Repurposing onshore hydrocarbon wells as deep borehole heat exchangers: A comprehensive modelling study for the UK

Onshore hydrocarbon wells offer geothermal energy potential. By converting liabilities into sustainable energy assets, well operators benefit from postponed decommissioning costs while geothermal system installation benefits from reduced drilling requirements. The study herein builds upon previous investigations into the theoretical extraction capacity from abandoned wells in the UK using closed-loop co-axial deep borehole heat exchanger (DBHE) systems. Multi-criteria screening analysis identified 48 vertical onshore hydrocarbon wells in the UK with potential suitability for repurposing as DBHEs. Bottom-hole temperature estimates at these sites are used to select ten wells for detailed numerical DBHE modelling in OpenGeoSys. In order of DBHE thermal power extraction potential over a 25-year operational lifetime, the ten candidates were: Kirby Misperton 8, Malton 4, Gainsborough 2, Crosby Warren 1, Wytch Farm F1, Gainsborough 1, Fiskerton Airfield F1, Stainton 1, Corringham 5, and Reepham 1. The candidate well with the highest thermal yield was identified as KM8 — an abandoned gas well in the Kirby Misperton gas field in north-east England – averaging 198 k W t h over a 25-year lifetime with constant flow rate. The modelling is extended to load-following control of KM8 suggesting that the monovalent DBHE system capacity could meet the heat demands of a modelled agricultural greenhouse with 3000 m 2 footprint. While DBHE repurposing could turn existing liabilities into green assets, the UK’s most attractive candidate site can seemingly only provide heating to a moderately-sized greenhouse without the addition of significant surface infrastructure build out such as cascade heat pump systems. This highlights the importance of integrating single-well technology within a multi-valent system complete with thermal energy storage to optimise efficiency and performance. The pre-feasibility study presented herein demonstrates a screening process and modelling approach which can be applied to abandoned onshore wells in jurisdictions outside the UK. • Performed a screening analysis to identify onshore hydrocarbon wells in the United Kingdom to be targetted for repurposing as deep borehole heat exchangers. • Modelled the 25-year thermal power capacity of the candidate repurposing sites with the highest expected bottom-hole temperature. • Demonstrated through computer-based modelling the capacity of a repurposed hydrocarbon well to function as the sole heat supplier to a commercial-scale agricultural greenhouse.