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Using Crude Oil Assays

Using Crude Oil Assays

Using Crude Oil Assays

I wish to find an Excel template or worksheet that will take crude assays, and allow me to determine the vol % of a given cut point range. I would also want to determine the sulfur content, gravity, etc. of the selected cut point range. Before I set about doing it, I was wondering if anyone has such a worksheet already. I have a fairly good collection of crude oil assays and some form of trade may be possible.

RE: Using Crude Oil Assays

To be able to properly reply, it is important to know the starting input and the expected output.  Your reference to crude assays suggests the input, but not all crude assays  are the same.

The spreadsheet you are in general asking for is a detailed numerical tool to develop.  The following will discuss what it would have to do to provide what would be required to work with any and all crude assays.

One of the difficulties is developing the numerical tool to work with all forms of crude assay.  Once one starts to look at crude assays in detail, it is apprarent that the form and quality can vary significantly.  If the data is not based on some form of tbp cut definition, the data has to be converted to a tbp format (e.g. volume or mass vs tbp).

The crude cuts - naphthas (light, heavy), kero, diesels, VGOs and resid - properties would have to be regressed and the values reconciled against the whole crude (but which is better the whole crude data, or the cut data?) and alternative cuts properties to minimize the errors.  So, the TBP, S, density, viscosity, etc properties would all be fitted to numerical curves (property = f(temperature as tbp) with the error minimized (the error becomes a function of the data and the form of the regression).

From this numerical definition of the crude one can look at the properties as a function of tbp.  Determining the properties of a cut requires integrating the property over the subject bp range.  This is a rather simple undertaking for properties that are linear, such as volume.  For non-linear properties such as viscosity, the requisite mixing rules complicate the task.  Note that the same non-linearity would have complicated the definition of the input data.

In conclusion, the more complete tools I am aware of are part of the larger chemical engineering simulation packages.  I can offer you some related spreadsheet work, but the use is not as simple as you may want - to take full advantage of the assay overlap cuts some adjustment of the cuts is necessary.  The spreadsheet is not set up for regression of all the properties.  It will take a little while to dig the spreadsheets out, please advise if you are interested.

In any case good luck with your undertaking.  It is a worthwhile project.

RE: Using Crude Oil Assays

I do strategic planning for a refiner who charges bitumen from a single source. The assay is in TBP deg F versus vol %. The various properties are as you suggest and include gravity, sulfur, viscosity, etc. I do not do any design work and do not usually pursure overlaps and existing unit performance. I have a fairly good viscosity correlation which I may use.
Your spreadsheets may be a good place for me to start.
Thanks for responding.

RE: Using Crude Oil Assays

I should be able to look for the spreadsheet and find it before the end of the week.

The operation you describe makes me think of Western Canadian heavy oil, Alaska North Slope and Venezuela.  It would be interesting to know the crude and operation.

With this type of heavy oil, you are into assay temperatures that are questionable re: the existing correlations.  Also the residue which cannot be vaporized without cracking would be very large.

Considering the upgrading conversion processes are dependent on carbon structure, the application of mass spectroscopy is appropriate.  Although this type of assay work has been carried out by various parties over the years (actually the last few decades), it is still not in common use.  The increased accuracy of the analyses and improved yield forcasting (assumes the availability of MS based models, which have been developed but are not in the public domain) would easily pay for the programs (assuming reasonable processing volumes).  The costs require very committed technical personnel to defend the work and related expenses.

I'll be intouch when I have found the spreadsheet.

RE: Using Crude Oil Assays

Please reply to my email - so that I can send you the spreadsheet that I had mentioned.  It took some looking but I did find a copy.

You are welcome to contat me at 'rjpat@home.ca'.

RE: Using Crude Oil Assays

I got the automatic notification email that there was a response on my thread. I sent an email to your @home address but it came back. Please post your email address again so I can double check it.

I look forward to seeing the spreadsheet.

RE: Using Crude Oil Assays

Apologies, my new ISP is consolidating their systems in my area.  Please use 'rjpat@shaw.ca'.

RE: Using Crude Oil Assays

hello owg,
I am also preparing one database for different crude. But I am not planning to make a spread sheet. I have collected some data from web sites. I want to know more about the available sources where I can find out thesed data.
If you can provide me the information in this regard, it will be helpful to me.


Nirav Kholiya

RE: Using Crude Oil Assays

I have been collecting crude assays for about 20 years. Most came from clients and employers. A few can be found from time to time in the Oil and Gas Journal. I found about 14 in a text book by Gary and Handwerk, the secondary reference was "US Government Printing Office 16-57835-3".

I have not made any progress on the spreadsheet provided by Mr. Patterson yet.        

RE: Using Crude Oil Assays

Thank you for providing the information. I have found the book you suggested. I will get back to you if require any further information regarding this.

thanks again

Nirav Kholiya

RE: Using Crude Oil Assays

Did you ever get an answer to your request for an Excel spread sheet?  yamaha, contact me at sandan95@covad.net  thanx

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