Petroleum Engineering Question

[Garak]

I've got a question for some of the big guns here, and hopefully it's in the right section, since it is about the science and technology of oils - albeit in the crude state. It's not about formulation; it's about petroleum engineering.

A number of days ago, a petroleum engineer came to see me, wanting to know if there was a way to calculate density on hydrocarbon compounds with more than 65 carbon atoms on first principles, for something he was doing with his graduate project. He had data for the various compounds with up to around 65 carbon atoms, but his sample had compounds with greater than 65 carbon atoms, and he was running into problems at the polymer injection phase.

I told him that such data would have to be established experimentally, and I don't know of a way to come up with a concrete density value for a given hydrocarbon by way of calculation. I told him when I need a value for a known compound and don't want to or cannot obtain it experimentally, I check the compendium, but it's not going to have something like he needs. I sent him off to the chemistry department in search of an organic chemistry prof and see if they had any ideas, and, barring that, to head back to engineering and find one of the polymer science guys, since they would have an approximation.

It turns out the latter answer was the correct one for his project, and there is an approximation for such samples. However, is there anything obvious that I've missed?

 

[MolaKule]

Just a predictive theory but:

Working backwards, find number of molecules (Avogadro's) per cubic Angstrom of higher molecular weight hydrocarbons < 65 in published literature.

Using ratio and proportions, and maybe interpolations, calculate density of >= 65 hydrocarbon molecules.

Other than that, advanced lab instrumentation could do it quickly.

 

[Garak]

Thanks. That makes sense. Given that the sample was crude, the more elementary lab methods weren't realistic. Finding the density of lead, given a chunk of lead, a graduated cylinder, and a scale, is only about a minute of work. A glob of crude oil made things more complex. Given his time frame, too, the approximation from the polymer science guys was the most effective.

As for your mathematical suggestion, I should try that and see how it compares to the number given to him by the polymer science guys, or any experimentally obtained values I could stumble across. Given all the varied compounds in crude, I didn't want to send him far astray, particularly on a project of such import to him. He's almost done, so maybe I can check his work and see if I can come up with some theoretical values with which to compare. Thanks!