Water and Oil Don't Mix or Do They?

Fresh water is critical to the processing of oil, according to an article by David Kujawski entitled New Trends in Oil Refinery Wastewater Reclamation. He states:

The average refinery requires 2.5 gallons of water for every gallon of crude oil processed.

He continues:

A typical large refinery will process 8-10 MGD [million gallons per day] of centrally collected dirty(TM) process wastewater. Usually this does not include stormwater and sanitary sewer which further add to the treatment burden.
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According to the United States Environmental Protection Agency website, the U.S. petroleum refining industry is the largest in the world, providing 23 percent of world production and including inputs to virtually all economic sectors, including the transportation and the chemical manufacturing sectors. In addition, this website notes:

Refineries use about 1 to 2.5 gallons of water for every gallon of product, meaning that the United States, which refines nearly 800 million gallons of petroleum products per day, consumes about 1 to 2 billion gallons of water each day to produce fuel (USDOE, 2006).

Why does refining of oil require so much water? The EPA website says that significant quantities of water are primarily for processing and cooling.

The Refining Process

There are two ways to process oil. The first process is called fractional distillation. You basically heat crude oil up, let it vaporize and then condense the vapor. Newer techniques use chemical processing on some of the fractions to make others, in a process called conversion. Chemical processing, for example, can break longer chains into shorter ones.

According to an OSHA technical manual on the petroleum refining process, petroleum refining begins with the distillation, or fractionation, of crude oils into separate hydrocarbon groups. The resultant products are directly related to the characteristics of the crude processed. Most distillation products are further converted into more usable products by changing the size and structure of the hydrocarbon molecules through cracking, reforming, and other conversion processes. These converted products are then subjected to various treatment and separation processes such as extraction, hydrotreating, and sweetening to remove undesirable constituents and improve product quality. Integrated refineries incorporate fractionation, conversion, treatment, and blending operations and may also include petrochemical processing.

Two examples of refinery water use show just how dependent our water and oil refining infrastructure is. Without either water or oil, the lifestyle we have is impossible.

A 1985 study by Jacobs Engineering entitled Water use, conservation and wastewater treatment alternatives for oil refineries in New Mexico states that New Mexico refineries presently use from 10.6 to 39.1 gallons of water per barrel of crude oil and generate 6.5 to 25.4 gallons of wastewater per barrel of crude.

Oil refineries are the top water users in the East Bay, according to the East Bay Municipal Utility District as related in an article on the Modern Transit Society website.

Water and economics of oil processing

The crude unit, vacuum unit, cat cracker, hydrotreating and coker are all incurring huge expenditures to procure supply water. Other major budgetary requirements include desalter wash water, cooling tower makeup water and boiler feed water. He states, the wastewater originating at the Crude Unit Overhead is one of the larger volumes of oil process wastewater generated.
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Contaminants include petroleum hydrocarbons, ammonia and organic sulfur. Without these contaminants the characteristic of this stream resemble a highly desirable supply water profile, similar to steam condensate.

According to an article on the http://www.eng-tips.com/ website:
A good and proper water wash would probably be the key to minimize corrosion problems on overhead distillation units. The quality of water wash is very important.
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In fact, large amounts of energy are used just to process and move water through the refinery. Mr. Kujawski notes that a large refinery will incur in excess of $100,000 per day for its total water related expenditures.
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Water Use and Oil Extraction

Secondary recovery of oil and gas is becoming the primary recovery method in many areas where the fields are depleted, including Saudi Arabia.

In addition to the refining process, it takes a large amount of water to extract oil from the ground. As pressures in oil fields fall, water injection into the oil bearing formations is used to keep the pressure up which is termed enhanced extraction. This became known in the oil business as secondary extraction. Enhanced recovery of oil, using fluids like CO2, water and steam is increasing oil output. Mathew Simmons in his book Twilight in the Desert notes:

However, by the late-1970s and 1980s water injection became part of the primary production (sometimes virtually from field startup) became a common practice in areas such as the North Sea, where it accelerated production buildup to peak levels and thereby gave the owners faster cash flow and payback on their considerable investment.

According to Mathew Simmons, author of Twilight in the Desert:

It typically takes 1.4 barrels of injected water to replace each barrel of oil produced, but the range of injected water can vary from as little as one barrel to as much as four to five barrels for every barrel of oil.

Water and Alternative Sources of Oil

There are several other sources of oil which are discussed as replacements for our traditional sources of oil. These alternative sources may be extensive, but they require even more water to produce the raw crude oil. Two excellent examples are the production of ethanol and the Canadian tar sands.
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A Department of Natural Resources, State of Minnesota paper notes that Minnesota [ethanol] plants use a range of 3.5 to 6 gallons of water per gallon of ethanol. In addition, it takes a large quantity of water to grow the corn in the first place. One acre of corn transpires, through the leaves, 4,000 gallons per acre per day of the growing season. This water comes from somewhere.

Another source of oil that is touted as a long term resource is the so called Canadian tar sands. Recent estimates state that it takes 2 to 4.5 barrels of water to produce bitumen from these tar sands located in the Athabasca River basin.

Total Water Use for Each Gallon of Oil

Estimates on water requirements for oil production vary widely. USGS estimates 1,851 gallons of water are required to extract transport and refine a barrel of oil (lifecycle). NREL estimates 65 to 90 gallons of water required per barrel of oil. Conservative estimates show the water requirement for a gallon of gasoline (2 to 2.5 gallons [NREL]) is similar to that of ethanol (3 gallons).

Using a reasonable estimate of 1 gallon of water per gallon of oil extracted and 2 gallons of water per gallon of oil processed, the amount of water used by the oil industry annually is truly staggering. Worldwide, we extract about 85 million barrels of oil per day. This equates to water use of 80-120 gallons per barrel or 6,800,000,000 gallons of water each day.

So the next time you drive to work, take a drink of your favorite bottled water or throw away the plastic packaging from your latest purchase, think of the oil and water that you are throwing away. Oil is becoming harder to get and water is irreplaceable.

By H. Court Young
Author, speaker, publisher and geologist
Promoting awareness through the written word
http://www.hcourtyoung.com
mailto: info@tmcco.com

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