Study identified geothermal aquifers at city of Dublin in Ireland

O'Connell Street, Dublin, Ireland (source: Commons, Wikimedia)
Alexander Richter 9 Dec 2019

An article published recently shares details about the findings of the study that see geothermal potential beneath the city of Dublin in the Republic of Ireland.

A geothermal energy assessment project named IRETHERM (IREland’s geoTHERMal potential) led by the Dublin Institute for Advanced Studies (DIAS) in collaboration with academic, government and industry partners conducted a study on the geothermal potential for Ireland. With participation of the Geological Survey of Ireland, IRETHERM was funded by Science Foundation Ireland under SFI grant number 10/IN.1/I3022.

IRETHERM aimed to develop a strategic and holistic understanding of Ireland’s geothermal energy potential through integrated modelling of new and existing geophysical and geological data.

The project studied eight different “types” of geological environments to identify those that may host geothermal resources: deep aquifers or hot, dry rock. A comprehensive suite of crustal rocks have been collected across Ireland and chemically analysed to determine their capacity for generating radiogenic heat.

New electromagnetic and gravity data were acquired in the type areas. High resolution geophysical modelling tools will be developed for imaging aquifers and granitic bodies to depths of 5 km. These innovative software tools allowed joint modelling of electromagnetic and other existing geophysical data.

Results of the studies were published in a paper recently. It presents modelling of the geophysical data from the Newcastle area, west of Dublin, Ireland within the framework of the IRETHERM project.

IRETHERM’s overarching objective was to facilitate a more thorough strategic understanding of Ireland’s geothermal energy potential through integrated modelling of new and existing geophysical, geochemical and geological data.

The Newcastle area, one of the target localities, is situated at the southern margin of the Dublin Basin, close to the largest conurbation on the island of Ireland in the City of Dublin and surrounds. As part of IRETHERM, magnetotelluric (MT) soundings were carried out in the highly urbanized Dublin suburb in 2011 and 2012, and a description of MT data acquisition, processing methods, multi-dimensional geoelectrical models and porosity modelling with other geophysical data are presented.

The investigated area below Newcastle can be divided into two domains of different depths, formed as depth zones. The first zone, from the surface down to 1–2 km, is dominated by NE-SW oriented conductors connected with shallow faults or folds probably filled with less saline waters. The conductors are also crossing the surface trace of the BNF. The second depth domain can be identified from depths of 2 km to 4 km, where structures are oriented along the BNF and the observed conductivity is lower. The deeper conductive layers are interpreted as geothermal-fluid-bearing rocks. Porosity and permeability estimations from the lithological borehole logs indicate the geothermal potential of the bedrock, to deliver warm water to the surface. The fluid permeability estimation, based on Archie’s law for porous structures and synthetic studies of fractured zones, suggests a permeability in the range 100 mD–100 D in the study area, which is prospective for geothermal energy exploitation.

Geophysical Journal International, ggz530,

Source: Geophysical Journal International