perforation 1

[ahmedchn]

my question is that if oil industry has to perforate a well (bullet perforating or jet perforating) so does the perforating gun passes form the tubing? the size of the tubing industry has maximum 4 inches so does it mean that perforating gun has the smaller diameter ? and after the perforation is done so doesnt the production starts as soon as we perforate ? and if production starts so how do we retrieve a gun?

 

[DrillerNic]

Yep- you get a perforation gun that fits inside the production tubing. There are lots of gun sizes- look at teh service company website to see them all.

If you have the tubing in place, you will also have the christmas tree in place, and the perforating will be done with pressure control equipment such as a lubricator, to allow you to remove the guns from the well without opening up the well. You could, if you want, perforate overbalance, so that the well won't flow, but that upsets the production people.

Other methods of perforating include doing the perforations before you have run the tubing, so you can use big guns, but you have to kill the well to run the tubing, which might be bad for the reservoir; or on the end of the tubing string, called Tubing Conveyed Perforating. This gives you big guns, no worries about killing the well afterwards and you can perforate underbalaance. But the guns either stay there (which means you can't do any productiuon logging) or the guns are dropped (which means you have to drill a long sump for them to fall into).

A good textbook or trawl through the service company websites will give you a better discussion of the perforating options avaialble and the pros and cons of each one.

 

[welltest1]

I have a horizontal well with multi-stage perfs and multi-stage fracs. Four stages have time-delayed perf guns. Three guns were used in each of these stages. The first gun perforated overbalanced. And it is not evident on the 2nd and 3rd (time-delayed) if these were over or underbalanced. We have pressure for the 2nd and 3rd guns on the first two stages, but not the last two stages. Is there anyway of determining overbalance/underbalanced or can you direct me to info on time-delayed perf guns?

The pressure at which the guns were fired, is this pressure at surface or pressure at the guns (bottomhole pressure)?

 

[DrillerNic]

I've never used time delayed guns, I'm afraid. the service company that did the perforating job would be the best place to start of information about them and so on.

The issue of underbalance or overbalance assumes you know what the reservoir pressure is- if you know that accurately,and you have downhole pressure reading, knowing if you were over or underblance is easy. Knowing the original reservoir pressure is usually the hard bit! If you have surface pressure only, you can make a good estiamte on teh bottom hole pressure if you have a fluid composition and a tubing performance simulator like Prosper