Pipeline Depressuring Procedures

[RRE]

Interested in shared learnings or places to find (resources) on how to deal with pipelines that are under pressure with natural gas that will need to be depressured to determine/inspect line strike impacts would be apprecaited. Some of these lines may also contain % levels of H2S.

 

[RayPig]

If you want to depressure a sour line I would recommend that you pig the line and push the pig with sweet gas to displace the sour downstream (if the line is piggable) if not just sweet out the sour with 1.5 to 2 times line volume. After you have accomplished this, shut the line down and blow it down to flare. Do this through a separator in case you get some solids or fluids. Once the line is depressured you can get right in and cut-out the impact site using bentonite (mud) plugs to isolate the area (safety may push you to a Nitrogen purge).

If your not at that point were you are actually planning to get right to the cut-out state. You can drop the line pressure to 60% of working pressure and have a look very safely. (I am assuming that the line has not actually been breached.)

I can give you more if you throw some feedback, this work is what I do.