8 replies to this topic

[CHEMSTRONG]

Dear Sir,

 

I have crude oil assay for 8 no of crudes from Mangla, Bombay High, Basra light/heavy crudes. I have paraffin content , pour point ,density , boiling point of all components, molecular weight of all crude components. I want to evaluate which all crude oils are paraffinic in nature with this data.

Request your advice on this.

 

1) Can I calculate UOP K factor to get this, if yes, will this data is sufficient ?

2) Can I calculate pour point from this assay for a particular crude blend to get insights into paraffinic content also? What will be blending rule ? is it always nonlinear ?

3) Any other method to get info on paraffinic nature of crude ?

 

 

Best Regards,

Chetan Chavan 

[PingPong]

First of all: DO NOT OPEN TWO TOPICS ABOUT BASICALLY THE SAME SUBJECT!!!

That can only lead to parallel discussions which is confusing for everybody.

 

I will put the similar question from your other topic here so that you can delete the other topic:

I have SARA Analysis of 5 diff crude oils with me. I wan to know the crude type like paraffin naphthenic and aromatic from this data , is it possible ? How to do it ?

 

I have crude oil diff components mol fractions also. but how to get total paraffins in crude from this?

 

SARA will not give you enough data as it does not distinguish between alkanes (paraffins) and naphthenes but only gives the sum of them (saturates).

https://www.e-educat...tion-crude-oils

 

But why would you bother to try to put a label on each crude?

It are the properties that matter, not the label.

Each decent crude assay will give all the relevant crude properties, including its pour point.

 

However it is not so much the label of the crude that matters, or even its properties, but the properties of the products (naphtha, kerosene, gasoils, VGO's) you can get from a certain crude. Those are also given in the crude assay.

For example: if a refinery wants to produce lube oils or naphthenic base oils the properties of the VGO's in the assay are important and determine the choice of crude oil.

 

There are methods for pour point blending but those are not very accurate and really only usable for distillate fractions, not whole crudes, or residues, or ....

Edited by PingPong, 03 May 2020 - 04:33 AM.

[CHEMSTRONG]

I have crude oil SARA analysis for say 8 diff crudes like Upper Zhakhum, Bombay High. I want to know if the crude is paraffin or not ? How to get this ? I have individual components composition, BP, Mol wt and all components properties like pour point .  high pour point and high API gravity is true indicator of high paraffin content ? Also wax content of higher than 3 percent denotes paraffinic crude ? 

 

Regards,

Chetan Chavan 

[PingPong]

I have crude oil SARA analysis for say 8 diff crudes like Upper Zhakhum, Bombay High. I want to know if the crude is paraffin or not ? How to get this ?

Did you already have time to read the link that I posted?

 

See also diagram below which uses the same criteria but is probably easier:

 

 Crude Oil Composition Ternary Diagram.jpg   47.83KB   1 downloads

 

 

It is true that paraffinic crudes often have a relatively high API gravity, a relatively high UOP-K, a relatively high pour point, a relatively high wax content but you can't characterize a crude based only on that.

 

If you really want to know it for a specific crude get a good assay of it and simply plot the data in the above ternary diagram.

 

For example: Upper Zhakum crude contains 40 % paraffins, 23 % naphthenes and 37 % aromatics.

That puts it exactly on the border line between Paraffinic and Paraffinic-naphthenic.

So what would you like to call it? Paraffinic? Or Paraffinic-naphthenic?

And would it matter which of the two it really is?

Of course not.

Once again: it is not the label that matters; it are the properties of the product fractions that matter!

 

 

Attached Files

•  Upper Zakum crude oil assay _ UPZAK17Y.pdf   229.31KB   13 downloads

[CHEMSTRONG]

Dear Sir,

Thanks for your message .

I hv following crudes assays like Murban, Basra Light, Basra Heavy , Mangla, Kuwait and upper Zhakhum etc. I want to know if they are paraffin or nt . I hv put Basra Light and Basra Heavy as paraffinic and naphthenic right now and others as paraffinic only. Is it correct selection? Also upper Zhakhum is paraffinic naphthenic ?

Secondly, though we have crude assay from web but I hv crude assay given . Also assay will differ for a free based on time it is taken right . So I want to consider my crude assay data and not general data available on web here.

