theleftcoast
Chemical
- Jul 4, 2017
- 7
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!
