HR: 10:40h
AN: T22A-02    [Abstracts]
TI: Research Drilling on the Mid-Atlantic Ridge: IDDP Wells of Opportunity at Reykjanes, Iceland
AU: * Fridleifsson, G O
EM: gof@isor.is
AF: ISOR, Iceland GeoSurvey, Grensasvegur 9, Reykjavik, IS 108, Iceland
AU: Franzson, H
EM: hf@isor.is
AF: ISOR, Iceland GeoSurvey, Grensasvegur 9, Reykjavik, IS 108, Iceland
AU: Thorhallsson, S
EM: s@isor.is
AF: ISOR, Iceland GeoSurvey, Grensasvegur 9, Reykjavik, IS 108, Iceland
AU: Elders, W A
EM: Wilfred.Elders@ucr.edu
AF: Dept. of Earth Sciences, University of California, Riverside, CA CA 92521 United States
AB: There are some 10 new geothermal wells at Reykjanes, in SW-Iceland, being considered by the Iceland Deep Drilling Project (IDDP) as potential candidate wells of opportunity to explore for deep (4-5 km) supercritical fluids. The drill field is located where the Mid-Atlantic Ridge emerges from the Atlantic ocean at the tip of the Reykjanes Peninsula. The site is an ideal locality for a combined study on the evolution of a rifted oceanic crust and an active black smoker-type geothermal system. However, the oceanic pillow basaltic crust at Reykjanes is some 2-3 times thicker than normal ocean floor crust, which undoubtedly relates to it being part of the Icelandic Large Igneous Province. The deepest of the geothermal wells at Reykjanes is Drillhole RN-17, that was completed to 3082 m depth in February 2005. It is currently the prime candidate for deepening by the IDDP. The plan is to deepen it to 4 km in 2006, and to 5 km depth in 2007, with funding coming from Icelandic energy companies (Hitaveita Sudurnesja, Landsvirkjun and Orkuveita Reykjavikur), the Government of Iceland, the International Scientific Continental Drilling Program (ICDP) and the US National Science Foundation (NSF). The well RN-17 was drilled as a conventional production well with a 12 ¼ inch drillbit to 3082 m depth, and left barefoot, with a 13 3/8 inch production casing cemented down to 900 m. It will be flow tested this autumn. If the RN-17 well is selected by the IDDP for deepening, a 9 5/8 inch in casing will be cemented to 3081 m and drilling will be continued with an 8 ½ inch tricone bit to 4 km in the autumn of 2006. The ICDP and NSF will fund spot coring for scientific studies in this depth interval and a second flow test would be performed in winter 2007. The following autumn, a 7 inch casing would be cemented to 4 km depth and then a 5 inch retrievable liner would be inserted to support a hybrid coring system to continuously core down to 5 km depth, retrieving HQ sized core. A third flow test would be carried out in 2008-2009. In RN-17 high-grade hydrothermal alteration occurs at shallower depth than in any other well at Reykjanes. This is revealed by the presence of widespread epidote, starting at only 312 m depth, that formed at temperature of ~ 250°C. Near the bottom of the well, lower greenschist facies rock replacement of pillow basalts is locally complete, indicating alteration temperatures in the 300°C to 350°C range. On-going studies on hydrothermal minerals such as amphiboles, and on fluid inclusions, are adding details to these estimates. Direct temperature logging of the borehole has so far been hampered by an obstruction at 2100 m, a problem that is currently being dealt with. In the next few months, studies of the other wells on the Reykjanes Peninsula will be concluded and the candidate best suited for deepening will be selected. The operating company, Hitaveita Sudurnesja, is contracted to deliver some 100 MWe of new electric power to the market by mid-year 2006, a situation of primary concern at the moment. Three new production wells will be drilled at Reykjanes this autumn and early winter, adding 3 new potential wells of opportunity for IDDP to consider. As all the production wells at Reykjanes are of identical design, the technical planning for deepening a borehole to 4 km autumn 2006 is more or less independent of which of the available wells is selected for deepening.
UR: http://www.iddp.is http://www.icdp-online.org/sites/iceland/news/
DE: 3614 Mid-oceanic ridge processes (1032, 8416)
DE: 3616 Hydrothermal systems (0450, 1034, 3017, 4832, 8135, 8424)
DE: 3653 Fluid flow
DE: 5114 Permeability and porosity
SC: Tectonophysics [T]
MN: Fall Meeting 2005