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

Journal Article (2023)
Author(s)

M.F.M.I. Eltayieb (TU Delft - Applied Geophysics and Petrophysics, ETH Zürich)

D. Werthmüller (TU Delft - Geoscience and Engineering)

G. Drijkoningen (TU Delft - Applied Geophysics and Petrophysics)

E.C. Slob (TU Delft - Applied Geophysics and Petrophysics)

Research Group
Applied Geophysics and Petrophysics
Copyright
© 2023 M.F.M.I. Eltayieb, D. Werthmüller, G.G. Drijkoningen, E.C. Slob
DOI related publication
https://doi.org/10.3390/app13169399
More Info
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Publication Year
2023
Language
English
Copyright
© 2023 M.F.M.I. Eltayieb, D. Werthmüller, G.G. Drijkoningen, E.C. Slob
Research Group
Applied Geophysics and Petrophysics
Issue number
16
Volume number
13
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Abstract

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.