Crude Oil Properties

[Krausen]

I understand there are hundreds of different kinds of crude oil, but would anyone know of any resource(s) with accepted published values for:

1. Bulk Modulus (or Compressibility ... the reciprocal of Bulk Modulus)
2. Critical Pressure

Even "ballpark" on-average values would be appreciated. There seems to be a lot of fluid property info on refined hydrocarbons out there, but crude oil seems to be limited. We have the crude assay info with specific gravity, viscosity, & RVP ... but nothing on bulk modulus or critical pressure. I'm specifically working with light, sweet crudes and have been using 182,000 psi for the bulk modulus & 700 psia for the critical pressure. This was based on inherited data from a co-worker that I've never been able to validate. Thanks!

 

[LittleInch]

You've answered your own question.

"hundreds of different kinds of crude oil" vs "accepted published values"

Doesn't work I'm afraid.

I think a lot of the time these things =you need the composition and then enter that data into PVT simulator and it works it out for you, but you need the compositional data.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

For a crude fraction with sg of 0.8, I get isentropic bulk modulus to be 153 800 psi, and at sg= 0.9 to be 213 000 psi.

For critical vapor pressure, safest to get this off your process simulation program outputs

 

[Krausen]

Thanks georgeverghese

Ok LI, let me re-phrase ... what would be the bulk modulus & critical vapor pressure of WTI?

 

[zdas04]

Krausen,
This is an incredibly complex topic. There is a Master's Thesis that takes 98 pages to show just how complex. See if that contains the numbers you want to mis-use.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[Krausen]

Thanks zdas04, appreciate the resource. Although I'm not sure how much stock to put into a canadian master's thesis where the author misspelled viscosity in the title. The dismal tide of modern education systems, I suppose ...

 

[georgeverghese]

The formula I have for isentropic bulk modulus for a petroleum crude fraction is

a = 100e3 x exp(1.995 - (0.0001343 x b) - (0.794/c^2) - (0.00233 x b/c^2))

where a = bulk modulus in psi
b = stream temp in degF
c = stream std specific gravity

You could check if this matches up with the results you'd get with the paper David has indicated.

It should also be possible to derive the bulk modulus from first principles when you have the defining thermodynamic expression for it. A process simulation program would help to generate the values to input into this thermo expression which is a differential, else it gets a little painful.