Well Integrity Technical Section

Dear Team,

We are producing two wells by using jet pump system, injection pressure is 3,000 psi. we work over wells last year to change tubing as it had holes in it and used another tubing Condition A.

ًW are now planning to have a two strings as stock. and we are in doubt either to buy new strings (condition A) or to reuse already available ones (condition B). In fact I do not know any test to measure stresses that old string have faced.

Cold you advise please.

BR

------------------------------
Safwat El-Rebba
Egyptian General Petroleum Corp
Cairo
------------------------------

Dear Safwat,

Let me try to look at your question from a reliability + safety perspective:

• You say the tubing you replaced last year had holes. That would point to corrosion, so the first thing to do is figuring out if it's internal or external corrosion (power fluid or production fluid) and its mechanisms.
• Then you should look at how quickly you can detect a tubing failure - that should be fast, as you should see a dramatic drop in produced oil - and how quickly (and cheaply) you can intervene. If high pressure is in the annulus, then you're safe. If it's in the tubing, then any continued leak will pierce your casing, so you must intervene.
• Ideally you should be able to get a good estimate of the corrosion rate and do a simple calculation on the minimum wall thickness in your tubing for which the savings from using condition B are offset by the shorter life.
• At this point you have a minimum acceptable wall thickness and you can test your used tubing with this condition. You may run a caliper tool while in the well before retrieving the tubing, or an inline electromagnetic test as you pull out. If you know that external corrosion is the hazard, then visual inspection is also possible.

Hope it helps,

------------------------------
Matteo Loizzo
Well integrity consultant
Berlin