Threaded PVC Strength

[CrudeDudeJr]

Can someone point me to theory or research on the tensile strength of threaded PVC connections? I'd like to estimate how deep I can use threaded PVC hanging vertically in a well, as the casing and as the production tubing (different sizes, of course). The casing might be on the order of 6" or 8" and the tubing might be on the order of 2". I'm thinking of using stainless steel couplers. I need to estimate how much weight I can hang from the top joint. With regard to the casing application this will pretty directly tell me how deep I can go with that arrangement. With regard to the production tubing, I will need to add in the weight of the downhole pump and wire. I'm willing to consider all different SDR's and such.

Thanks,

 

[EdStainless]

how about next to zero?
The strength of the threads is minor compared to the long-term creep of the PVC.
There are papers on the creep of PVC, search.

 

[LittleInch]

Why threaded couplings? Never heard of them on PE as they don't work.

Just fuse it or use heat couplings surely. Then they are as strong as the pipe itself.

But creep is your long term issue.

Is this for a hydrocarbon well??

What depth are you looking at?

 

[CrudeDudeJr]

Why threaded couplings? Never heard of them on PE as they don't work.

Just fuse it or use heat couplings surely. Then they are as strong as the pipe itself.

But creep is your long term issue.

Is this for a hydrocarbon well??

What depth are you looking

Why threaded couplings? Never heard of them on PE as they don't work.

Just fuse it or use heat couplings surely. Then they are as strong as the pipe itself.

But creep is your long term issue.

Is this for a hydrocarbon well??

What depth are you looking at?

For non-potable water production. Currently one well at 500’ and another (different location) at 700’. Others will follow at currently unknown depths, thus the desire to have a general design understanding.

The casing can be fused. That is a fine approach.

The production tubing will be removed occasionally to service the downhole pump. That is the purpose of the threaded connections. Fusing the production tubing would mean cutting it on the way out and repairing the cuts on the way back in. I suppose that is an option. I admit I had not considered that.

You mention PE (polyethylene). I was considering PVC (polyvinyl chloride). I’ll need to find the data for PE to see how the tensile strengths compare at various sizes.

Thanks for the thoughts.

 

[LittleInch]

Sorry, I hadn't read it properly. PVC is generally a lot more brittle so more likely to fail when screwing together.

PE pipe is very flexible and comes in reels of about 2m diam in smaller diameters so maybe you could just coil it like coiled tubing? Or a 2" braided hose?

 

[CrudeDudeJr]

Sorry, I hadn't read it properly. PVC is generally a lot more brittle so more likely to fail when screwing together.

PE pipe is very flexible and comes in reels of about 2m diam in smaller diameters so maybe you could just coil it like coiled tubing? Or a 2" braided hose?

I'm familiar with PE in that we use it for horizontal flow lines. Quite a few miles of it installed. But I don't have the equipment to reel it back in. The unreeling is a pretty passive process from the point of view of the reel. Reeling it back in will require a motor and controls and such, like a coiled tubing rig. I would need to find it or create it. The available equipment for servicing wells in this area is geared to pulling tubing of ~35' lengths. There can be variability there but that is the general concept.

 

[LittleInch]

It's like I'm always telling people though, don't think of PE or PVC as just a different type of metal. It isn't and things you can do with metal, you can't normally do with PE/PVC and vice versa. You need to think differently.

Do you have a few hundred feet of spare land you can lie it out on? Then just design a radiused bend of say 2 m radius, clip the end to a truck and just drag it out.

 

[CrudeDudeJr]

It's like I'm always telling people though, don't think of PE or PVC as just a different type of metal. It isn't and things you can do with metal, you can't normally do with PE/PVC and vice versa. You need to think differently.

Do you have a few hundred feet of spare land you can lie it out on? Then just design a radiused bend of say 2 m radius, clip the end to a truck and just drag it out.

Thanks for the encouragement. I appreciate thinking differently.

I could probably have the 500' or 700' or 1,000' necessary. Each case will be different. I could likely fashion a radius like you mentioned and figure out how to attach it to the wellhead. It's possible I could find a way to "clip it to a truck" (the PE pipe) and pull it out. Putting it back in isn't just a reverse process, but I might be able to use a pulling unit (well service equipment) to pull segments toward the well while raising them to encourage them to drop back into the well.

Likely the biggest problem to overcome next is management's objection to all of this "different thinking". Many people have a big fear of failure. As far as they know it's never been done before and as such is fraught with peril. What if it doesn't work? What if any part fails? All the potential failures ...

Ok. Thanks. Great stuff to consider. Then to develop a presentation to get it approved ...
But it does provide one potential path forward.

 

[LittleInch]

Good luck and let us know how it goes. PE is a very resilient material which will withstand quite a bit of rough treatment, especially at the smaller sizes.

A trial on a well which is least important is probably the way to experiment / convince people.