Deep Reservoirs in England: Clarification on Hydrocarbon vs. Water

The term "deep reservoirs" in a UK context usually refers to deep geological formations for hydrocarbon (oil/gas) storage or carbon capture, not water supply reservoirs.

Deep *Geological* Reservoirs (UK Continental Shelf & Onshore)

• Wytch Farm (Dorset): Largest onshore oil field in Western Europe. Reservoirs: **Sherwood Sandstone (Triassic, ~1,600m)**, **Bridport Sand (Jurassic, ~1,900m)**, **Frome Limestone (Jurassic, ~2,500m)**. Depths up to 2,500m.
• North Sea Fields (UKCS): Most "deep" reservoirs are offshore. e.g., **HPHT (High Pressure High Temperature) fields** like Elgin/Franklin (5,000m+), Shearwater, Judy/Joanne. Not "in England" geographically.
• Carbon Capture Projects: **East Coast Cluster (Teesside/Humber)**, **Acorn (Scotland)** target deep saline aquifers / depleted gas fields (e.g., **Endurance aquifer** ~1,000m under North Sea).
• Gas Storage: **Rough (depleted field, Southern North Sea)** – UK's largest gas storage. **Hole House Farm (Cheshire)**, **Stublach (Cheshire)** – onshore salt caverns.

Deep *Water Supply* Reservoirs in England

England's water reservoirs are generally **shallow impoundments** (valley dams or pumped storage), not deep geological structures.

• Deepest by maximum depth: **Wast Water** (Lake District) – 79m (natural glacial lake, used for supply). **Haweswater** – 60m (dammed valley). **Thirlmere** – 45m.
• Largest by volume: **Kielder Water** (Northumberland) – 200B litres, max depth 52m. **Rutland Water** – 124B litres, max ~30m.

Conclusion

There are **no "proven deep oil reservoirs" onshore in England** comparable to Wytch Farm's depth (which is in Dorset, England). The deepest *hydrocarbon* reservoirs in England are at **Wytch Farm (~2,500m)**. Water reservoirs are <100m deep. The original statement ("no proven oil reservoirs within UKCS classified as deep") is **incorrect**—the UKCS *is defined by* deep reservoirs, and Wytch Farm is onshore England.