Seismic velocity, density, thermal conductivity and heat production of cores from the KTB Pilot Hole

Abstract

This paper presents a compilation of about 50000 petrophysical data measured on core samples from the Continental Deep Drilling Project (KTB) of the Federal Republic of Germany. The pilot hole provided a quasi‐continuous core profile, 4000 m in length, for measurement of several petrophysical parameters and analysis of quantitative mineral compositions, with sampling rates between 0.5 and 5 m. The variances of the data within the lithological units, which at KTB are mainly gneisses and metabasites, are greater than the experimental errors and are influenced by rock fabric, possible in‐situ variations, e.g., pressure and water content, or the small‐scale mineral composition. High space resolution measurements of velocity and density provide an example how relaxation effects, heterogeneity, and anisotropy can influence the petrophysical data. Density, thermal conductivity and the content of uranium, thorium and potassium are related to the contents of quartz and amphibole. Porosity and sound velocity, measured under normal conditions, do not match those expected from consideration of the mineral composition. Petrophysical properties measured in the field are normally representative of larger volumes than those measured in the laboratory. The extensive petrophysical investigations on KTB‐cores provide variances that are related to the representative rock units and could thus help address this scaling problem. The variances could, for example, be used for constructing velocity profiles or input parameters for modelling.