Integrated geoscience–engineering–economic assessment of intermediate-deep geothermal heat pump systems in Hot Sedimentary Aquifers: a case study from Northern Ireland.

Northern Ireland hosts extensive Permian–Mesozoic Warm–Hot Sedimentary Aquifers (HSA) including the Sherwood Sandstone Group, yet geothermal utilisation remains minimal. We present an integrated geoscience–engineering–economic assessment to show how the resource can be harnessed economically. Lithosphere heat-flow modelling calibrated to wells and depth surfaces yields temperature–depth maps to ∼2 km. Reservoir quality is constrained by core porosity–permeability trends, legacy drill-stem tests, and >100 shallow pump tests, accounting for diagenesis, fractures, and dyke/fault compartmentalisation. Coupled groundwater–heat simulations of doublets at ∼1 km evaluate sustainable flows (10–30 L s⁻¹) and thermal interference ( Δ T 10–20 °C). Techno-economics combine drilling cost estimates, industrial heat-pump (IHP) costs and performance, and O&M to derive levelised cost of heat (LCOH) and emissions estimates.

An economic “Goldilocks zone” at ∼500–1500 m (25–65 °C) enables IHP lift to 70 °C with COP ∼5–8 (rising toward ∼14 at ∼74 °C), delivering ∼1.7–2.5 MW per doublet and ∼335–493 GWh over 25 years (90% utilisation). First-of-a-kind LCOH is ∼£61–£74/MWh, competitive with gas (∼£77/MWh), while emissions fall to ∼10–54 vs ∼214 kgCO₂e/MWh. Mapping against heat-network demand highlights multiple town-to-city scale opportunities for geothermal deployment, as well as local geological risks. Prioritising shallower, lower-risk pathfinders can de-risk and scale regional rollout. The integrated assessment methodology is transferable to other regions with comparable HSA resources, such as the onshore Permo-Triassic basins of England and similar settings in continental Europe and beyond.