temperature and pressure in the svartsengi ... - Orkustofnun
temperature and pressure in the svartsengi ... - Orkustofnun temperature and pressure in the svartsengi ... - Orkustofnun
76In Fig. 3. Significant temperature changes were notrecognized until 1983 In the main liquid part of thereservoir I.e. beneath 600 m depth. However as hasbeen shown In the previous chapters. there were signs ofsmall changes prior to 1983. These changes In temperaturewere not signIficantly larger than the absolute accuracyof the instruments used for temperature measurements.Therefore, significant temperature changes 1n thereservoir could not be detected until 1983.At present. the response of the Svartsengi reservoir toutIlizatIon has been both a decrease In pressure andtemperature. The pressure decline Is considered to bepredictable Crom natural hydrological considerations. Thetemerature decline, however. is still a matter ofdiscussion. as the mechanism of cooling has not beendefined. The purpose of the present study is to put someconstraints on the cooling process presently observed Inthe reservoir.
777 CAUSES OF TEMPERATURE CHANGESExploitation of the Svartsengl reservoir has caused thewithdrawal of about 40 million tonnes of geothermal fluid(Thorhallsson, personal communication, 1983), This hascaused about 13 bar pressure drawdown In the reservoir . Adecrease In pressure causes increased boIling in the top ofthe reservoir. The recharge of cold water can increase aspressure decreases In the reservoir. Episodic cold inflowfrom the overlying ground water can take place In associationwith earthquakes. The decrease In the temperaturecould also be caused by a decrease In the lateral flow ofhot fluid. This chapter will deal with some of thepossible cooling processes in the Svartsengl reservoir.7.1 BoilingThe salini ty of the geothermal fluid of the Svartsengireservoir is roughly 2/3 that of sea water. The saturationtemperature of this salt solution is higher than thesaturation temperature of pure water by a maximum of 2°C ata depth of about 2000 m (Michaelides, 1981; Grant, 1982)Little or no correction is thus needed when using thesteam tables.Exploitation has caused a pressure drawdown which makes itpossible for the reservoir fluid t o boil at greater depththan it could initially. In other words. the drop inpressure caused by the exploitation has increased theboiling In the upper part of the reservoir. During boiling.thermal energy is used in changing the state of the fluidfrom liquid to vapour and this causes cooling in thereservoir. However, as the level of boiling is migratingdownwards, hotter and hotter water comes into boilingconditions. This boiling sustalns the steam cap locatedaround wells SG-2. SG-3 and SG-l O. The effect of theboiling Is therefore to increase the temperature of thesteam cap. The temperature of the steam z one was about
- Page 25 and 26: 25commissioned. Well SG - 7 was dri
- Page 27 and 28: 27~ J H D-HS~ - 9 0 00 Gl:iL.J::..J
- Page 29 and 30: 293.2 Temperature elementThe bourdo
- Page 31 and 32: SVARTSENG I ,WEL L SG-1SVAR TSENG I
- Page 33 and 34: 33temperature at the bottom of the
- Page 35 and 36: -".(!)'W (!)rJ)rJ)fa...J WrJ) 3-"
- Page 37 and 38: SVARTSENGIWELL SG-5SVARTSENGIWELL S
- Page 39 and 40: SVARTSENGIWELL SG-6SVARTSENGIWELL S
- Page 41 and 42: SVARTSENGI\JELL SG-7SVARTSENGIwELL
- Page 43 and 44: 430NNN~~•-••;;• •~0l•0
- Page 45 and 46: 45pressure profiles in Fig. 32. In
- Page 47 and 48: 47N,~• ~, •8 •"•a'i:i•L-N
- Page 49 and 50: ;-r-::I J HO - HS" - 2 300 Gq\//Ll:
- Page 51 and 52: EI]JHO-HSI> . 2300 GGI 83.08.1020 A
- Page 53 and 54: 53reservoir during 1976- 1981 Is fr
- Page 55 and 56: 55~ JHD-HSP-2300 GC!L...C.J 83.08.1
- Page 57 and 58: 575.1.~ Cross-section DIt is an E-W
- Page 59 and 60: 59rnJHO-HSI:>-Z300 GG.83 .08 .1010
- Page 61 and 62: I"jT'=I~ HD-H S P - 2 500 GC;L..t.J
- Page 63 and 64: time , but the change in temperatur
- Page 65 and 66: f"i'T"':lJHO~HSP-2]OO GGL.:..L...J
- Page 67 and 68: 67r;r.:I~HO ·Hs~-noo GGL.:..J::J l
- Page 69 and 70: 69["j'T'=l JHO·HS ~- 2.100 GGL.:..
- Page 71 and 72: 7 1r,r::l JHO-HS P- 2 300 GG~ a3 .
- Page 73 and 74: 73~ JHD·HSJ> · 2300 GOt..:J:.J 83
- Page 75: 75rn JHD·HS~-2300GG83.09.1274 A"AS
- Page 79 and 80: 797.4 Decreased lateral inflow of h
- Page 81 and 82: 818 CONCLUSIONS1. The Svartsengl re
- Page 83 and 84: 83REFERENCESArnason, B .• 1976: G
76In Fig. 3. Significant <strong>temperature</strong> changes were notrecognized until 1983 In <strong>the</strong> ma<strong>in</strong> liquid part of <strong>the</strong>reservoir I.e. beneath 600 m depth. However as hasbeen shown In <strong>the</strong> previous chapters. <strong>the</strong>re were signs ofsmall changes prior to 1983. These changes In <strong>temperature</strong>were not signIficantly larger than <strong>the</strong> absolute accuracyof <strong>the</strong> <strong>in</strong>struments used for <strong>temperature</strong> measurements.Therefore, significant <strong>temperature</strong> changes 1n <strong>the</strong>reservoir could not be detected until 1983.At present. <strong>the</strong> response of <strong>the</strong> Svartsengi reservoir toutIlizatIon has been both a decrease In <strong>pressure</strong> <strong>and</strong><strong>temperature</strong>. The <strong>pressure</strong> decl<strong>in</strong>e Is considered to bepredictable Crom natural hydrological considerations. Thetemerature decl<strong>in</strong>e, however. is still a matter ofdiscussion. as <strong>the</strong> mechanism of cool<strong>in</strong>g has not beendef<strong>in</strong>ed. The purpose of <strong>the</strong> present study is to put someconstra<strong>in</strong>ts on <strong>the</strong> cool<strong>in</strong>g process presently observed In<strong>the</strong> reservoir.
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