TheLittlestGuy

What is crude oil and what is all this talk about it? Crude oil is a dark black or brown slurry of different hydrocarbons, some organics, and trace amounts of metals. Hydrocarbons are highly combustible chains of carbon and hydrogen atoms. Hydrocarbon molecules with different length and configuration have different physical and chemical properties. Learn more about hydrocarbons here (link). Compressed and heated organic materials that have died and sunk to the bottom of the ocean (mostly algae and zooplankton) slowly undergo chemical changes over long periods of time to become crude oil. This process is not fully understood and is relatively complicated. Different time lengths, organic material, and conditions change the properties of the oil that results.

Crude oil is extracted from the ground and then separated into different components according to how big the molecules are. Differences in boiling points (which are highly dependent on hydrocarbon chain length) allow for the separation of different components, called fractions, from one another. The process uses the same ideas that distillation uses. If you want to take liquor that’s 20% alcohol and 80% water and make it stronger you can heat it up so that the alcohol vaporizes while most of the water stays as a liquid. If you can capture this alcohol vapor and condense it back into a liquid, it will be a higher percent alcohol by volume. There’s no chemical reaction here, its just a separation technique. A refinery basically separates crude oil (which has millions of unique molecules of thousands of different lengths) into different fractions. The heaviest fractions, like asphalt, have very long carbon chains and are actually solids while shorted chains (as short as just one carbon atom and four hydrogen atoms) are light and are usually gases like natural gas. In between these two extremes are liquid hydrocarbons which are the main components of gasoline, kerosene, heating oil etc. The picture below shows how crude enters a fractionating column and is separated into light and heavy components by chain lengths.

[Click to enlarge. Image from www.energyinst.org.uk/education/coryton/page7.htm]

Different fractions have different uses. Below is a short list of products that come from crude oil with little alteration:

• Petroleum coke
• Sulfur
• Asphalt
• Waxes
• Lubricants
• Alkenes (olefins, which are polymerized into plastics)
• Fuel oils
• Jet fuel
• Diesel
• Gasoline
• Kerosene
• Aromatics (used in chemical production)
• Lights ends (ethane, propane, butane, pentane and other short chain hydrocarbons)
• Natural gas

why is oil used?

Wikipedia [http://en.wikipedia.org/wiki/Petroleum] says that “Due to its high energy density, easy transportability and relative abundance, it [oil] has become the world’s most important source of energy since the mid-1950s.” I think that sums things up well. Thanks wiki. During the 1970’s oil got a great deal of attention because of the energy crisis caused by inconsistent OPEC exports and alternative sources of energy were researched for a while. When it became apparent that finding clean, abundant, and cheap energy was not going to happen for a while and the energy crisis died down, then the focus went back to oil.

Extracting oil from the earth is a difficult process. The earth is quickly running out of easy-to-access oil. Usually less than 50% of the oil in a reservoir can be extracted by current cost effective techniques, so we’re not even getting all of the oil out of current wells. Some energy companies are trying to find new ways to reach oil in existing wells. Most oil is less dense than water so it floats on top of water (like grease sits on top of water when you add water to a dirty cooking pan). But some oil, called heavy oil, is more dense than water and sits lower in reservoirs. Some energy companies may try to pump a liquid that is even denser than this heavy oil into wells and make the heavy oil rise towards the top of the reservoir. The picture below shows what a typical reservoir looks like. Other types of petroleum resources exist. Oil shale and oil sands are far more abundant on the earth but also much more difficult to extract energy from without high costs and potential environmental damage.

[Image from: techalive.mtu.edu/meec/module19/Page1.htm]

production and consumption

Petroleum fuels 90% of transportation vehicles and provides 40% of the United States’ energy (wiki). The top three oil producing countries are Saudi Arabia, Russia, and the United States but most of the world’s readily accessible reserves are located in the Middle East (Saudi Arabia, Kuwait, Qatar, UAE, and Iraq). Venezuela has large reserves of heavy, sour crude (sour crude has a lot of molecules with sulfur atoms in them while sweet crude does not) and currently has the world’s largest refinery according to maximum capacity in barrels of oil per day. The United States, China, and Japan are the top consumers of Crude supplies, but the USA consumes around 20,588,000 barrels a day of crude oil, almost three times as much as the number two consumer, China.

the trouble with oil

The organic material that is found in crude oil sometimes contain sulfur atoms which if combusted turns into SO₂ and then into H₂SO₄, which causes acid rain. Acid rain kills everything from fish to forests. Soot is also produced when molecules containing sulfur are combusted. In an attempt to reduce emissions and the effects of acid rain, sulfur emissions have some of the tightest governmental regulations in the refining industry. LSD, Low Sulfur Diesel is diesel with a sulfur concentration below 500 ppm – the old standard. Ultra Low Sulfur Diesel (ULSD), the required diesel for new trucks starting in 2007, must have sulfur concentrations below 15 ppm. In a few more years, all highway vehicles will use ULSD by law. Below are the stickers you may have seen on diesel gas pumps.

[Image from: http://www.factsonfuel.org/images/labels.jpg]

While it is a step in the right direction to remove sulfur from petroleum before it is combusted, it’s far from enough. The real problem with oil as an energy source isn’t the sulfur, it’s the carbon. When hydrocarbons are combusted they necessarily release CO₂, which is a greenhouse gas. Climate change, a part of which is global warming, has been directly linked to the increased CO₂ levels in the over the last 100 years.

According to wikipedia, “petroleum’s worth as a portable, dense energy source powering the vast majority of vehicles and as the base of many industrial chemicals makes it one of the world’s most important commodities.” If we want to stop climate change, and eventually have a chance at reversing it, we must stop combusting fossil fuels like crude oil. It’s just that simple. How to replace the energy lost by not burning oil is the challenge. It’s a challenge, but not impossible. We’ll have to work in order to find a suitable solution or our grand childen will pay dearly for our mistakes.