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The Environmental Impacts of Offshore Oil Drilling

An offshore oil rig off the coast of Santa Barbara (photo courtesy of web_guy94301 on flickr)

An offshore oil rig off the coast of Santa Barbara (photo courtesy of web_guy94301 on flickr)

The 2010 catastrophe on the Deepwater Horizon in the Gulf of Mexico drove 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 were 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.

To drill or not to drill

Photo courtesy of the Energy Institute

Photo courtesy of the Energy Institute

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, this How Stuff Works article is a good source.

Photo courtesy of marinephotobank on flickr

Photo courtesy of marinephotobank on flickr

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 catastrophe 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.

Photo courtesy of the EPA

Photo courtesy of the EPA

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.

This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.

© 2010 chirls


James Pacey on December 24, 2019:

Is it possible that the massive voids left by oil and gas mining is at least partly responsible for global warming due to the relocation of surface water to deep underground locations where it is no longer part of regular weather events like rain and snow and cloud vapour which helps cool the planet?

Roland Katak on December 19, 2017:

In the USA article it says drilling under US ocean. That's just it...now being territorial countries "own" oceans and airspace. But the seas n the air belong to earth n what happens in one territory's oceans or air, because of the nature of the medium in which whatever it is that occurs, can not b controlled by other territories. And therein lies this issues of greater alliances to control the only place humans have thus far lived n will do so for a considerable time to come. It's now for some ever or never ever (for life on earth if Carr trend is continued).

Dr on October 23, 2017:


Good work

Nice article

Keep up the good work

Thanks for sharing


Glen Rix from UK on July 14, 2017:

This article caught my attention because one of my sons works in the industry.

The Culzean field in the North Sea will produce 5% of the UK energy needs (oil and gas) for the next 50 years. There seems to be no easy answer to the vexed question of energy production. I would favour drilling in the sea bed over nuclear energy, which seems to me to be potentially more dangerous for the planet. A big debate is going on in the UK at the moment about the environmental impact of fracking. Wind and water power is perhaps the way to go.

Crane on April 11, 2017:

Drilling is good as you can use your own resources rather than buying form other at a high cost. Mico Equipment of Houston,Texas

XAVIER on February 14, 2017:

Good blog

hannah on December 09, 2016:


ebi on November 02, 2016:

i am deverstated with what i read but i am a lover of animals and also very good at human rights but animals are my favourite animals and just to say i love dolphins and to hear what oil drilling dose makes me sad about the animals that are out there are safocating

sofia@3008 on October 13, 2016:

Great blog you help me on my project

sathyam on October 04, 2013:

It was a great blog i got many information from here but some more information can make this blog better you can try http://www.oilandgasinvestments-usa.com/

http://friends2care.co.in/ on November 05, 2012:

Nice . thank you chirsl.

liyana on June 03, 2012:

Hi Chirls,

Thanks a lot . Well I was looking something like this for my project.

kenny on June 03, 2012:


I like the way you wrote .It was so understantable

Jerry on February 27, 2012:

Firstly drilling mud has very little Petroleum product in it. Sure oil based mud used to be made from diesel, but that was banned many years ago. Today it is largely made from food grade oils. Plus oil based mud is not as common as water based muds which are made from fresh water, brines and powdered rock or clays. Drilling muds have to pass brine shrimp tests before being dumped.

Then we get to zero discharge. All rigs built today are zero discharge. They skip and ship cuttings and even rainwater that falls on the rig is not discharged to the sea, before being totally checked to be inert.

Your view of the oil business is one that was valid twenty to thirty years ago, but is just not the case now. Please do some real research and not just swallow whole the propaganda from the anti-oil lobby.

Oh and fish stocks have actually increased since the Macondo disaster. Can it be that all that naturally occurring oil fed enough bacteria to feed more plankton, that feeds more fish?

Now if you want to see what is really killing the gulf of Mexico, then check out fertilisers used by farmers.

Debby Bruck on April 03, 2011:

Thanks Chiris. I was aghast to read today's headlines, "BP Asks Permission to Resume Drilling." What? Are they nuts? After the decimation and desecration of natural ocean, bogs and wildlife that poisoned the air, land and water and the recent earthquakes in Japan, we recognize the fragility of the planet. Not only does this present a delicate balance in nature, but also in the economic-political arena of world and business leaders, decision makers, and power brokers for energy resources. Your timely hub on the oil issue has already garnished over 80 poll results, mostly folks who say, "NO" let's not try that one again. Who can check that this action is truly safe for man, beast and environment? Be well, Chiris.

chirls (author) from Indiana (for now) on January 27, 2011:

Hi USA Cheerleader, I'd say that the cons of offshore drilling are largely environmental - it causes a huge impact to the marine and coastal environments. I hope this answers your question. Thanks for the suggestion to add a bibliography. I've been meaning to do this anyway so I will try to add some references in the next couple of weeks.

