Geophysical borehole logging – using existing data for petrophysical and regional characterisation of claystone formations

Claystones in the deep subsurface have various barrier-effective properties for solute transport. Changes in the mineralogical composition (incl. fluids), the structure of claystones in the strict sense, as well for claystone formations in a broader sense, and their regionally different geological development cause a great variety of petrophysical, mineralogical and geochemical properties of claystone sequences. Therefore, sound knowledge of the characteristics of claystone formations is required for the different usage options of the subsurface in order to provide technical support for economic, political and scientific investigations or decisions and to ensure the safety of underground geosystems. In our study MECHTON existing data will be used and evaluated for petrophysical and further regional characterisation of the lithological expression of claystone formations. For this purpose, statistical methods are used for the interpretation of geophysical borehole measurements in order to record changes in the regional lithological characteristics and the spatial-petrophysical characteristics of a potentially repository-relevant claystone formation, the Opalinus Clay. The objectives of the study will be presented and methods for characterising the lithological and petrophysical properties of claystone on basis of logs will be discussed. The focus is: How can regionally characteristic properties of claystone be recorded from logs and transferred to a larger study area?