3D modelling of controlled-source electromagnetic fields adopted to mineral prospecting



Thomas Kalscheuer


Purpose and goal

Ore exploration with electromagnetic (EM) measurements aims at ever greater depths (>1 km). The EM field is generated by an electric current in a 2 km * 2 km cable loop and is measured on the surface and in boreholes. However, computer modeling with simplifications of ore bodies as thin sheets in electrically insulating bedrock and of the varying current in the loop as a constant leads to unreliable models. We intend to improve the modeling with the spectral element method, a volumetric description of ore bodies and bedrock and an appropriate representation of the transmitter current.

Expected results and effects

We will modify an existing program that uses the spectral element method and apply the program to model synthetic models with ore bodies. The modifications shall enable an accurate description of geometrically complex ore bodies and other structures in the bedrock and describe the transmitter current in an appropriate manner. In this way, we hope to contribute to improved models of ore bodies, which in turn will lead to reduced exploration costs, more efficient drilling programs and sustainable ore mining.

Planned approach and implementation

The arrangement of the project consists largely of two phases. During the first phase, which will last for four months, we will modify our existing SEM program so that geometric descriptions of complex 3D ore bodies can be translated into volumetric descriptions suitable for SEM modelling and that the varying phase of the current along the transmitter loop is accounted for. During the second phase, we will model EM fields for a number of synthetic models of ore bodies and other bedrock structures provided by Boliden AB.