A fundamental obligation of H100 Fife development for transition to 100% hydrogen is to ensure consumers have security of supply. Therefore, it is imperative for us to identify strategic, long-term storage sites to provide assurance to regulators and consumers that a hydrogen network is compatible with our obligations. Large scale subsurface storage is one of a number of important ingredients in the larger deployment of hydrogen to support conversion of the gas network in Fife and the East Coast of Scotland.
This project will provide invaluable insight into the roadmap for development of subsurface large-scale hydrogen storage in the Balgonie field that will support the development of hydrogen in the Fife region. The project will provide a critical demonstrator methodology for the storage of hydrogen, with the ability to scale the Balgonie anticline hydrogen storage site to other regions of the UK Continental Shelf (UKCS).
Benefits
The project will provide invaluable insight into the roadmap for development of subsurface large-scale hydrogen storage in the Balgonie field that will support the development of hydrogen in the Fife region. The project will provide a critical demonstrator methodology for the storage of hydrogen, with the ability to scale the Balgonie anticline hydrogen storage site to other regions of the UK Continental Shelf (UKCS).
Learnings
Outcomes
The following summary details work completed and associated outputs as part of this early feasibility study:
- Legacy data, originally acquired in the 1980’s, comprising well logs and seismic has been digitised, reprocessed:
- Improvements are evident in all three reprocessed legacy lines; the lateral continuity of shallow reflectors is better resolved, weak reflectors are enhanced, and reflectors lying below the Midland Valley Sill are moderately enhanced. Professionally reprocessing legacy lines has improved confidence in presence and extent of the shallow target horizon.
- New seismic data has been obtained along two 2km lines in directions complimentary to the legacy lines. The acquisition methodology was deemed sensitive to ambient noise and achieved satisfactory penetration depths.
- The analysis of legacy and newly acquired data facilitated the identification of two target storage formations (one shallow at ~700m depth, one deep at ~1km depth) as potential injection sites for seasonal geological storage of hydrogen.
- Geological modelling enabled the compilation of optimistic and pessimistic (best/worst case) storage scenarios for the shallow target structure, placing the reservoir storage capacity within the range 0.1 – 10 Mt of hydrogen.
- Seismic behaviour under different injection scenarios has been modelled and a cut-off saturation of hydrogen identified, demonstrating the ability of seismic surveying to image hydrogen under safe storage/leakage scenarios for the shallow candidate reservoir.
- An investigation into historic coal mining activities in the local area was undertaken by renewable energy consultancy, Greencat Renewables, to assess the impact of historic mines on potential hydrogen storage operations. This investigation suggests only few abandoned mines are present within the study area, however, those which are present may present a leakage pathway if hydrogen is allowed to migrate to the shallow overburden.
A summary of key geological risks and uncertainties, as identified and quantified in the quantitative risk assessment, follows:
- Potential for destructive microbial activity – hydrogen acts as an electron donor for microbial processes, when injected into a porous reservoir, microorganisms may alter the composition of the storage inventory by consuming hydrogen and producing e.g., methane, and clog pore space with biofilms. Due to a lack of experimental data, there is a high degree of uncertainty regarding the potential impact of microbes on geological hydrogen storage.
- Petrophysical properties of shallow and deep target structures – certain characteristics e.g., porosity and permeability, are key for identifying target hydrogen reservoirs. Reservoir permeability is an important determining factor governing injection and withdrawal rates, whilst an assessment of porosity was achievable from legacy data, permeability data is unknown for both shallow and deep targets
- Geological heterogeneity – it has been possible to produce a high-level estimate of potential capacity, but there remain many assumptions deriving from many unknowns, including presence and nature of faults. Identifying the presence of faults is a key factor in characterising the reservoir geometry
- Seal quality/integrity – the regional geological history suggests that target caprock horizons may be fractured as a result of uplift events. Furthermore, a lack of data determining the capillary entry pressure results in a largely uncertain appraisal of seal integrity.
To address the above uncertainties, further data collection and analysis is recommended:
- A 3D seismic survey should be undertaken to assess fractures, faulting and generate more accurate capacity estimates. A full 3D seismic survey can provide necessary confidence in mapping the extent of the structure, as well as inform assessment of seal integrity and enhance mapping of faults above the spill point, all of which are risk factors that might negatively affect the success of the project. Designing such a survey should take into consideration monetary constraints in conjunction with penetration depth required (for instance vibrator trucks are more expensive to transport but provide better imaging, non-intrusive dynamite provides good imaging but takes long to drill holes resulting in more expensive survey etc.), as well as planning (for instance if the fields are inaccessible to the trucks, tramline surveying would have to be planned). Although an extensive 3D surveying strategy is not implemented in this report, experience with the 2D planning can inform such a strategy
- The drilling of a well should be undertaken to enable sample collection and assessment of seal quality (from borehole pressure test and laboratory analysis).
- Reservoir simulation is recommended to reduce uncertainty by investigating capacity and potential injection and withdrawal rates in various scenarios with varying geological parameters.
The methodology presented in this report is appropriate and suitable to be used in a later stage of this work where improved seismic imaging, as well as laboratory tests on microbial and elastic behaviour of core data can enhance the findings.
Lessons Learnt
The most significant lessons learned relate to the timescales required to manage communication. These outcomes are useful and applicable to future developmental stages of this project.
- Some delays were experienced during negotiations pertaining to liability for operations associated with practical seismic data acquisition methodology. For future phases, it is recommended that communication and engagement with relevant parties is established early to reach a consensus with causing undue delay to the project.
- Some delays were experienced during negotiations regarding access to private land. Early engagement with an experienced seismic subcontractor who is familiar with the process of planning a seismic survey and has a competent understanding of permit requirements and experience of landowner negotiation is recommended. Early engagement with stakeholders is recommended.
- Communication with local council members and local public is recommended; the support and interaction experienced in this project proved valuable and provided insight to local culture and ambitions
- Some technical lessons learned suggest that the methodology for undertaking a similar data collection exercise should: (i) account for predominant seasonal weather patterns, and how this might be accommodated in the overall project time scale, and (ii) incorporate flexibility for site specific incidentals.
