H2S vs CO2 vs Chlorides w.r.t. optimum pipe metallurgy for PW

[SNORGY]

Hello folks.

I am not a metallurgist, so I am looking for some opinions on what to do in a produced water environment in which you have all four of these hypothetical but representative conditions:

(1) it is NACE sour
(2) it has measurable CO2
(3) it has chlorides above, say, 1000 ppm
(4) 2000 psig @ ~75 F

I see a lot of clients asking for ASTM A312 TP316/316L in such service. My thoughts are:

High PREN is good to address the CO2; H2S resistance probably good; not sure that I like the 1000 ppm chlorides with this metallurgy.

Might try Duplex SS...at a cost.

I think the optimum approach is to use internally coated carbon steel with something like a baked fusion bond epoxy.

Also, I have seen aluminum-bronze valves in such service...not sure I like such metallurgy in a NACE sour environment although I have been told that NAB offers acceptable resistance. In any case, I would propose an internally coated carbon steel valve and maybe try Impreglon.

Can anyone provide any thoughts / opinions?

Thanks all in advance.

Regards,

SNORGY.

 

[SJones]

Start with ISO 21457 and take it from there to develop a corrosion control strategy.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[zdas04]

It really depends on your flow rate. For the last decade or so I've preferentially used Spoolable Composite piping in service where I used to would have agonized over what to worry about most. Now I don't really worry about any of them. At that temp and pressure basically every Spoolable Composite manufacturer has products that would work. If you temp was 50F higher you would pretty much be limited to FiberSpar, but at 75F you can use FiberSpar, FlexPipe, or even FlexSteel.

In the 2000 psig range, you are probably limited to something like FiberSpar's (for example) FS LPJ 4-1/2 2250E (rated to 2250 psig and 115F. This pipe will handle 8400 bbl/day before it is running full. If you limit flow to 100 ft/s / density, then it can move 13,541 bbl/day of SG=1.0 water.

FlexSteel (which is a bit pricier) has a 2250 psig 6-inch product (5.604 ID) which requires 26,000 bbl/day to run full and maxes at 33,000 bbl/day.

Both of these products are inert to CO2, H2S, and Chlorides. It really saves a lot of angst deciding if you are going to design for H2S or Chlorides.

Oh yeah, this is metallurgy forum. I guess everyone will now yell at me. I'll apologise in advance for dragging the forum into the plastic weeds.
David

 

[SNORGY]

Flex"Steel" has metal in it, so you're still legal.

Thanks David.

Regards,

SNORGY.

 

[SJones]

GRP is one of the options in ISO 21457 if it meets the selection criteria, e.g. CAPEX, ease of design, fire resistance offshore, qualified diameter range, etc. etc. Internal FBE coating is the staple approach of the largest producing company on the Arabian peninsula, but personally, I can't see it as a full design life option for a typical 20 years plus. That would leave you solid CRA for the valves. In spite of all this, your first real objective is: to determine whether the water is actually too corrosive for carbon steel when judged against the criteria to be applied.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[SNORGY]

Thanks Steve.

I will endeavour to obtain a copy of ISO 21457 and take it from there.

I should have been more specific in my OP, but this installation is a modification to an existing facility (to B31.3 Code) and will not require 20 year life. 5 years is realistic; 10 is optimistic.

Regards,

SNORGY.

 

[zdas04]

Again with the plastic. I feel a bit like Dustin Hoffman's uncle in The Graduate.

I'm currently working on an 8-inch gas gathering project where the pipe is too thin and the accumulated water is too corrosive. The solution I'm recommending to my client is an HDPE liner from United Pipeline. Like Spoolable Composite, this liner is inert to most chemicals and solves the problem of what kind of corrosion to be worried about.

David

 

[SJones]

Again, a liner could be fine but can the number of flanges be tolerated, instrument intrusions in piping, requirements for having to vent and so on. If 5 years is the design life, can a 6 mm corrosion allowance on carbon steel be accepted? Do the economics stack up against the predicted or observed corrosion rates?

We're always onto a loser trying to perform materials selection in an online forum: we never get the full picture of the technical and economic drivers.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[SNORGY]

David:

Thanks...I have used United Pipeline Systems for liner pulls in the past (pipelines). Good system, never had any issues.

Steve:

"...onto a loser..." - I do apologize for not specifying all applicable drivers. Upstream O&G, small client, no float in the schedule, budget constrained...you know...same old, same old. I was merely asking for opinions from folks whom I have come to respect. I take them all under advisement, and at the end of the day, in combination with my own judgement, I apply the extent of judgement and engineering that the client will tolerate paying.

Regards,

SNORGY.

 

[SJones]

That's OK. The picture is now building into a classic recipe of 'carbon steel with corrosion allowance and fingers crossed'!!

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[SNORGY]

Yes...unfortunately, with the sophistication (or lack thereof) with most of the clients I know, that's the way it usually ends up.

My recommendation in any event will be other than austenitic SS.

Regards,

SNORGY.

 

[blacksmith37]

One more data point: I was involved in Ni Al bronze wellheads for injecting PW and CO2 about 30 yr ago. I don't remember the corrosion specifics, but no one ever called back to say there had been corrosion problems.

 

[SNORGY]

Thanks, blacksmith37.

On first inspection, it was the H2S that concerned me in combination with a yellow metal, albeit alloy. Aluminum-bronze by itself would not be my first choice, whereas I would rather use nickel-aluminum-bronze to deal with the relatively low (but still sour) H2S than use 316-SS in combination with unspecified chlorides.

Thanks all for input.

Regards,

SNORGY.

 

[SNORGY]

As an update, the fluid analyses reveal approximately 5000 ppm H2S, 2% CO2 in the evolved entrained gas, and 2800 mg/l chlorides.

My thoughts are, do not use 316 SS.

Regards,

SNORGY.