The development of large-scale storage of hydrogen is widely accepted to be a critical element of the transition to a future net zero energy system. Most focus at present is on the development of depleted gas fields as hydrogen stores. This project will advance the alternative of development of aquifer structures for hydrogen storage. As a lower cost option, this clearly offers a lower cost integrated energy system to the benefit of all system participants. Aquifers are also significantly more accessible than depleted gas fields, with some regions not having access close to them: e.g. South Wales or the Southwest of England.
The objective of this project is to extend the earlier concept work undertaken for the Hydrogen Storage in Aquifers SIF Round 3 Discovery (SIF_WWU_3_1) project into a pre-feasibility study relating to a small number of specific structures.
Benefits
The development of large-scale storage of hydrogen is widely-accepted to be a critical element of the transition to the future net zero energy system. Most focus at present is on the development of depleted gas fields as hydrogen stores. The earlier work found that aquifer storage of hydrogen offered significant cost advantages over depleted gas field storage. This study will advance these findings with specific reference to a number of potential storage sites which could be developed and used by WWU on behalf of its customers. As a lower cost option than that of depleted gas field storage, the project clearly offers benefits to consumers. For WWU and its customers, aquifers are significantly more accessible than depleted gas fields, none of which are close to South Wales or the Southwest of England. The benefits to consumers would arise from the development and use of lower cost bulk hydrogen storage options than currently under consideration.
Learnings
Outcomes
The project identified two appropriate structures for detailed consideration – B1 and OM7. B1 is a Bunter closure in the Southern North Sea and OM7 is a closure in the Ormskirk Sandstone in the East Irish Sea.
Seismic and geological data relevant to these two structures was obtained, and seismic interpretation and mapping completed. Petrographical and petrophysical assessment of the reservoirs in these structures was undertaken, informing a reservoir model which allowed quantitative evaluation of the hydrogen storage potential (rates and capacity).
In parallel, laboratory-scale modelling was undertaken of the storage performance of a system in which an inert “barrier” gas (likely nitrogen) is used to reduce the losses in the working gas. Findings from this analysis provided data which informs mathematical scaling rules for application at reservoir scale, and appear to confirm that use of a barrier gas can significantly reduce the losses of working gas. This work also gave insight into the blending of injected hydrogen with the inert barrier gas, which could be used in further work to refine reservoir modelling of an aquifer storage system which adopted the barrier gas approach.
Modelling of hydrogen supply and demand confirmed that very significant volumes of hydrogen storage will be required in the Net Zero energy system, and finds that the storage requirement may require multiple stores each with multiple wells available. The additional reservoir modelling case, with 10 wells, showed that acceptable injection and production rates could be achieved with multiple wells on a single structure.
The project also considered the broad technical requirements for the surface (injection, compression, gas conditioning) facilities required for an aquifer-based hydrogen store.
Additionally, the project engaged with relevant stakeholders as far as was possible, to inform them of the viability of aquifer storage of hydrogen as a concept, and to make them aware that licensing, consenting, regulation and economic support models would be required for aquifer storage, as well as for the counterfactual of depleted gas field storage.
Lessons Learnt
The project confirmed the key result of the SIF project – that aquifer storage of hydrogen was technically viable and that it had potential to be lower cost than the counterfactual of depleted gas field storage. However, results from reservoir modelling were less favourable than the earlier SIF-based results (although still positive), and this opens up lines of further work. Specifically, the additional reservoir modelling case, in which the storage structures were used more effectively and filled to a greater degree showed better gas recovery: this needs further examination.
Specific further work identified was:
- Refinement of relative permeability estimates for hydrogen/nitrogen/brine systems, and refinement of reservoir modelling based on new and better data
- Further reservoir modelling to assess how degree of fill affects storage efficiency, effect of additional wells on storage efficiency and achievable flow rates
- Extension of reservoir modelling to integrate lab-based findings on use of inert barrier gas
- Identification and reservoir modelling of alternative structures with more favourable storage geometry
- Fuller concept engineering and outline costing of facilities, including sources of inert barrier gas
