Thermal conductivity in relation to porosity and geological stratigraphy

Abstract

Thermal conductivity of rocks is one of the most important parameters in thermal studies of geothermal features. The best estimation of heat quantity and heat flow of geothermal systems depends on accurate calculations of thermal conductivity in porous media. Several authors have studied thermal conductivity and have found it to be connected to several parameters including rock porosity, the most influential parameter. The aim of this project is to analyse small scale variations in thermal conductivity in context with porosity and the stratigraphic column. High resolution temperature logs were made for this project in well HS-36 located in Reykjavík, SW-Iceland. A detailed study focusing primarily on the depth between 400 and 600 m was completed. The temperature gradient was studied where the vertical heat flow is constant and does not have a horizontal component. The results obtained show that thermal conductivity decreases with increasing porosity and the relationship between thermal conductivity and porosity is close to the harmonic average theoretical equation. The relationship between resistivity and porosity was also studied. The results from HS-36 were relatively close to a theoretical curve when a scale factor was applied.