| Title | Correlating Magnetotelluric Sounding With Borehole Data for Geothermal Parameter Characterization in Sulitjelma Area, Norway |
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| Authors | Beka, Birkelund, Smirnov |
| Year | 2013 |
| Conference | European Geothermal Conference |
| Keywords | Correlation, clustering, magnetotellurics, resistivity, natural gamma ray, heat production, geothermal resource |
| Abstract | Some recent subsurface thermal studies in Norwegian crystalline basement have indicated a reason to expect temperature greater than 150 °C within a 5km depth range, especially in areas where there is high radiogenic granite or significant sediment coverage. However, present knowledge on subsurface temperature and other geothermal characteristics is mostly constrained by the depth of available scientific boreholes, and is subjected to large geological correction as well as extrapolation over many kilometers. On the other hand, the passive electromagnetic method of magnetotellurics (MT) is sensitive to local subsurface resistivity contrasts and is easy to deploy. Based on orthogonal electric and magnetic fields measured at the surface, MT enables to construct conductivity profiles of the subsurface up to a large depth. MT is appealing in geothermal exploration due to the effect of geothermally important properties on electrical properties of petrophysics. In this paper, we construct a lithological map from the gross deep borehole natural gamma ray (NGR) measurement through unsupervised classification, estimate the heat production of the identified classes individually and correlate the results with 1D interpretations of a broadband MT measurements. As a test project, the method is tried out to assess the geothermal potential of Sulitjelma, part of the Central Scandinavian Caledonedes north of the Arctic boundary. |