New to Completions: Some Basic Questions

[dberman]

Hello,

Recently switched from being a subsea engineer to a production/compeletions engineer. Need some basic questions answered!

1) What are the purpose of X or XN nipples? How do they differ? My general understanding is that nipples allow you to anchor or land something in a tubing string at a later date? An XN nipple has a no go?( which I think means that only certain things through it? An X nipple does not have a no go? So how does anything anchor in an X nipple?

2) What exactly is a no go?

3) What is a bridge plug? Why would you want to use one?

4) Is it common to run tubing or perform a cleanout while flowing the well?

5) IF I have a vertical deep well, is there any advantage to running an X nipple directly above an XN nipple at the end of the tubing string? Or is this redundant?

I'm sure I'll have more questions!

Thanks!
Danny

 

[Roylance]

Some answers for you dberman.

2) A "no-go" is a restriction in the completion bore which will be a integral feature of one of its component parts eg top sub in the completion packer. The no-go is intended to be used to to determine position within the completion.

3) Bridge plug - basically a packer with one end closed off (hence the "plug"). Can be permanent or retrievable. Used to isolate the lower zone of the wellbore.

Schlumberger have an "oilfield glossary" which you might find useful.

 

[DrillerNic]

1. A nipple allows you to land something in the tubing (the other alternative is to use a tool with slips that grip the tubing, but such things are harder to set and even harder to retrieve, so nipples are preferred). At it most basic, a nipple is just a section of reduced ID with a shoulder and the tool just rests on the shoulder. More advanced nipples have a lock ring that engage a set of dogs on the tool, so you can check if the tool has landed correctly by applying a slight up weight. Two of the commonly used lock ring profiles are the X nipple profile and the R nipple profile. Nipples are available in a range of sizes so that you can choose where in the tubing the tool should go- ideally, if you have more than one nipple, the smallest one should go at the bottom and the largest at the top- that way you can run a tool through the top nipple and set it in the bottom nipple (you'd be surprised how often people either forget to specify different sized nipples or which order they should be run!).

2) A Nogo niplpe is a nipple with an ID smaller than any of the tools that is run as the bottom nipple- that way, if you drop a tool it will always (ha ha) be caught in the bottom nipple rather than flying south and ending up as junk in the bottom of the well.

3) Just as Roylance says a bridge plug is a tool run into tubing or casing to seal it. Most correctly it has a set of slips on it, so it doesn't need a nipple. Run on wireline or slickline with a wireline or slickline setting kit or on pipe. Can be permanent (you have to drill it out) or retrievable. If retrievable, ideally run with a prong, which lets you equalise pressure across the plug before unsetting it.

4) I'd be absolutely shitting myself if I was doing anything on a well with the well flowing (unless I'm set up for underbalanced or managed pressure drilling). It's not ususual to run a completion on a well that is open to the formation (an open hole completion or a workover on a cased & perforated well) but full well control must remain: the well is killed, you have overbalanced fluid, you monitor the fluid level, you have a trip sheet with the amount of fluid that should be displaced from the well as you RIH with the completion (and if the actual volume in the trip tank doesn't match the expected volume on the trip sheet, you stop and work out why rather than carry on). The one exeption as I said, is managed pressure or underbalanced operations, where the well is flowing at all times, but you're using a rotating BOP and all sorts of other gear to maintain well control.

5. You might want to run two nipples above each other in a well that is going to be expensive to workover- a deep well perhaps. That way, if you have problems seal in the upper nipple (corrosion, or erosion, say), you can still use the lower nipple and avoid a workover. A few hundred bucks for an extra nipple against tens of millions of bucks for a full workover- not a difficult choice!