We use numerical simulations to investigate the possibility of enabling steel-cased wells as galvanic sources to detect and quantify spatial variations of electrical conductivity in the subsurface. The study assumes a vertical steel-cased well that penetrates electrically anisotropic horizontal layers. Simulations include a steel-cased vertical well with a finite-length thin wire of piecewise-constant electric conductivity and magnetic permeability. The steel-cased well is energized at the surface or within the borehole at an arbitrary depth with an electrode connected to a current source of variable frequency. Electromagnetic (EM) fields excited by the energized steel-cased well are simulated with an integral-equation approach. Results confirm the accuracy of the simulations when benchmarked against the whole-space solution of EM fields excited by a vertical electric dipole. Additional simulations consider a wide range of frequencies and subsurface conductivity values for several transmitter-receiver configurations, including borehole-to-surface and crosswell. The distribution of electric current along the steel-cased well is sensitive to vertical variations of electric conductivity in the host rock. In addition, numerical simulations indicate that crosswell and borehole-to-surface receiver configurations could reliably estimate vertical variations of electric conductivity within radial distances of up to 500m for frequencies below 100Hz and for average host rock electric conductivities below 1S/m⁠.

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