Oil Spill Density: Answers to Questions

[gwangi]

this oil leak in the Gulf has got me wondering about a few things. There are a lot of questions being asked and the only answers seem vague and uninformed. I'm new here so bear with me as I learn the etiquette.
My primary question is why is this oil staying near the bottom when its STP density is less than water? I know that unlike water the long chain hydrocarbon molecules are subject to compression, so I assume that the low temperature and high pressure have a definite affect, but does anyone have any actual numbers? How dense is crude at +10 F and 5000 feet down? What is the temp of the oil itself as it exits the pipe?
additionally: under what natural conditions does its specific gravity (is that the correct use of the term?) become less than water and the stuff begin to rise to the surface?
thanks in advance for any information you can provide

 

[phyzguy]

Who says it is staying near the bottom? I thought that it is rising up to the top.

 

[gwangi]

Who says it is staying near the bottom? I thought that it is rising up to the top.

The only source of information I have is the standard news that everyone hears, and according to that the vast majority of the stuff is billowing around a few hundred feet above the bottom, while only a small quantity is actually floating. And even that description changes day by day. Is it slowly rising to the top? Is it slowly sinking to the bottom? Is it stable at its current depth? It all depends on who you listen to. I'm hoping somebody here can provide me with some actual facts based on science rather than media speculation.

 

[Astronuc]

See Table 1, page 11/15 - The Density Behaviour of Heavy Oils in Freshwater:
http://www.epa.gov/oem/docs/oil/fss/fss06/fingas_1.pdf

and Table 2.

 

[croghan27]

Wonder if the chemicals that are being adding make a difference to the API Gravity? I have used it in oil plants.

You go to the spill. cover it with the liquid (it was called XZIT) then use water to wash the heavy oil away. It certainly stops it from clinging to the ground, pavement or any structure.

 

[gwangi]

I misread an earlier comment in another thread. The poster said that the temp at the wellwead leak was +10 F above freezing (+42 F) not +10 F.
Found some interesting and pertinent at engineering toolbox. but it looks like I have to spend some in a relearning curve before I can apply any of it. thanks for the link astronuc.

 

[PRDan4th]

Crude oil is a mixture of many hydrocarbon components ranging from light ends (propane & Butane) and mid range components C5-C8 or C9 (natural gasoline) and very heavy hydrocarbons which can have a density greater than water. When this crude first emerges from the pipeline at the sea floor it is hot relative to the sea water, this oil temperature is known by the oil company, but I have not seen it published.

During the mixing with the sea water as it rises, some of the heavier components can become split from the lighter components and sink. Tar is the end stage of crude oil with the light ends removed. this can be very sticky and aglomerate with sand and stay near the bottom and move with the currents like light rocks.

 

[croghan27]

Very good PRDan4th ... best explanation I have seen so far. :)

That process is obvious in the oil sands of Fort McMurray.

 

[mheslep]

Crude oil is a mixture of many hydrocarbon components ranging from light ends (propane & Butane) and mid range components C5-C8 or C9 (natural gasoline) and very heavy hydrocarbons which can have a density greater than water. [...]

While the very heavy asphaltene components may have a density of ~1.1 g/cm^3, I believe these are an extremely small fraction of the total petroleum product failing to rise to the surface, especially with cold seawater density at ~1.03 g/cm^3. My (limited) understanding is that the majority of the (less dense than water) petroleum products that fail to rise to the surface do so because they http://en.wikipedia.org/wiki/Emulsion" with various temperature layers in the water column; the density of the emulsified hydrocarbon + cold water is still greater the clean warmer water above, trapping the hydrocarbons in the thermal layer.

 

[socean]

Why not introduce bio-active particles that bind to hydrocarbons and each other, and also produce some kind of gas, e.g. methane that is trapped? Result: oil "coagulates" into jelly-like, huge blobs that float and can be collected.

 

[croghan27]

Why not introduce bio-active particles that bind to hydrocarbons and each other, and also produce some kind of gas, e.g. methane that is trapped? Result: oil "coagulates" into jelly-like, huge blobs that float and can be collected.

The same thing could be accomplished by just stopping the Corexit.

Then the 60,000bpd (so it seems now) would just make a big blanket and kill even more of the Gulph.

 

[croghan27]

Oil is a general term used to denote petroleum products which mainly consist of hydrocarbons. Crude oils are made up of a wide spectrum of hydrocarbons ranging from very volatile, light materials such as propane and benzene to more complex heavy compounds such as bitumens, asphaltenes, resins and waxes. Refined products such as petrol or fuel oil are composed of smaller and more specific ranges of these hydrocarbons.

Piterson: Crude oil is indeed made up of many hydrocarbon constituents, yet by now the methanes, ethanes, propanes and butanes have all weathered away. Propane becomes a gas around -37F and butane around +36F. (Did you know that when you buy 'propane' for your BBQ it is about 35% butane in the winter and up to 70% butane in the summer?) It is the C5s and heaver that are problematic.

This is what has happened in the oil sands ... the lighter elements have disappeared into the atmosphere and only the heavy are left - this means the oil can be (must be) mined using conventional (and some unconventional) methods.

 

[mheslep]

Piterson: Crude oil is indeed made up of many hydrocarbon constituents, yet by now the methanes, ethanes, propanes and butanes have all weathered away. Propane becomes a gas around -37F and butane around +36F. (Did you know that when you buy 'propane' for your BBQ it is about 35% butane in the winter and up to 70% butane in the summer?)

At standard atmospheric pressure propane is a gas at low temperatures. Double the pressure and in the presence of water it can remain a ~semi-solid clathrate up to +32F and beyond.
https://eee.uci.edu/programs/hongchem/RDGPhaseDiagrams.pdf

 

[Evo]

You guys have been responding to a mass spammer. That's what they do now days, they search for keywords, find a post on the internet, post a canned blurb to go with the keyword and insert a spam link.

 

[croghan27]

You guys have been responding to a mass spammer. That's what they do now days, they search for keywords, find a post on the internet, post a canned blurb to go with the keyword and insert a spam link.

A mass spammer??

Has that person found the Higg's boson of etalk?

 

[uart]

You guys have been responding to a mass spammer. That's what they do now days, they search for keywords, find a post on the internet, post a canned blurb to go with the keyword and insert a spam link.

I must be missing something becasue I can't see any "spam link". Could you please explain this further EVO?