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Methane Solubility

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01 Jun 2012 (Updated )

Calculates the solubility of methane in water.

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Description

Given pressure (in MPa), Temperature (in Kelvin) and Salinity (in either mol/kg or parts per thousand), this function uses the formulae in Tischenko et al (2005) and Duan et al (1992, 2006) to calculate the solubility of methane inside and outside the methane hydrate stability field.
This function will compute solubilities either over a range of pressures, temperatures or salinities, or for discrete pressure, temperature, salinity points. Two demonstration can be seen using the following code:

To calculate solubility over a range of conditions:

    P = [5:.5:15]';
    T = [273:.5:293]';
    S = [0:10:30];
    SalinityUnits = 'ppt';
    Datatype = 'range';
    NetCH4Solubility = MethaneSolubility(P,T,S,SalinityUnits,Datatype);
    surf(T,P,NetCH4Solubility(:,:,1))
    xlabel('Temperature (K)')
    ylabel('Pressure (MPa)')
    zlabel('Methane Solubility (moles CH4 per kg water)')

To calculate solubility for discrete data points:

P = [5:.5:15]';
    T = [273:1:293]';
    S = [0:1:20]';
    SalinityUnits = 'ppt';
    Datatype = 'points';
    NetCH4Solubility = MethaneSolubility(P,T,S,SalinityUnits,Datatype);
    plot(T,NetCH4Solubility,'bo')

Acknowledgements

Progressbar and X Steam, Thermodynamic Properties Of Water And Steam. inspired this file.

This file inspired Methane Hydrate Stability Toolbox.

Required Products MATLAB
MATLAB release MATLAB 7.14 (R2012a)
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Comments and Ratings (1)
29 Apr 2013 David

I might be converting wrong, because I am getting very high methane solubility equilibrium concentrations when I use real data from 10m depth.. see below

Temp_K=283
Press_MPa= 0.1014
Sal_ppt=22
ch4_eqsol_M=methanesolubility(Press_MPa, Temp_K, Sal_ppt, 'ppt','points');

I get a value of 0.0013 M, but it should be closer to 3nM

Can someone please help me figure out why this is?

Thanks,

Dave

Updates
07 Jun 2012

This update is only to ensure the acknowledgments written in the script are also included on the Mathworks download page. "Methane Solubility" gratefully acknowledges the XSteam script by Magnus Holmgren and the Progressbar script by Steve Hoelzer.

11 Jun 2012

This version updates the U.S. Geological Survey disclaimer.

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