Comparative Study of an Electro Seismic Investigation of the BR52 and BR53 Geothermal Wells Located on the Ohaaki Geothermal System Near Taupo, NZ

Abstract

The BR52 and BR53 geothermal well site in the Ohaaki Geothermal System located near the town of Taupo in New Zealand was chosen for an Electro Seismic comparative study. The aim of the study is to determine the effectiveness of electro seismic geophysical methods on evaluating aquifer permeability in deep earth geothermal systems. In order to achieve this, a profile of electro seismic soundings were done on a blind test site around the vertically drilled Test BR52 and BR53 geothermal wells. This electro seismic data was analysed using the ATS Geothermal Geo- Suite tools, for aquifer permeability tomography, electro seismic coupling coefficient tomography, geological interface tomography, geological fracturing tomography, change in absolute gradient responce, change in total gradient responce, temperature estimation, geothermal resource potencial and fractures assocaited with geothermal reserves. An interpretation of the depth of the main permeable aquifers, site geolocial model, geothermal resource probability and secondary permability assocaited with geothermal reserves around the test wells was completed. This data was then compared to the known geological, hydrological, lithological and temperature for the test geothermal wells. There is a good correlation between the interpreted electro seismic permeable levels and the known permeable levels in the wells, interpreted from temperature and fluid velocity profiles by the owners of the well, Contact Energy, prior to the blind study. The correlation is good for both the shallow aquifers and deep ones to a depth of 1150m.