Repurposing of idle wells from the oil and gas industry into deep borehole heat exchangers
- 1Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems (IEG), CC121 Exploration and Simulation, Bochum, Germany (nora.koltzer@ieg.fraunhofer.de)
- 2ExxonMobil Production Deutschland GmbH, Hannover, Germany
- 3Department of Electrical and Thermal Energy Systems, Brandenburg University of Technology Cottbus-Senftenberg BTU, Cottbus, Germany
- 4RWTH Aachen University, Computational Geoscience, Geothermics and Reservoir Geophysics (CGGR), Aachen, Germany
The motivation behind this study is to repurpose idle wells from hydrocarbon exploration and production to provide heat for end users being located near the idle well. This is possible by prolonging the value-added chain of idle wells from the gas and oil industry by re-completion as geothermal closed loop wells. This is the most efficient way to produce green energy without drilling new wells by saving the carbon emission and costs of building a new geothermal well.
With this feasibility study we quantify the concept of re-completing idle wells in the North German Basin (NGB) into deep coaxial borehole heat exchangers. With numerical models of two typical geological settings of the NGB and two different completion schemes it was possible to simulate the thermal performance over a lifetime of 30 years. The calculated heat extraction rates are in the range of 200 kW to 400 kW with maximum values of up to 600 kW. This is higher than from already installed deep borehole heat exchangers. Sensitivity analyses demonstrate that flow rate, injection temperature and the final depths of re-completion are the most impacting parameters of thermal output determination.
In the final project stage, the heat demand around two exemplary boreholes was mapped and possible heating networks were simulated. The initial production costs for heat are comparable to other renewable energy resources like biomass and - depending on distance between source and user – well competitive against current gas prices. These calculations highlight not only the environmental valuable motivation behind the concept of repurposing idle wells but could also save capital expenditures for the geothermal industry.
Using a vacuum isolated tubing characterized by very low thermal conductivity of 0.02 W/(m*K), would make it possible to use the geothermal resources even more efficiently from idle wells. This project highlights the major potential of usable geothermal resources in already installed deep wells. The application has almost no geological risk, as the concept is independent of reservoir uncertainties like permeability and reservoir fluid composition, drilling risks are skipped completely and it is realizable at any location.
How to cite: Koltzer, N., Schoenherr, J., Sporleder, M., Steininger, S. A., Halm, M., Kettermann, M., and Wellmann, F.: Repurposing of idle wells from the oil and gas industry into deep borehole heat exchangers, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9352, https://doi.org/10.5194/egusphere-egu23-9352, 2023.
