15 replies to this topic

[sp3d2]

Hi everyone.

Which methods are correct to determine salt content in PTB (pounds per thousand barrel)?

I have done a test to determine the value of Chloride for Crude oil entering Desalter using Mercury Nitrate titration method. The value of Chloride is 10 ppm.

My laboratory method to determine salt content (ptb) is 10 ppm Chloride x 1.65 divide by 2.853 which yield 5.78 ptb.

However, when i check Oilfield Processing of Petroleum - Volume 2 - Manning & Thompson book, the equation use is very different. I need to put BS&W value. The equation is

Assuming BS&W in = 0.5 vol%, SG = 1.02 and Chloride ppm = 10 ppm, therefore the value would be 0.018 ptb.

Which one of these equations are correct to determine salt content in PTB? I your guidance.

[kkala]

Below is a try to clarify the matter, despite my lack of relevant experience.
1. W. L. Nelson in 'Petroleum Refinery Engineering' (McGraw-Hill, 1958), Table 4-6, presents salt content of several crudes, with average value varying from 1 to 261 lb salt per 1000 bbl. Thus reported 0.018 lb/1000 bbl must be incorrect.
2. Assuming a crude oil sg=0.9, and that measured Cl is 10 ppm w/w, NaCl content can be calculated as follows:
NaCl content =10*1.65=16.5 ppm w/w. Volume of 1000 bbl=159 m3. Mass of 1000 bbl crude=159*0.9*1000=143100 kg =315476 lb. NaCl content in 1000 bbl crude=315476*16.5E-6 = 5.2 lb. Found value of 5.2 PTB is close to 5.78 PTB, corresponding to crude oil sg=1.0 (exceptionally heavy crude, but possible; see Nelson, ibid, appendices 1 & 2).
3. Consequently the right value is 5.78 PTB.
4. An interpretation of the formula in Manning & Thompson book:
4.1 First two terms represent volume of Sediment & Water (S&W) per 1000 bbl of crude, although denominator (100-%S&W) is not clear to me. Volume of sediment is considered negligible compared to water volume.
4.2 (350*SGbrine) represents brine density in lb/bbl.
4.3 So (ppmw) refers to NaCl content in brine(w/w), not in total crude. This could explain the difference reported.

[sp3d2]

Below is a try to clarify the matter, despite my lack of relevant experience.
1. W. L. Nelson in 'Petroleum Refinery Engineering' (McGraw-Hill, 1958), Table 4-6, presents salt content of several crudes, with average value varying from 1 to 261 lb salt per 1000 bbl. Thus reported 0.018 lb/1000 bbl must be incorrect.
2. Assuming a crude oil sg=0.9, and that measured Cl is 10 ppm w/w, NaCl content can be calculated as follows:
NaCl content =10*1.65=16.5 ppm w/w. Volume of 1000 bbl=159 m3. Mass of 1000 bbl crude=159*0.9*1000=143100 kg =315476 lb. NaCl content in 1000 bbl crude=315476*16.5E-6 = 5.2 lb. Found value of 5.2 PTB is close to 5.78 PTB, corresponding to crude oil sg=1.0 (exceptionally heavy crude, but possible; see Nelson, ibid, appendices 1 & 2).
3. Consequently the right value is 5.78 PTB.
4. An interpretation of the formula in Manning & Thompson book:
4.1 First two terms represent volume of Sediment & Water (S&W) per 1000 bbl of crude, although denominator (100-%S&W) is not clear to me. Volume of sediment is considered negligible compared to water volume.
4.2 (350*SGbrine) represents brine density in lb/bbl.
4.3 So (ppmw) refers to NaCl content in brine(w/w), not in total crude. This could explain the difference reported.

thanks kkala. you really enlightened me!

[sp3d2]

one more question, ppm Chloride times with 1.65 to convert it to ppm NaCl.

1.65 stands for what actually?


Thank You

Edited by sp3d2, 19 July 2011 - 10:36 PM.

[breizh]

one more question, ppm Chloride times with 1.65 to convert it to ppm NaCl.

1.65 stands for what actually?


Thank You

cl-/ nacl = 35.5/58,5 = 1.647

[sp3d2]

one more question, ppm Chloride times with 1.65 to convert it to ppm NaCl.

1.65 stands for what actually?


Thank You

cl-/ nacl = 35.5/58,5 = 1.647

thanks bro.

