Detecting a tubing leak

[UsmanHWU]

1. Most reliable - most expensive: Pull the production tubing and run a re-settable packer, use a re-settable inflatable if there are restrictions in the casing. Set and fill annulus above packer - repeat by unsetting and pulling up hole until leak is pinpointed. Make sure you set above the leak and hold pressure to really define the length of the leak as well as depth
2. Cheaper - Run temperature log inside tubing and fill/inject into annulus. Should be able to see the temperature profile change easily
3. Cheap and dirty - pull tubing tie a nylon panty hose on the bottom of a weight bar - inject into annulus - weight bar will stop as nylon hangs up by being pulled into the leak - may need to be a fairly large leak - this works really well inside tubing and up to 4 1/2" casing

Comments are welcome

[moscow01]

Not sure about your reasoning here? Are you trying to detect a tubing leak or a casing leak? If you are trying to "detect" a tubing leak, then why would you pull tubing? You would run temperature log as you suggest in 2. Or - you would run and set retrievable bridge plug at various intervals until the tubing tests and then you will know the area of interest. Also, using a "pony tail" as you describe in 3, you would not pull tubing and you would inject into tubing and not into annulus. A pony tail (i.e. nylon stocking or piece of old frayed rope), as you rightly point out, requires that the leak be quite substantial. Additionally, because it requires injection down the tubing often involves killing the well in depleted reservoirs.

[Yengineer]

If tubing has a confirmed leak you don't piss around to locate the leak. WHY? Tubing needs a repair which means the tubing has to be pulled out. Depending on what might have caused the leak (corrosion or mechanical) tubing might be visually inspected or have it scaned on the way out.
IF you want to confirm a tubing leak then you run and set a plug in the tubing and pressure test it.