GEOTHERMOMETER

• KETIKA CAIRAN KELUARPERMUKAAN MELALUI MATAAIR PANAS/FUMAROLE,KOMPOSISI KIMIADIGUNAKAN UNTUKMENGETAHUI TEMPERATURBAWAH PERMUKAAN

• KONSENTRASI DARI UNSURYANG BERHUBUNGANDENGAN TEMPERATURYANG ADA DI DALAMDIKENAL DENGAN UNSURKIMIA GEOTHERMOMETER

When the fluids reach the surface by the way of hot spring or fumarole, the chemical composition may often be used to deduce sub-surface temperature

Concentration of constituent that relate to deep temperature are called chemical geothermometer

UNSUR KIMIA GEOTHERMOMETER

• TERGANTUNG TEMPERATUR PADA KEDALAMAN

• KESETIMBANGAN MINERAL –FLUID

• ASUMSI YANG DI PAKAI :

1. FLUID MINERAL MEMPUNYAI KESETIMBANGAN DI KEDALAMAN

2. TEMPERATUR MEMPENGARUHI REAKSI

3. SUPPLY PHASE PADATAN YANG CUKUP

CAIRAN MENJADI JENUH

HUBUNGAN UNSUR YANG AKAN DIGUNAKAN DALAM GEOTHERMOMETER

Depend on the existence at depth of temperature dependant mineral fluid equilibria

Assumption Fluid- mineral equilibrium at

depth

Temperature dependantreaction at depth

Adequate solid phases supply Fluid became saturated with respect

to contituents used for geothermometer

DIDOMINASI OLEH BATUAN

Dominated by rock

4. PROSES KESETIMBANGAN KEMBALI TIDAK BERPENGARUH

AIR MENGALIR PADA PERMUKAAN

5. DILLUTION/MIXING COLD & HOT WATER TIDAK TERJADI

Negligible re equilibrium

Water flow to the surface

No Dilution/mixing of cold and hot water

• pH NEUTRAL, ALKALI CHLORIDE

• Very informative

• Acid Sulfate water:

Not suitable

Leaching from the rocks

• Sea water

Misleading temperature prediction

Prevent establishment of fluid-mineral equilibrium

KwarsaQuartz

Asumsi

• Sangat baik untuktemperatur bawahpermukaan > 150oC

• Effek dari pemisahan steam akibat subsurface boiling

• Presipitasi SiO2 sebelumsampling

• Presipitasi SiO2 setelahsampling

• Kelarutan SiO2 dikontrol olehpadatan lain

• Pengaruh pH pada kelarutan

• Dilution

Consideration Work best for water with

subsurface > 150OC

Effect of steam separation due to subsurface boiling

Polymerisation or presipitationof SiO2 before sampling

Polymerisation or presipitationof SiO2 after sampling (due to sample preservation)

Dissolved SiO2 controlled by solid other than quartz

Effect of pH on quartz solubility

Dilution

KwarsaQuartz

Suhu/temperature

Baik untuk/good between 100-250oC

>250oC diperlukan persamaanuntuk menerangkan kelarutankwarsa/different equation are required to describe quartz solubility

PEMISAHAN UAP/Steam separation(ADIABATIK VS CONDUCTIVE COOLING)

MATA AIR SANGAT PANAS, ALIRAN 120 – 130 kg/menit atau 2 kg/s

ADIABATIK

ALIRAN CEPAT

TIDAK ADA HEAT LOSS

PERSAMAAN AKAN BENAR KARENA CAIRAN YANG DIGUNAKAN (SILICA TIDAK MENGUAP WAKTU MENDIDIH)

MATA AIR BERKURANG DAN TEMPERATUR KURANGADIABATIK DAN KONDUKTIF COOLING

Re 200OC, DEPTH = 500 m

CONDUCTIVE COOLING 200OC –100OC

Very hot spring, Flow120 – 130 kg/menit or2 kg/s ADIABATIK

Rapid ascent

No heat lost

The equation correct due to steam loss is used (silica does not vaporiseupon boiling)

Reducing flow rate and temperatureADIABATIC AND CONDUCTICVE COOLING

Reservoir = 200OC, DEPTH = 500 m

CONDUCTIVE COOLING 200OC – 100OC

PRESIPITASI SILICA SEBELUM SAMPLINGPrecipitation of silica before sampling

KWARSA LARUT DI AIR 200 – 250OC, pH 5 – 8, KADAR GARAM TINGGI

T > 225OC CAIRANSUPER JENUH

AMORPHOUS SILICA 100OC

SAMPLING TERBAIK PADA 225OC

Quartz dissolves in water 200 –250OC, pH 5 – 8, high salinity

T>225 become supersaturated with respect to amorphous silica before cooling to 100

