Thermal conductivity models fro two-phase systems

Abstract

Measured values of thermal conductivity from crystalline and sedimentary rocks are compared with values calculated from measurements on cuttings. Various models have been suggested to describe the thermal conductivity of n-phase systems. The geometric mean model, the layer model and the dispersion model are most practical because no structural information is required. These models are tested for crystalline KTB rocks and sedimentary rocks from the north-east part of the German sedimentary basin. Cores were measured intact, as well as ground to cuttings and the matrix conductivity was determined from measurements on fragment-water mixture (two-phase system). Different structural characteristics of these systems require different models. However, in general and despite the lack of a physical argument, the geometric mean model provides the best agreement between measured and calculated values for rocks with low porosity (e.g. crystalline rocks). For sedimentary rocks with high porosity and high contrast between the thermal conductivity of the rock matrix and water thermal conductivity a good agreement for calculated and measured rock thermal conductivity was attained using a combination of layer and geometric mean model.