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Re: Fw: Question on PhreeqcI and glycol

> Is there a way of using PhreeqcI to model the interaction of a relatively
low solids brine containing both CO2 and H2S, plus some glycol?  I am
interested in modeling the behavior of such a brine vs. temperature and
pressure, to determine the extent of degradation of the glycol.

I'm not sure what you need. PHREEQC is not good with high ionic strength
waters, say 1 molal and greater. On the other hand, I'm not sure what part
of the thermodynamics you need. If it is just solubility of gases, it might
be adequate; it has a linear log activity coefficient expression for
uncharged species. Charged species will get more unreliable the higher the
ionic strength. PHREEQC has no explicit pressure dependence in the aqueous
model, but it is possible to specify partial pressures of ideal gases. I'd
be reluctant to push things past a few atmospheres total pressure. You
would have to define a new "Element" glycol and any
dissociation/complexation that are pertinent. If you are trying to do all
this a priori, I suspect you can't do it. If you are trying to model some
experiments, you may be able to use some of the features of PHREEQC.


David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

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