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Abstract

In the past 10 to 15 years, the interest in the deep subsurface of the North German basin and its oil and gas potential has grown considerably . Geophysical studies on the geologicaltectonic structure of the deep basin, its genesis and development as well as the time-space distribution of hydrocarbons have been concentrated primarily on reflection seismics. However, at depths below the prominent Zechstein-base reflector, few structural details are available. Besides other potential methods providing information at this depth range, e.g. magnetics and gravity, the magnetotelluric method is well suited to investigate the electrical conductivity distribution. Since 1993, magnetotelluric surveys (Fig. 1) focused on hydrocarbon exploration have been performed in Northern Germany by the Federal Institute for Geosciences and Natural Resources (BGR) in cooperation with the Institute of Geophysics of the University of Mtinster (HOFFMANNet al. 1998). This not very often used hydrocarbon exploration method is based on the observation that the electrical properties of highly mature source rock drastically change from poor to extremely good conductivity due to the pre-graphitization of organic matter when the metaanthracite stage of coalification is reached (JODICKE 1991). Using the magnetotelluric method, such conductors may be readily localized at large depths.