2D structural and thermal models in southeastern Norway based on the recently drilled Årvollskogen borehole and 2D density, magnetic and thermal modelling

Abstract

Background

We have made an attempt to understand the main mechanism which controls the conductive heat transfer in the Årvollskogen borehole. This has been done in order to determine the 2D subsurface temperature distribution within the deep-seated crystalline rocks and, therefore, to estimate the geothermal potential in the Moss area near Oslo.

Methods

An integrated 2D density, magnetic and conductive thermal analysis has been performed in order to recognise the major structural features and thermal pattern of the crystalline crust.

Results

Based on 2D density and magnetic modelling, a 2D structural model has been constructed for the Moss area. This 2D model has been used during the 2D thermal modelling. The results of the 2D thermal modelling demonstrate that a significant decrease of the Earth's surface temperatures during the last glaciations still affects the subsurface thermal field of the study area in terms of reduced temperatures within the uppermost crystalline crust. The modelled temperatures are characterised by almost horizontal isotherms without considerable vertical disturbances, reflecting the predominance of subhorizontal layering within the crystalline crust of the Moss area.

Conclusion

The 2D density and magnetic modelling, with consideration of all available geological and structural data, allows us to reveal the deep structure of the crystalline crust within the Moss area. According to the results of the 2D thermal modelling, the predicted temperatures within the upper crystalline crust are in the range of expected values for this part of Fennoscandia.