Assam Oil Spill Case Study and Impacts of Oil Spills

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Context: An oil well in Assam recently experienced a blowout and caught fire. The spewing of gas from the well and the subsequent fire has forced people to leave their homes, also causing damage to the surrounding ecosystems. In this case study, we will learn about the impacts of such oil spills and fires on people and biodiversity. 


  • Current events of national and international importance.
  • General issues on Environmental Ecology, Bio-diversity and Climate Change 


  • GS III- Conservation, environmental pollution and degradation, environmental impact assessment.
  • Disaster and disaster management.


Case Study: Assam Oil Spill

  • An oil well in eastern Assam’s Tinsukia district experienced a blowout on the morning of May 27, 2020.
  • Machinery failure usually leads to a blowout, which is an uncontrolled release of crude oil or gas from a production well.
  • This particular well is under Oil India Limited or OIL's Baghjan oilfield
  • It adjoins the Maguri-Motapung wetland and is not far from the Dibru-Saikhowa National Park. 
  • Gas had been flowing out uncontrollably despite the pumping in of water.
  • The well caught fire 13 days after it started spewing gas and associated elements.
  • Around 11,000 people from the surrounding villages are now in relief camps set up by the administration.
  • Locals and environmentalists are worried about the impact of the gas leak and there have been reports of damage to the ecology of the area.
  • The Maguri-Motapung Beel (wetlands, in Assamese) is 500m away from the oil well.
    • The Dibru river passes through the wetland and is full of dead fish. A thin film of oil has covered the river. 
    • The wetland hosts 80 fish species, and 300 bird species every year.
    • Of those, six are vulnerable species (like the Swamp Francolin and the Marsh Babbler), two endangered (Greater Adjutant and Pallas’s Fish-eagle) and six critically endangered (like Baer’s Pochard, Red-headed Vulture and White-bellied Heron).
    • BirdLife International had recognised it as an Important Bird and Biodiversity Area in 1996- it is one of 12,000 in the world.
    • The irony is that because of the wetlands, villages on the other side did not get affected by the fire. The wetlands bore the brunt. But restoration will take years.
  • For the Dibru-Saikhowa national park, the concern is about oil condensate.
    • The condensates that are falling on the park poses a great threat to the biodiversity there.
    • It may take up to four weeks for the fire to be put out because oil wells keep burning as long as there is a huge supply of fuel and oxygen. The outlook is catastrophic.
  • There have been protests since June 9 around the site and Assam Chief Minister Sarbananda Sonowal has ordered a probe into the oil well catching fire.
  • The Assam Pollution Control Board had issued a closure notice to Oil India to shut down all production and drilling operations of all the installations of Baghjan oilfield.
  • The pollution body informed that Oil India has been allegedly operating the Baghjan oilfield activities without obtaining prior consent and clearance from the board. 
  • “It is mandatory to obtain prior permission/clearance from MoEF&CC as well as State PCB for production, drilling, pumping of crude oil and laying pipeline activities as per EIA notification, 2006 and various provisions under the Section 25/26 of the Water (Prevention of Control of Pollution) Act, 1974 and Section 21 of the Air (Prevention of Control of Pollution) Act, 1981 and Authorization under the Hazardous & other waste (Management & Transboundary Movement) Rules, 2016 as amended upto date”.


Examples of Major Oil Spill around the world
  • While only major accidents that result in spills receive most of the attention, a number of smaller and chronic incidents take place on a regular basis.
  • And, it takes month-long oil cleaning operations to bring back the areas around the accident back to normality.
  • At the same time, efforts have been made to prevent them with the help of technology.
  • Yet, the world has been racked by major oil spill disasters many times.

Here are some of the largest and worst oil spills in world history:

Gulf war oil spill

  • The world’s largest oil spill was not an accident. It was the result of a war.
  • During the Gulf war in 1991, as the Iraqi forces withdrew from Kuwait, they opened pipelines and the valves of oil wells and set the fire as a measure to block the forces of United States from landing in the area.
  • The fire started after the opening of the first well in January 1991 had lasted till the capping of last well in the month of April that year.
  • As a result, around 240 million gallons of oil are believed to have been discharged into the Persian Gulf, killing hundreds of fishes and marine mammals.

