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How does crude oil become "heavy"
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How does crude oil become "heavy"
by FossilFool » Fri 10 Feb 2006, 00:26:03
I don't get that. They say it will be so much harder to get out later.
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Re: How does crude oil become "heavy" the instant
by Micki » Fri 10 Feb 2006, 00:37:43
WHAT???
Not sure I understood what you were asking, but lets give it a try anyway..
Oil doesn't just become heavy.
Normally the light sweet crude is at the top and oil with higer degree of impurities such as sulphur (heavy) falls to the bottom.
The heavy stuff requires more refining.
But generally I think both of them are about as easy to pump up.
What however happens when a well has peaked is that the preassure that makes the oil gush up to the surface dies off. It is therefore necessary to pump in water into the the ground to artificially drive up the preassure.
Besides more effort and cost this may also ruin the well.
Alternatively horizontal drilling may be done to cover a larger area at once.
Hope this was the type of answer you were after.
Not sure I understood what you were asking, but lets give it a try anyway..
Oil doesn't just become heavy.
Normally the light sweet crude is at the top and oil with higer degree of impurities such as sulphur (heavy) falls to the bottom.
The heavy stuff requires more refining.
But generally I think both of them are about as easy to pump up.
What however happens when a well has peaked is that the preassure that makes the oil gush up to the surface dies off. It is therefore necessary to pump in water into the the ground to artificially drive up the preassure.
Besides more effort and cost this may also ruin the well.
Alternatively horizontal drilling may be done to cover a larger area at once.
Hope this was the type of answer you were after.
- Micki
Re: How does crude oil become "heavy"
by SHiFTY » Fri 10 Feb 2006, 09:45:19
Clarification: the weight and sulphur content are not necessarily related. You can have heavy sweet and light sour crude too.
Essentially, crude oil consists of a mixture of hydrocarbons, from very light (dissolved natural gas, propane, gasoline etc) to very heavy (bunker oil, tar, asphalt). All oilfields have different mixtures of hydrocarbons which are fractionated (distilled) at a refinery into end products- gasoline, diesel, jet fuel etc.
Heavy oil is a tar-like crude which contains the heavy, 'long chain' hydrocarbons. These can be cracked in a refinery into lighter products like diesel, but it requires energy.
Sweet/Sour refers to the sulphur content. Sour oil generally has a lot of acidic sulphur compounds which must be removed (they cause massive pollution). Again, this requires energy to do.
So in summary light & sweet = good, easy to refine; heavy & sour = bad, takes a lot more energy to refine.
Obviously it is easier to use the light sweet stuff first.
Essentially, crude oil consists of a mixture of hydrocarbons, from very light (dissolved natural gas, propane, gasoline etc) to very heavy (bunker oil, tar, asphalt). All oilfields have different mixtures of hydrocarbons which are fractionated (distilled) at a refinery into end products- gasoline, diesel, jet fuel etc.
Heavy oil is a tar-like crude which contains the heavy, 'long chain' hydrocarbons. These can be cracked in a refinery into lighter products like diesel, but it requires energy.
Sweet/Sour refers to the sulphur content. Sour oil generally has a lot of acidic sulphur compounds which must be removed (they cause massive pollution). Again, this requires energy to do.
So in summary light & sweet = good, easy to refine; heavy & sour = bad, takes a lot more energy to refine.
Obviously it is easier to use the light sweet stuff first.
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Re: How does crude oil become "heavy"
by drew » Fri 10 Feb 2006, 10:22:47
In chemical formula for you; ps I have forgotten much of my nomenclature
From light to heavy
Methane ch4
ethane ch3-ch3
propane ch3-ch2-ch3
???? ch3-ch2-ch2-ch3
pentane ch3-ch2-ch2-ch2-ch3
etc....
For those not in the know a ch3-is called a methyl group and is attached at the ends of the chains, it contains 3 hydrogens and one carbon, and has one open bond site. The CH2 groups have two open bond sites.
Heavy crude has a preponderance of long chain hydrocarbons, light crude has a higher percent of the shorter ones.
Drew
From light to heavy
Methane ch4
ethane ch3-ch3
propane ch3-ch2-ch3
???? ch3-ch2-ch2-ch3
pentane ch3-ch2-ch2-ch2-ch3
etc....
For those not in the know a ch3-is called a methyl group and is attached at the ends of the chains, it contains 3 hydrogens and one carbon, and has one open bond site. The CH2 groups have two open bond sites.
Heavy crude has a preponderance of long chain hydrocarbons, light crude has a higher percent of the shorter ones.
Drew
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drew - Tar Sands
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Re: How does crude oil become "heavy"
by rockdoc123 » Fri 10 Feb 2006, 19:51:03
$this->bbcode_second_pass_quote('', 'N')ormally the light sweet crude is at the top and oil with higer degree of impurities such as sulphur (heavy) falls to the bottom.
Nope....you see that in places where you have tar mats...possibly due to water washing by underlying freshwater but more often you actually see the more biodegraded and hence heavier from an API perspective crude at the top. A good example of this is Venezuela where the heavy oil is underlayen by relatively light oil.
$this->bbcode_second_pass_quote('', 'T')he heavy stuff requires more refining.
But generally I think both of them are about as easy to pump up
not always....it really has to do with viscosity. Sometimes heavy oils are very viscous and difficult to move in pipelines unless you put additives in like drag reducers.
$this->bbcode_second_pass_quote('', 'W')hat however happens when a well has peaked is that the preassure that makes the oil gush up to the surface dies off. It is therefore necessary to pump in water into the the ground to artificially drive up the preassure.
Besides more effort and cost this may also ruin the well.
Alternatively horizontal drilling may be done to cover a larger area at once
some major misunderstanding here. Pressure in an oil well will die off only in the case where you are not connected to an active acquifer that provides water drive support (eg. gas depletion drive). In this case you will just gradually produce higher and higher water cuts. Although horizontal wells can be used to access greater drainage areas they are more often used to allow for high offtake rates at relatively low drawdown, hence avoiding gas or water coning.
$this->bbcode_second_pass_quote('', 'M')ethane ch4
ethane ch3-ch3
propane ch3-ch2-ch3
???? ch3-ch2-ch2-ch3
pentane ch3-ch2-ch2-ch2
You're missing butane, heptane, octane
Just so everyone will know there are basically two ways that heavy oil occurs (or as theory would have it). The first method is by water washing whereby continual flux of fresh water through the oil interface removes the light ends. This does require continual replinishment of the fresh water. The Chinese really like to favor this model....even though in some cases it doesn't make sense.
The most popular theory is that heavy oil is created through biodegradation whereby bacteria "eat up" the light ends. Up until a few years ago it was believed that this required continual replinishment of oxygenated waters but recently it was found anerobic bacteria are possibly responsible. The one thing we know is there is a temperature limit at which such bateria is active....so beyond 80 degrees C you would not see biodegradation happening.
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