Produced water chemical analysis evaluation 4

[Alaa1992]

Hy guys

I've presented perviously through a couples of posts, a problem discussing leaks appeared suddenly in process API 5L PSL1 piping (3 and 6 inchs) carying produced water in an oil&gas facility, after only 100 days of utilization and the shape of corroded areas (holes) founded.

An investigation have been ocuured on both pipe metallurgy and water chimical composition to identify the reason.

For pipe metallurgy, Mechanical and chemical paraleters of the nuance are fine and within the composition required in API 5L PSL1 standard and material certificate.

The interesting is about water chemical results which showed those values

PH= 6.73 @20°C
Chloride = 52895 mg/litre
Water hardness = 2022.43 °F
Water conductivity = 125 mS/cm
Sulfur = <2 mg/litre
SRB= <1 cfu/100 ml
Fe = 1.67 mg/litre
Co2= 96 mgCO2/l
Salinity = 95.18 g/l

As specialists, I want to know your evaluations guys about those compositions (if this water is highly corrosive). because, i have been told, friendly, that those values, espeacialy of water condicutivity, salinity and % cloride are very huge and can lead to a severe corrosion.
And if there are any standards in which i can rely to evaluate/find out criterias, through it, i can judge the degree of corrosivity of this process water a'd method of corrosion monitoring.

Thanks in advance

Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[Dhurjati Sen]

Few additions above what you have already gathered -

Did you notice tubercles {presence of iron bacteria)?

Presence of SRB below such tubercles are causes of many failures.

You need to go for a water treatment programme. There are various companies like Thermax, Nalco etc. Check their websites, contact their local office, arrange for site visit and take their feedback.

Subsequently you can prepare for an RFQ and then tendering.





DHURJATI SEN
Kolkata, India

 

[Alaa1992]

@SEN
Thanks for your answer
Look to the following picture to see wath we have found inside pipe (visual investigation) before acceding to the analyses:

My priority now is to identify failure cause based on the mentionned chemical analysis and it is clear that there are something strange with that composition.and i want to know your comments on it and if there any standards can help me to evaluate the degree of corrosivity.

We can suggest a treatment and corrosion monotoring method later.



Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[0707]

Alaa1992

From your photo, as being high corrosive water in an oil&gas facility, it seems that the flow in your pipe pipe is low and you are in presence of a microbiological corrosion caused by ALWC accelerated low water corrosion, because of that orange colour inside your pipe. Maybe you need some kind of biocide injection and for that reason as Dhurjati Sen, said contact Thermax, Nalco or Baker Hugges, for sure they could be of help.

luis

 

[EdStainless]

There are lots of other microbes than SRBs that you can have trouble with.
The corrosion looks to be at the water/air interface when there is just residual fluid is sitting in the bottom of the pipe.
Looks like a biocide and/or inhibitor is in order.
With that level of Cl don't fool around, once it begins corroding you can get a lot of damage.

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P.E. Metallurgy, consulting work welcomed

 

[SJones]

For the water corrosivity, try running a CO2 corrosion prediction model. The chloride is a pretty average value and not unusually high.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

Good thought Steve, I am not sure how acid that amount of CO2 will drive it, but it might be a lot lower than you think. Especially if the only samples that you have ever measured are at ambient pressure.

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P.E. Metallurgy, consulting work welcomed

 

[Dhurjati Sen]

I can see Fe tubercles in the attached pic.

I can suggest applicable chemical treatment based on the results you have provided but that is outside the scope of this forum.

There are no standards as such, but google "water chemistry treatment" to enhance your knowledge.

https://chlorine.americanchemistry....hlorination),because they are very effective.

DHURJATI SEN
Kolkata, India

 

[Alaa1992]

Thanks guys for your replies

According to your opinions, i can evaluate (it is just the most propable thing), that the cause of corrosion can be combined into 4 factors:

CO2 Amount: That quantity showed above (96 mgCO2/l) was mesuared at ambiant pressure, that means the real quatity @CO2 partial pressure can be much more higher (As Edstainless said), so the formation of acids can be fast and high damage can be occured.
API571 identify a CO2 corrosion type, in which CO2 dissolves in water to form carbonic acid (H2CO3)

Cloride, water conductivity & Salts: their chemical percentages are very high (Compared to non corrosive water), which can be a perfect environnement FOR a rapid corrosion accident.

Fe chemical %: As Dhurjati Sen, Said, the presence of tubecercles at pipe walls indicates that this value (1.67 mg/litre) is elevated and can lead to shuch things formation.

SRB %: It is not totally 0 cfu/100 ml (which is required,as per tunisan norm 09.14 V2013) but a value between 0 and 1, and this can be an additional factor of this corrosion.

So if i can samurize, the whole thing is something between MIC and CO2 corrosion phenomenas. I don't know how far i'm right, but most of those factors are complementary, and can double the effect of corrosion in term of damage and time.
Meanwhile, As a piping engineer, and to get sure about this assumption, i'm trying to review standards identifying criterias used when pipe nuance selection (As API579, ASME31G, ASME 31-4 etc) hopping to find wath chemical composition limits are fixed for each material (nuance) and from there i can conclude if my water chemical compositions is corrosive for my A106 steel or not





Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[EdStainless]

This is when you grab a water treatment expert and hand it off. All of the various steel grades have nearly identical corrosion resistance. This water needs chemical treatment.

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P.E. Metallurgy, consulting work welcomed

 

[oal223]

pH of 6.7 is very low for water service that indicates the presence of acids (either high CO2 & Chloride)

as per API 581 Carbon dioxide corrosion table, corrosion rate can be as high as 0.9 to 1.02 mm/y at pH of 6.5 & temperature of 40 - 80 C.

Normally, for water service, pH target is above 8

 

[SJones]

Run a CO2 corrosion model using the partial pressure of CO2 last in contact with the liquid. There are at least two free to download models available - NORSOK M-506 might be the more straightforward one, but get someone to cross check the work whichever one you use. You will get a better idea of the corrosion rate estimate for that mechanism. The models will also give a better representation of pH at pressure. Again, the chloride concentration is not that high. There is also no mention of total suspended solids, flow rate, and many other influencing parameters. Crowd sourcing a corrosion failure assessment is never a good idea.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

oal, My hunch is that at pressure, with all of the CO2 in the system the pH is closer to 5. And hence some of the issues.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[oal223]

Well, for sure increasing the partial pressure will decrease the pH as the solubility will increase. However, from corrosion point the pH is a strong factor as it complete the electrochemical reaction. the low pH indicates the high H+ in the stream, which will act as cathodic reaction.

maybe this formula will help.

 

[SJones]

It doesn't take much bicarbonate to keep the pH up, and the OP hasn't given much of a water composition. The good old de Waard - Milliams equation was fine in its day, but things have moved on a great deal since those early times. NORSOK M-506

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[CH. Lee]

are you producing H2S also? what's the CO2 partial pressure of the preceding separation?
if you have the operating parameters, pressure, CO2, H2S, temp, i will run a quick check on ECE and Hydrocorr; nevertheless, the morphology suggests it's quite unlike a CO2 corrosion, further, it broke after only 100 days.

CH. Lee, PhD P.E
Lead Materials and Corrosion Engineer
Intecorr Consultancy

http://www.intecorr.com

twitter.com/intecorr