Thirdly, I hv crude assay data in the form of individual components composition, pour point for all components density cloud point and SARA analysis for all components but I don't hv paraffins vol percent on whole crude here . How to calculate this based on this ?

Fourthly, I hv some crudes for which there is a low pour point and high API how is it possible ? Still can it be paraffinic crude ?? My understanding is higher API higher pour point and higher wax content leads to paraffinic crude is it correct ?

Also I hv calculated uop k factor based on specific gravity bit u could nt get AVG boiling point for this which is generally determined based on TBP distillation data which I don't hv now . So I calculated AVG BP based on individual componejts Bp

Regards,
Chetan Chavan

[PingPong]

1) Upper Zakhum is either paraffinic or paraffinic-naphthenic, depending on what you like to believe. See ternary diagram.

Of the others you mention I don't have paraffin/naphthene/aromatics content so I don't know whether they are officially to be called paraffinic or not.

 

2) We don't know what assays you have, so we have no opinion about them.

The Upper Zakhum assay that I posted is from ExxonMobil. You may have heard of them. They are an American oil company. The biggest in the world. They are not amateurs.

 

3) Such a detailed crude assay is suspect as it is probably computer generated from the few product fractions of a real crude assay. In that case the properties (pour point, cloud point, SARA) of each pseudocomponent were generated using dubious correlations that have low accuracy.

But even then: if you don't have the paraffinic content of a crude oil then you can't say whether it is paraffinic or not. That should be obvious.

 

4) High API gravity is often, but not always, an indication of paraffinic crude. A light crude, with not much residue in it, will have a high API even if it is not paraffinic.

Moreover one paraffinic crude may have mainly light paraffins with a low pour point, while another paraffinic crude may have more heavy paraffins with a high pour point. So two crudes with the same amount of paraffins but with a different light/heavy paraffin ratio will have different PP.

Also normal-paraffins have a much higher pour point than iso-paraffins, so two crudes with the same amount of paraffins but with a different normal/iso ratio will have different PP.

Also the rest of the crude plays a role in the value of the PP, so two crudes with the same amount of paraffins but with a different naphthenes/aromatics ratio will have different PP.

 

5) The crude oil UOP-K is not a reliable indicator of type of crude, unless it has an extreme value like 12.5 or below 11.

In any case to calculate the UOP-K you need to use the Mean Average Boiling Point (MeABP) of the whole crude which is to be calculated from whole crude ASTM distillation data, not TBP data. Check API technical databook and GPSA engineering databook.

[CHEMSTRONG]

Dear Sir,

 

Thanks for your reply.

 

1. I am assuming Upper Zhakhum as Paraffinic naphthenic for now.

 

2. I know Exxon, but my point was crude assay they have got from lab testing of that sample and assay sample I have will be different depending upon time when sample was drawn. though reservoir conditions affect this a lot here. So I wanted to analyze my assay data in details. 

 

3) I understand now clearly why high pour point and high API alone can not predict this.

 

Regards,

Chetan Chavan 

 

 

 

Regards,

Chetan Chavan 

[CHEMSTRONG]

Crude Assay i have has standard density, PP, cloud point, molecular weight, SARA analysis vol percent of all crude components here.

 

So based on this how to determine Paraffinic volume percent here ?

 

I have individual component density and component mol fraction composition also .Can I take weightage avg and calculate avg density and thereby specific gravity using linear blending rule and can I apply same rule to calculate avg BP using linear blending rule.?

 

Actually I have done using composition of all components and this data., found UOP k factor , but for all crudes, t is higher than 12 always. I do not know if it is right procedure heere

 

Regards,

Chetan Chavan 

[PingPong]

So based on this how to determine Paraffinic volume percent here ?

Based on that you cannot.

 

To calculate the UOP-K factor you need the Mean Average Boiling Point (MeABP) as defined in API technical databook, GPSA engineering databook and many other sources.

To calculate the MeABP you need an ASTM distillation curve of the crude oil.

 

I would expect that when you enter your crude assay data into Hysys it can calculate the ASTM distillation curve.

I would even expect that Hysys can also calculate UOP-K or Watson K as it is also called.