The state-of-the-art in 3D orebody modelling: a case study of KDC East gold mine, South Africa

Abstract

The state-of-the-art in 3D modelling of the structurally complex orebody begins with (1) 3D seismic imaging, (2) horizon picking, (3) data conditioning, (4) fault detection, (5) fault-horizon projection, (6) data integration, and (7) statistical analysis. A variety of 3D seismic imaging and interpretation techniques have played an integral part in improving the quality of the orebody modelling for deep mineral mining industries. This paper presents the world-class model of the VCR orebody across KDC East gold mines (Witwatersrand Basin) as derived from the 3D seismic reflection data, underground geological mapping, and exploration boreholes. The re-processing of the 1994 seismic data using advanced seismic imaging algorithms, such as Kirchhoff prestack time migration (KPSTM), has increased the signal-to-noise (S/N) ratio of the data. The technique has proven to be effective in imaging the steeply horizons and structures (e.g., faults, dikes) in the areas characterized by major lateral velocity variations (such as the Witwatersrand Basin), compared to finite-difference poststack migration (PSDM). The seismic attributes such as dip, dip-azimuth and edge detection have been successfully applied in delineating complex structural architectures, such as multiple fault bifurcations, intersecting and cross-cutting faults that cannot be interpreted using conventional picking on seismic sections. Consequently, these complex structures and their geometries were modeled and projected to the VCR horizon using the advanced modelling techniques derived from Non-Uniform Rational B-spline (NURBS). The computed compartment maps from the integrated data have resolved orebody compartment sizes below the dominant seismic wavelength (~124 m). Using these different techniques, a geologically reasonable 3D structural orebody model was developed. The model could be used for future mine planning and designs.