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Predicting H2S in Liquid and Vapour Phase of Oil

Predicting H2S in Liquid and Vapour Phase of Oil

I've been using a rough 'rule of thumb' to convert the concentration of H2S in oil to the concentration in the vapour phase as being 1ppm w/v ~= 100ppm v/v.

Is this a valid estimation?
Are there other ways to predict it more accurately?
Can anyone describe the reasoning behind it and state any assumptions i.e. does it only apply to systems within a certain temperature and pressure and oil density ranges etc?

RE: Predicting H2S in Liquid and Vapour Phase of Oil

What are the dimensional units of your ppm w/v? Is it pounds per million cubic feet, kg per million cubic meters, or what?

Can't answer your question without that information.

Milton Beychok
(Visit me at

RE: Predicting H2S in Liquid and Vapour Phase of Oil

I recall having read somewhere that H2S in the vapors coming out of the ullage opening of a tank receiving crude oil of 70-ppm H2S (on a w/w basis), showed a concentration of ca. 7000 ppm H2 by volume. I assume the T,P conditions were not far away from 1 ata and 70oF.

RE: Predicting H2S in Liquid and Vapour Phase of Oil


The numbers you recall for crude oil equate to 1 ppm w/w = 100 ppm v/v which is the same as the original poster's ... except that the original poster wrote 1 ppm w/v = 100 ppm v/v. Perhaps, he/she simply made a mistake in his/her units?

Milton Beychok
(Visit me at

RE: Predicting H2S in Liquid and Vapour Phase of Oil

To mbeychok,

I was aware of that. In particular, after reading your first response. Thanks. smile

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