The Environmental Impacts of Offshore Oil Drilling
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The Environmental Impacts of Offshore Oil Drilling


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If there had been any doubt before, the 2010 catastrophe on the Deepwater Horizon in the Gulf of Mexico has really driven home the message that drilling for oil is a messy and risky business. Consequently, decisions are now being made that affect the future of offshore oil drilling. But how risky is it really? Should we stop offshore drilling?

Even following the devastating oil spill, opinions are split on offshore oil drilling. A USA Today article summed it up quite nicely: 

"Environmental hazard or energy bonanza: Oil and natural gas trapped beneath the USA's ocean floor mean different things to different people". 

Oil drilling will continue to be a big deal unless we become less dependent on fossil fuels (or the oil runs out). Understanding the process and looking at the environmental impacts involved will help to shed some light on offshore oil drilling.

Offshore oil drilling: how does it work?

Before an offshore oil well can be drilled, it must first be located. Geologists locate oil wells beneath the ocean floor through the use of magnetic and seismic surveys. Magnetic surveys work by mapping the magnetic properties of the ocean floor, which can help indicate where oil and gas are located. Seismic surveys work by sending shock waves into the ocean floor, and then interpreting the waves that are reflected back to hydrophones on the surface. They don't know for certain whether a site contains oil until exploratory drilling takes place.

In order to drill exploratory wells, government permission must first be obtained. An environmental impact assessment may be carried out at this stage. Then, using an exploratory drilling rig, geologists drill four or so temporary wells to find out if there's a viable source of oil. If they think they've found a good source of oil, then more drilling takes place to substantiate the findings.

Once oil or gas is discovered, then a production well is drilled and a production oil rig built to replace the exploratory drilling rig. An average well will last from ten to twenty years, and even after it has run dry an oil rig may still be used for processing or storage of petroleum from other wells, so the production oil rig is built to last. The platforms are normally made of steel and are secured to the seabed using concrete or metal foundations.

The drilling itself takes place by connecting the drill site to the platform with a marine riser, a flexible tube in which all of the equipment descends. The wells can often be located deep in the earth's crust, so the drill is made up of multiple drill pipes all connected together in a drill string. Drilling mud (also called drilling fluid) is pumped into the well to remove the drill cuttings, cool the drill bit and maintain the pressure. The drilling mud then flows back to the surface, where it's filtered and pumped back down again. A blowout prevention system is also installed to guard against pressurized oil and gas flowing up the well.

Once the oil is reached, the drill string is removed and a more permanent pipe called a casing is installed. This casing helps to control the flow of oil and gas from the well up to the surface. Initially the pressure from the reservoir is enough to pump the oil or gas, but as the pressure decreases various techniques are used to increase the pressure in the reservoir. These techniques include pumping in gas, water, compressed air or steam. The crude oil obtained from the well is then refined at oil refineries onshore.

Please note that I have simplified the process in order to give a quick overview of how offshore drilling works. If you'd prefer a more detailed explanation, the How Stuff Works article and the Hub Oil Drilling: Demystified are both good sources.

The environmental impacts of offshore drilling

Many aspects of the offshore drilling process can cause environmental impacts, from locating the oil, to drilling and pumping the oil to the surface, to the infrastructure required to drill and transport it. These environmental impacts may vary in intensity depending on many factors, so this is just a summary of some of the potential impacts that are likely to occur.

Locating the oil

Seismic surveys have been reported to impact fish and marine life. Whales in particular are extremely sensitive to the seismic waves generated when searching for oil and gas deposits in the sea bed. The noise causes them to become disoriented, which can lead to disruption to migratory patterns and even mass beachings. It is also reported to impair the health and hearing of fish.

Effects on the ocean floor

Offshore drilling physically disrupts the seafloor habitat and the benthic community. Between the actual footprint of the drill rig, undersea pipelines, dredging ship channels, and the cuttings and other drilling debris, there are many elements of drilling that leave a lasting impact on the ocean floor. This is important to note, especially when considering that many of the world's most sensitive ocean floor habitats are also good sources of oil and gas. For instance, the Gulf of Mexico, the arctic and the Great Barrier Reef are all extremely diverse ecosystems with significant oil and gas deposits.

Some experts claim that oil rig platforms are good habitat for fish. In fact, as part of the "rigs to reefs" program, old oil rigs are tipped over and left on the ocean floor to become artificial reefs.

Water pollution

There are two main sources of water pollution from offshore drilling: drilling fluid and oil spills and leaks.

Firstly, the drilling fluid is claimed to be toxic to marine life. This fluid, used to lubricate, cool and regulate pressure when drilling, contains petroleum products and heavy metals. The impacts of drilling fluid differ significantly, because it's so often made up of different concentrations of the above elements and applied in different ways. Reported impacts include affecting the health and reproduction of marine life, reducing the populations of bottom-dwelling creatures and biomagnifying toxic substances in the food chain.

