Terrestrial Heat Flow Density in the Zagreb – Karlovac Area

Miron Kovačić

doi:10.4154/gc.2014.10

Abstract

AbstractWithin the project „Geothermal map of the Republic of Croatia”, initiated in 2007, the wide area of the cities of Zagreb and Karlovac has been investigated (approx. 5500 km2). In this work the results of investigation of the Terrestrial Heat Flow Density (THFD) are presented. These include the results of computation of THFD at locations of boreholes and maps of THFD of the investigated area. It has been determined that THFD at the boreholes’ locations varies in a wide range and values differ from those previously published. In the most part of the investigated area THFD is in accordance with mean values for the continental areas. Two positive (Zagreb and Karlovac) and one negative (Žumberak) geothermal value can be singled out. The map of THFD, as presented in this work, is different from the previously published maps and is considerably more precise. It is determined that hydrogeothermal sources in the investigated area are not associated with THFD in the above mentioned areas.

Highlights

In the last twenty years there has been increasing interest in the geothermal potential in Croatia, as this has become an attractive energy resource
Published data sources include: the Heat Flow Map of Europe ČERMAK and RYBACH (1979) which displays the territory of Croatia; the Geothermal Atlas of Europe (HURTIG et al, 1992) shows a map of Terrestrial Heat Flow Density (THFD), including the territory of Croatia; RAVNIK et al (1995) presented the Heat Flow Density Map of Slovenia of the area which partially includes the territory of Croatia; the THFD map of Croatia
Over most of the investigated area THFD ranges between 50 and 70 mWm-2 which is in accordance with the average values for the continental areas

Summary

Introduction

In the last twenty years there has been increasing interest in the geothermal potential in Croatia, as this has become an attractive energy resource. In order to compute THFD at a given location it is necessary to acquire more knowledge on the changes in heat transfer in a conductive regime through the geological formations – geothermal gradient (G), depth of formation at particular location, and coefficient of thermal conductivity of individual formations. This information is acquired by measurements, data processing and studying of materials from deep boreholes.

Methods

Results

Discussion

Conclusion