Electromagnetic borehole fields in a layered, dipping-bed environment with invasion

Abstract

Electromagnetic modeling of an induction sonde (1-100 kHz) in a dipping-bed environment is a 3-D problem. The method accounts for transverse magnetic mode (TM) coupling arising from surface charges deposited by eddy currents passing through bed boundaries. If borehole and invasion effects are included, the only available rigorous analytical methods are finite elements or finite-difference techniques. These approaches require large-scale computing. In contrast, the described method is approximate and is an extension of the geometrical-factor theory and Born approximation. The method uses a new electric field vector integral equation. Results for dip angles up to 60 degrees for variational results and eigenfunction solutions for the case of no borehole or invasion show good agreement. -from Authors