Borehole Geology and Alteration Mineralogy of Well NWS-4, Mt.Sabalan Geothermal Field, NW-Iran

Abstract

Drilling of well NWS-4 was finished in 29 March 2004 during 98 day at western side of Sabalan Volcano in Northwest of Iran. Refer to MT results, there is <4?m anomaly beneath the western side of Moil valley with about 500m thickness. Lithology of the well consists of Lava flows and volcanic ash and hypabyssal rocks in the lower parts of the well. Surface deposits are unaltered and in lower parts, secondary hydrothermal minerals mainly consist of clays, Silica, Pyrite and in lower parts and quartz, clay, magnetite and epidote in high temperature zone. Heat up test in 4rth day survey shows the maximum temperature at T.D (211oC) and also behind of production casing there is high enough (about 205oC). After 1612 m depth there is tectonized permeable zone due to encountered faults. At 1220m depth and 1620m there are 2 cooler zones created by faults. At 950m depth there is a clear increase in high temperature hydrothermal minerals as epidote that 4th heat up test emphasized it. Correlation between measured temperature and alteration temperature indicates that alteration temperature is close to measured temperature at maximum of about 230oC in interval 950-1170m depth.