Estudo da aplicabilidade do método sísmico MASW na prospecção de carvão: um estudo de caso na mina de Candiota/RS

Abstract

The main coal reserves in Brazil are located in the southern region, where the most important coalfield, the Candiota mine, is inserted. The mineral research and mine planning programs of the companies operating in these coal deposits are generally restricted to drilling data and cores, despite the exploratory potential of geophysical methods in coal prospecting. This work aimed to investigate the ability of the seismic method known as Multichannel Analysis of Surface Waves (MASW) to identify coal seams in the Candiota area. The MASW method allows obtaining a layer model composed of a low-velocity (blind layer) and/or relatively thin layer (hidden layer) from the surface wave dispersion curves. The hidden and blind layer problems are pitfalls of the traditional seismic refraction method and the geological setting related to coal seams may encompass both problems. In addition, the Candiota mine has favorable conditions for applying the MASW method due to the shallow depths of the coal seams. The study was based on the analysis of synthetic seismic data generated from a 3-layer conceptual model of the Candiota deposit. The dispersion curves of the fundamental mode of the Rayleigh surface waves were generated and the effects of each of the parameters of the seismic model were evaluated, as well as the relationship between the parameters through objective function tests. A new inversion algorithm capable of obtaining the true model was implemented. The results obtained from the application of the inversion algorithm demonstrated the potential of the MASW method in identifying coal seams from S-wave profiles and proved to be a powerful tool for coal mineral exploration programs.