[sp3d2]

Below is a try to clarify the matter, despite my lack of relevant experience.
1. W. L. Nelson in 'Petroleum Refinery Engineering' (McGraw-Hill, 1958), Table 4-6, presents salt content of several crudes, with average value varying from 1 to 261 lb salt per 1000 bbl. Thus reported 0.018 lb/1000 bbl must be incorrect.
2. Assuming a crude oil sg=0.9, and that measured Cl is 10 ppm w/w, NaCl content can be calculated as follows:
NaCl content =10*1.65=16.5 ppm w/w. Volume of 1000 bbl=159 m3. Mass of 1000 bbl crude=159*0.9*1000=143100 kg =315476 lb. NaCl content in 1000 bbl crude=315476*16.5E-6 = 5.2 lb. Found value of 5.2 PTB is close to 5.78 PTB, corresponding to crude oil sg=1.0 (exceptionally heavy crude, but possible; see Nelson, ibid, appendices 1 & 2).
3. Consequently the right value is 5.78 PTB.
4. An interpretation of the formula in Manning & Thompson book:
4.1 First two terms represent volume of Sediment & Water (S&W) per 1000 bbl of crude, although denominator (100-%S&W) is not clear to me. Volume of sediment is considered negligible compared to water volume.
4.2 (350*SGbrine) represents brine density in lb/bbl.
4.3 So (ppmw) refers to NaCl content in brine(w/w), not in total crude. This could explain the difference reported.

kkala. I did mentioned the difference of salt content value by using the actual value of crude oil density = 0.819 in our refinery, however the Chemist in my workplace told me that as the chloride is extracted from crude oil using the water during the titration method, then SG = 1 must be used.

I know this is not an accurate practice as we are converting 1000 bbl to mass and we need to convert it using crude oil SG.

This is his response :

[The chloride measurement for salt content was carried out in aqueous layer based on our method. Water is used to extract the salt from the crude and that was a reason why we didn’t border about the crude density. Unless you are using ASTM D3230 for salt measurement definitely you ought to consider density variation for each crude in the calculation.

Do you have any idea?

Edited by sp3d2, 20 July 2011 - 10:02 PM.

[kkala]

....
2. Assuming a crude oil sg=0.9, and that measured Cl is 10 ppm w/w, NaCl content can be calculated as follows:
NaCl content =10*1.65=16.5 ppm w/w. Volume of 1000 bbl=159 m3. Mass of 1000 bbl crude=159*0.9*1000=143100 kg =315476 lb. NaCl content in 1000 bbl crude=315476*16.5E-6 = 5.2 lb. Found value of 5.2 PTB is close to 5.78 PTB, corresponding to crude oil sg=1.0 (exceptionally heavy crude, but possible).
3. Consequently the right value is 5.78 PTB....

... I did mentioned the difference of salt content value by using the actual value of crude oil density = 0.819 in our refinery, however the Chemist in my workplace told me that as the chloride is extracted from crude oil using the water during the titration method, then SG = 1 must be used.
I know this is not an accurate practice as we are converting 1000 bbl to mass and we need to convert it using crude oil SG. This is his response :

[The chloride measurement for salt content was carried out in aqueous layer based on our method. Water is used to extract the salt from the crude and that was a reason why we didn’t border about the crude density. Unless you are using ASTM D3230 for salt measurement definitely you ought to consider density variation for each crude in the calculation.

Do you have any idea?

.
From lab's answer it is understood that measured 10 ppm Cl means 10 mg Cl /l (correct for water), not 10 ppm Cl w/w (as assumed); and that this is supported by ASTM D3230.
Accordingly: NaCl content =10*1.65=16.5 mg/l (mg NaCl per l of crude). Volume of 1000 bbl=159 m3. NaCl content in 1000 bbl = 16.5 g/m3 * 159 m3 = 2623.5 g = 5.78 lb. So NaCl content is 5.78 lb/1000 bbl.
So NaCl content of 5.78 LTB is correct, since Cl concentration was measured in mg/l of crude.Your laboratory method gives same result, so its coefficient 2.853 contains this assumption.
ASTM D3230 (http://www.astm.org/...AL/D3230-08.htm is not free, available information on the subject is not clear to me (compare 1.1 vs 1.3.1 in the web reference). Anyway this is not significant, if Cl concentration is measured in mg / l of crude.

Edited by kkala, 22 July 2011 - 12:01 AM.

[sp3d2]

kkala.

Yes. lab guys and you are right. The chloride concentration obtained is mg/L not mg/kg.

