Magnetotelluric research of the Rathlin Basin
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2018-12-24Author
Delhaye, Robert
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Abstract
The IRETHERM Project was funded under SFI PI Grant 10/IN.1/I3022, with the aim of addressing uncertainties and gaps in the knowledge of potential geothermal resources within Ireland. This thesis presents geophysical exploration and research of the Rathlin Basin in Northern Ireland, an area of great interest to the IRETHERM Project as it comprises sediments of known favourable reservoir qualities in a region with elevated geothermal conditions. The magnetotelluric method (MT) was selected for exploration of the basin as MT is highly sensitive to the presence of conductors (i.e. saline-filled porous sandstones), and insensitive to resistors (i.e. the regional overburden of Paleogene flood basalts in Northern Ireland).
MT data were measured at 56 sites over a portion of the Rathlin Basin on mainland Ireland. To account for distortion and poor quality MT data, new approaches to data treatment and inversion have been applied as part of extensive inverse modelling in one- and three-dimensional frameworks; chief amongst these are the use of Tellus airborne electromagnetic data to correct static shift distortion. The recovered resistivity models successfully resolve the sedimentary bodies of interest at depths of 1000 m to 2500 m below sea level as conductors with resistivities of less than 10 Ohm.m.
The resistivity models of the mainland portion of the basin allow interpretation of a reservoir volume that can be used for geothermal resource estimation. The Indicated Geothermal Reserve estimated in this manner represents 2900 PJ of thermal energy, an amount significantly greater than estimates in adjacent sedimentary basins.