THE ICELAND DEEP DRILLING PROJECT 4.5 KM DEEP WELL IN THE REYKJANES GEOTHERMAL FIELD, IN SW ICELAND, HAS SUCCESSFULLY REACHED ITS SUPERCRITICAL TARGET

In January, the well IDDP-2 reached supercritical conditions at a depth of 4.5 km. After only 6 days of heating, the bottom hole temperature was 427°C, and fluid pressure 340 bars, with good permeability. The Iceland Deep Drilling Project is a consortium of Icelandic energy companies aiming to improve geothermal economics by producing supercritical fluids. Supercritical wells could yield an order of magnitude more usable energy than that from conventional geothermal wells because of higher enthalpy and better flow properties.

In 2009, the IDDP-1 well failed to reach supercritical conditions in the Krafla caldera in NE Iceland, after encountering rhyolite magma at only 2.1 km depth. The completed well produced superheated steam with a well head temperature of 453^oC with a flow sufficient to generate ~35 MWe. The project then moved to the southern tip of the Reykjanes Peninsula, the landward extension if the Mid-Atlantic Ridge, where we can probe an analog of the roots of a black smoker. It is unique among Icelandic geothermal systems because it is recharged by seawater, which has a critical point of the 406°C at 298 bars.

Drilling the IDDP-2 began by deepening an existing 2.5 km deep production well to 3 km depth, and then angling it towards the main upflow zone of the system, for a total slant depth of 4,659 m (4.5 km vertical depth). Total circulation losses were encountered below 3 km that could not be cured by lost circulation materials or by multiple cement jobs. Accordingly, drilling continued to total depth without return of drill cuttings. We attempted 13 core runs below 3 km depth, only half of which recovered core. The cores are basalts and dolerites with alteration ranging from lower greenschist facies to lower amphibolite facies, suggesting formation temperatures >450°C, but with low water/rock ratios.

After a perforated liner was inserted to 4,570 m, logging indicated permeable zones at 3,360 m, 4,200 m, 4,370 m, and 4,550 m depths. The deepest feed zones accepted ~30% of the injected water. Later this year we will attempt soft stimulation of this deep permeability. This is funded by the DEEPEGS program of the European Union. The drilling of the IDDP-2 was funded by HS Orka, the field operator, by the IDDP consortium, and by Statoil, the Norwegian oil and gas company. The coring was funded by ICDP and by the science program of the IDDP.