Ecological Preservation : Offshore Drilling: Impacts & Counts

Offshore Drilling

Offshore drilling refers to a mechanical process where a wellbore is drilled through the seabed. It is typically carried out in order to explore for and subsequently extract petroleum which lies in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the continental shelf, though the term can also be applied to drilling in lakes, inshore waters and inland seas.

Offshore drilling presents environmental challenges, both from the produced hydrocarbons and the materials used during the drilling operation. 

Offshore drilling operations to create various forms of pollution that have considerable negative effects on marine and other wildlife.

These include drilling muds, brine wastes, deck runoff water and flowline and pipeline leaks. Catastrophic spills and blowouts are also a threat from offshore drilling operations. These operations also pose a threat to human health, especially to oil platform workers themselves.

Drilling muds and produced water are disposed of daily by offshore rigs. Offshore rigs can dump tons of drilling fluid, metal coatings, including toxic metals, such as lead, chromium and mercury, as well as carcinogens, such as benzene, into the ocean.

Effects of Drilling Muds

Drilling muds are used for the lubrication and cooling of the drill bit and pipe. The muds also remove the cuttings that come from the bottom of the oil well and help prevent blowouts by acting as a sealant. There are different types of drilling muds used in oil drilling operations, but all release toxic chemicals that can affect marine life. One drilling platform normally drills between seventy and one hundred wells and discharges more than 90,000 metric tons of drilling fluids and metal cuttings into the ocean.

Effects of Produced Water

Produced water is fluid trapped underground and brought up with oil and gas. It makes up about 20 percent of the waste associated with offshore drilling. Produced waters usually have an oil content of 30 to 40 parts per million. As a result, the nearly 2 billion gallons of producing water released into the Cook Inlet in Alaska each year contain about 70,000 gallons of oil.

Effects of Exploration

Factors other than pollutants can affect marine wildlife as well. Exploration for offshore oil involves firing air guns which send a strong shock across the seabed that can decrease fish catch, damage the hearing capacity of various marine species and may lead to marine mammal strandings.

More drilling muds and fluids are discharged into the ocean during exploratory drilling than in developmental drilling because exploratory wells are generally deeper, drilled slower and are larger in diameter. The drilling waste, including metal cuttings, from exploratory drilling are generally dumped in the ocean, rather than being brought back up to the platform.

Effects of Offshore Oil Rigs

Offshore oil rigs may also attract seabirds at night due to their lighting and flaring and because fish aggregate near them. Bird mortality has been associated with physical collisions with the rigs, as well as incineration by the flare and oil from leaks. This process of flaring involves the burning off of fossil fuels which produces black carbon.

Black carbon contributes to climate change as it is a potent warmer both in the atmosphere and when deposited on snow and ice. Drilling activity around oil rigs is suspected of contributing to elevated levels of mercury in Gulf of Mexico fish.

No. of Offshore Rigs in the World

Region Name

Rigs Contracted

Rig Fleet

Africa – Other

6 rigs

9 rigs

Africa – West

71 rigs

91 rigs

Asia – Caspian

18 rigs

31 rigs

Asia – Far East

40 rigs

168 rigs

Asia – South

43 rigs

54 rigs

Asia – SouthEast

102 rigs

181 rigs


11 rigs

15 rigs

Black Sea

12 rigs

13 rigs

Europe – East

3 rigs

5 rigs

Europe – North Sea

167 rigs

176 rigs


19 rigs

25 rigs

MidEast – Persian Gulf

98 rigs

134 rigs

MidEast – Red Sea

9 rigs

17 rigs

N. America – Canadian Atlantic

6 rigs

6 rigs

N. America – Canadian Pacific

0 rigs

1 rigs

N. America – Mexico

47 rigs

81 rigs

N. America – US Alaska

2 rigs

5 rigs

N. America – US GOM

80 rigs

217 rigs

N. America – US Other

1 rigs

28 rigs

S. America – Brazil

86 rigs

119 rigs

S. America – Other & Carib.

10 rigs

16 rigs

S. America – Venezuela

25 rigs

48 rigs

Courtesy & Sources : Rig Report, Wikipedia and Google

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