temperature and pressure in the svartsengi ... - Orkustofnun

304 INDIVIDUAL WELLSThere have been drilled 12 wells In the high temperaturefield of Svartsengi (Fig. 2). The temperature changes withrespect to time and the boiling conditions are discussedIn this chapter.Well SG -l Is a shallow well with relatively low tempera ­ture. It was drilled for the purpose of using its water Indrilling the other wells. The depth of the well Is 250 mand the temperature is less than 50°C. A peak in tempera -ture Is measured at the ground water level of 25 m depth(Fig. 10). This indicates a considerable horizontal flowIn this shallow acquirer, most probably a run off from themain geothermal field (Stefansson and Stelngrimsson.1981). The maximum temperature measured In this well is47°C at the bottom at 250 m depth. The temperature at thisdepth in the nearest well (SG-5) is about 200°C, showingthe abrupt demarcation of the geothermal system at thislocation and depth. The cold ground water reaches down tolittle more than 200 m depth, but beneath that the temperatureincreases more steeply, which might be a sign that ahotter fluid can be found at greater depth at thislocation.The pressure gradient in the well is hydrostatic (~ig. 11)corresponding to a mean density of 1022 kg/~. The densityof seawater at 35°C is 1021 kg/m 3 .Well SG-2 is a shallow well (about 250 m deep) located inthe area where the geothermal system is vented to theatmosphere. It was initially boiling up to at least 115 m.Now It Is boiling from top to bottom. Unlike many otherwells ofincreasedresult ofthe Svartsengi geothermal field, this well hasin temperature with time (~ig. 12). This is theincreased boiling In the top of the reservoirdue to the pressure drawdown In the reservoir. The boilinglevel Is continuously migrating to larger depths, whichresults In higher pressure and temperature of the steamcap in the top of the system. Between 1976 and 1981 the