MT, CSEM and Gravity Joint Interpretation for a Geothermal Study the Vallès Basin (Catalan Costal Range, NE Spain)

Abstract

In the frame of the GEO-URBAN project, two low-enthalpy deep geothermal reservoirs in urban areas, Dublin basin (Ireland) and Vallès Basin (Spain), will be evaluated using novel geophysical exploration techniques. In particular, in the Vallès Basin (Catalan Coastal Ranges, NE Spain) the geothermal reservoir corresponds to a fractured granite bedrock. In its NE part (La Garriga-Samalús) significant geothermal anomalies were detected from geophysical surveys a few years ago. New gravity data shows a strong gravity gradient in the NE-SW VallèsVallès half-graben system and recent magnetotelluric (MT) profiles have imaged, with high resolution, the main fault (Vallès fault) of that system. To complete these data and to test novel geophysical techniques to be used in the GEO-URBAN project, a control source electromagnetic (CSEM) profile coinciding with one of the MT profiles were acquired. For the CSEM measurements, different configurations were tested (single-Long Electrode Mise À La Masse (LEMAM), double LEMAM, etc.) to explore how the source signal and/or the recorded signal could increase the signal/noise ratio in noisy environments. In this works we will present the results of these tests as well as the 2D MT-CSEM joint inversion and the MT and gravity joint interpretation.