Borehole radar system analysis in stratified geological systems applied to imaging of platiniferous reefs in the bushveld igneous

[摘要] The imaging of platiniferous reefs in the Bushveld Igneous Complex (BIC) is of greateconomical and sociological importance. Borehole radar technology has beenidentified as a viable mapping tool to be used in day-to-day mining operations, but acritical assessment has to be made on the feasibility of this postulation.The system analysis made of the borehole radar deployed in the BIC is presented inthis dissertation. The analysis is done using a specific example - the GeoMoleborehole radar system.A novel procedure, based on the basic theory of electromagnetic radiation andpropagation, is proposed by which the entire physical radar system can becharacterized. The power transmitted by an unconventional borehole-deployedtransmitter is estimated by a sequence of free space measurements, numericalsimulations and theoretic derivations and approximations. Antenna transfer functions(magnitude and phase) are numerically simulated for a variety of deploymentconfigurations. The total system transfer function of the receiver analogue and digitalchain is determined. This enables the calculation of the radar's performance figuresnecessary to determine the applicability of the radar in a specific geological setting.A radar system is only complete when considered in its environment. The BIC is astratified system of numerous rock layers. An in-depth study is done on thepropagation of radiowaves in stratified lossy media. Only the case for non-magneticmedia is discussed in this dissertation. The developed theory is used to predict thesystem response to a typical transmitted radar pulse in the UG1 - UG2 stratigraphy ofthe BIC, determine the maximum detection range of reef horizons and estimate thereflectivity of the reefs.Resolution is one of the key parameters that determine the performance and accuracyof imaging. An algorithm is proposed, developed and tested by which the resolutionof the system is increased and overlapping echoes become resolvable.Even though some of the techniques are developed with a specific system in mind, theapplicability of the concepts and algorithms is universal.

[发布机构] Stellenbosch University