Stratigraphy, alteration mineralogy, permeability and temperature conditions of well IDDP-1, Krafla, NE-Iceland

Abstract The stratigraphy, alteration mineralogy and temperature conditions in well IDDP-1 were established through drill cutting analyses and geophysical logs. The stratigraphy comprises basaltic lava and hyaloclastite sequences extending to 1362 m succeeded by an intrusive complex. Intrusions comprise basaltic dykes, dolerites and below 2020 m, granophyre and felsites. Rhyolitic magma was intersected below 2100 m. Alteration reflects cooling in the upper ∼1500 m of the reservoir. Below 1600 m temperature follows the boiling-point-depth curve. Alteration minerals are scarce in vicinity to the feed zone at 2035–2080 m correlating with a superheated steam zone above the magma, but estimated bottom-hole temperature is ∼500 °C.