Deepwater Horizon

  • Also known as the Gulf of Mexico Oil spill and British Petroleum (Company) oil spill, the Deepwater Horizon oil spill is considered to be the largest oil spill in the petroleum industry’s history.
  • In April 2010, the accident began after a spill from a seafloor oil gusher, leading to the explosion of the BP’s oil rig, Deepwater Horizon, in its Macondo Prospect.
  • The accident killed 11 men working abroad the rig and also resulted in an oil spill that continued for over three months.
  • An estimated 53,000 barrels were flowing into the Gulf of Mexico every day.
  • The accident also made extensive damages to the marine environment.
  • According to the Centre for Biological Diversity, the oil spill killed over 82,000 birds, 25,900 marine mammals, 6,000 sea turtles and tens of thousands of fish, among others.

Arctic Oil Spill

  • In the first week of June 2020, Russian President Vladimir Putin declared an emergency after 20,000 tons of diesel fuel spilt into a river in the Arctic Circle. 
  • The spill happened when a fuel tank at a power plant near the Siberian city of Norilsk collapsed
  • The accident is the second-largest oil spill in terms of volume in modern Russian history according to the World Wildlife Fund (WWF).
  • The oil spread around 7.5 miles from the fuel site, turning the Ambarnaya river bright red, and contaminated a total of 135 square miles.
  • Drilling activity and oil spills per se in the Arctic causes long-term exposure and thus chronic effects on Arctic marine ecosystems.
  • The local ecosystem sustains damage as there are notable changes in species composition, dominance and biomass, made worse by oil spills.
  • The pursuit of fossil fuel and exploration in the ecologically sensitive Arctic region – whether it originates from shipping activities or drilling activity- destroys all aspects of the environmental integrity of the marine ecosystems including fisheries, marine mammals, corals, ocean and shorebirds, and the coastal wildlife.
  • This hurts not only the growth and reproduction of the native species but also leads to behavioural changes seen reflected in the feeding, activity and motility, avoidance reactions etc of the marine birds and animals.


Impacts of Oil Spills on Humans and Environment
  • Almost all the mistakes we make harm the environment and the species on the planet in one way or another.
  • While some human errors affect nature eventually, few make immediate and huge impacts on the environment, with even ending the lives of thousands of species at a time.
  • When the incidents like wildfire and bombing end up destroying the environment in a minute of time on land, it is events such as oil spills that put our seas and oceans into trouble in a short period of time.
  • Oil spill disasters have been one of the major concerns of the marine world for a long time now.
  • They are commercial and environmental catastrophes.
  • As a result of an accident involving ships or oil rigs, the ocean water became contaminated by liquid petroleum hydrocarbon, causing damages to the environment for decades to come.
  • In addition to killing fish, marine mammals and birds, oil spills damage beaches and wildlife habitats, among others.
  • When an oil slick reaches the beach, it also affects human settlement on the beaches and mangrove forests etc.
  • In short, an oil spill completely disturbs an entire ecosystem for a quite long period of time.

Human impact

  • An oil spill represents an immediate fire hazard. The Kuwaiti oil fires produced air pollution that caused respiratory distress.
    • The Deepwater Horizon explosion killed eleven oil rig workers.
    • The fire resulting from the Lac-Mégantic derailment killed 47 and destroyed half of the town's centre.
  • Spilled oil can also contaminate drinking water supplies.
    • For example, in 2013 two different oil spills contaminated water supplies for 300,000 in Miri, Malaysia; 80,000 people in Coca, Ecuador.
    • In 2000, springs were contaminated by an oil spill in Clark County, Kentucky.
  • Thousands of people are displaced where oil spills contaminate the land and water resources near human settlements.
  • Contamination can have an economic impact on tourism and marine resource extraction industries.
  • For example, the Deepwater Horizon oil spill impacted beach tourism and fishing along the Gulf Coast, and the responsible parties were required to compensate economic victims.
  • The chemicals in crude oil are mostly hydrocarbons that contain toxic chemicals such as benzenes, toluene, poly-aromatic hydrocarbon and oxygenated polycyclic aromatic hydrocarbons.
  • These chemicals can introduce adverse health effects when being inhaled into the human body.
  • In addition, these chemicals can be oxidized by oxidants in the atmosphere to form fine particulate matter after they evaporate into the atmosphere.
  • These particulates can penetrate the lungs and carry toxic chemicals into the human body. Burning surface oil can also be a source for pollution such as soot particles.