Secondly, the risk of oil spills, leaks and catastrophes is another key consideration. Opponents of offshore oil drilling claim that one oil rig can "dump more than 90,000 metric tons of drilling fluid and metal cuttings into the ocean" over its lifetime (data from Culture Change). Although we are all aware of the effects of oil on seabirds, oil is also extremely toxic to marine life (see Pew Trusts' "The Future of Oil and Water" for a good explanation). However, it should be noted that some specialists say that significantly more oil is spilled into US waters by marine transportation and industrial and municipal sources than offshore oil and gas drilling. Some proponents of offshore drilling in the Gulf of Mexico claim that the marine life in that region is pre-adapted to oil in the water due to natural seeps. There have also been claims that offshore oil drilling can reduce the amount of oil leaking into the ocean from these natural seeps.

There is mixed opinion about the amount of water pollution caused by offshore oil drilling (when there are no catastrophic oil spills). Some specialists claim that discharges into the ocean from offshore drilling (in the US) contain insignificant levels of toxic chemicals due to the regulations at the state and federal level. Environmental groups would disagree, claiming that offshore oil drilling has a significant negative impact on fragile marine and coastal ecosystems, and that the risk of a devastating spill isn't worth taking.

Oil Spills

The effects from large offshore oil spills like the recent Deepwater Horizon catastophe are twofold; we must consider the effect of the oil spill itself and the effects of cleanup efforts. When a large amount of oil spills into a body of water, the oil spreads mainly onto the surface of the water and can either remain cohesive or break up due to wave action. Over time, the oil may degrade naturally by weathering, the effects of sunlight, or be broken down by microorganisms. If the oil spill reaches the shore, then terrestrial environments will also be contaminated. Oil spills are extremely detrimental to fisheries and wildlife in both coastal and marine environments, due to the toxicity of the oil and its lasting impacts on the food chain.

Oil spill cleanups can introduce other impacts onto the environment. Floating rings are often used to contain the oil, while other physical, biological and chemical methods are used to remove the oil. Physical removal of the oil can remove large amounts of oil, but decontamination efforts can damage marine and coastal environments. Biological methods include bioremediation; the addition of microorganisms to speed up the degradation of the oil. Finally, chemical methods include the addition of dispersants, which break the oil down into smaller particles. Some dispersants, including Corexit, which was used in the Gulf of Mexico cleanup in 2010, are considered toxic in some parts of the world. The long term effects of the use of bioremediation and chemical dispersants, especially on such a large scale, are unknown.

Air Pollution

Air pollution is generated from the operation of machinery on offshore oil rigs as well as the burn-off of gases. Without factoring in the air pollution from its end product or the refinement process, the oil platforms themselves have an impact on local air quality and globally on climate change. It is estimated that over its lifetime, which is ten to twenty years, "a single rig can pollute as much as 7,000 cars driving 50 miles per day" (USPIRG). The NRDC States that "an average oil and gas exploration well spews roughly 50 tons of nitrogen oxides, 13 tons of carbon monoxide, 6 tons of sulfur oxides, and 5 tons of volatile organic chemicals.

Can we make offshore drilling better for the environment?

Apart from simply stopping the drilling, there are ways to guard against some of the negative environmental impacts of offshore oil drilling:

  1. Apply a thorough environmental assessment process before beginning the oil exploration. For projects in ecologically sensitive areas, sophisticated analyses will be required.
  2. Use alternative solutions to standard seismic surveys that are safer for marine life.
  3. Use drilling fluids that have low aquatic toxicity and high biodegradability.
  4. Develop a comprehensive waste management plan to ensure waste is disposed of in a responsible manner.
  5. Ensure that environmental health and safety standards are sufficient and enforced to help prevent oil spills.

Other options?

Energy conservation

Many opponents of offshore oil drilling point out that better energy efficiency will actually save more barrels of oil than could be gained by all US offshore reserves. They claim that better fuel efficiency standards would save around 3 million barrels a day, while tapping US offshore oil reserves would result in somewhere between 0.2 and 1 million barrels per day.

Alternative sources of energy

We all know that there are many sources of energy that don't involve fossil fuels. Alternative energy sources include wind, solar, hydroelectricity, wave generated and geothermal - but can these really supply our energy needs? The truth is that there are more than enough renewable sources of energy to supply the whole world. The challenge is to find a way to capture, store and deliver all of this energy in an effective and economic way.

My two cents

There's no easy answer to the offshore oil drilling debate. In my mind it's clear that offshore drilling has a very negative environmental impact. However, even if there wasn't an environmental impact from its day to day operations, I would probably still be opposed to it because of the risk of catastrophic oil spills. But where would we be without fossil fuels? For now, they seem to be a necessary evil. Until we can increase fuel efficiency standards and develop our network of alternative sources of energy, we still need fossil fuels. Which means that, for now, all we can do is conserve energy as well as we can, ensure that environmental, health and safety standards for drilling operations are as high as they can possibly be, and hope for the best.

Comments (2)


Very good analysis! Interesting how the government justifies the continuing oil drilling...


Add federal tax to gasoline usage. Just an idea...))


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