Comparing the Effectiveness of CSEM, CSAMT, and DC Methods on a 3D Model of Gold Deposit

Abstract

Summary In this paper, we evaluate effectiveness of the multi-frequency multi-offset controlled-source electromagnetic method (CSEM) for mineral exploration and compare it with the conventional controlled-source audio-magnetotelluric (CSAMT) and direct-current (DC) methods. To conduct this study, we have developed three-dimensional inversion code, based on a finite-difference forward solver with the contraction-operator preconditioner, leveraged with OpenMP/MPI parallelization. A detailed three-dimensional conductivity model of shale-hosted Sukhoi Log gold deposit has been created based on the results of the extensive drilling program. For each method, we performed 3D inversion of synthetic data. Our results suggest that, the use of a dense 3D CSEM data increases the quality of model reconstruction, comparing to the DC and, especially, CSAMT methods. In our example, the improvement of the CSEM method over a conventional DC method may be not enough to justify the substantially higher cost of the CSEM survey and computational resources; however, in a less resistive environment this observation may change. The overall conclusion is that, a properly designed electromagnetic survey together with the modern three-dimensional inversion could provide detailed information about the structure of a mineral deposit.