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Table 1 Updated compilation of gas geothermometers reported in the literature for determining geothermal reservoir temperatures

From: GaS_GeoT: A computer program for an effective use of newly improved gas geothermometers in predicting reliable geothermal reservoir temperatures

No Gas geothermometer Acronym Gas-Mineral equilibria reactions Gas concentration units Geothermal reservoir-typea Calculation method Temperature interval (°C) References
1 CO2-H2S-CH4-H2 DP80 CaSO4 + FeS2 + 3H2O + CO2 ↔ CaCO3 + 1/3Fe3O4 + 3H2S + 7/3O2
C + CO2 + H2 ↔ 2CH4 + 2H2O
% volume LIQDR and VAPDR Analytical 145–300 D’Amore and Panichi (1980)
2 H2O-CO2-CH4-H2 G80a CO2 + 4H2 ↔ CH4 + 2H2O
2NH3 ↔ N2 + 3H2
mmol/mol LIQDR Numericalb 100–340 Giggenbach (1980)
3 NH3-H2-N2 G80b CO2 + 4H2 ↔ CH4 + 2H2O
2NH3 ↔ N2 + 3H2
mmol/mol LIQDR Numericalb 100–340 Giggenbach (1980)
4 CO2-CH4-H2 ND84a CO2 + 4H2 ↔ CH4 + 2H2O Mole fraction LIQDR Analytical 150–350 Nehring and D’Amore (1984)
5 CO2-H2 ND84b H2 + 1/2O2 ↔ H2O
C + O2 ↔ CO2
Mole fraction LIQDR Analytical 150–350 Nehring and D’Amore (1984)
6 CO2-H2S ND84c 3FeS2 + 2H2 + 4H2O ↔ Fe3O4 + 6H2S
C + O2 ↔ CO2
Mole fraction LIQDR Analytical 150–350 Nehring and D’Amore (1984)
7 CO2 AG85a 2clinozoisite + 2calcite + 3quartz + 2H2O ↔ 3prehnite + 2CO2 mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
8 CO2-H2 AG85b 2clinozoisite + 2calcite + 3quartz + 2H2O ↔ 3prehnite + 2CO2
4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2
mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
9 CO2-H2 AG85c 2clinozoisite + 2calcite + 3quartz + 2H2O ↔ 3prehnite + 2CO2
4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2
mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
10 H2 AG85d 4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2 mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
11 H2 AG85e 4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2 mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
12 H2S AG85f pyrite + pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 3H2S mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
13 H2S AG85g pyrite + pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 3H2S mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
14 H2S-H2 AG85h pyrite + pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 3H2S
4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2
mmol/kg LIQDR and VAPDR Analytical 200–300 Arnórsson and Gunnlaugsson (1985)
15 CO2-CH4-CO B85 CO2 + H2 ↔ CO + H2O
CH4 + 3CO2 ↔ 4CO + 2H2O
Mole fraction LIQDR and VAPDR Numericalb n.r Bertrami et al. (1985)
16 CO2-N2 A87a n.a mmol/kg LIQDR Analytical 200–300 Arnórsson (1987)
17 CO2-N2 A87b n.a mmol/kg LIQDR Analytical 200–300 Arnórsson (1987)
18 CO2-H2S-CH4-H2-CO SD89 CO2 + 4H2 ↔ CH4 + 2H2O
H2 + 1/2O2 ↔ H2O
H2 + 1/2S2 ↔ H2S
H2 + CO2 ↔ CO + H2O
1/3Fe3O4 + S2 ↔ FeS2 + 2/3O2
% mol VAPDR Numericalb 140–370 Saracco and D’Amore (1989)
19 CO2-CH4 G91a 3CO2 + CH4 ↔ 4CO + 2H2O mmol/mol LIQDR Analytical 100–350 Giggenbach (1991)
20 H2-Ar G91b 2Fe3O4 + H2O ↔ 3Fe2O3 + H2 + O2 mmol/mol LIQDR Analyticalb 100–350 Giggenbach (1991)
21 CO2-Ar G91c n.a mmol/mol LIQDR Analyticalb 100–350 Giggenbach (1991)
22 H2-Ar GG92a FeS2 + FeO + 2H2O ↔ Fe2O3 + 2H2S mmol/mol LIQDR Analyticalb 100–350 Giggenbach and Glover (1992)
