Filter on Gas line to Injection Well

[asghar]

Produced natural gas at a pressure of 2000 psig needs to be injected in a gas well to maintain pressure. Two Ariel compressors are in Series to raise the produced natural gas pressure from 300 psig to 2200 psig.

Is it a normal practice to install a filter before the wing valve of the well to trap the line corrosion particles? It is understandble to put a temporary stainer for startup to trap the deberies in the line. If filter is required, what micron filter to be installed? Please guide,

 

[TD2K]

I worked on one facility that reinjected produced gas at up to 5000 psig, we did not filter the gas before the injection wells.

 

[asghar]

Thanks Bruce for the quick response.

khanag@bp.com

 

[asghar]

Another question: what type of check valve could be a better choice on the gas line before the wing valve. I am recommending a Wafer type as swing type check valve may flutter due pulses developed by compressors operation.

 

[olef]

One: Why would you put the filter after the compressors? Wouldn't it be better to filter the gas before you put it into the rotating machinery if you need it at all? I guess you have a scrubber upstream the compressors that takes care of knocked out liquid (and heavy particles). The compressor is usually a lot more sensitive than the reservoir that you are injecting to.

Two: Consider a more expensive, non slam check valve.

Regards
OleF

 

[asghar]

Olef,
The gas fed to the compressor is already filterd and I agree to your point that compressor is more sensitive than the well. There are two resons that we were thinking of:

1) to trap the line conteminents (rust particles and small debries).
2 to trap the heavy ends in case these are condensed.

However, I have now decided to put basket strainer to trap the debries during commissioning period. I am looking for a manufacturar that manufactures 1500 # rating basket strainer. If you can recommend one, will be appreciated.

Thanks

 

[olef]

I will not recommend any specific manufacturer, as I'm sure they all will be pretty confident. However, I can tell you a few of the problems I have run into with such basket strainers in high pressure systems:

1. Nobody knows if the strainer is in there :-/ (yes, it's true)
2. High pressure rating means heavy parts.
3. Such system are often fire proofed which makes it even more cumbersome to clean the strainer.
4. One more leakage source

For the trapping of debris in a new line, I totally agree - you never know what is in there - somebody might have forgotten a welder.

For the heavy ends I do not agree, just adjust the aftercooler so it doesn't knock out liquids, and what is the consequence of knocking out some heavy ends? Are your velocities that high?

Regards
OleF

 

[asghar]

Olef,
I agree to your first point and that is the main reason to have some kind of protection for commissioning the line. Your second point also valid and justified but considering the length of the line to around 3 to 4 KM one can not be sure if there is liquid or not.

TD2K: I did recieve your 3-phase separator article and will go through during the weekend. Thanks