Effect of biofilm formation on multiphase flow and wetting properties during cyclic injection of hydrogen in rocks

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In response to increasing concerns of global warming and climate change, today's society is seeking to shift towards environmentally friendly and renewable energy sources. Among various energy options, hydrogen (H2) is receiving significant attention, and is likely to form a major asset of the UK's economy with an expected GVA of £18 billion/year by 2050. However, large-scale storage of H2 to account for future demand poses major challenges. Underground storage of H2 can provide an effective solution; however, substantial fundamental research is needed before implementing this technique at the field scale. Some of the challenges that H2 storage presents are: (i) the limited fundamental understanding of pore-scale behaviour of cyclic injection of H2 in porous rocks. This aspect is currently being investigated by our PhD student Zaid Jangda at IGE; and (ii) the formation of biofilms due to long-term interaction of H2 with the microbes present in the resident brine (H2 is an effective energy source for subsurface microbial activities), which will be investigated in this project. The formation of biofilms can block the available pore space, which can adversely affect porosity and permeability, and consequently the storage capacity for further cycles. Moreover, it is unknown if the formation of biofilms can alter the wettability of rock samples in a H2-brine-rock system. If wettability alteration occurs, it can significantly affect the flow properties of H2 in rocks. This project will address these challenges by conducting an experimental and 3D X-ray imaging study using batch and flow through experiments. The results will allow us to scrutinise various parameters that can impact the formation of biofilms during H2 injection in rocks. Moreover, it will enable us to characterise the pore space variations and wettability alteration due to biofilms and their impact on flow properties. The results will allow us to develop robust models for the prediction of H2 storage (modelling is not in the scope of this project). The long-term goal, beyond the proposed work, is to develop experimental strategies to prevent biofilms that can adversely affect H2 storage.