Table 3 Existing gas geothermometers reported in the geothermal literature which were used in the present work

1

DP80

If %CO₂ ≥ 75

\(\frac{24775}{{2log\left( {\frac{{CH_{4} }}{{CO_{2} }}} \right) - 6log\left( {\frac{{H_{2} }}{{CO_{2} }}} \right) - 3log\left( {\frac{{H_{2} S}}{{CO_{2} }}} \right) + 36.05}} - 273.15\)

If %CO₂ < 75

\(\frac{24775}{{2log\left( {\frac{{CH_{4} }}{{CO_{2} }}} \right) - 6log\left( {\frac{{H_{2} }}{{CO_{2} }}} \right) - 3log\left( {\frac{{H_{2} S}}{{CO_{2} }}} \right) - 7log\left( {0.1} \right) + 36.05}} - 273.15\)

% volume

D’Amore and Panichi (1980)

2

ND84a

\(\frac{{\sqrt{{\left( {5.5697 - R} \right) + \left( {R - 5.5697} \right)^{2} + 1056.34368}}}}{0.03936} - 273.15\)

\(R = log\left( {X_{{CH_{4} }} } \right) - 4log\left( {X_{{H_{2} }} } \right) - log\left( {X_{{CO_{2} }} } \right)\)

Mole fraction

Nehring and D’Amore (1984)

3

ND84b

\(\frac{{\sqrt{{\left( {S + 1.89499} \right) + \left( {S + 1.89499} \right)^{2} + 128.90864}}}}{0.01432} - 273.15\)

\(S = log\left( {X_{{H_{2} }} } \right) + \frac{1}{2}log\left( {X_{{CO_{2} }} } \right)\)

Mole fraction

Nehring and D’Amore (1984)

4

ND84c

\(5.78356V^{2} + 110.212V + 662.814\)

\(V = log\left( {X_{{H_{2} S}} } \right) + \frac{1}{6}log\left( {X_{{CO_{2} }} } \right)\)

Mole fraction

Nehring and D’Amore (1984)

5

AG85a

\(- 44.1 + 269.25\left[ {log\left( {CO_{2} } \right)} \right] - 76.88\left[ {log\left( {CO_{2} } \right)} \right]^{2} + 9.52\left[ {log\left( {CO_{2} } \right)} \right]^{3}\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

6

AG85b

\(341.7 - 28.57log\left( {\frac{{CO_{2} }}{{H_{2} }}} \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

7

AG85c

\(311.7 - 66.72log\left( {\frac{{CO_{2} }}{{H_{2} }}} \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

8

AG85d

\(277.2 + 20.99log\left( {H_{2} } \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

9

AG85e

\(212.2 + 38.59log\left( {H_{2} } \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

10

AG85f

\(246.7 + 44log\left( {H_{2} S} \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

11

AG85g

\(173.2 + 65.04log\left( {H_{2} S} \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

12

AG85h

\(304.1 - 39.48log\left( {\frac{{H_{2} S}}{{H_{2} }}} \right)\)

mmol/kg

Arnórsson and Gunnlaugsson (1985)

13

A87a

\(148.5 + 64.35log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right) + 5.239\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{2} - 1.832\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{3}\)

mmol/kg

Arnórsson (1987)

14

A87b

\(135.9 + 63.14log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right) + 6.241\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{2} - 1.813\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{3}\)

mmol/kg

Arnórsson (1987)

15

G91a

\(\frac{4625}{{10.4 + log\left( {\frac{{CH_{4} }}{{CO_{2} }}} \right)}} - 273.15\)

mmol/mol

Giggenbach (1991)

16

K95a

\(352.45 - 53.36log\left( {\frac{{CO_{2} }}{{H_{2} }}} \right)\)

% volume

Koga et al. (1995)

17

K95b

\(228.95 - 24.06\left( {\frac{{CH_{4} }}{{H_{2} }}} \right)\)

% volume

Koga et al. (1995)

18

S96a

\(\frac{738.3091}{{\left( {\% gas^{0.0008} } \right)\left( {\frac{{\% CO_{2} }}{{\% H_{2} S}}} \right)^{0.1037} }} - 273.15\)

% volume

Supranto et al. (1996)

19

S96b

\(\frac{{1138.9501\left( {\% Gas} \right)^{0.0037} \left( {\% H_{2} S} \right)^{0.1076} }}{{\left( {\% CO_{2}^{0.2019} } \right)\left( {\% CH_{4} } \right)^{0.0056} }} - 273.15\)

% volume

Supranto et al. (1996)

20

A98a

\(121.8 + 72.012log\left( {CO_{2} } \right) + 11.068\left[ {log\left( {CO_{2} } \right)} \right]^{2} - 4.724\left[ {log\left( {CO_{2} } \right)} \right]^{3}\)

mmol/kg

Arnórsson et al. (1998)

21

A98b

\(129.2 + 88.299\log \left( {CO_{2} } \right) + 21.946\left[ {\log \left( {CO_{2} } \right)} \right]^{2} - 10.103\left[ {log\left( {CO_{2} } \right)} \right]^{3}\)

mmol/kg

Arnórsson et al. (1998)

22

A98c

\(177.6 + 66.152log\left( {H_{2} S} \right) + 4.811\left[ {log\left( {H_{2} S} \right)} \right]^{2}\)

mmol/kg

Arnórsson et al. (1998)

23

A98d

\(227.1 + 56.168log\left( {H_{2} } \right) + 5.836\left[ {log\left( {H_{2} } \right)} \right]^{2} + 6.630\left[ {log\left( {H_{2} } \right)} \right]^{3}\)

mmol/kg

Arnórsson et al. (1998)

24

A98e

\(173.2 + 48.751log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right) + 7.599\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{2} + 1.793\left[ {log\left( {\frac{{CO_{2} }}{{N_{2} }}} \right)} \right]^{3}\)

mmol/kg

Arnórsson et al. (1998)

25

B06

For H₂S concentrations ≥ 0.00175 \(75.85log\left( {H_{2} S} \right) + 458.6\)

For H₂S concentrations < 0.00175

\(64.68log\left( {H_{2} S} \right) + 427.8\)

%mol

Blamey (2006)