temperature and pressure in the svartsengi ... - Orkustofnun

1 42 GENERAL DESCRIPTION OF THE FIELDLocation of wells, faults and dikes in the Svartsengl fieldIs shown in Fig. 2 . The Svartsengi high-temperature area 1nIceland is a part of the Reykjanes geothermal system. Thegeothermal wells at Svartsengi yield 235°C water in 1983which Is 5°C less than the 240°C before production began.The salinity Is roughly two - thirds that of sea water(Thorhallsson, 1979) .2.1 Geological settingThe geological succession of the field consists of lavasuccess ions wit h intervening hyaloclastlte formations(Franzsson, 1983) . Some 20 - 40 % of the succession below800 ID depth consists of intrusions . The reservoir acquifersare predominantly controlled by intrusives and sometectonic fractures/faults. The alteration pattern can besubdivided into distinct episodes where low temperatureconditions are seen to have prevailed prior to hightemperatureconditions. Two distinct episodes of h1ghtemperatureactivity are observed, where the latter onerises separately to higher elevation. The dominant alterationpattern conforms reasonably well to the presentthermal regime in the field (Franzsson, 1983 ) .2.2 Chemical studiesChemical analysis of the geothermal water indicates about67 % sea water, but deuterium measurements give only about57 % sea water (Arnason, 1976). The difference isexplained by flashing of the water in the conceptual modelof Kj aran et 01.(1979). It 1s assumed that the rechargearea for the geothermal water is located in the vicinityof lake Kleifarvatn.