Review of the Heat Flow Mapping in Polish Sedimentary Basin across Different Tectonic Terrains

Jacek Majorowicz

doi:10.3390/en14196103

Abstract

Heat flow patterns variability related to the age of the consolidated, and differences in, sedimentary thickness of the sedimentary succession are important constraints upon the thermal state of the sedimentary fill and its geothermal energy potential. Heat flow in the Permian basin of central Europe varies from a low of 40 mWm−2 in the Precambrian Platform to 80 mWm−2 in the Paleozoic basement platform influencing temperature for geothermal potential drilling depth. Continuity of thermal patterns and compatibility of heat flow Q across the Permian basin across the Polish–German basin was known from heat flow data ever since the first heat flow map of Europe in 1979. Both Polish and German heat flow determinations used lab-measured thermal conductivity on cores. This is not the case for the recent heat flow map of Poland published in 2009 widely referenced in Polish geological literature. Significant differences in heat flow magnitude exist between many historical heat flow maps of Poland over the 1970s–1990s and recent 21st century patterns. We find that the differences in heat flow values of some 20–30 mWm−2 in Western Poland exist between heat flow maps using thermal conductivity models using well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivity versus those measured on cores. These differences in heat flow are discussed in the context of resulting mantle heat flow and the Lithosphere-Asthenosphere Boundary depth modelled differences and possible overestimates of deep thermal conditions for enhanced geothermal energy prospects in Poland.

Highlights

The knowledge of heat flow Q, (Q = λ*gradT, where λ is thermal conductivity and gradT is geothermal gradient of temperature T) is crucial for the prediction of deep geothermal resources below maximum depth of temperature logs and the estimate of geothermal energy potential of sedimentary basins and potential of the enhanced geothermal systems (EGS) [1,2,3,4]
The Central European transition from the Precambrian platform to younger tectonic basement Caledonian, Variscan, Alpine terrains shows significant differences in crustal structure, age (Figure 1a,b), [5,6] and magnitude of Q, especially evident in Poland where all these differing tectonic elements are present under sedimentary succession reaching as high as 13 km [7] in the axis of the Polish–German basin
We cannot exclude that the Moho heat flow calculated in [16] and here (Figure 8), which indicates “warm” lithospheric mantle, can be an artefact, resulting from underestimation of radiogenic heat generation in the crust A as we do not consider the volume of rhyolites/granites related to the Permian igneous province which is not known

Summary

Introduction

The knowledge of heat flow Q, (Q = λ*gradT, where λ is thermal conductivity and gradT is geothermal gradient of temperature T) is crucial for the prediction of deep geothermal resources below maximum depth of temperature logs and the estimate of geothermal energy potential of sedimentary basins and potential of the enhanced geothermal systems (EGS) [1,2,3,4]. I will focus on apparent differences in magnitude of some 20–30 mWm−2 between Polish heat flow maps. The context of such discrepancy in surface heat flow upon heat flow at the consolidated basement and mantle heat flow will be reviewed. The estimates of depth of LAB (Lithosphere-Asthenosphere Boundary) from the observed differing heat flow maps of Poland and seismological constraints on the LAB boundary will be reviewed and discussed

The Tectonic Background

Historical Evolution of Heat Flow Maps of Poland—Materials and Methods

Findings

Discussion

Conclusions