Hydrate dissociation curve in software packages

[anuradha]

Hey all,

I have few queries relation to hydrate formation & dissociation curve used for operational strategy for any field.The literature i have read says that the operational strategy should consider the dissociation curve as a boundary for hydrate formation, because the area between the dissociation and formation curve named as metastable region considered as operating in risk of hydrate formation.
And literature also mentions that in this metastable region there is a possibility and risk of hydrate formation, whereas at the hydrate formation point the spontaneous hydrate will form.
Now for hydrate formation curve we are using PVTsim18 in our organisation, (EOS - SRK & PR peneloux), does this software provide hydrate dissociation curve also, or it gives hydrate formation curve itself as hydrate disssociation curve to eliminate the risk of operating in metastable region.


Thanks
Anu

[tinom]

Previous models (based on experimental curves) provided only
the initial limits of hydrate formation but actual models based on phase equilibria
(multiphase equilibria with hydrate phase) can predict transiction and hydrate-phase amount.
For hydrate prediction in addition to PVTsim (which was provided by our client as reference software) I have tested Prode Properties (see "http://www.prode.com/en/properties.htm") and CSMGem (see "http://hydrates.mines.edu"), in my test cases the results were quite similar (differences of 1-3 degrees in formation temperatures), so I can recommend these packages, but other applications capable of multiphase equilibria can do the work.

[anuradha]

Hey dear tinom,

Please clear me if i am wrong does PVTsim 18 considers dissociation curve as a hydrate formation curve or its plots both the curve seperately. As per my understanding on Pvtsim and the literature i have read it says there are software packages which includes both the curves.
But i need specificaly information about PVTsim 18, because our company own currently this software only...
and thanks for usefull information ...keep sharing...
Do you have any literature on hydrate formation curve and dissociation curve and its importance from field operational strategy point of view.

[tinom]

I would recommend “Clathrate Hydrates of Natural Gases, Third Edition” E. Dendy Sloan, Jr. and Carolyn A. Koh CRC Press, 2007 , there you'll find detailed information about methods to calculate hydrate's phase equilibria.
With PVTSIM you can calculate phase equilibria (given p,t and composition PVTSIM calculates the amount gas, oil, aqueous, Hydrate I, Hydrate II, Hydrate H, Ice and pure salt) or given p,t the expected temperature/pressure of hydrate formation, with these values you can evaluate the specific risk of hydrates in your application.
Other software may give additional information but I would expect that a careful evaluation of hydrate formation temperature or pressure gives a good idea of the risk, I use these values (in my case calculated by Prode Properties).

[mouss]

please share “Clathrate Hydrates of Natural Gases, Third Edition” E. Dendy Sloan, Jr. and Carolyn A. Koh CRC Press, 2007
or send it to me at : samouss00@hotmail.fr

Many thanks