1]

June 2017 Poster: Olivia Milton-Thompson Jun17