Re-using depleted oil and gas fields—and their existing wells—for underground hydrogen (H₂) storage is moving from concept to careful evaluation. Teams at the University of Edinburgh and partners have produced some of the clearest, openly accessible evidence on the opportunity and the risks. Here’s a concise, source-backed synthesis you can rely on.
Why depleted fields and legacy wells?
Depleted gas fields offer proven traps, known petrophysics, and existing infrastructure. That combination makes them attractive candidates for seasonal H₂ storage to balance wind- and solar-driven swings in the UK’s energy system. Edinburgh’s HyStorPor programme summarises the case for porous-rock (reservoir) storage and outlines how engineering, geochemical, and microbial factors govern feasibility and performance.
What the Edinburgh work actually shows
System-scale potential (screening & capacity)
HyStorPor’s 2023 synthesis estimates an aggregate technical storage capacity of ~2,662 TWh across UK gas fields and argues that only a small number of offshore fields could, in principle, balance UK domestic heating’s seasonal demand if converted for H₂ storage. Those are headline screening figures—not field development plans—but they set the scale for what porous-rock storage could deliver if site-specific risks are managed.
Complementing that, a University of Edinburgh PhD (Scafidi, 2022) develops methods and simulations for seasonal H₂ storage in depleted gas fields, focused on the UK. It treats practical issues like cushion gas, injection/withdrawal deliverability, and purity management—key inputs if you plan to repurpose existing wells.
Site-specific reality checks (Cousland field, near Edinburgh)
A 2024 geological re-evaluation of the Cousland onshore gas field (Midland Valley, ~15 km SE of Edinburgh) concluded that available data are insufficient and the site does not currently meet criteria for safe H₂ storage. The value of the study is its candour: not every depleted field is suitable, and legacy data quality, caprock confidence, and well status can be disqualifying without new evidence.
Wellbore integrity and materials (critical for reusing old wells)
Hydrogen must move through cemented and cased wells, so materials performance is pivotal. Lab work led from Edinburgh (Aftab et al., 2023) tested representative wellbore cements under North Sea-like conditions and, under those experimental parameters, found no geochemical or structural degradation from H₂ exposure—a positive (but bounded) result that informs material selection and integrity assessments.
Engineering the gas mix (cushion vs working gas)
Recent Edinburgh-affiliated modelling explores using CO₂ as cushion gas to improve H₂ storage economics and purity by limiting mixing surfaces between cushion and working gases. This work targets laterally extensive reservoirs like those in the Southern North Sea and speaks directly to field-scale design choices for repurposed assets.
Industry collaboration
A University of Edinburgh–CGG collaboration launched in 2022 to characterise heterogeneity in depleted fields and assess cushion-gas strategies and site selection—the sort of upstream subsurface work needed before any legacy wells are reused at scale.
What this means for re-using existing wells
- No “copy-paste” conversions: Even with strong national capacity potential, suitability is field-by-field. Cousland shows that legacy data gaps and uncertain seals can halt plans until new subsurface evidence is gathered.
- Integrity first: Positive cement findings are encouraging but bounded by test conditions; real wells vary in cement chemistry, ageing, defects, and steel metallurgy. Re-use plans need full integrity campaigns (bond logs, pressure tests, materials audits) and often recompletions.
- Gas management matters: Cushion-gas choice and field geometry drive deliverability and H₂ purity. Modelling evidence suggests designs that minimise mixing to protect offtake quality—vital for power, industrial, or grid-blend end uses.
- Regulatory & data discipline: Transparent datasets, robust subsurface models, and staged pilots are prerequisites to meet UK regulatory expectations for storage safety and environmental protection (implied throughout the Edinburgh/HyStorPor body of work).
A pragmatic takeaway for Scotland and the UK
- The opportunity is large at system scale (few suitable fields could shift the seasonal balance), but conversion is not automatic and demands rigorous screening.
- Academic–industry programmes centered in Edinburgh are already filling key evidence gaps—from capacity modelling and cushion-gas strategies to cement integrity—and publishing results that decision-makers can scrutinise.
- Legacy wells can be assets or liabilities; whether they’re reused or re-drilled hinges on measured integrity, materials compatibility, and long-term monitoring plans—proved by site-specific investigations like Cousland.
Key open-access references
- HyStorPor storage briefing (University of Edinburgh). blogs.ed.ac.uk
- HyStorPor 2023 brochure (system-scale UK capacity & screening). blogs.ed.ac.uk
- Scafidi (2022) PhD thesis: Hydrogen Storage in Depleted Gas Fields: Capacity and Performance. ERA
- Butler & Underhill (2024): Cousland field evaluation (Midland Valley of Scotland). ukogl.org.uk
- Aftab et al. (2023): Geochemical Integrity of Wellbore Cements during geological H₂ storage. ACS Publications
- CGG–University of Edinburgh collaboration on subsurface H₂ storage (news release). viridiengroup.com
- Williams et al. (2025): H₂ storage with CO₂ cushion gas—reservoir-scale mixing & purity modelling.