A Multi-Disciplinary Investigation of Irish Warm Springs and Their Potential for the Provision of Geothermal Energy

Abstract:

Irish warm springs are one of several target types being evaluated for their geothermal energy potential during the IRETHERM project (www.iretherm.ie, funded by Science Foundation Ireland), an academia-government-industry, island-wide assessment of the geothermal energy potential of Ireland. Forty-two warm springs and warm shallow groundwater occurrences have been recorded in Ireland; water temperatures in the springs (approx. 12-25 °C) are elevated with respect to average Irish groundwater temperatures (10-11 °C). This study focuses on warm springs in east-central Ireland found in the Carboniferous limestone of the Dublin Basin. Electromagnetic geophysical methods (CSEM and AMT) have been used in conjunction with time-lapse hydrogeological and hydrochemical analyses to determine the source of the heated waters at depth and the nature of the geological structures that facilitate the upward movement of the water. High-resolution AMT surveys at three warm spring locations in Leinster consisted of a grid of 40 soundings recorded at approximately 200 m intervals centred on each spring. A CSEM survey (25 sounding localities with 100 m spacings along two profiles) was carried out at one spring location to provide superior resolution of near-surface features. The aim of these surveys was to identify any (electrically conductive) fluid conduit systems associated with the springs and to provide an understanding of the observed association of the springs with major structural lineaments, e.g. the Iapetus Suture Zone that bisects Ireland. We present subsurface models derived from new AMT data collected at St. Gorman’s Well, Co. Meath in 2013.

Seasonal hydrochemical sampling of six warm spring locations commenced in July 2013. Data loggers installed at each location will measure temperature and electrical conductivity (15-minute sampling intervals) throughout the sampling period (July 2013 – early 2015). The hydrochemical results and the data from the logger at St. Gorman’s Well are examined here in conjunction with regional rainfall and available hydrogeological information in order to establish the nature of the relationship between the hydrological cycle and fluctuations in the hydrochemistry of the spring.