23 CO2-CO GG92b FeS2 + FeO + 2H2O ↔ Fe2O3 + 2H2S mmol/mol LIQDR Analyticalb 100–350 Giggenbach and Glover (1992)
24 CO2-H2 K95a Empirical geothermometer. Regression approach % volume LIQDR Analytical n.r Koga et al. (1995)
25 CH4-H2 K95b Empirical geothermometer. Regression approach % volume LIQDR Analytical n.r Koga et al. (1995)
26 CO2-H2S S96a Empirical geothermometer. Multidimensional approach % volume LIQDR Analytical n.r Supranto et al. (1996)
27 CO2-H2S-CH4 S96b Empirical geothermometer. Multidimensional approach % volume LIQDR Analytical n.r Supranto et al. (1996)
28 CO2 A98a 2clinozoisite + 2calcite + 3quartz + 2H2O ↔ 3prehnite + 2CO2 mmol/kg LIQDR Analytical  > 230 Arnórsson et al. (1998)
29 CO2 A98b 2clinozoisite + 2calcite + 3quartz + 2H2O ↔ 3prehnite + 2CO2 mmol/kg LIQDR Analytical  > 230 Arnórsson et al. (1998)
30 H2S A98c pyrite + pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 3H2S mmol/kg LIQDR Analytical  > 150 Arnórsson et al. (1998)
31 H2 A98d 4pyrrhotite + 2prehnite + 2H2O ↔ 2epidote + 2pyrite + 3H2 mmol/kg LIQDR Analytical  > 150 Arnórsson et al. (1998)
32 CO2-N2 A98e n.r mmol/kg LIQDR Analytical n.r Arnórsson et al. (1998)
33 H2S-Ar A98f n.r mmol/kg LIQDR Analyticalb n.r Arnórsson et al. (1998)
34 H2-Ar A98g n.r mmol/kg LIQDR Analyticalb n.r Arnórsson et al. (1998)
35 H2S B06 2Fe3O4 + 12H2S + CO2 ↔ 6FeS2 + 10H2O + CH4 % mol LIQDR Analytical 200–300 Blamey (2006)
36 CO2-H2-Ar PC10a 2Fe3O4 + H2O ↔ 3Fe2O3 + H2 + O2
2H2O + C ↔ 2H2 + CO2
% mol LIQDR and VAPDR Gridb 100–350 Powell and Cumming (2010)
37 CO2-CO-CH4 PC10b CacO3 + K-mica ↔ CaAl2-silciate + K-feldspar + CO2
CO2 + H2O ↔ CO + H2O
3CO2 + CH4 ↔ 4CO + 2H2O
% mol Liquid—and VAPDR Gridb 100–350 Powell and Cumming (2010)
38 CO2-CH4-H2-H2S PC10c CO2 + 4H2 ↔ CH4 + 2H2O
3FeS2 + 2H2 + 4H2O ↔ Fe3O4 + 6H2S
FeS2 + H2 ↔ FeS + H2S
% mol LIQDR and VAPDR Gridb 100–350 Powell and Cumming (2010)
39 CO2-CH4-H2 PC10d CO2 + 4H2 ↔ CH4 + 2H2O
CaCO3 + K-mica ↔ CaAl2-silicate + K-feldspar + CO2
% mol LIQDR and VAPDR Gridb 100–350 Powell and Cumming (2010)
40 CO2-CH4-H2-H2S PC10e CO2 + 4H2 ↔ CH4 + 2H2O
3FeS2 + 2H2 + 4H2O ↔ Fe3O4 + 6H2S
FeS2 + H2 ↔ FeS + H2S
% mol LIQDR and VAPDR Gridb 200–350 Powell and Cumming (2010)
41 CO2-H2S-H2 B16a CO2 + 4H2 ↔ CH4 + 2H2O
H2 + 2H2O + 3/2FeS2 ↔ 3H2S + 1/2Fe3O4
% volume LIQDR Numericalb 125–350 Barragán et al. (2016)
42 CO2-H2S-H2 B16b CO2 + 4H2 ↔ CH4 + 2H2O
5/4H2 + 3/4Fe2O3 + 3/2FeS2 + 7/4H2O ↔ 3H2S + Fe3O4
% volume LIQDR Numericalb 150–350 Barragán et al. (2016)
43 CO2-H2S-H2 B16c CO2 + 4H2 ↔ CH4 + 2H2O
H2 + FeS2 ↔ H2S + FeS
% volume LIQDR Numericalb 100–350 Barragán et al. (2016)
  1. aType of geothermal reservoir used to calibrate the gas geothermometers
  2. bGas geothermometers that were not considered in this work
  3. n.r. = not reported; n.a. = not available. Analytical method refers to a gas geothermometer that provides a direct mathematical function for the calculation of the reservoir temperatures, i.e., BHT = f(gas concentration); whereas Numerical method refers to a more complex function that correlate multiple variables (i.e., gas concentration, pressure, the fraction of water, temperature, among others); Grid geothermometric method refers to a gas geothermometer that provides a complex grid-numerical algorithm for the estimation of temperatures and other key parameters of the reservoir (i.e., steam fraction, distribution coefficients, and the steam/gas ratio)