The best sampling at 225

KELARUTAN SILICASilica solubility

Quartz stable, solid silica least soluble

Control silica solubility in geothermal water > 150OC

If Solid silica (CHALCEDONY, AMORPHOUS SILICA) higher solubility > quartz

PENGARUH pHpH effect

KELARUTAN NAIK MAKA pH NAIK

Quartz solubility increase when pH

increase

JARAK DI KOREKSI

Distance is corrected

DILLUTION

SUBSURFACE DILLUTION Decreasing the silica content

Equilibrium between fluid and rockReflect cooler condition

If equilibrium is not attained

Error temperature too cool

Na - K

Consideration

1. The fluid have equilibrated with

SODIUM – BEARING FELDSPAR (ALBITE)

POTASSIUM – BEARING FELDSPAR (ADULARIA)

Common and abundant in geothermal

Na Al Si3 O8 + K+ K Al Si3O8 + Na+A

Albite Adularia

Very suitable for T > 180OC

LOW CALCIUM

Less affected by DILLUTION and STEAM SEPARATION

Flow less than

QUARTZ GEOTHERMOMETER

1Na

Ca

C

C

K - Mg

Consideration

The fluid have equilibrated with

K – FELDSPAR (ADULARIA)

K – MICA (ILLITE DAN MUSCOVITE)

CHLORITE (CLINOCLORE)

CHALCEDONY (SILICA PHASE with T

slightly cooler than quartz)

ILLITE CLINOCLORE

0.8 KAl3Si3O10(OH)2 + 0.2 MgAl2Si308(OH)8 +

CHALCEDONY ADULARIA

5.4 SiO2 + 2 K+ 2.8 KAlSi3O8 + 1.6 H2O + Mg+2

1000 – 3000 C

CLORIDE WATER with CMg < 1 ppm

SENSITIVE

Mixing with Mg ; temperature will be cooler

Mg

K

C

C 2

Na - K - Ca

High calcium content

Fluid mineral equilibria occur Na and K-FELDSPAR

CALCIC MINERAL (CALCIUM FELDSPAR, EPIDOTE, CALCITE)

CLAY

Larger range of thermal fluid than Na-K

Affected by BOILING

DILLUTION

BOILING

PRECIPITATION CaCO3; reduce the dissolved calcium concentration

No Methode Persamaan/

Equation

Batasan Ket

1 Quartz-no steam loss

T<100-250

Fournier,1981

2 Quartz-max steam loss

100-250 Fournier,1981

3 Na-K >180 Fournier,1981

Giggenbach,

1988

4 K-Mg 100-300 Giggenbach,

1988

5 Na-K-Ca

273clog19,5

1309

2SiO

o

Ct

15,273clog75,5

1522

2SiO

o

Ct

27375,1)/log(c

1390

273483,1)/log(c

1217

Na

o

Na

o

K

K

cCt

cCt

273/clog14

4410

2K

o

Mgc

Ct

273

47,206,2/log)/(c log

1647

2

1Na

o

NaCa

K ccc

Ct

If t<100oC and >0, so β=4/3If t>100oC and <0, so β=1/3C in ppm

06,2/log

2

1 NaCa

cc

GEOTHERMALDesa Wansalib, features geothermal yang muncul

Fumarole

Rock alteration

Hot water

0,69IB (%)

45,55meq an.

46,19meq cat

1034,64CO3

116,88HCO3

82,30SO4

261,99Cl

1,00F

40,00B

0,75NH4

0,40As

6,30Li

68,00K

1000,00Na

0,03Mg

0,04Ca

0,00Fe

0,03Al (mg/l)

261,00SiO2

4260DHL/EC (mmhos/cm)

9,3pH

7Elev.(m)

WansalibKode Conto

421No.Lab.

1No.Conto

Water analysisin Wansalib

Example

No Metode Temperatur (C )

1Silika tanpa kehilangan uap

Silica no steam loss199,2

2

Silika dengan kehilangan uap maksimum

Silica with maximum steam loss

183,4

3 Na/K 203,3

Diagram segitiga tipeair panas Wansalib

Diagram segitigakandungan relatif Na, K, dan Mg di Wansalib

Diagram segitigakandungan relatif Cl, Li, dan B di Wansalib

KETERANGAN :

WansalibKETERANGAN :

Wansalib

KETERANGAN :

Wansalib