Feasibility Study of Controlled-Source Electromagnetic Method for Monitoring Low-Enthalpy Geothermal Reservoirs

Feasibility Study of Controlled-Source Electromagnetic Method for Monitoring Low-Enthalpy Geothermal Reservoirs

Eltayieb, M.F.M.I. (TU Delft Applied Geophysics and Petrophysics; Swiss Federal Institute of Technology Zürich)
Werthmüller, D. (TU Delft Geoscience and Engineering)
Drijkoningen, G.G. (TU Delft Applied Geophysics and Petrophysics)
Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)

Geoscience and Engineering

2023

Tracking temperature changes by measuring the resulting resistivity changes inside low-enthalpy reservoirs is crucial to avoid early thermal breakthroughs and maintain sustainable energy production. The controlled-source electromagnetic method (CSEM) allows for the estimation of sub-surface resistivity. However, it has not yet been proven that the CSEM can monitor the subtle resistivity changes typical of low-enthalpy reservoirs. In this paper, we present a feasibility study considering the CSEM monitoring of 4–8 Ω·m resistivity changes in a deep low-enthalpy reservoir model, as part of the Delft University of Technology (TU Delft) campus geothermal project. We consider the use of a surface-to-borehole CSEM for the detection of resistivity changes in a simplified model of the TU Delft campus reservoir. We investigate the sensitivity of CSEM data to disk-shaped resistivity changes with a radius of 300, 600, 900, or 1200 m at return temperatures equal to 25, 30, …, 50 °C. We test the robustness of CSEM monitoring against various undesired effects, such as random noise, survey repeatability errors, and steel-cased wells. The modelled differences in the electric field suggest that they are sufficient for the successful CSEM detection of resistivity changes in the low-enthalpy reservoir. The difference in monitoring data increases when increasing the resistivity change radius from 300 to 1200 m or from 4 to 8 Ω·m. Furthermore, all considered changes lead to differences that would be detectable in CSEM data impacted by undesired effects. The obtained results indicate that the CSEM could be a promising geophysical tool for the monitoring of small resistivity changes in low-enthalpy reservoirs, which would be beneficial for geothermal energy production.

low-enthalpy reservoirs
TU Delft campus geothermal project
geothermal energy
sustainable utilization
CSEM monitoring
feasibility study

http://resolver.tudelft.nl/uuid:abe04394-053f-44fc-9a79-52fe14bd1c22

https://doi.org/10.3390/app13169399

2076-3417

Applied Sciences, 13 (16)

Institutional Repository

journal article

© 2023 M.F.M.I. Eltayieb, D. Werthmüller, G.G. Drijkoningen, E.C. Slob