Environmental Impacts

  • The oil environmental impact on water in damaging in a variety of ways. When there are oil spills in the ocean or fresh water, it does not blend with the water. 
  • Oil floats on the surface of salt and freshwater.
  • Over a very short period of time, the oil spreads out into a very thin layer across the surface of the water.
  • This can block sunlight from reaching oceanic environments, which can severely impact producers and, thus, the entire food chain of an ecosystem. 
  • This layer, called a slick, expands until the oil layer is extremely thin and can spread hundreds of miles wide.
  • Rough seas can split an oil slick apart, carrying some oil in one direction and more in another.
  • In contrast, a nearshore oil spill can be totally controlled by currents and wave action that causes the oil to come ashore, damaging marine shoreline habitat.

Environmental Impact on the Coastline

  • Perhaps the most visual part of an oil spill is the harsh effects oil has on the coastline. Pictures of oil-covered birds and sea mammals are common.
  • Oil is thick and sticks to everything it touches. While the most visual part of the damage might be the birds and wildlife, consider that the oil covers everything right down to a grain of sand.
  • Every rock, piece of driftwood, saw grass, sand, soil and microscopic habitat is destroyed or affected by the thick oil that washes ashore after a spill.
  • Unless there is a concerted effort to clean the shoreline, the oil will stay onshore until weather and time break the oil down.
  • The process is extremely slow, which is why so many environmentalists work diligently to clean beach areas, rocks and shoreline that have been contaminated.
  • The gooey mass that makes up an oil slick litters the shoreline with ugly black tar.
  • What makes it so very dangerous is that the coastline is where so much marine life is concentrated.
  • Typically, shore areas are the nurseries for fish and marine life, in addition to being the home of many young marine mammals.

Effects on Marine Life and Wildlife

The effects of oil spills in the ocean are far-reaching.

Marine Life Direct Impact:

  • Marine and coastal life can be contaminated in a number of ways, through poison by ingestion, destruction of habitat and direct contact with oil.
  • For example, when oil floats on the water surface, a marine mammal that surfaces in the centre of the slick ingests the oil.
  • Marine animals and organisms that swim through the slick area can also ingest oil through their gills.
  • Even if a marine animal is miles from the oil spill, but they eat another organism that was close by, they'll ingest that oil, which is poisonous.
  • Ingesting oil can cause any number of problems besides death and sickness.
  • If an animal or other marine organisms ingest the oil, it can affect their ability to reproduce and produce viable offspring.

Oil Environmental Impact on Habitat and Wildlife:

  • Habitat destruction is all too obvious with an oil spill.
  • The most visible would be seen onshore, but beneath the water, there is a very delicate balance in the reefs and shallow-water habitats.
  • Plankton, producers at the bottom of the food chain, are often killed by oil spills as a result of changes to the water and lack of sunlight beneath the oil slick.
  • This effect moves right on up the food chain.
  • Of particular concern are the very delicate sea animals, such as clams and mussels that feed on plankton.
  • Direct contact with oil harms any organism that comes in contact with the oil.
  • For example, when oil cakes the feathers of a bird, it keeps their feather from repelling water. Oil also weighs down the bird, keeping it from flying.
    • If a bird isn't cleaned off the oil, it's a sure license to death.
    • Many birds also ingest deadly amounts of oil trying to clean their feathers.
  • The same holds true for marine mammals. Marine mammal fur acts as an insulator to keep the animal warm in the coldest waters.
  • When oil saturates the fur, it ruins the ability of the fur to retain heat. Again, marine mammals can ingest the oil when trying to clean their fur.
  • There are three kinds of oil-consuming bacteria. Sulfate-reducing bacteria (SRB) and acid-producing bacteria are anaerobic, while general aerobic bacteria (GAB) are aerobic.
  • These bacteria occur naturally and will act to remove oil from an ecosystem, and their biomass will tend to replace other populations in the food chain.

