injection of hydrate inhibitor

[reihane1]

Dear all

I want to inject hydrate inhibitor into a oil well because in start up of well hydrate may form. but I do not know where is the best injection point? is there any difference in injection in to well or injecting into pipe up stream of choke valve?
thanks a lot
reihane

 

[zdas04]

It depends on where your problem is likely to be. How much pressure drop do you have across the choke? Is the downstream pressure still in the hydrate range? How much dT do you have across the choke (will J-T cooling trip a hydrate event?).

I've seen some flow assurance work offshore that said for those streams studied you had to inject at the bottom of the tubing. I've seen other situations where you wanted to inject upstream of the choke on the surface. It just depends on the thermodynamics of the particular stream and rules of thumb are absolutely worthless.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[MortenA]

Without knowing you well shut-in pressure you should consider that injection upstream the choke or any downstream ESD (upstream a seperator) will complicate things wrt design pressure etc.

 

[reihane1]

Dear all
the well shut in pressure is 459barg and normal operating temperature of wellstream in winter is about 54 degree centigrade. the normal operating pressure is about 170 barg. I do some calculation using hysys and find out that hydrate will perform in start up condition. but I do not know where is the injection point. upstream of choke valve our in tubing? another question is that when u do flow assurance study if the initial and worse condition is fluid with enviroment temperature and shut in pressure and the down stream pressure will be atmospheric pressure? I mean if it is correct to consider that in prolong shut down with depressurizing we have fluid in tubing with environment temperature and shut in pressure?
Thank u
ps: if we have manual depressurizing in well head and manifold and calculation using hysys show that we have hydrate in this case,is it necessary to have hydrate injection point between all ESD valves? I have 2 HIPPS valve with one manual depressurizing connection,is it necessary to add one connection between these two valves as well?