Estimation of viscosity

[Jamesxpe]

If I know a certain crude oil's density and viscosity at a certain temperature, can I estimate the density and viscosity at other temperatures? How? I am new. This might be a dummy question. Thanks.

 

[monaco8774]

You need to have more information to estimate change in crude properties with temperature. At the very least to characterise a crude you need either the composition or you need some empirical tests on the crude prefferably with at least three data points. However if you dont have any of that, if they have given you viscosity and density at a lower temperature than operating then it should be conservatively high for design as the viscosity and density drop as temperature increases.

 

[TD2K]

The GSPA has curves for 'typical' hydrocarbon specific gravities as a function of temperature. Plot your value on that chart (figure 23.12) and then go to your new temperature to read off the new specific gravity. The various lines (various SGs at 60F) are fairly linear and parallel until you get into the lighter fractions at higher temperatures where they start to deviate from straight, parallel lines.

For viscosity, you need 2 points at two temperatures to estimate the value at a 3rd point from the methods I've seen. However, most hydrocarbons also have the log viscosity/temperature curves that are reasonably linear with other hydrocarbon fractions. If you can find someone with a set of those, I've plotted my 'fluid' on it and then extrapolated to the new temperature assuming my fluid's viscosity/temperature line has the same/similar slope. For crudes, there is more variation but the slopes still 'tend' to be similar. All depends on your accuracy requirements.

 

[jmw]

For viscosity you need the viscosity at two temperatures but for density, simply at one.
You may find the desnity and viscosity spreadsheets at

http://www.viscoanalyser.com/xls.html

useful.

JMW

http://www.ViscoAnalyser.com

 

[UmeshMathur]

Jamesxpe:

The variation of crude oil viscosity with temperature is heavily dependent on the type of crude - paraffinic, naphthenic, or aromatic. Generally, one needs two types of information about the crude to be able to characterize it. If you provide the density and viscosity data for your crude, I can help you develop the required estimates at other temperatures. Even better, I'll show you the steps involved so you can do it yourself next time.

As others have noted, having viscosity available at two temperatures enables prediction at other temperatures more reliably. However, if only one viscosity measurement is available along with the density, we can still do a decent job. I am assuming you need viscosity for fluid flow calculations. If not, please advise.