In addition, oil spills can also harm air quality.

  • During the cleanup and recovery process, it will also generate air pollutants such as nitric oxides and ozone from ships. Lastly, bubble bursting can also be a generation pathway for particulate matter during an oil spill.
  • During the Deepwater Horizon oil spill, significant air quality issues were found on the Gulf Coast, which is the downwind of the DWH oil spill.
  • Air quality monitoring data showed that criteria pollutants had exceeded the health-based standard in the coastal regions.


Cleanup and recovery of Oil Spill

Cleanup and recovery from an oil spill is difficult and depends upon many factors, including the type of oil spilled, the temperature of the water (affecting evaporation and biodegradation), and the types of shorelines and beaches involved.

Physical cleanups of oil spills are also very expensive. However, microorganisms such as Fusobacteria species demonstrate the potential for future oil spill cleanup because of their ability to colonize and degrade oil slicks on the sea surface.

Methods for cleaning up include:

  1. Bioremediation: use of microorganisms or biological agents to break down or remove oil.
  2. Bioremediation Accelerator: a binder molecule that moves hydrocarbons out of the water and into gels, when combined with nutrients, encourages natural bioremediation. 
  3. Controlled burning can effectively reduce the amount of oil in water if done properly. But it can only be done in low wind and can cause air pollution.
  4. Dispersants can be used to dissipate oil slicks.
    • A dispersant is either a non-surface active polymer or a surface-active substance added to a suspension, usually a colloid, to improve the separation of particles and to prevent settling or clumping. 
  5. Watch and wait: in some cases, natural attenuation of oil may be most appropriate, due to the invasive nature of facilitated methods of remediation, particularly in ecologically sensitive areas such as wetlands.
  6. Dredging: for oils dispersed with detergents and other oils denser than water.
  7. Skimming: Requires calm waters at all times during the process.
  8. Solidifying: 
    • Solidifiers are composed of tiny, floating, dry ice pellets, and hydrophobic polymers that both adsorb and absorb.
    • They clean up oil spills by changing the physical state of spilled oil from liquid to a solid, semi-solid or a rubber-like material that floats on water.
  9. Vacuum and centrifuge: Oil can be sucked up along with the water, and then a centrifuge can be used to separate the oil from the water – allowing a tanker to be filled with near pure oil. 
  10. Beach Raking: coagulated oil that is left on the beach can be picked up by machinery.



  • Secondary containment– methods to prevent releases of oil or hydrocarbons into the environment.
  • Oil Spill Prevention Control and Countermeasures (SPCC) program by the United States Environmental Protection Agency.
  • Double-hulling – build double hulls into vessels, which reduces the risk and severity of a spill in case of a collision or grounding. Existing single-hull vessels can also be rebuilt to have a double hull.
  • Thick-hulled railroad transport tanks.
  • Spill response procedures should include elements such as;
    • A listing of appropriate protective clothing, safety equipment, and cleanup materials required for spill cleanup (gloves, respirators, etc.) and an explanation of their proper use;
    • Appropriate evacuation zones and procedures;
    • Availability of fire suppression equipment;
    • Disposal containers for spill cleanup materials; and
    • The first aid procedures that might be required.

Environmental Sensitivity Index (ESI) mapping

Environmental Sensitivity Index (ESI) maps are used to identify sensitive shoreline resources prior to an oil spill event in order to set priorities for protection and plan cleanup strategies.

By planning spill response ahead of time, the impact on the environment can be minimized or prevented. Environmental sensitivity index maps are basically made up of information within the following three categories: shoreline type, and biological and human-use resources.

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