oil spills

oil spills

Large oil spills, like the Exxon Valdez in Alaska in 1989, get a lot of attention, as they should. Besides these large spills, though, much more oil enters the oceans from small leaks that are only a problem locally. In this concept, well take a look at a large recent oil spill in the Gulf of Mexico.

the gulf of mexico oil spill

New drilling techniques have allowed oil companies to drill in deeper waters than ever before. This allows us to access oil deposits that were never before accessible, but only with great technological difficulty. The risks from deepwater drilling and the consequences when something goes wrong are greater than those associated with shallower wells.

spill

Two days after the explosion, the drill rig sank. The 5,000-foot pipe that connected the wellhead to the drilling platform bent. Oil was free to gush into the Gulf of Mexico from nearly a mile deep (Figure 1.2). Initial efforts to cap or contain the spill at or near its source all failed to stop the vast oil spill. It was not until July 15, nearly three months after the accident, that the well was successfully capped. Estimating the flow of oil into the Gulf from the well was extremely difficult because the leak was so far below the surface. The U.S. government estimates that about 4.9 million barrels entered the Gulf at a rate of 35,000 to 60,000 barrels a day. The largest previous oil spill in the United States was of 300,000 barrels by the Exxon Valdez in 1989 in Prince William Sound, Alaska.

explosion

Working on oil platforms is dangerous. Workers are exposed to harsh ocean conditions and gas explosions. The danger was never more obvious than on April 20, 2010, when 11 workers were killed and 17 injured in an explosion on a deepwater oil rig in the Gulf of Mexico (Figure 1.1). The drilling rig, operated by BP, was 77 km (48 miles) offshore and the depth to the well was more than 5,000 feet. The U.S. Coast Guard tries to put out the fire and search for missing workers after the explosion on the Deepwater Horizon drilling rig. Eleven workers were killed.

textbook_image

plugging the well

BP drilled two relief wells into the original well. When the relief wells entered the original borehole, specialized liquids were pumped into the original well to stop the flow. Operation of the relief wells began in August 2010. The original well was declared effectively dead on September 19, 2010.

cleanup

Once the oil is in the water, there are three types of methods for dealing with it: 1. Removal: Oil is corralled and then burned; natural gas is flared off (Figure 1.3). Machines that can separate oil from the water are placed aboard ships stationed in the area. These ships cleaned tens of thousands of barrels of contaminated seawater each day. 2. Containment: Floating containment booms are placed on the surface offshore of the most sensitive coastal areas in an attempt to attempt to trap the oil. But the seas must be calm for the booms to be effective, and so were not very useful in the Gulf (Figure 1.4). Sand berms have been constructed off of the Louisiana coast to keep the oil from reaching shore. (a) On May 17, 2010, oil had been leaking into the Gulf for nearly one month. On that date government estimates put the maximum total oil leak at 1,600,000 barrels, according to the New York Times. (b) The BP oil spill on June 19, 2010. The government estimates for total oil leaked by this date was 3,200,000 barrels. 3. Dispersal: Oil disperses naturally over time because it mixes with the water. However, such large amounts of oil will take decades to disperse. To speed the process up, BP has sprayed unprecedented amounts of chemical dispersants on the spill. That action did not receive support from the scientific community since no one knows the risks to people and the environment from such a large amount of these harmful chemicals. Some workers may have become ill from exposure to the chemicals.

textbook_image

textbook_image

textbook_image

longterm effects

There is still oil on beaches and in sediment on the seafloor in the region. Chemicals from the oil dispersants are still in the water. In October 2011 a report was issued that showed that whales and dolphins are dying in the Gulf at twice their normal rate. The long-term effects will be with us for a long time. Click image to the left or use the URL below. URL:

impact

The economic and environmental impact of this spill will be felt for many years. Many people rely on the Gulf for their livelihoods or for recreation. Commercial fishing, tourism, and oil-related jobs are the economic engines of the region. Fearing contamination, NOAA imposed a fishing ban on approximately one-third of the Gulf (Figure 1.5). Tourism is down in the region as beach goers find other ways to spend their time. Real estate prices along the Gulf have declined precipitously. This was the extent of the banned area on June 21, 2010. The Gulf of Mexico is one of only two places in the world where bluefin tuna spawn and they are also already endangered. Marine mammals in the Gulf may come up into the slick as they come to the surface to breathe. Eight national parks and seashores are found along the Gulf shores. Other locations may be ecologically sensitive habitats such as mangroves or marshlands.

textbook_image

instructional diagrams

No diagram descriptions associated with this lesson

questions

the largest oil spill in the united states waters was

a) the santa barbara oil spill in 1969.

b) the hawaiian patriot in honolulu, hawaii in 1977.

c) the exxon valdez spill in alaska in 1989.

-->  d) the deepwater horizon spill in the gulf of mexico spill in 2010.

the deepwater horizon spill of 2010,

a) injured a few workers and sank an offshore drilling rig.

b) took place mostly in mexican waters.

-->  c) was caused by an explosion on a deepwater oil rig.

d) all of these.

what is true about deepwater drilling?

a) it is technologically very difficult.

b) it opens up petroleum deposits that were never accessible before.

c) it is extremely risky.

-->  d) all of the above

the deepwater horizon spill ____ barrels of oil a day entered the gulf.

a) 10,000 to 20,000

b) 25,000 to 35,000

-->  c) 35,000 to 60,000

d) 60,000 to 75,000

oil companies will continue to go for hard-to-get-at deposits as long as

-->  a) people will pay for the oil.

b) they are interested in meeting the technological challenge.

c) there is oil to get.

d) none of these.

dispersal of oil

a) is not naturally effective.

-->  b) with chemicals may cause more harm to the environment than the oil itself.

c) can often be accomplished with a small amount of chemical dispersants.

d) with chemicals is a simple, harmless process.

one of the ways to clean up spilled oil is to

-->  a) corral it and then burn it.

b) blow it onto shore where it wont damage marine creatures.

c) drop giant sponges on it then burn the sponges.

d) get boats with propellers into it to mix the oil with the water.

when we no longer hear about an oil spill in the news, it is because the region has been cleaned up and is back to normal.

a) true

-->  b) false

which of the following is not true?

a) seabirds dive into an oil slick because the surface looks like calmer water.

b) plankton, which form the base of the marine food chain, are killed by oil.

c) whales and dolphins are killed by oil and/or the chemical dispersants.

-->  d) petroleum acts like a fertilizer to increase the amount of life in an area with a spill.

more oil enters the oceans from small leaks than from large spills.

-->  a) true

b) false

diagram questions

No diagram questions associated with this lesson