316 Chloride Cracking - Short Duration Exposure
316 Chloride Cracking - Short Duration Exposure
(OP)
Does anyone have experience with the chloride cracking resistance of 316L for short exposures to environments normally associated with cracking? Specifically, high temperature solutions containing a moderate concentration of sodium chloride?
This is a thermal oil recovery application where steam is temporarily injected into producing wells. These wells usually have alloy screens at the bottom to keep sand out. Wells typically produce a mixture of oil, water, and gas over their 15-20 year service life. The producing conditions are approximately 100-115C, 20-50psi CO2 partial pressure, 100-1000ppm H2S, and water with 20g/L NaCL (no oxygen present). Occasionally (meaning 3-4 times over service life of well), steam is injected to lower the viscosity of the oil to increase production. During these short duration steam injection periods (7-10 days), the alloy screens are exposed to 50g/L NaCL at 200-220C (again, no oxygen present).
Based on the literature (see the example linked below from the Nickel Institute, figure 4), our normal producing conditions are no problem for 316L and no cracking is expected. On the other hand, short periods of steam injection conditions are a potential problem because they fall outside the recommended service envelope (shown in figure 4).
Nickel Institute - Corrosion Resistant Alloys in the Oil and Gas Industry
I have field experiences with 316L screens NOT showing signs cracking for short exposures (250 hours) to 50g/L NaCL at 200-220C. This is contrary to what the literature suggests is an environment where cracking failure would be expected. After exposure steam conditions, the 316L is then returned to production and exposed to oil/water/gas at 100-115C, 20-50psi CO2 partial pressure, 100-1000ppm H2S, and water with 20g/L NaCL.
My question: How long do you need to be in a cracking environment you expect to start seeing cracking problems? 1 hour? 10 hours? 100 hours? 300 hours? 500 hours? 1000 hours? Is there some sort of "incubation period" or "threshold exposure time" required to initiate cracking? Does re-exposure to normal producing conditions somehow re-passivate the 316L and prevent cracking?
I am trying to reconcile my practical experiences of 316L succeeding in a service environment that the literature suggests would almost certainly cause cracking failures. Any experience, opinions, or literature references you have that could provide background would be very helpful.
Thanks in advance for your input!
This is a thermal oil recovery application where steam is temporarily injected into producing wells. These wells usually have alloy screens at the bottom to keep sand out. Wells typically produce a mixture of oil, water, and gas over their 15-20 year service life. The producing conditions are approximately 100-115C, 20-50psi CO2 partial pressure, 100-1000ppm H2S, and water with 20g/L NaCL (no oxygen present). Occasionally (meaning 3-4 times over service life of well), steam is injected to lower the viscosity of the oil to increase production. During these short duration steam injection periods (7-10 days), the alloy screens are exposed to 50g/L NaCL at 200-220C (again, no oxygen present).
Based on the literature (see the example linked below from the Nickel Institute, figure 4), our normal producing conditions are no problem for 316L and no cracking is expected. On the other hand, short periods of steam injection conditions are a potential problem because they fall outside the recommended service envelope (shown in figure 4).
Nickel Institute - Corrosion Resistant Alloys in the Oil and Gas Industry
I have field experiences with 316L screens NOT showing signs cracking for short exposures (250 hours) to 50g/L NaCL at 200-220C. This is contrary to what the literature suggests is an environment where cracking failure would be expected. After exposure steam conditions, the 316L is then returned to production and exposed to oil/water/gas at 100-115C, 20-50psi CO2 partial pressure, 100-1000ppm H2S, and water with 20g/L NaCL.
My question: How long do you need to be in a cracking environment you expect to start seeing cracking problems? 1 hour? 10 hours? 100 hours? 300 hours? 500 hours? 1000 hours? Is there some sort of "incubation period" or "threshold exposure time" required to initiate cracking? Does re-exposure to normal producing conditions somehow re-passivate the 316L and prevent cracking?
I am trying to reconcile my practical experiences of 316L succeeding in a service environment that the literature suggests would almost certainly cause cracking failures. Any experience, opinions, or literature references you have that could provide background would be very helpful.
Thanks in advance for your input!





RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
Under steam injection conditions, the pH is much higher. There are no acid gases present. The steam quality is low (about 50% by mass steam) and the liquid fraction of the steam has 50g/L NaCl at a pH of 8-9 (or more).
RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
Your practical experience may be your best guide and don't necessarily be fooled into having corrosion test data in literature be your guide. I agree with blacksmith37 suggesting test coupons but it sounds like you have already established a baseline with 316L screens and no cracking.
RE: 316 Chloride Cracking - Short Duration Exposure
In the mildly acidic producing conditions (low pH caused by acid gases), the 316 screens have a long service record without failure.
RE: 316 Chloride Cracking - Short Duration Exposure
My primary goal with this post is to gain understanding around why short term exposure success might not agree with literature data. How long does an exposure need to be? What mechanism might be offering protection? I really don't have the background to answer any of these so I wanted to ask the community.
I never thought about the steam pH impacting the chloride cracking performance. Not sure why that wasn't on my radar until now. Does a higher pH somehow help the 316 remain protected?
Just a thought, does anyone have experience with 316 in low pressure steam systems? That is probably a relatively analogous environment to bottom hole cyclic steam conditions.
RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
A well is the only place where I would believe is truly oxygen free.
If there is no active corrosion there will not be any CSCC.
But if the low pH and temp result in pitting initiation then I would bet on cracking as well.
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P.E. Metallurgy, Plymouth Tube
RE: 316 Chloride Cracking - Short Duration Exposure
316L is limited to a few parts ppm (grams per liter) for useful lifetime, low pH, just a few hours even with stress levels below a 1000 psi,Hast. C works
RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
The Nickel Institute application domain for 316L is based on the complete absence of H2S, so you may wish to rethink that statement. One element of the rethink could be an examination of the stresses experienced by the screens. Generally, they are not highly stressed items and it could be that the cold work in their forming is not overly severe either. It would be expected that cracking initiates from sites of pitting, so pitting might be the critical parameter.
Literature and real life can be two different worlds. Does your "field experience" include an assessment of the pitting behaviour?
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: 316 Chloride Cracking - Short Duration Exposure
SJones - The combination of H2S and chlorides under producing conditions hasn't resulted in problems for us (oil/water/gas at 100-115C, 20-50psi CO2 partial pressure, 100-1000ppm H2S, and water with 20g/L NaCL). There is data in the literature under even more severe producing circumstances (5% NaCl, 200-300F, 1.5psi H2S partial pressure) that have not resulted in cracking problems with 316. The paper is NACE 06156 -"Operation limits for austenitic stainless steels in H2S containing environments".
Thank you all for the discussion. I am learning a lot from your comments.
RE: 316 Chloride Cracking - Short Duration Exposure
H2S actually helps since it will assure that there is no oxygen.
pH and temp are critical, and it needs to be actual downhole pH, with CO2 you will get down to ~4 if pressures are high.
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P.E. Metallurgy, Plymouth Tube
RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: 316 Chloride Cracking - Short Duration Exposure
RE: 316 Chloride Cracking - Short Duration Exposure
If saw what looked like a threshold value for CSCC.
Working from memory I recall that nothing below 30% yield cracked.
But remember, this was high strength material.
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P.E. Metallurgy, Plymouth Tube
RE: 316 Chloride Cracking - Short Duration Exposure
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.