Using weigh to volume basis (mg/L) eliminate the need to use SG of crude oil.

Thank you for sharing with us.

Edited by sp3d2, 21 July 2011 - 11:07 PM.

[kkala]

Thus Cl concentration had better be expressed as mg / l of crude (not as ppm). Notation of "ppm" is dimensionless (pure number), usually showing mass fraction or mole fraction (see http://en.wikipedia....ts-per_notation.
Water may create some confusion, since its specific gravity = 1; dilute aqueous solutions have same specific gravity, so 1 ppm = 1/1*E6 g/g = 1*E-3/1*E3 g/g = 1 mg/1 kg. Seeing that 1 kg of water has a volume of 1 l (in normal ambient temperatures, say 0-30 oC), 1 ppm has the same meaning as 1 mg/l. This is met in aqueous effluents and environmental matters in general.

[sp3d2]

Thus Cl concentration had better be expressed as mg / l of crude (not as ppm). Notation of "ppm" is dimensionless (pure number), usually showing mass fraction or mole fraction (see http://en.wikipedia....ts-per_notation.
Water may create some confusion, since its specific gravity = 1; dilute aqueous solutions have same specific gravity, so 1 ppm = 1/1*E6 g/g = 1*E-3/1*E3 g/g = 1 mg/1 kg. Seeing that 1 kg of water has a volume of 1 l (in normal ambient temperatures, say 0-30 oC), 1 ppm has the same meaning as 1 mg/l. This is met in aqueous effluents and environmental matters in general.

Thanks mr Kkala. I will clarify it with the chemist

Now I need to convert mg/L of Chloride (in wash water going to Desalter) to lb Nacl/ bbl brine. Please check the link.

My link

Another one is to convert mg/L of Chloride (in Crude oil going to Desalter) to lb NaCL/ bbl brine. Please check the link.

My link

Note : the portion (100 - BS&W)/ BS&W is referring to bbl crude/ bbl brine.

Can anyone please check my calculations below for any mistakes. I really appreciate the reply.

[breizh]

Hi ,
To support your query :
part 1 .


Start to convert mg Cl- into Nacl : x mg / 35.5 * 58.5 = y mg Nacl then
y*1e-3/373.242 = z lb of NaCl

Convert 1 l to barrel : 1 bbl=158.987 liters

The final result should be z lb of NaCL * 158.987

or

x (mg) /35.5*58.5*1e-3/373.242*158.987/1 ( lb Nacl / BBL)

Hope this helps

Breizh


Note : Download from Internet UCONEER (katmar software) , it will support you very much

Edited by breizh, 25 July 2011 - 05:55 PM.

[sp3d2]

Hi ,
To support your query :
part 1 .


Start to convert mg Cl- into Nacl : x mg / 35.5 * 58.5 = y mg Nacl then
y*1e-3/373.242 = z lb of NaCl

Convert 1 l to barrel : 1 bbl=158.987 liters

The final result should be z lb of NaCL * 158.987

or

x (mg) /35.5*58.5*1e-3/374.242*158.987/1 ( lb Nacl / BBL)

Hope this helps

Breizh


Note : Download from Internet UCONEER (katmar software) , it will support you very much

Thank you sir. i just downloaded the software. Where did you get the 374.242?

[breizh]

Pound = 453,6 g ( sorry for the mistake)
Breizh

Edited by breizh, 27 July 2011 - 06:14 AM.

[kkala]

Now I need to convert mg/L of Chloride (in wash water going to Desalter) to lb Nacl/ bbl brine. Please check the link.
My link
Another one is to convert mg/L of Chloride (in Crude oil going to Desalter) to lb NaCL/ bbl brine. Please check the link.
My link
Note : the portion (100 - BS&W)/ BS&W is referring to bbl crude/ bbl brine.
Can anyone please check my calculations below for any mistakes. I really appreciate the reply.

I think your conversions are correct. Applied scheme in your links seems methodical to avoid errors; these are common in such "easy" unit conversions.
1 mg/l Cl = 0.0005776 lb NaCl/bbl (both referring to brine) to my calculations, versus 0.00057848 per your scheme. The difference is insignificant, due to round off. It is noted that 1 lb=453.6 g.
In the second scheme you find lb NaCl per bbl of crude, then you correctly multiply it by the volume ratio crude/brine to find lb NaCl / bbl of brine.

[sp3d2]

thanks everyone. Now i wish to get the on how to get the mixing efficiency of desalter. will post about that soon.