| Title | Volcano-Tectonic-Geothermal Interaction at the Hengill Triple Juncation, SW Iceland |
|---|---|
| Authors | Hardarson, B. S.; Einarsson, G. M.; Franzson, H.; Gunnlaugsson, E. |
| Year | 2009 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Iceland; Hengill; Hellisheidi; Central Volcano; Volcanic; Intrusion; Triple Junction; Geothermal; High-Temperature Field; Alteration; Aquifer; Fault; Tectonic |
| Abstract | The active volcanic zones in Iceland are characterized by high heat flow and extensive geothermal activity. The high-temperature geothermal areas are mainly confined to volcanic systems, in particular central volcanoes, and are subject to strong tectonic control. The heat source is considered to be magmatic associated with shallow level crustal magma chambers or dyke swarms. The prevalent permeability, in general, seems to be affiliated with intrusions and sub-vertical faults/fractures. The Hengill central volcano, which is seismically very active, hosts one of the most powerful geothermal fields in Iceland. Structurally it is dominated by NE-SW striking faults which are, however, in places intersected by easterly striking features which may play a role in the permeability of the geothermal reservoir. The Hengill low resistivity area covers about 112 km2 and is located at a triple junction where two active rift zones meet a seismically active transform zone. At present Reykjavik Energy is constructing 300 MWe and 400 MWt power stations at the Hellisheidi high-temperature field, which is situated SW of the Hengill central volcano. Reykjavik Energy has to date drilled 46 deep (1300-3300 m) exploration and production wells and 12 reinjection wells into the Hellisheiði field. Here we present new well data (cutting analyses and geophysical borehole logs) and regional geophysical surveys from the Hellisheidi geothermal field focusing on the western margin of the field. The data are used in conjunction with apparent aquifers to evaluate the relationship between permeability and geological structures. |