Lithological interpretation of the spectral dielectric properties of limestone

ABSTRACT Limestone is a raw material used in the building and chemical industries. To guarantee good quality, it is important to investigate the limestone before mining to get information about the lithology and the mineral content. The chemical properties of rock cannot be measured directly by geophysical methods. Therefore extensive laboratory work was carried out to find relationships between the chemical, mineralogical, petrophysical and spectral dielectric properties of artificially mixed and natural limestone rock samples. A comprehensive interpretation is possible by using a complex dielectric parameter model. An interpretation scheme was developed. It is based on the fact that the specific internal surface area and the water saturation have the most influence on the spectral properties of rock at constant water salinities. These results were applied to field data measured with a borehole radar system. In order to interpret the field data directly using the results of the laboratory investigations, a new spectral interpretation method was developed. The method is focused on in‐hole and cross‐hole measurements with one receiving and one transmitting antenna. It was shown that all impurities causing an increase in the specific internal surface area compared to that of pure limestone could be detected by spectral dielectric measurements.