USA Cheerleader on January 26, 2011:

Hi chirls,

your website is GREAT! i just need to know something... is the cons basically like the negative effects of the environmental and economic?

is it the same? or different?

thanks so much... your website helped a lot!

by the way... could you post the things needed to create a bibliography? thank you!

American Tiger on October 29, 2010:

You've been lead to "believe" hydrocarbons will run out by people with a direct interest in you believing that. I know exactly how you feel. I felt that way myself for the longest time. Then, when I dug into the real science behind the claims, this is what I found:



chirls (author) from Indiana (for now) on October 27, 2010:

American Tiger, you raise some interesting points, but we'll have to agree to disagree! While I agree that hydrocarbons have done a lot of good in the past, I believe that the supply is very limited and it's time to find cleaner sources of energy. Thanks for reading and commenting.

American Tiger on October 21, 2010:

Well written Hub Chiris, even if I completely disagree with your conclusions. Thanks for presenting both sides.

Coal, Oil and Natural Gas have proven to be far more environmentally friendly than any alternative, were that alternative used as much as hydrocarbons are. (Wind farms the size of Kazakhstan, Solar farms the size of Spain...) The food shortages and environmental damage caused by Corn Ethenal production, not to mention its gross inefficiency as a fuel, should be enough to make you pull your hair out.

Hydrocarbon based fuels have done more to end poverty, alleviate hunger, heal the sick and extend life expectancy, Globally, than any "alternative" could ever conceive. And, they are infinitely renewable. We will run out of Hydrocarbon based fuels around the same time we run out of sunlight and seawater.

I would propose we solve the deep-water spill issues by allowing drilling ON LAND. Environmental regulations are directly responsible for forcing oil rigs to drill 5 miles out and a mile deep.

chirls (author) from Indiana (for now) on August 23, 2010:

Thanks for reading and commenting, oceansnsunsets. I'm with you - I wish it weren't so risky, but unfortunately it is! If only we would wake up and realize that the time to act is now. We have to stop being so dependent on oil!

Paula from The Midwest, USA on August 22, 2010:

Chirls, great hub! I was very impressed with all you said, and the pictures were great too. Thank you for sharing this information. I wish it all were not so risky.

chirls (author) from Indiana (for now) on August 13, 2010:

LRCBlogger, I completely agree with your thoughts on oil. I also think they should tighten up on fuel efficiency and emissions standards. Interesting points from Schmidt - as an environmental professional, I feel we're definitely lagging on sustainability issues. I feel like I came into this profession about 10 years too early!

LRCBlogger on August 13, 2010:

great hub, our dependence on fossil fuel in the US is not an accident. It stems from policies and legislation that has supported the oil & Gas industry for decades. Eric Schmidt, CEO of google, commented that he believes the clean energy revolution will create 10x more jobs than the IT revolution in the US. However, he also pointed out that the US is starting to severely lag behind in leading the clean energy technology revolution

My thoughts on oil are simple. Reduce. How, Ban plastic bags. Add a federal tax to gasoline. Give venture capitalist tax breaks when they invest in clean energy companies. End all oil subsidies and turn that money over to clean energy start-ups.

chirls (author) from Indiana (for now) on July 25, 2010:

Thanks! I thought it was only fair to present both sides of the argument as well as I can, although I'm the first to admit that I'm completely biased.

I was in total disbelief when I first heard about the Deepwater Horizon spill, and researching this hub made me realize that the global situation is much worse than I thought. It IS sad, but at least it seems like people are starting to come around to the environmental message... though perhaps not quickly enough!

Audrey Kirchner from Washington on July 25, 2010:

You outlined all the pros and cons very well! I'm like you though - there is just no 'safe' thing about it and I think we will yet see so much that this devastating oil spill has cost us. It is the saddest thing. I always have been a conservative thinker I suppose though - why take risks when we do not know how 'safe' procedures are? I tend to look at taking chances with our environment as a quick path to our own destruction.

Great hub although a very sad subject for me as I just can't imagine how we can justify continuing on with offshore drilling. Change is needed but will it occur - as in our reliance on oil - or will it be too late after all is said and done anyway?

I only wish we were as smart as we thought we were! We have such a tremendous gift on this earth of ours - may be continue to enjoy it and not muck it up any further!

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