Coil Tube Material for geothermal well. Dublex or Incoloy? 2

[mufasa1]

Gentlemen,

We are drilling geothermal wells on a reservoir where the geothermal fluid is saline, has similar Na and Cl concentrations as seawater. Here, I am trying to select the proper material for coil capillary tubes which we use to inject anti scaling chemicals downhole.

I have received recommendations especially on Dublex 2205 and Alloy 825 (Incoloy). Some manufacturer say dublex is superior and some say that incoloy is better.

Is it possible to compare these two materials? Which would be a better pick for saline geothermal fluid?

Awaiting your comments on this matter?

Thanks,

 

[EdStainless]

How hot is the well? Neither of these alloys has fantastic corrosion resistance to chlorides. Of the two 2205 has better pitting resistance, and 825 has better stress corrosion cracking resistance.
You may be better off looking at a 6% Mo alloy like AL-6XN.
With any of these grades remember how strong they are and use the thinnest wall tubing that you can get.

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Plymouth Tube

 

[btrueblood]

Better yet, use a valve (e.g. Sko Flo valve) that doesn't rely on a capillary tube for flow control, then issues of corrosion and/or scaling/filming don't cause the injection flow rate to vary due to uncontrollable parameters.

 

[strider6]

what is the composition of the fluid?
AS ed said 2205 has some problems in high conc of NaCl but if the fluid does not contains oxygen then the limit for duplex is higher than seawater.
Geothermal is a complex system and the materials selection needs special attention.
I've found some times ago this documents on materials selection in geothermal than can help u:

Corrosion and Material Selection for Geothermal Systems

http://iga.igg.cnr.it/geoworld/pdf/WGC/2005/2039.pdf

COMPANION STUDY GUIDE TO SHORT COURSE ON GEOTHERMAL CORROSION AND MITIGATION IN LOW TEMPERATURE GEOTHERMAL HEATING SYSTEMS

http://www.osti.gov/geothermal/servlets/purl/894036-6X5f9k/894036.pdf

Corrosivity of Geothermal Brines Progress Report for Period Ending December 1976

http://www.osti.gov/bridge/servlets/purl/7220903-jhGCyS/7220903.PDF

hoep this help u

S

Corrosion Prevention & Corrosion Control

 

[mufasa1]

Gentlemen,

Thank you very much for your comments.

Dear Ed,

The downhole temperature is 150 Cdeg.
Do you recommend the thinnest wall tubing for economic
reasons?

Regards,

 

[EdStainless]

Yes, save your money.
I mention that because most tubing sizes are based on plain steel or 304 SS. The alloys that you are looking at are much stronger. In addition there is no such thing as a corrosion allowance in stainless steel. Since failure is because of localized (pitting) corrosion instead of general corrosion making things thicker does not help make them last longer.

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Plymouth Tube